Progress 10/01/12 to 09/30/17
Outputs
Target Audience:Some of the results from this study are most relevant to plant breeders and scientists. An improved understanding of senescence and postproduction crop quality is also relevant to floriculture industry stakeholders, including greenhouse producers, shippers, and retailers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project provided professional training for 3 graduate students, 1 undergraduate intern, 1 visiting scholar and 1 research associate. How have the results been disseminated to communities of interest?Experimental results were presented at national and international scientific conferences including: the American Society for Horticultural Sciences Annual Conference, the International Horticultural Congress, the Plant Senescence Gordon Conference, the International Conference on the Plant Hormone Ethylene, and the Quality Management in Supply Chain of Ornamentals Conference. Results were also presented to industry stakeholders at regional and state extension and outreach meetings. These included seminars for national and local audiences at the Ohio Nursery and Landscape Association Short Course, Greater Cleveland Area Flower Growers Association, Cincinnati Flower Growers Association, Maumee Valley Growers Association, Toledo Area Flower and Vegetable Growers Association, Tri-State Industry Conference, OSU Annual Trials Open House, OSU Poinsettia Trials Open House, OSU Greenhouse Management Workshop and American Hort's Cultivate Short Course (formerly called OFA Short Course). Articles have been published in scientific journals, trade magazines and newsletters. Content has also been made available via the D.C. Kiplinger Floriculture Crop Improvement Program website (https://u.osu.edu/joneslab/) and the Greenhouse Industry Roundtable of the Midwest (https://u.osu.edu/greenhouse/) blog. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The wholesale value of floriculture crops in the United States was $4.37 billion in 2016. Seventy percent of U.S. floriculture production occurs in only seven states (including Ohio). The availability of ornamental plants with enhanced tolerance to postproduction stresses will increase shelf life, reduce shrink, and enhance the profitability of the floriculture industry. Consumers must also be provided with simple care instructions for maintaining the quality and display life of interior and garden plants. Consumer successes are essential for repeat sales and for the future growth of the industry. The first part of objective 1 involved the identification of genes putatively involved in regulating senescence in flower petals. We used Petunia × hybrida as a model for this research. High-throughput sequencing was conducted to identify transcripts that were differentially expressed between the corollas of pollinated, senescing petunia flowers and their unpollinated controls at 12, 18, and 24 hours after opening. These time points were chosen because they include early stages of pollination-induced senescence in the flower, and are before fertilization, ethylene production by the petals, or visual symptoms of corolla wilting. In total, close to 0.5 billion Illumina 101 bp reads were generated, de novo assembled, and annotated, to generate an EST library of approximately 33K genes from Petunia x hybrida corollas. Over 4,700 unique, differentially expressed genes were identified when comparing corollas from pollinated and unpollinated flowers. Over 500 gene ontology terms were enriched, providing insight into the biological processes that are occurring during petal senescence. The response to auxin and 1- aminocyclopropane-1-carboxylic acid terms were enriched at 12 hours after pollination (hap). Genes involved in autophagy and plant pathogen-interactions were up-regulated and ribosomal genes and genes involved in carbon fixation were consistently down regulated. More than 300 differentially expressed transcription factors were identified. This sequence data has greatly expanded the genetic resources available in petunia, and it will guide future research that is aimed at identifying the best targets for increasing flower longevity by delaying corolla senescence. Engineered viruses that contain a fragment of a plant gene can be used to down-regulate the endogenous expression of senescence-related genes and confirm their role in flower and leaf senescence. The tobacco rattle virus (TRV) has been used for virus-induced gene silencing (VIGS) in Petunia x hybrida. VIGS provides a tool for functional analysis that is much more rapid than creating stably transformed plants in which specific endogenous genes have been modified. VIGS efficiency in all plants is affected by the severity and uniformity of the viral infection, and VIGS often results in tissues within the plant with different levels of gene down-regulation. This can make it difficult to phenotype VIGS plants. Experiments were conducted to further optimize the VIGS efficiency in petunia. We compared methods of inoculating the plant with Agrobacterium containing the TRV constructs. These included an apical meristem application, leaf infiltration with a needless syringe, media drench and vacuum infiltration of the plant. The chalcone synthase (CHS) gene was used as a visual indicator of silencing in flower petals. Silencing CHS causes colored petals to turn white, and the area of white sectors was quantified to determine the efficiency of gene silencing between the different treatments. Silencing phytoene desaturase (PDS) causes photobleaching in the leaves and the color changes in the leaves were also quantified to evaluate silencing efficiency in the vegetative tissues. The inoculation of mechanically wounded shoot apical meristems gave the greatest silencing in leaves and petals. Differences in PDS and CHS silencing were observed among commercial petunia cultivars and 'Picobella Blue' was selected for subsequent experiments. Growth temperature and seedling age at inoculation also had an impact on silencing efficiency. Younger seedlings at 3 to 4 weeks after seeding showed the quickest and most uniform silencing, and silencing was greatest when plants were grown at 20° F days/ 18° F nights. Successful phenotying of VIGS plants requires the proper control plants. After VIGS had been optimized in petunia, plants showed increasingly severe viral symptoms when inoculated with the control empty vector TRV2. Adding a fragment of the green fluorescent protein (GFP) reduced viral symptoms and these plants served as adequate controls for assessing phenotypes caused by the down-regulation of specific genes of interest. We have used this optimized technique to evaluate senescence-associated genes in petunia, and we continue to evaluate genes identified in the RNA seq experiment. This method can also be used by other researchers who are using petunia as a model to investigate growth, development, and stress responses. Objective 2 involved applied horticulture research that was aimed at generating data-driven recommendations for the proper retail and consumer care and handling of floriculture crops to increase quality and display life. Phalaenopsis orchids are becoming more popular as potted house plants, but their display life is often reduced by improper watering. These epiphytes are often over-watered, leading to root damage and the eventual death of the plant. Irrigating potted Phalaenopsis orchids weekly with ice cubes has been suggested as a simple care method to ensure consumer success and prevent overwatering. Four cultivars of Phalaenopsis orchids, growing in bark-based media, were irrigated weekly with three ice cubes or the equivalent volume of room temperature water. Flower longevity and plant display life was monitored for up to 6 months in an interior evaluation room. The quantum yield of photosystem II was measured monthly in the roots and the leaves to determine if photosynthetic efficiency was affected by the ice irrigation The volume of leachate in the decorative outer pots was measured monthly after irrigation to determine how much water was being retained by the plants and the media. The temperature of the media was also monitored using GS3 soil/ moisture/EC/temperature probes (Decagon Devices, Pullman, WA). Individual flower longevity and the display life of Phalaenopsis orchids were unaffected by the irrigation treatment. The volume of leachate that accumulated in the outer pots was the same or lower when orchids were irrigated with ice cubes compared to water. Orchid roots in the bark media were not exposed to freezing temperatures, and the lowest recorded temperature in the top 5.5 cm of the media after ice irrigation was only 11 °C. The quantum yield of photosystem II in both roots and leaves was the same in ice and water irrigated plants, confirming that ice did not have a negative impact on photosynthesis during the 6 months of evaluation. Placing ice cubes on the media surface or on the surface roots did not decrease the display life or flower quality. Ice cubes should not be placed directly on the leaves as this can cause damage. Ice cubes are a viable method of irrigating Phalaenopsis orchids that can prevent overwatering. This research provides valuable recommendations for consumers, retailers, and growers, which will increase consumer success with potted Phalaenopsis orchids.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
South K.A., Thomas P.A., van Iersel M.W., Young C., and M.L. Jones (2017) Ice cube irrigation of potted Phalaenopsis orchids in bark media does not decrease display life. HortScience 52:1271-1277.
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Chapin L.J., Moon Y., and M.L. Jones (2017) Downregulating a type I metacaspase in petunia accelerates flower senescence. Journal of the American Society for Horticultural Science. 142:405-414.
- Type:
Theses/Dissertations
Status:
Submitted
Year Published:
2017
Citation:
Quijia Pillajo J.O. (2017) The role of autophagy in flower senescence and abiotic stress responses of Petunia x hybrida 'Mitchell Diploid'. The Ohio State University, M.S. thesis.
|
Progress 10/01/15 to 09/30/16
Outputs
Target Audience:The target audience for this research is plant scientists interested in plant development and hormone signaling Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This research provided training for a research associate in the areas of horticulture, molecular biology, bioinformatics, and statistics. How have the results been disseminated to communities of interest?Results from this project have been presented at scientific conferences. The results of this research are relevant to researchers interested in senescence and flower development. What do you plan to do during the next reporting period to accomplish the goals?We will continue to evaluate petunias in which additional genes of interest have been down regulated. We will evaluate the role of senescence related genes in regulating the timing and execution of developmental senescence and stress-induced senescence in leaves and flowers. These studies will help identify gene targets to delay senescence and improve the postproduction quality of containerized ornamental plants.
Impacts
What was accomplished under these goals?
An RNA sequencing project in Petunia x hybrida identified four thousand seven hundred genes that were up or down regulated at the very early stages of flower petal senescence. Many of the up regulated genes were involved in hormone synthesis or signaling, including a putative EIN3-binding F-box protein (PhEBF). Gene expression studies using reverse transcription quantitative PCR (RT-qPCR) confirmed that the expression of this gene increased in petals during flower senescence. We hypothesized that EBF's may regulate the initiation of flower senescence, and that down-regulating (or silencing) PhEBF1 would alter flower longevity. Tobacco Rattle Virus (TRV) mediated virus-induced gene silencing (VIGS) was used to down regulate the expression of the endogenous PhEBF1 gene in petunia. These experiments were conducted to determine if PhEBF1 has a functional role in the timing of flower petal senescence. The TRV silencing construct contained a fragment of the PhEBF1 gene in tandem with a fragment of the Petunia x hybrida chalcone synthase (CHS) gene. Chalcone synthase was included to provide a visual indicator of senescence. In blue flowering petunias, silencing CHS causes petals to turn partially or entirely white. Control constructs included the PhCHS gene but not the PhEBF1 gene. PhEBF1 silenced petunias and control petunias were grown to flowering. The life span or longevity of individual flowers was determined by tagging flowers on the day of flower opening and then determining the number of days it took for the flowers to show petal wilting, the first visual symptoms of corolla senescence. Unpollinated, naturally senescing PhEBF1 VIGS petunia flowers wilted 2 days earlier than control flowers. The down regulation of EBFs causes a hypersensitivity to ethylene. Flowers do not produce more ethylene, but senescence is initiated earlier because the corollas are sensitive to lower levels of ethylene. The longevity of individual flowers determines the value of ornamental species which are sold based on their aesthetic beauty. Studies like these provide important information about how flower senescence is regulated.
Publications
|
Progress 10/01/14 to 09/30/15
Outputs
Target Audience:The target audience for this research is plant scientists interested in plant development and hormone signaling. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This research provided training in the areas of horticulture, molecular biology, bioinformatics, and statistics. How have the results been disseminated to communities of interest?Results from this project have been presented at International scientific conferences and published in scientific journals. Sequence data is available in the GenBank database. The results of this research are relevant to researchers interested in senescence and flower development. What do you plan to do during the next reporting period to accomplish the goals?We will continue to evaluate plants in which genes of interest have been down regulated in petunias using Virus Induced Gene Silencing. We will evaluate the role of senescence related genes in regulating the timing and execution of developmental senescence and stress-induced senescence in leaves and flowers. These studies will help identify gene targets to delay senescence and improve the postproduction quality of containerized ornamental plants.
Impacts
What was accomplished under these goals?
Four thousand seven hundred unique, differentially expressed genes were identified when comparing corollas from pollinated and unpollinated flowers. Over 500 gene ontology terms were enriched, providing insight into the biological processes that are occurring during petal senescence. Many of the up regulated genes were involved in hormone synthesis or signaling. The response to auxin and 1-aminocyclopropane-1-carboxylic acid terms were enriched at 12 hours after pollination (hap). A putative EIN3-binding F-box protein (EBF) was identified among the genes that was differentially regulated between pollinated and unpollinated corollas. A reciprocal BLASTx identified three putative EBFs in the petunia RNA seq data set. PhEBF1a and PhEBF1b share 96.2% amino acid identity. Only PhEBF1b and PhEBF2 had predicted F-box domains. Reverse transcription quantitative PCR (RT-qPCR) was used to characterize the expression of these three EBFs during flower senescence. All three EBFs were upregulated in petunia corollas after pollination. PhEBF1a expression increased after pollination with the greatest transcript abundance at 36 hours, before visible wilting. PhEBF1b had a different expression pattern, with higher transcript levels at 12 to 36 hours after pollination, followed by a large decrease at 48 hours. PhEBF2 transcript levels in pollinated and unpollinated corollas were similar except at 12 and 18 hours when PhEBF2 expression was slightly higher in pollinated corollas. The functional role of these EBFs is currently being investigated by down regulating the endogenous gene expression in petunias using virus induced gene silencing.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Broderick, S.R. and M.L. Jones (2015) EIN3-binding F-box proteins identified from petunia corollas using RNA-seq. Acta Hortic. 1104, 327-332
DOI: 10.17660/ActaHortic.2015.1104.49
http://dx.doi.org/10.17660/ActaHortic.2015.1104.49
|
Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Scientists and plant breeders. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research was primarily conducted by a PhD student, and it provided the opportunity for training in horticulture, molecular biology, bioinformatics, and statistics. How have the results been disseminated to communities of interest? Results from this project have been presented at scientific conferences and published in peer-reviewed scientific journals and in a dissertation. Sequence data has been deposited in the GenBank database. The results of this research are relevant to researchers interested in senescence and flower development. What do you plan to do during the next reporting period to accomplish the goals? We will use the optimized VIGS system in petunia for the functional characterization of genes identified in this RNA sequencing project. These studies will be used to confirm that the identified genes have an important regulatory role in the initiation of senescence.
Impacts
What was accomplished under these goals?
The postproduction shelf life of ornamental plants is reduced by flower senescence. In many species, pollination initiates corolla senescence. Pollination can therefore be used in flower senescence research to coordinate the senescence program between flowers. Petal senescence results in the degradation of cellular components to allow for nutrient remobilization to developing seeds. To identify genes that are involved in initiating the senescence program in petals, we conducted RNA sequencing of Petunia × hybrida corollas. High-throughput sequencing and analysis of this data identified transcripts that were differentially expressed between the corollas of pollinated petunia flowers and their unpollinated controls at 12, 18, and 24 hours after opening. These time points were chosen because they include early stages of pollination-induced senescence in the flower, and are before fertilization, ethylene production by the petals, or visual symptoms of corolla wilting. In total, close to 0.5 billion Illumina 101 bp reads were generated, de novo assembled, and annotated, to generate an EST library of approximately 33K genes from Petunia x hybrida corollas. Over 4,700 unique, differentially expressed genes were identified when comparing corollas from pollinated and unpollinated flowers. Over 500 gene ontology terms were enriched, providing insight into the biological processes that are occurring during petal senescence. The response to auxin and 1-aminocyclopropane-1-carboxylic acid terms were enriched at 12 hours after pollination (hap). Genes involved in autophagy and plant pathogen-interactions were up-regulated and ribosomal genes and genes involved in carbon fixation were consistently down regulated. More than 300 differentially expressed transcription factors were identified. This sequence data will greatly expand the genetic resources available in petunia, and guide future research that is aimed at identifying the best targets for increasing flower longevity by delaying corolla senescence.
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2014
Citation:
Broderick S.R. and M.L. Jones (2014) EIN3-binding F-box proteins identified from petunia corollas using RNA-seq. ACTA Horticulturae (In press).
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Broderick S.R., Wijeratne S., Wijeratne A.J., Chapin L.J., Meulia T., and M.L. Jones (2014) RNA-sequencing reveals early dynamic transcriptome changes in the corollas of pollinated petunias. BMC Plant Biology 14:307. DOI: 10.1186/s12870-014-0307-2
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2014
Citation:
Broderick S.R. Pollination-Induced Gene Changes That Lead to Senescence in Petunia � hybrida. The Ohio State University Dissertation.
|
Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Plant breeders and scientists were the target audiences for our scientific publications. Trade magazine publications, thefloriculture blog, and presentations at local and national trade organizations andeducational programs targeted industry stakeholders. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The research was conducted by a PhD student and an MS student. The PI provided guidance on experimental design, implementation, data analysis, and manuscript preparation. How have the results been disseminated to communities of interest? Results from this project have been presented at industry and university seminars.Results have been published in trade magazines and peer reviewed scientific journals. What do you plan to do during the next reporting period to accomplish the goals? We will use the optimized VIGS system in petunia for functional characterization of additional senescence-related genes. Phenotypic analysis will focus on drought stress and flower senescence.
Impacts
What was accomplished under these goals?
The postproduction shelf life of ornamentals is reduced by senescence. We have therefore utilized proteomic and genomic approaches to identify targets to manipulate senescence and increase postproduction quality. Engineered viruses that contain a fragment of a plant gene can be used to down-regulate the endogenous expression of senescence-related genes and confirm their role in flower and leaf senescence. The tobacco rattle virus (TRV) has been used for virus-induced gene silencing (VIGS) in Petunia x hybrida. VIGS efficiency in all plants is affected by the severity and uniformity of the viral infection, and VIGS often results in tissues within the plant with different levels of gene down-regulation. This can make it difficult to phenotype VIGS plants. Experiments were conducted to further optimize the VIGS efficiency in petunia. We compared methods of inoculating the plant with Agrobacterium containing the TRV constructs. These included an apical meristem application, leaf infiltration with a needless syringe, media drench and vacuum infiltration of the plant. The chalcone synthase (CHS) gene was used as a visual indicator of silencing in flower petals. Silencing CHS causes colored petals to turn white, and the area of white sectors was quantified to determine the efficiency of gene silencing between the different treatments. Silencing phytoene desaturase (PDS) causes photobleaching in the leaves and the color changes in the leaves were also quantified to evaluate silencing efficiency in the vegetative tissues. The inoculation of mechanically wounded shoot apical meristems gave the greatest silencing in leaves and petals. Differences in PDS and CHS silencing were observed among commercial petunia cultivars and ‘Picobella Blue’ was selected for subsequent experiments. Growth temperature and seedling age at inoculation also had an impact on silencing efficiency. Younger seedlings at 3 to 4 weeks after seeding showed the quickest and most uniform silencing and silencing was greatest when plants were grown at 20° F days/ 18° F nights. Phenotying VIGS plants requires the proper control plants. After VIGS had been optimized in petunia, plants showed increasingly severe viral symptoms when inoculated with the control empty vector TRV2. Adding a fragment of the green fluorescent protein (GFP) reduced viral symptoms and these plants severed as adequate controls for assessing phenotypes caused by the down-regulation of specific genes of interest. We are currently using this optimized technique to evaluate senescence-related genes in petunia.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Broderick S.R. and M.L. Jones (2013) An optimized protocol to increase virus-induced gene silencing efficiency and minimize viral symptoms in petunia. Plant Molecular Biology Reporter DOI 10.1007/s11105-013-0647-3.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Jones, M.L. (2013) Mineral nutrient remobilization during corolla senescence in ethylene-sensitive and insensitive flowers. AoB Plants 5: plt023; doi:10.1093/aobpla/plt023.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Waterland N.L. and M.L. Jones (2013) Exogenous ABA applications delay drought-induced wilting but cause leaf and flower abscission in fuchsia. Act Horticulturae (ISHS). 970: 29-35.http://www.actahort.org/books/970/970_2.htm.
|
Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Results from this project have been presented at scientific conferences and at industry and university invited seminars. Presentations were given to industry stakeholders at the Ohio Nursery and Landscape Association Short Course and the OFA Short Course. Seminars were presented at the American Society for Horticultural Sciences annual conference (Miami, FL), the Plant Senescence Gordon Conference (Easton, NH), the International Conference on the Plant Hormone Ethylene (Rotorua, New Zealand), and the Quality Management in Supply Chains of Ornamentals Conference (Bangkok, Thailand). PARTICIPANTS: The research was conducted by a PhD student and a Research Associate. The PI provided guidance on experimental design, implementation and data analysis. She supervised the graduate student and the Research Associate who conducted the majority of the experiments. TARGET AUDIENCES: Some of the results from this study are most relevant to plant breeders and scientists. An improved understanding of senescence and postproduction crop quality is also relevant to floriculture industry stakeholders, including greenhouse producers, shippers, and retailers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The postproduction shelf life of ornamental plants is often reduced by premature senescence. Leaf and flower senescence can be accelerated by exposure to ethylene gas or abiotic and biotic stresses. We have used both proteomic and genomic approaches to identify components of the senescence program in Petunia xhybrida. Both developmental (i.e. age-related) and stress-induced senescence allows the plant to break down cell constituents and remobilize nutrients from dying organs. Petunia flowers remobilize over 60% and 70% of the total nitrogen and phosophorus content from the petals. We have focused much of our studies on the genes that encode enzymes involved in degradation and remobilization. In the past year we have completed the characterization of three genes that encode proteolytic enzymes hypothesized to be involved in the degradation of proteins during senescence. Gene expression was evaluated using quantitative RT-PCR. All three senescence associated genes (SAGs) are up regulated in leaves and petals by treatment with ethylene. They are also upregulated during the developmental senescence of leaves and petals. Gene expression was also evaluated under nutrient stress (P, N and K deficiency) and drought stress. Plants often experience drought and nutrient stress in postproduction environments so these studies help determine which genes are involved in regulating both stress-induced and developmental senescence. All three genes were up regulated by nitrogen and phosphorus deficiency. Drought stress resulted in up regulation of transcript abundance only at the very late stages of the stress when the lower leaves were visibly yellowing. Biochemical characterization has confirmed that all three genes encode cysteine proteases and experiments are underway to determine substrate specificity, pH and ion cofactors required for activity. This research contributes to our understanding of the molecular regulation of senescence. Delaying the senescence of flowers would benefit the floriculture industry by increasing the quality and salability of flowering plants. Plants also experience ethylene, drought and temperature stresses during shipping and in retail displays. This postproduction stress can reduce the retail shelf life and landscape performance of these plants. The results from this research can be used to enhance the postproduction quality of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L. and P. Ling (2012) Preventing ethylene damage in the production greenhouse. Greenhouse Management 31(11): 45-49.
- Jones M., Staby G., Starman T., Pasian C., and C. Hall (2012). Taking it to the Max. How to maintain the quality of your plants during shipping and maximize their shelf life. Greenhouse Management 32 (2): 62-66.
- Jones M.L., Chapin L., and E. Ramsay (2012) Nutrient reallocation during flower petal senescence. American Society for Horticultural Sciences Annual Conference. Pg 128. Miami, FL (abstract)
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Experimental results were presented at the Annual Conference for the American Society for Horticultural Science and national and state extension and outreach meetings. A seminar was presented to floriculture industry stakeholders at the OFA Short course in Columbus, OH. PARTICIPANTS: A postdoctoral research associate and a research assistant worked on this project. This project provided the postdoctoral researcher with training in plant molecular biology techniques, tissue culture and transformation. TARGET AUDIENCES: Some of the results from this study (i.e. gene regulation) are most relevant to plant breeders and scientists. An improved understanding of senescence and postproduction quality is also relevant to floriculture industry stakeholders, including greenhouse producers, shippers, and retailers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The retail shelf life of an ornamental plant is often reduced by the premature senescence or abscission of its flowers. In many plants, flower senescence is initiated and coordinated by the gaseous plant hormone ethylene. Senescence can also be accelerated by abiotic and biotic stresses. We have used both proteomic and genomic approaches to identify components of the senescence program in Petunia xhybrida flower petals. The goal of this research is to identify genes that can be manipulated to increase the postproduction quality of ornamental plants by delaying developmental and stress-induced senescence. As reported last year, two genes from these studies have been identified as ethylene primary response genes, and they may be involved in the early regulation of senescence signaling. One of these genes is also regulated by drought stress in vegetative tissues (PhSEN22). We have completed a detailed characterization of PhSEN22 gene expression following drought stress, salinity, and cold stress. Transcripts are up regulated by salinity shock in young seedlings and when plants are under water deficit. We are currently correlating gene expression with endogenous ABA and ethylene levels during developmental and stress-induced senescence. Transgenic petunias have been created that over express the PhSEN22 gene and screening for drought tolerance is almost complete. This research contributes to our understanding of the molecular regulation of senescence. Delaying the senescence of flowers would benefit the floriculture industry by increasing the quality and salability of flowering plants. Plants experience ethylene, drought and temperature stresses during shipping and in retail displays. This postproduction stress can reduce the retail shelf life and landscape performance of these plants. The results from this research can be used to enhance the postproduction quality of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L and C. Pasian (2011) Managing Postproduction Shrink in the Greenhouse Industry. The Buckeye (October 2011) 22(9):23
- Jones M.L. and N.L. Waterland 2011. ABA applications delay drought-induced wilting in garden mums. The Indiana Flower Grower. Spring 2011. 5 (1): 7-8.
- Starman, T., M. Jones, G. Staby, C. Pasion, and C. Hall. 2011 (July). Shrink the shrink. Part 2. Greenhouse Management 31(7):36-38, 63-64.
- Hall, C., M. Jones, T. Starman, C. Pasion, and G. Staby. 2011 (Jan). Shrink the shrink. Part 1. January 2011. Greenhouse Management 31(1):38-42.
- Jones M.L. and N. Waterland (2011) s-ABA: A new PGR to extend shelf life & increase sell-through. OFA Bulletin 929: 20-12.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Results from this project have been presented at scientific conferences and at industry and university invited seminars. A seminar was presented at the Postharvest Gordon Conference (Tilton, NH) in June 2010. PARTICIPANTS: This project involved the training of one PhD student. TARGET AUDIENCES: Research results have also been presented to greenhouse growers at local and national meetings. This information has increased awareness of the symptoms of ethylene damage during the production and marketing of floriculture crops. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The shelf life of flowering plants is determined by the aesthetic beauty and longevity of its flowers. The lifespan of a flower is often terminated by the senescence (i.e. death) or abscission of its petals. In many plants, flower senescence is initiated and coordinated by the gaseous plant hormone ethylene. Senescence can also be accelerated by abiotic and biotic stresses. We have used both proteomic and genomic approaches to identify components of the senescence program in Petunia xhybrida flower petals. As reported last year, we have identified 14 senescence-specific proteins from pollinated petals. The past year we have focused on cloning the genes encoding these senescence-specific proteins and investigating transcriptional regulation during senescence. Flowers have been treated with ethylene at various concentrations (0.1, 1.0 and 10 ppm) to determine if gene expression is regulated by ethylene. Flowers (plus and minus ethylene) were treated with the protein synthesis inhibitor, cycloheximide, to determine if protein synthesis is required for increased transcript abundance in ethylene treated tissues. Based on these experiments, two genes have been identified as ethylene primary response genes that may be involved in the early regulation of senescence signaling. One of these genes is also regulated by drought stress in vegetative tissues. We are currently investigating expression of these genes following nutrient, salinity and temperature stress. Biochemical and functional analysis of all of the senescence-specific genes is currently underway. This research contributes to our understanding of the molecular regulation of senescence. Delaying the senescence of flowers would benefit the floriculture industry by increasing the quality and salability of flowering plants. Plants also experience ethylene, drought and temperature stresses during shipping and in retail displays. This postproduction stress can reduce the retail shelf life and landscape performance of these plants. The results from this research can be used to enhance the postproduction quality of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L., Chapin L.J. and S. Bai (2010) Proteomic Analysis Identified Proteases Up Regulated during Petunia Corolla Senescence. Acta Horticulturae. 880: 377-386.
- Bai S., Willard B., Kinter, M., Chapin L.J. Stead A., and M.L. Jones (2010) Proteomic analysis of post-pollination senescence. Journal of Experimental Botany. 61: 1089-1109.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Results from this project have been presented at scientific conferences. Seminars were presented at the Annual Conference for the American Society for Horticultural Science (St. Louis, MO), The 8th International Symposium on the Plant Hormone Ethylene (Ithaca, NY) and The Postharvest Pacifica 2009- Pathways to Quality Conference (Napier, New Zealand). PARTICIPANTS: An OSU PhD student was involved in this research. Collaborators included scientists from the Cleveland Clinic proteomics laboratory and from Royal Holloway, University of London. TARGET AUDIENCES: This research will directly benefit greenhouse producers in Ohio and throughout the United States. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The lifespan of a flower is often terminated by the senescence (or death) of its petals. Most studies of petal senescence have focused on changes in gene expression(i.e. the transcriptome), but there is increasing evidence that senescence is also regulated post-transcriptionally. A proteomic approach was therefore utilized to identify proteins that increased or decreased in abundance during the pollination-induced senescence of Petunia x hybrida cv Mitchell Diploid corollas. As reported in previous years, we used two-dimensional gel electrophoresis followed by image analysis to separate total soluble proteins from petals and to identify protein spots that were differentially expressed in nonsenescing (unpollinated) and senescing (pollinated) corollas at various time points. These differentially expressed proteins were sequenced using tandem mass spectroscopy and identified by database searches. No protein differences were observed between 24 h pollinated and unpollinated corollas, even though gene expression changes induced by pollination were detected by 24 h. Seventy-three protein spots were identified that were up regulated at 48 h after pollination and 112 proteins were up regulated by 72 h after pollination. Clustering analysis was used to determine which proteins were up regulated by senescence and which increased in abundance due to the developmental age of the flowers. The majority of the up regulated proteins were detected in nonsenescing corollas (i.e. from unpollinated flowers) and increased in abundance following pollination. Fourteen protein spots were detected only in senescing corollas at either 48 or 72 h after pollination. These may be proteins that are newly translated during senescence or they may change position on the 2-D gels due to various post-translational modifications. The biological function of the senescence up regulated proteins was determined by searching the TAIR gene ontology database. The senescence specific proteins were largely involved in cellular catabolism and remobilization, with the largest number of proteins in the category of carbohydrate metabolism. This supports the central role of cellular degradation and nutrient remobilization during petal senescence. One quarter of the senescence specific proteins had a higher observed than theoretical molecular weight, which may be the result of post-translational modifications during senescence. Ten genes encoding selected senescence up regulated genes involved in protein, nucleic acid and carbohydrate catabolism were cloned by RT-PCR. Gene expression patterns during flower development and senescence were determined using quantitative RT-PCR. Forty percent of the genes were not up regulated during senescence. This research contributes to our understanding of the molecular regulation of flower senescence, and indicates that both genomic and proteomic approaches are needed to identify the best genetic targets for delaying flower senescence. Delaying the senescence of flowers would benefit the floriculture industry by increasing the quality and salability of flowering plants.
Publications
- Chapin LJ and ML Jones (2009) Ethylene regulates phosphorus remobilization and expression of a phosphate transporter (PhPT1) during petal senescence in petunia. Journal of Experimental Botany. 60: 2179-2190.
- Jones ML, Stead AD and DG Clark (2009) Petunia flower senescence. In Petunia: A Model System for Comparative Research. T. Gerats and J Strommer eds. Springer, New York. 301-324.
- Underwood BA, Clark DG and ML Jones (2009) Petunia biotechnology. In Petunia: A Model System for Comparative Research. T. Gerats and J Strommer eds. Springer, New York. 411-433.
- Jones ML, Chapin LJ and NL Waterland (2009) Phosphorus remobilization during developmental and nutrient stress-induced senescence in petunias. American Society for Horticultural Science Annual meeting, July 28, 2009. HortScience 44:1072. (seminar)
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Results from this project have been presented at scientific conferences. This includes a seminar at the Annual Conference for the American Society for Horticultural Science in Orlando on July 21, 2008. The presentation was entitled "Proteomic analysis of flower senescence". A podcast of the presentation is available on the ASHS website. PARTICIPANTS: One PhD candidate was involved in this research project TARGET AUDIENCES: Target audiences for this project include greenhouse industry professionals as well as floriculture students. Information was disseminated in workshops, during classroom lectures and laboratory exercises and during extension presentations within the state of Ohio and nationally. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
These studies were designed to increase our understanding of nutrient reallocation during flower senescence. Most studies of leaf and flower senescence have focused on genes involved in cellular degradation, but comparatively little is known about the genes involved in remobilizing the nutrients released from the catabolism of macromolecules and organelles. Phosphorus deficiencies can limit plant growth and Pi that is remobilized from dying petals may therefore serve as an important source of phosphorus for developing tissues. Phosphate uptake from the soil is mediated by high affinity phosphate transporters. To determine if phosphate transporters are involved in remobilizing Pi from senescing tissues, a putative high-affinity phosphate transporter (PhPT1) was cloned from petunia. This phosphate transporter is expressed in leaves and petals and transcript abundance increases during senescence. The increases in PhPT1 transcript abundance correlate with decreases in the total P content of corollas during senescence. The plant hormone ethylene accelerates the senescence of petunia flowers and results in increased abundance of PhPT1 mRNAs. Searches of GenBank identified 4 additional phosphate transporter genes in petunia. These genes are expressed primarily in roots. While most studies of high-affinity phosphate transporters have focused on roots and the role of phosphate transporters in Pi uptake from the soil, this is one of only a few studies to investigate the role of phosphate transporters in nutrient reallocation within the plant. While the other Petunia phosphate transporters may function primarily in Pi uptake, PhPT1 seems to have a primary role in Pi reallocation during senescence. This research contributes to our understanding of the molecular regulation of flower senescence, and to our understanding of nutrient reallocation during senescence. The ability to delay flower senescence will have an important impact on the floriculture industry by extending the postproduction shelf life of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L. (2008) Ethylene signaling is required for pollination-accelerated corolla senescence in petunias. Plant Science 175: 190-196.
- Jones M.L., Chapin L, and S. Bai (2008) Proteomic analysis of flower senescence. American Society for Horticultural Science Annual Conference. HortSci 43: 1079-1080 (Abstract).
- Waterland N., Finer J.J. and Jones M.L. (2008) Characterization of the senescence-specific cysteine protease PhCP10 in Petunia x hybrida. American Society for Horticultural Science Annual Conference. HortSci 43: 1196 (Abstract).
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Progress 01/01/07 to 12/31/07
Outputs
Results from this project have been presented at scientific conferences. This includes a seminar at the International Conference on Quality Management in Supply Chains of Ornamentals, in Bangkok, Thailand on Dec 3-6, 2007. The presentation was entitled "Nutrient remobilization during pollination-induced corolla senescence in petunia."
Impacts
We have utilized a proteomic approach to identify important regulators of the senescence process in flowers. Two dimensional electrophoresis followed by tandem mass spectroscopy was used to identify protein changes during pollination-induced corolla senescence in petunia flowers. Fifty three proteins were identified that were down-regulated and 89 proteins were up-regulated during senescence. A majority of the proteins that increased in abundance during the progression of senescence encode enzymes involved in breaking down cellular constituents. These include a number of proteases and endonucleases that are believed to function in the large scale degradation of proteins and nucleic acids. The catabolism of macromolecules during the later stages of petal senescence allows the plant to remobilize nutrients before the corolla is shed. While many genes involved in macromolecule degradation have been cloned and characterized, much less in known about nutrient
remobilization. This study was designed to determine which nutrients are remobilized during pollination-induced corolla senescence and to determine how this process is controlled by plant hormones. Senescence in petunia flowers is associated with corolla wilting. While unpollinated flowers do not show senescence symptoms until approximately 8 days after opening, pollination accelerates corolla senescence and wilting is observed on day 2. Macronutrients and micronutrients were measured from corollas at various times after pollination. The senescence of pollinated flowers was associated with a decrease in the dry weight of the corolla, indicating that nutrients were being remobilized. C levels decreased by approximately 35% due to C recycling or tissue respiration. When comparing corollas on the day of flower opening to those that were completely wilted (very late senescence stage), the largest decreases were observed in the P and N content. P levels were reduced by 82% and N levels
were reduced by 67%. Reductions of around 30% were detected for Fe, K and S, while the levels of Mg, Mo and Zn decreased by only 11-14%. To further these investigations we are currently cloning and characterizing genes involved in nutrient remobilization and we plan to conduct functional analysis of these genes using virus induced gene silencing techniques. Ethylene's role in nutrient remobilization is also currently being investigated. This research contributes to our understanding of the molecular regulation of flower senescence. The ability to delay flower senescence will have an important impact on the floriculture industry by extending the postproduction shelf life of cut flowers, flowering potted plants, and bedding plants.
Publications
- Chapin L., and M.L. Jones (2007) Nutrient remobilization during pollination-induced corolla senescence in petunia. Acta Horticulturae 755: 181-190. Jones, M.L., Shuangyi B., Willard B., Stead A., and M. Kinter (2007) Proteomic Analysis of Pollination-induced Senescence in Petunia Flowers. Proceedings of the 7th International Ethylene Symposium. A. Ramina, C. Chang, J. Giovannoni, H. Klee, P. Perata, and E. Woltering eds. Springer, The Netherlands, Pgs. 279-284.
- Jones M.L. and L. Chapin L (2007) Nutrient remobilization during pollination-induced corolla senescence in petunia. International Conference on Quality Management in Supply Chains of Ornamentals. Bangkok, Thailand, Dec 3-6, 2007. Abstract.
- Waterland N.L., Chapin L., Finer J.J. and M.L. Jones (2007) Characterization of the cysteine protease, PhCP10, during the senescence of Petunia x hybrida flowers. OARDC Annual Conference. The Ohio State University. Abstract.
- Waterland N.L., Chapin L., Finer J.J. and M.L. Jones (2007). Characterization of the cysteine protease, PhCP10, during the senescence of Petunia x hybrida flowers. PMBB Research Symposium. The Ohio State University. Abstract.
- Waterland N.L., Chapin L., Finer J.J. and M.L. Jones (2007). Characterization of the cysteine protease, PhCP10, during the senescence of Petunia x hybrida flowers. The Ohio State University Department of Horticulture and Crop Science Graduate Research Retreat. The Ohio State University. Abstract.
- Bai S., Francis D., Willard B., Kinter M. and M. L. Jones (2007) Functional characterization of petunia petal senescence related proteins by virus-induced gene silencing. American Society of plant Biologists Annual Meeting Chicago, IL. Abstract #P28042.
- Bai S., Francis D., Willard B., Kinter M. and M. L. Jones (2007) Functional characterization of petunia petal senescence related proteins by virus-induced gene silencing. 24th Annual Missouri Plant Biology Sympsoium (Plant Protein Phosphorylation-Dephosphorylation; Plant Proteomics Mini-Symposium), Columbia, MO. Abstract #18.
- Bai S., Francis D., Willard B., Kinter M. and M. L. Jones (2007) Functional characterization of petunia petal senescence related proteins by virus-induced gene silencing. OARDC Annual Conference. The Ohio State University. Abstract.
- Bai S., Francis D., Willard B., Kinter M. and M. L. Jones (2007) Functional characterization of petunia petal senescence related proteins by virus-induced gene silencing. 9th Annual Plant Molecular Biology and Biotechnology Research Symposium, The Ohio State University. Abstract.
- Bai S., Francis D., Willard B., Kinter M. and M. L. Jones (2007) Functional characterization of petunia petal senescence related proteins by virus-induced gene silencing. The Ohio State University Department of Horticulture and Crop Science Graduate Research Retreat. Abstract.
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Progress 01/01/06 to 12/31/06
Outputs
Flower senescence is accompanied by changes in the abundance of specific proteins. Treatment of petunia flowers with cycloheximide, an inhibitor of protein synthesis, delays petal wilting and prolongs the life of the flowers. These experiments indicate that the senescence program is dependent on newly synthesized proteins. Therefore, identifying those proteins that increase in abundance or are only detectable during petal senescence will provide insight into the biochemical pathways that control senescence. A proteomic approach was utilized to identify proteins that are differentially expressed in nonsenescing and senescing petunia petals. Proteomics is the qualitative and quantitative analysis of proteins in a particular cell or tissue under specific conditions. Petunia flowers were pollinated to induce petal senescence. Total proteins were extracted from petals at 24, 48 and 72 hours after pollination. This represents early, mid and late stages of senescence. Total
proteins were also extracted from the petals of non senescing, unpollinated flowers at 24, 48 and 72 hours after flower opening. Two-dimensional polyacrylamide gel electrophoresis (2-DE) was used to separate the individual components of the protein extracts from petals. Following staining with Coomassie Brilliant Blue individual protein spots were visualized and the patterns of protein expression were compared in nonsenescing and senescing petals. Digital images of the 2-D gels were analyzed using PDQuest software (BioRad). Fifty three proteins were identified that were down-regulated during senescence and 89 proteins were up-regulated during senescence. Those proteins that were down-regulated during senescence included proteins that were detected in nonsenescing petals but not in senescing petals as well as those that decreased in abundance during senescence. Those identified as up-regulated included proteins that were detected in senescing but not in nonsenescing petals and those
that increased in abundance during senescence. Protein spots were excised from the gels and the proteins were sequenced by mass spectroscopy (Cleveland Clinic Proteomics Laboratory). Over 90% of the proteins have been identified based on sequence homology to proteins in the NCBI nonredundant protein database or a Solanaceae protein database that was developed at the OARDC (Ohio Agricultural Research and Development Center). The largest number of up- regulated proteins were functionally classified as defense or stress response proteins. Other functional categories for up proteins were energy metabolism, protein metabolism, lipid metabolism, carbohydrate metabolism, amino acid synthesis and cytoskeleton organization. The identity of the senescence-related proteins indicates a probable function during senescence. We are currently cloning the genes encoding the senescence up-regulated proteins. We will confirm the importance of selected proteins during flower senescence by knocking them
out in transgenic petunias.
Impacts
This research contributes to our understanding of the molecular regulation of flower senescence by the plant hormone ethylene. We have identified genes involved in senescence that are regulated by ethylene and those that appear to be independent of ethylene. The ability to delay flower senescence will have an important impact on the floriculture industry by extending the postproduction shelf life of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L. and A.D. Stead (2006) Creation of the D.C. Kiplinger Petunia Microarray: A Floriculture Resource for the Future. OFA Bulletin 898: 20-21.
- Stead A.D., van Doorn W.G., Jones M.L., and C. Wagstaff (2006) Flower senescence: fundamental and applied aspects. In Flowering and its Manipulation. Annual Plant Reviews. Vol 20. C. Ainsworth ed. Blackwell Publishing, Oxford, UK. Pgs 261- 296.
- Jones, M.L., Shuangyi B., Willard B., Stead A., and M. Kinter (2007) Proteomic Analysis of Pollination-induced Senescence in Petunia Flowers. Proceedings of the 7th International Ethylene Symposium. In Press.
- Shuangyi B., Francis D., Willard B., Kinter M., and M.L. Jones (2006) Proteomic analysis of post-pollination and senescence signaling pathways in petunia flowers. American Society of Plant Biologists Annual Meeting. Boston, MA. Abstract P31001.
- Shuangyi B., Francis D., Willard B., Kinter M., and M.L. Jones (2006) Proteomic analysis of post-pollination senescence in petunia flowers. OARDC Annual Conference.
- Shuangyi B., Francis D., Willard B., Kinter M., and M.L. Jones (2006) Proteomic analysis of post-pollination senescence in petunia flowers. 8th Annual Plant Molecular Biology and Biotechnology Research Symposium, The Ohio State University.
- Shuangyi B., Francis D., Willard B., Kinter M., and M.L. Jones (2006) Proteomic Profiling of Pollination-induced Senescence in Petunia corollas. 8th World Petunia Days Meeting, Jacksonville Beach, Fl
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Progress 01/01/05 to 12/31/05
Outputs
Changes in total protein, protease activity and the expression of nine cysteine protease genes were investigated during flower senescence. These experiments were conducted to determine the role of protein degradation in the death of flower petals and to determine if ethylene regulates this process. The later stages of petal senescence in petunia (Petunia x hybrida Mitchell Diploid, MD) flowers were associated with decreased fresh weight, decreased total protein levels, and increased protease activity. Petal senescence was delayed by 8 days in transgenic petunias (etr1-1) with reduced sensitivity to the plant hormone ethylene. Decreased petal fresh weight and protein content and maximum protease activity were similarly delayed in the etr1-1 transgenic petunias. Protease inhibitor experiments indicated that the majority of the protease activity detected during the senescence of both MD and etr1-1 petals was the result of cysteine proteases. Nine cysteine protease genes
that were expressed in petals were subsequently identified from a search of the BlastQuest petunia database at the University of Florida. Northern blot analysis indicated that six of the nine cysteine proteases showed an increase in transcript abundance during petal senescence. Expression of four of the senescence-associated cysteine proteases was delayed but not prevented in etr1-1 petals. The other two senescence-associated cysteine proteases had high levels of transcript accumulation in the etr1-1 petals at 8 days after flower opening. This corresponded with wilting and senescence of MD flowers. The delays in visible symptoms and molecular markers of petal senescence observed in the etr1-1 flowers is consistent with the idea that ethylene modulates the timing of senescence pathways in petals. The characterization of additional senescence-associated genes identified from petunia DNA microarray experiments is currently underway.
Impacts
This research contributes to our understanding of the molecular regulation of flower senescence by the plant hormone ethylene. We have identified genes involved in senescence that are regulated by ethylene and those that appear to be independent of ethylene. The ability to delay flower senescence will have an important impact on the floriculture industry by extending the postproduction shelf life of cut flowers, flowering potted plants, and bedding plants.
Publications
- Jones M.L., G.S. Chaffin, J.R. Eason and D. Clark (2005) Ethylene Sensitivity Regulates Proteolytic Activity and Cysteine Protease Gene Expression in Petunia Corollas. Journal of Experimental Botany 56:2733-2744
- Chiang Y-C., C. Stushnoff, A.E. McSay, M.L. Jones and H. Bohnert (2005) Overexpression of Mannitol-1-Phosphate Dehydrogenase Increases Mannitol Accumulation and Adds Protection Against Chilling Injury in Petunia. Journal of the American Society for Horticultural Science 130:605-610
- Langston B.L., S. Bai and M.L. Jones (2005) Increases in DNA Fragmentation and Induction of a Senescence-Specific Nuclease are delayed during the Senescence of Ethylene-insensitive (etr1-1) Transgenic Petunias. Journal of Experimental Botany 56:15-23
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Progress 01/01/04 to 12/31/04
Outputs
Nuclear DNA fragmentation was detected late in the life of petunia petals when they were producing ethylene and were visibly wilted. Induction of a senescence-specific nuclease with activity against both double- and single-stranded DNA corresponded with increased DNA fragmentation. This nuclease, referred to as PhNUC1 (Petunia x hybrida Nuclease), is a glycoprotein with a pH optimum of 7.5. EDTA inhibited PhNUC1 activity, but activity could be restored by the addition of Co2+. Neither Mg2+ nor Ca2+ had an affect on PhNUC1 activity, but Zn2+ inhibited the increase in activity detected in the presence of Co2+. When total protein extracts from petals were fractionated by differential centrifugation, PhNUC1 activity was detected in the nuclear enriched fraction. The pH optimum and subcellular location support a putative role for PhNUC1 in nuclear DNA catabolism during senescence. Decreases in total N and P within the corolla during senescence suggest that N and P released
during nucleic acid catabolism may be mobilized out of the petals during senescence. PhNUC1 activity was induced in nonsenescing flowers by treatment with exogenous ethylene (2ul per L) for 12 hours. In ethylene-insensitive transgenic petunias (35S:etr1-1), flower senescence is delayed by approximately 8 days compared to wild type flowers. The induction of PhNUC1 activity was also delayed in etr1-1 transgenic petunias, but it corresponded with corolla wilting and ethylene production from these flowers. These studies suggest that ethylene modulates the timing of nucleic acid catabolism during petal senescence, but that it is not an absolute requirement for this component of the senescence program to occur.
Impacts
This research contributes to our understanding of the genetic and molecular regulation of flower senescence by plant hormones. This knowledge can be used to extend the vase life of cut flowers and enhance the display life of potted plants and bedding plants. The ability to reduce postproduction losses caused by flower senescence will have a positive economic impact on the floriculture industry.
Publications
- Jones ML, Cochran KK, Anderson GA, and DC Ferree (2004) Effects of Preservatives and Cold Storage on Performance of Cut Branches of Various Cultivars of Deciduous Holly. HortTechnology. 14:230-234.
- Pennycooke JC, Vepachedu R, Stushnoff C, and ML Jones (2004) Expression of an a-Galactosidase Gene in Petunia is Up-regulated during Low Temperature Deacclimation. J. Amer. Soc. Hort. Sci. 129:491-496.
- Clark DG, Dervinis C, Barrett JE, Klee H, and ML Jones (2004) Drought-induced Leaf Senescence and Horticultural Performance of Transgenic PSAG12-IPT Petunias. J. Amer. Soc. Hort. Sci. 129: 93-99.
- Jones ML (2004) Changes in Gene Expression. In Plant Cell Death Processes. L Nooden ed. Elsevier Science, San Diego, Calif. Pgs 51-72.
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Progress 01/01/03 to 12/31/03
Outputs
The senescence of flowers is regulated by a genetic program that is mediated in part by the plant hormones ethylene and cytokinin. Transgenic petunias with delayed senescence were used to study the interactions between these signaling mechanisms. The senescence of petunia flowers was accompanied by increases in nuclease and protease activities. These enzyme activities are involved in the degradation of nucleic acids and proteins, respectively, and allow for macromolecules from the flower petals to be degraded and their components remobilized to sink tissues like the developing ovary. Decreases in total N and P within the corolla during senescence support this remobilization. A nuclease with activity against both double- and single-stranded DNA was identified in petunia flowers. This nuclease, (PHNUC1), was detectable only in senescing corollas and its activity was enhanced by cobalt and inhibited by zinc. PHNUC1 was also induced by ethylene. Increases in protease
activity were observed during the senescence of both ethylene sensitive (wild type) and ethylene insensitive (etr1-1) petunia flowers. This increase was delayed in etr1-1 flowers, which did not wilt until 10 to 14 days after anthesis compared to 6 to 8 days after anthesis for wild type flowers. The increased proteolytic activity detected in senescing petals was mainly the result of cysteine proteases, as protease activity was reduced when the class specific inhibitor, E-64 was added to the assay. Seventeen cysteine protease genes were identified from a petunia flower EST database. Northern blots have shown that 13 of the genes are up regulated during senescence. Further characterization of these genes is underway. To study the interaction of cytokinins in the regulation of senescence, petunia plants expressing IPT, a cytokinin biosynthetic gene from Agrobacterium, under the control of the promoter from a senescence-associated gene (SAG12) were utilized. Floral senescence in two
independently transformed lines (IPT22 and IPT34) was delayed 5 to 9 days relative to wild type (WT) flowers. IPT transcripts increased in abundance following pollination and this was accompanied by increased cytokinin accumulation. The predominant cytokinin accumulating in petunia corollas was zeatin-riboside. Flowers from IPT plants were less sensitive to exogenous ethylene and required longer treatment times to induce endogenous ethylene production, senescence-related gene expression and corolla senescence. Senescence-related increases in protease activity and membrane leakage were also delayed compared to wild type flowers. The expression of additional senescence-related genes is currently being investigated and will extend our understanding of the regulation of flower senescence by cytokinins.
Impacts
42. Impact This research contributes to our understanding of the genetic and molecular regulation of flower senescence by plant hormones. This knowledge can be used to extend the vase life of cut flowers and enhance the display life of potted plants and bedding plants. The ability to reduce postproduction losses caused by flower senescence will have a positive economic impact on the floriculture industry.
Publications
- JONES, M.L. (2002) Ethylene Responsiveness in Carnation Styles is Associated with Stigma Receptivity. Sex Plant Reprod. 15:107-112.
- JONES, M.L. (2003) Ethylene Biosynthetic Genes are Differentially Regulated by Ethylene and ACC in Carnation Styles. Plant Growth Regulation 40:129-138.
- CHANG, H., JONES, M.L., BANOWETZ, G.M., and CLARK, D.G. (2003) Overproduction of Cytokinins in Petunia Flowers Transformed with PSAG12-IPT Delays Corolla Senescence and Decreases Sensitivity to Ethylene. Plant Physiol. 132: 2174-2183.
- PENNYCOOKE, J.P., JONES, M.L., and STUSHNOFF, C. (2003) Down-Regulating Alpha-Galactosidase Enhances Freezing Tolerance in Transgenic Petunia. Plant Physiol. 133: 901-909.
- WOODSON, W.R. and JONES, M.L. (2003) In Search of Eternal Youth: the Delay of Postharvest Senescence in Flowers. Acta Hort. (ISHS) 624:305-314.
- JONES, M.L., LANGSTON, B.J., and JOHNSON, F. (2003) Pollination-induced Senescence of Ethylene Sensitive and Insensitive Petunias. In Biology and Biotechnology of the Plant Hormone Ethylene III. M Vendrell, H Klee, JC Pech and F Romojaro eds. IOS Press, Amsterdam. pgs 324-327.
- JONES, M.L. (2003) Changes in Gene Expression. In Plant Cell Death Processes. L Nooden ed. Elsevier Science, San Diego, Calif. Pgs 51-72.
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Progress 01/01/02 to 12/31/02
Outputs
Senescence represents the final stage in the development of a whole plant, tissue or organ. The senescence of flowers is regulated by a genetic program mediated in part by the plant hormones ethylene and cytokinin. Components of programmed cell death including increases in nuclease and protease activity have been studied during the progression of senescence in petunia flowers. Transgenic petunias with delayed senescence have been used to study the interactions between these signaling mechanisms. The senescence of petunia flowers is accompanied by increases in nuclease and protease activities. These enzyme activities are involved in the degradation of nucleic acids and proteins, respectively, and allow for macromolecules from the flower petals to be degraded and their components remobilized to sink tissues like the developing ovary. A nuclease identified from activity gels (pH 7) was found to have increased activity against both double and single stranded DNA at 48
hours after pollination when the corollas were wilted (senescent). This was found to be a Co- dependent nuclease and had activity in senescing petals only in the presence of Co2+. This upregulation of activity appeared to be regulated by ethylene as the Co-dependent nuclease was not observed in ethylene insensitive petunia corollas following pollination. Ethylene insensitive petunias, transformed with the mutated ethylene receptor from Arabidopsis thaliana (etr1-1), were obtained from Dr. David Clark at the University of Florida for use in these studies. Increases in protease activity were observed during the senescence of both ethylene sensitive (wild type) and ethylene insensitive (etr1-1) petunias. This increase was delayed in etr1-1 flowers, which did not wilt until 6 to 8 days after pollination compared to 2 days after pollination in wild type flowers. The increase in proteolytic activity in senescing petals was mainly due to cysteine proteases, as activity was reduced when the
class specific inhibitors, E-64 and leupeptin, were added to the assay mixture. To study the interaction of cytokinins in the regulation of senescence, petunia plants expressing ipt, a cytokinin biosynthetic gene from Agrobacterium, under the control of the promoter from a senescence-associated gene (SAG12) were utilized. Floral senescence in two independently transformed lines (IPT22 and IPT34) was delayed 5 to 9 days relative to wild type (WT) flowers. Ipt transcripts increased in abundance following pollination and this was accompanied by increased cytokinin accumulation. The increased cytokinin levels altered patterns of ethylene production in IPT corollas but did not significantly decrease overall rates of production. Flowers from IPT plants were less sensitive to exogenous ethylene and required longer treatment times to induce endogenous ethylene production and corolla senescence. These results extend our understanding of the regulation of flower senescence.
Impacts
This research contributes to our understanding of the initiation and progression of senescence in flowers. This knowledge can be used to extend the vase life of cut flowers and extend the longevity and enhance the display life of potted plants and bedding plants. The ability to reduce postproduction losses caused by flower senescence will have a positive economic impact on the floriculture industry.
Publications
- Langston, B.J. 2002. Characterization of senescence related nuclease activity in ethylene-sensitive and insensitive petunia corollas. M.S. Thesis. The Ohio State University.
- Chang, H. 2002. Cytokinin regulation during flower senescence in Petunia x hybrida `V26' transformed with SAG12-ipt. Ph.D. Dissertation. Colorado State University.
- Jones, M.L., Johnson, F., Langston, B.J. 2001. Molecular Regulation of Flower Senescence by Ethylene, Proceedings of the Twenty-Eighth Annual Meeting, Plant Growth Regulation Society of America, July 1-5, G.W. Stutte - Dymanac Corporation eds., Omnipress, Madison, WI. pp. 20
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