Progress 12/15/08 to 12/14/13
Outputs
Progress Report Objectives (from AD-416): Objective 1: Determine the effects of the plant growth regulator TDZ on the quality and display life of cut flowers and potted flowering plants. Objective 2: Develop effective and environmentally-sound treatments to protect cut rose flowers from postharvest loss due to infection by Botrytis cinerea. Sub-objectives: 2a) Determine optimal time for applying treatments to control Botrytis on cut roses; 2b) Evaluate efficacy of anti-fungal GRAS compounds for the control of Botrytis cinerea on cut roses. Objective 3: Determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. Sub-objectives: 3a) Utilize virus-induced gene silencing (VIGS) technology to down-regulate the expression of NAC and MADS-box transcription factor genes and to test the effect of silencing these genes on flower longevity; 3b) Test a range of genes that are associated with floral aging and senescence for use as molecular indicators of freshness. Approach (from AD-416): In Objective 1, we will test TDZ, a non-metabolized cytokinin, for its potential to extend the display life of cut flowers and potted flowering plants. In Objective 2, we will characterize the basic biology of Botrytis-rose flower interactions with a view to developing effective disease control measures. We will evaluate GRAS chemicals as they offer a cost effective and environmentally friendly alternative to current conventional fungicides. In Objective 3, we will identify regulatory genes that mediate retardation or acceleration of petal senescence. This will provide a foundation for the development of diagnostic molecular indicators of 'freshness' for cut flowers and for downstream analysis of the effects of loss of function of these genes on the genetic regulation of the senescence network. The integrated nature of this project will enhance the quality and longevity of flowers, leading to greater industry- wide profitability. This is the final report documenting the progress for 5306-21000-019-00D which terminated on December 14, 2013, and was replaced with project 5306- 21000-022-00D, "Improvement of Postharvest Performance of Ornamentals Using Molecular Genetic Approaches". Please see the new project for additional information. Postharvest losses and poor quality for floricultural crops usually results from the combination of infection by Botrytis cinerea, earlier leaf and flower senescence and abscission, and germplasm that lacks desirable postharvest qualities. Over the lifespan of this project, the laboratory 1) tested the efficacy of thidiazuron (TDZ), a phenyl urea compound with cytokinin-like activity, to improve opening and longevity for some cut flowers. A postharvest pulse with TDZ significantly extended the vase life of iris flowers. TDZ treatment also stimulated an extension in the length of flower shoots that, in turn, led to more complete opening of flowers. These findings highlight the potential use for TDZ as a postharvest pulse treatment to improve the opening and longevity of cut flowers. 2) Developed a postharvest control method for Botrytis cinerea infection of rose varieties using environmentally-friendly chemicals. We demonstrated that a common household disinfectant Clorox (sodium hypochlorite) could be used as a potential biocide for effectively controlling Botrytis in cut rose flowers. Efficacy of the fungicide to prevent Botrytis infection on rose flowers was greatest when fungistatic compounds were applied at about 6 hours after harvest. These data indicate the opportunity to optimize the effectiveness of the relatively benign biocides, by treating the fungus when is at its most vulnerable development stage. 3) Flower senescence and abscission are under tight genetic control. Using Virus-Induced Gene Silencing (VIGS) technology, we found that the transcription level of many transcription factors that may play an important regulatory role in the controlling of flower senescence were highly up-regulated during flower aging process. Silencing some of them by using virus-induced gene silencing (VIGS) technology extended flower longevity dramatically (from 8 days to 11 days in intact flowers). The results suggest that the transcription factors play important roles in regulating flower senescence. We also found that a plant hormone, ethylene, plays very important roles in the regulation of flower senescence. Our laboratory generated petunia plants in which the dysfunctional ethylene receptor (etr1-1) is over-expressed under the control of a chemically-inducible system. The plants develop normally, and the life of the flowers is almost doubled when the plants or excised flowers are exposed to low concentrations of the inducer chemical (dexamethasone). This approach overcomes a variety of defects including poor germination, poor root growth and high susceptibility to disease when plants are constitutively expressing the trans-gene. The technology provides an effective means for extending flower longevity and improving quality of flower products. Accomplishments 01 Flower life extended. Postharvest losses and poor quality for ornamental crops often result from shorter shelf life caused by earlier flower senescence. ARS scientists in Davis, California, found that the transcription level of many transcription factors that may play an important regulatory role in controlling flower senescence were highly up-regulated during the flower aging process. Silencing some of them by using virus-induced gene silencing (VIGS) technology extended flower longevity dramatically (from 8 days to 11 days in intact flowers). The expression of ethylene biosynthesis genes was down-regulated and ethylene production was reduced in the silenced flowers. The results suggest that the transcription factors regulate flower senescence through ethylene pathways. These transcription factors can be used to improve the shelf life of cut flowers and floricultural crops.
Impacts
(N/A)
Publications
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Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): Objective 1: Determine the effects of the plant growth regulator TDZ on the quality and display life of cut flowers and potted flowering plants. Objective 2: Develop effective and environmentally-sound treatments to protect cut rose flowers from postharvest loss due to infection by Botrytis cinerea. Sub-objectives: 2a) Determine optimal time for applying treatments to control Botrytis on cut roses; 2b) Evaluate efficacy of anti-fungal GRAS compounds for the control of Botrytis cinerea on cut roses. Objective 3: Determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. Sub-objectives: 3a) Utilize virus-induced gene silencing (VIGS) technology to down-regulate the expression of NAC and MADS-box transcription factor genes and to test the effect of silencing these genes on flower longevity; 3b) Test a range of genes that are associated with floral aging and senescence for use as molecular indicators of freshness. Approach (from AD-416): In Objective 1, we will test TDZ, a non-metabolized cytokinin, for its potential to extend the display life of cut flowers and potted flowering plants. In Objective 2, we will characterize the basic biology of Botrytis-rose flower interactions with a view to developing effective disease control measures. We will evaluate GRAS chemicals as they offer a cost effective and environmentally friendly alternative to current conventional fungicides. In Objective 3, we will identify regulatory genes that mediate retardation or acceleration of petal senescence. This will provide a foundation for the development of diagnostic molecular indicators of 'freshness' for cut flowers and for downstream analysis of the effects of loss of function of these genes on the genetic regulation of the senescence network. The integrated nature of this project will enhance the quality and longevity of flowers, leading to greater industry- wide profitability. Formerly 5306-13210-002-00D (11/08). Postharvest losses and poor quality for ornamental crops often result from a combination of factors which includes, disease damages caused by Botrytis cinerea, shorter shelf life caused by earlier senescence and germplasm that lacks desirable postharvest qualities. This past year, ARS scientists in Davis, California, continued to investigate, develop and implement strategies for improving postharvest performance for ornamental crops. Specific areas advanced included the following: 1) Generated petunia plants in which the dysfunctional ethylene receptor is over-expressed under the control of a chemically-inducible system. The plants develop normally, and flower longevity is almost doubled when the chemical inducer is used. This approach is able to convert the ethylene sensitive flowers into ethylene insensitive ones. ARS scientists in Davis, California, conducted the global gene expression analysis used a powerful microarray technology and these transgenic plants. Results indicated that transcripts of many putative genes encoding transcription factors were down-regulated at the early stage. In addition, putative genes involved in gibberellin biosynthesis, response to jasmonic acid/ gibberellins stimulus, cell wall modification, ethylene biosynthesis, and cell death were down-regulated, suggesting that those transcription factors down-regulated at early stage might exert a major role in regulating the senescence process. Furthermore, when these transgenic petunia plants were inoculated with Botrytis cinerea, disease symptoms on detached leaves and flowers or intact plants were dramatically reduced. 2) Flower senescence is under tight genetic control and involves changes in the gene expression. To identify a common set of genes that are up- or down-regulated during floral senescence in ethylene insensitive flower species, ARS scientists in Davis, California, have developed Virus- Induced Gene Silencing (VIGS) technology in ethylene insensitive, extremely short flower longevity (approximately 16 hours from opening to wilting) of flowering plants. Results from this study suggested that co- silencing of endogenous anti-viral proteins may increase the range of taxa that are amenable to the use of VIGS for functional gene analysis. 3) Regulatory transcription factors play an important role in controlling flower senescence. ARS scientists in Davis, California, found that the transcription level of several classes of transcription factors were upregulated during flower aging process. Silencing one of them by using virus-induced gene silencing (VIGS) method extended flower longevity significantly (from 4 days to 6 days in detached flowers). The expression of ethylene biosynthesis genes, a key abscisic acid (ABA) biosynthesis gene, and senescence reporters (SAG12, and SAG29) was down regulated in the silenced flowers. Furthermore, the transcript level of this regulatory gene in the normal petunia flowers was induced by hormone (ethylene, ABA) and abiotic stress conditions (dehydration, sodium chloride [NaCl] and cold). The results suggest that this transcription factor regulates flower senescence through both ethylene and ABA pathways. Accomplishments 01 Generation of ethylene insensitive flowers by inducing expression of a mutant ethylene receptor. Ethylene plays very important roles throughout growth and development, including regulation of flower senescence. Plants expressing the dysfunctional ethylene receptor to reduce ethylene sensitivity dramatically extend flower longevity but show a variety of defects including poor germination, poor root growth and high susceptibility to disease. ARS scientists in Davis, California, have generated transgenic petunia plants in which the mutated receptor is over-expressed under the control of a chemically-inducible system to block ethylene perception. The plants develop normally, and flower longevity is doubled when the chemical inducer is used. Furthermore, when these transgenic petunia plants were inoculated with Botrytis cinerea, disease symptoms on detached leaves and flowers or intact plants were dramatically reduced. This innovative approach overcomes most of defects associated with constitutively inhibition of the ethylene pathway, being able to convert the ethylene sensitive flowers into ethylene insensitive ones, and provides excellent means for controlling flower senescence and improving disease resistance. 02 Development of Virus-Induced Gene Silencing (VIGS) technology in ethylene insensitive flowers for functional gene analysis. Flower senescence is under tight genetic control and involves changes in the gene expression. To identify a common set of genes that are up- or down- regulated during floral senescence in ethylene insensitive flower species and functional analysis of these genes, ARS scientists in Davis, California, have developed Virus-Induced Gene Silencing (VIGS) technology in ethylene insensitive, extremely short flower longevity (approximately 16 hours from opening to wilting) of flower plant. Results from this study suggested that co-silencing of endogenous anti- viral proteins may increase the range of taxa, including ethylene insensitive species, that are amenable to the use of VIGS for functional gene analysis. This technology provides an effective tool to solve what regulates flower senescence and to extend flower longevity in ethylene-insentitive flowers for the ornamental industry.
Impacts
(N/A)
Publications
- Wang, H., Liu, G., Li, C., Jiang, C., Reid, M.S., Zhang, Z., Powell, A.L. 2013. Defense responses regulated by jasmonate and delayed senescence caused by ethylene receptor mutation contribute to tolerance of petunia to Botrytis cinerea. Molecular Plant Pathology. 14(5):453-469.
- Deng, L., Jiang, C., Mu, W., Wang, Q. 2013. Influence of 1-MCP treatments on eating quality and consumer preferences of �Qinmei� kiwifruit during shelf life. Journal of Food Science and Technology. DOI 10.1007/s13197-013- 0986-y.
- Wang, H., Stier, G., Lin, J., Liu, G., Zhang, Z., Chang, Y., Reid, M.S., Jiang, C. 2013. Transcriptome changes associated wtih delayed flower senescence on transgenic petunia by inducing expression of etr1-1, a mutant ethylene receptor. PLoS One. 8(7):1-14.
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): Objective 1: Determine the effects of the plant growth regulator TDZ on the quality and display life of cut flowers and potted flowering plants. Objective 2: Develop effective and environmentally-sound treatments to protect cut rose flowers from postharvest loss due to infection by Botrytis cinerea. Sub-objectives: 2a) Determine optimal time for applying treatments to control Botrytis on cut roses; 2b) Evaluate efficacy of anti-fungal GRAS compounds for the control of Botrytis cinerea on cut roses. Objective 3: Determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. Sub-objectives: 3a) Utilize virus-induced gene silencing (VIGS) technology to down-regulate the expression of NAC and MADS-box transcription factor genes and to test the effect of silencing these genes on flower longevity; 3b) Test a range of genes that are associated with floral aging and senescence for use as molecular indicators of freshness. Approach (from AD-416): In Objective 1, we will test TDZ, a non-metabolized cytokinin, for its potential to extend the display life of cut flowers and potted flowering plants. In Objective 2, we will characterize the basic biology of Botrytis-rose flower interactions with a view to developing effective disease control measures. We will evaluate GRAS chemicals as they offer a cost effective and environmentally friendly alternative to current conventional fungicides. In Objective 3, we will identify regulatory genes that mediate retardation or acceleration of petal senescence. This will provide a foundation for the development of diagnostic molecular indicators of 'freshness' for cut flowers and for downstream analysis of the effects of loss of function of these genes on the genetic regulation of the senescence network. The integrated nature of this project will enhance the quality and longevity of flowers, leading to greater industry- wide profitability. Postharvest losses and poor quality for potted plants and cut flowers usually results from a combination of factors which includes, infection by Botrytis cinerea, earlier leaf and flower senescence and abscission, and germplasm which lacks desirable postharvest qualities. This past year we continued to investigate, develop and implement strategies for improving postharvest performance for potted plants and cut flowers. Specific areas advanced include; 1) Confirmed potential utility of thidiazuron (TDZ), a compound with plant hormone cytokinin-like activity, to control plant growth in potted plants. Spraying with TDZ up to 400 ppm significantly reduced plant growth of potted minirose plants. Plants treated with TDZ showed shorter internodes and thicker stems compared with plants treated with water as control. 2) Investigated the potential of an environmentally-friendly household disinfectant bleach (sodium hypochlorite) to reduce Botrytis infection on minirose plants. Our results demonstrated bleach solutions (200 ppm) reduced Botrytis infection on rose flowers when sprayed or applied as a dip treatment. 3). Flower senescence and abscission are under tight genetic control. Using Virus-Induced Gene Silencing (VIGS) technology, ARS scientists in Davis, CA, have identified a large number of genes that may play key roles in controlling leaf and flower senescence and abscission. VIGS-silencing of regulatory genes delayed leaf and flower senescence and abscission. 4). Plant hormone abscisic acid (ABA) plays important roles in the plant drought tolerance pathway. ARS scientists in Davis, CA, have generated petunia plants in which a key limited factor gene in the ABA biosynthesis pathway (NCED) is over-expressed under the control of a specific stress- inducible promoter. The plants develop normally under non-stress conditions. The transgenic plants survived and recovered much better after re-watering when the plants are held under extremely drought conditions (i.e. two weeks without water). Characterization of the genes controlling drought tolerance and an understanding of their regulation will facilitate development of drought tolerant genotypes for all crop species. Accomplishments 01 Improving drought tolerance in potted plants. Plant hormone abscisic ac (ABA) plays important roles in the plant stress tolerance pathway agains drought. Plants constitutively expressing a key gene in the ABA biosynthesis pathway (NCED) exhibit dramatically enhanced drought tolerance, but show a variety of defects including poor germination, growth and development. We have generated transgenic petunia plants in which NCED is over-expressed under the control of a specific stress- inducible promoter. The plants develop normally under non-stress conditions. The transgenic plants survived and recovered after re-wateri when the plants are exposed to low water availability under extreme drought conditions (two weeks without water). This approach overcomes mo of the defects associated with constitutive ABA production and provides excellent means for improving drought tolerance. 02 Application of thidiazuron (TDZ) reduced plant height. A common problem in the production of ornamental potted plants is undesirably tall growth so inhibitors of gibberellic acid (GA) biosynthesis including A-rest (ancymidol), B-nine (daminozide), Bonzi (paclobutrazol), Cycocel (chlormequat chloride), and Sumagic (uniconazole), are commonly used to control plant height. We studied the effects of TDZ applications on the growth and development of potted miniature roses. Plants treated with foliar sprays of TDZ (up to 200�M) exhibited a considerable reduction in plant height compared to the controls (0 �M). TDZ-treated plants tended have shorter internodes and thicker stems. Our results indicate significant potential for TDZ as an alternative way to control plant height.
Impacts
(N/A)
Publications
- De Freitas, S.T., Jiang, C., Mitcham, E.J. 2011. Mechanisms involved in calcium deficiency development in tomato fruit in response to gibberellins. Journal of Plant Growth Regulation. DOI 10.1007/s00344-011-9233-9.
- Reid, M.S., Jiang, C. 2011. Florigen unmasked - exciting prospects for horticulture. Chronica Horticulturae. 51:7-9.
- Singh, A., Liang, Y., Kumar, P., Reid, M., Jiang, C. 2012. Co-silencing the mirabilis antiviral protein permits virus-induced gene silencing in Mirabilis jalapa. Journal of Horticultural Science and Biotechnology. 87:334-340.
- Reid, M.S., Jiang, C. 2012. Postharvest: Cut flowers and potted plants. Review Article. In "Ornamental Geophytes: From Basic Science to Sustainable Production" by CRC Press, Eds. Rina Kamenetsky, Hiroshi Okubo.
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) Objective 1: Determine the effects of the plant growth regulator TDZ on the quality and display life of cut flowers and potted flowering plants. Objective 2: Develop effective and environmentally-sound treatments to protect cut rose flowers from postharvest loss due to infection by Botrytis cinerea. Sub-objectives: 2a) Determine optimal time for applying treatments to control Botrytis on cut roses; 2b) Evaluate efficacy of anti-fungal GRAS compounds for the control of Botrytis cinerea on cut roses. Objective 3: Determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. Sub-objectives: 3a) Utilize virus-induced gene silencing (VIGS) technology to down-regulate the expression of NAC and MADS-box transcription factor genes and to test the effect of silencing these genes on flower longevity; 3b) Test a range of genes that are associated with floral aging and senescence for use as molecular indicators of freshness. Approach (from AD-416) In Objective 1, we will test TDZ, a non-metabolized cytokinin, for its potential to extend the display life of cut flowers and potted flowering plants. In Objective 2, we will characterize the basic biology of Botrytis-rose flower interactions with a view to developing effective disease control measures. We will evaluate GRAS chemicals as they offer a cost effective and environmentally friendly alternative to current conventional fungicides. In Objective 3, we will identify regulatory genes that mediate retardation or acceleration of petal senescence. This will provide a foundation for the development of diagnostic molecular indicators of 'freshness' for cut flowers and for downstream analysis of the effects of loss of function of these genes on the genetic regulation of the senescence network. The integrated nature of this project will enhance the quality and longevity of flowers, leading to greater industry- wide profitability. Postharvest losses and poor quality for floricultural crops usually results from the combination of infection by Botrytis cinerea, earlier leaf and flower senescence and abscission, and germplasm that lacks desirable postharvest qualities. This past year we continued to investigate, develop and implement strategies for improving postharvest performance for floriculture crops. Specific areas advanced included the following: 1). We continued to test the efficacy of thidiazuron (TDZ), a compound with plant hormone cytokinin-like activity, to improve longevity and to prevent leaf yellowing in potted plants such as lilies and tulips. A spray with low concentrations (5 to 10 ppm) of TDZ significantly extended the flower life of these potted plants. Leaves treated with TDZ delayed yellowing for more than two weeks. Furthermore, application of TDZ promoted ovary enlargement and permitted seed production. 2). We further investigated the potential of an environmentally-friendly household disinfectant bleach (sodium hypochlorite) to reduce Botrytis infection on minirose plants. Our preliminary data suggested that low concentrations of bleach solutions could reduce Botrytis infection on rose flowers when sprayed or applied as a dip treatment. 3). Flower senescence is under tight genetic control and involves changes in the gene expression. To identify a common set of genes that are up- or down- regulated during floral senescence in a broad range of flower species, we have developed a powerful microarray analysis that represents approximately 93,000 unique ESTs collected from genetic resource databases of petunia, tomato and potato. Gene expression analysis comparing young petals from senescing petal of petunia flowers suggest that more than a hundred genes are up-regulated or down-regulated during floral senescence, including some of regulatory genes that may control the initiation of flower senescence program. 4). We have developed Virus- Induced Gene Silencing (VIGS) technology in monocotyledon flower plant- gladiolus. We are continuing to investigate a large numbers of genes that may play key roles in the controlling of leaf and flower senescence and abscission. VIGS-silencing some of these genes delayed leaf and flower senescence and abscission. 5). Ethylene plays very important roles throughout growth and development, including regulation of flower senescence. We have generated petunia plants in which the dysfunctional ethylene receptor (etr1-1) is over-expressed under the control of a chemically-inducible system. The plants develop normally, and the life of the flowers is almost doubled when the plants or excised flowers are exposed to low concentrations of the inducer chemical (dexamethasone). This approach overcomes a variety of defects including poor germination, poor root growth and high susceptibility to disease when plants are constitutively expressing the trans-gene. Accomplishments 01 Flower senescence is a genetically controlled developmental process. To determine changes in the global gene expression during onset of floral senescence, ARS scientists at Davis, CA, have developed a Solanaceae mic array including a total of 93,688 expressed sequence tags (EST) from fou Solanum species (tomato, potato, pepper and petunia). We compared gene expression profiles of petunia petal tissues collected from different developmental stages ranging from two days prior to opening until seven days after opening (right before visible wilting). There were hundreds o up- or down-regulated sequences on day 2 and thousands on day 7 compared to day 0 samples. Proteins encoded by genes identified in these studies include many likely candidates for a role in the processes of petal senescence and resource remobilization including protein kinases that ma be involved in senescence regulation, cysteine proteases and other enzym that are associated with protein turnover, nucleases, and cell-wall associated proteins. Many transcription factors, including representativ of more than 10 different families (NAC, MYB, WRKY, ARF, HSF, C2H2-type zinc finger, homeodomain-leucine zipper, AP2/EREBP, bZIP, bHLH, and GRAS were up- and/or down-regulated during onset of senescence, suggesting th a gene network may regulate floral senescence. Our studies demonstrate t utility of comparative gene profiling using a cross-species microarray approach for identifying genes with roles in the onset of flower senescence. 02 Controlling flower senescence by inducing expression of a mutant ethylen receptor etr1-1. Ethylene plays very important roles throughout growth and development, including regulation of flower senescence. Plants constitutively expressing the dysfunctional ethylene receptor (etr1-1) t reduce ethylene sensitivity dramatically extend flower longevity but sho a variety of defects including poor germination, poor root growth and hi susceptibility to disease. ARS scientists at Davis, CA, have generated transgenic petunia plants in which the etr1-1 is over-expressed under th control of a chemically-inducible system to block ethylene perception. The plants develop normally, and the life of the flowers is almost doubl when the plants or excised flowers are exposed to low concentrations of the inducer chemical (dexamethasone). This approach overcomes most defec associated with constitutively inhibition of the ethylene pathway and provides excellent means for controlling flower senescence. 03 Significant quality problems in ornamental potted and bedding plants. T quality of potted flowers is important to the ornamental industry. ARS scientists at Davis, CA, studied the effects of thidiazuron (TDZ) applications on the growth and development of potted Tulipa gesneriana �Christmas Dream�. Plants were treated with foliar sprays of a range of concentrations of TDZ (deionized water, 10�M, 100�M) at two developmenta stages - four days prior to flower opening (stage 1) and the day flowers were just fully-opened (stage 2). Spray treatments with 10 to 100 �M TDZ at both stages resulted in a considerable delay in leaf yellowing compar to the controls (0 �M) and TDZ-treated tulip leaves tended to maintain higher chlorophyll contents through the lifecycle. More importantly, treatments with TDZ at 10 and 100 �M at both stages significantly increased the display life of potted tulip flowers, up to 10 days from 6 days in controls. In addition, TDZ-treated plants produced considerably larger (at least 2 fold) ovaries. Our results indicate significant potential for TDZ as a tool to improve the postharvest life of potted tulip plants.
Impacts
(N/A)
Publications
- Meir, S., Philosoph-Hadas, S., Sundaresan, S., Selvaraj, V.K., Burd, S., Ophir, R., Kochanek, B., Reid, M.S., Jiang, C., Lers, A. 2011. Identification of defense-related genes newly-associated with tomato flower abscission. Plant Signaling and Behavior. 6:4, 590-593.
- Jiang, C., Chen, J., Reid, M.S. 2011. Virus-Induced gene silencing in ornamental plants. Book Chapter. 744:81-96.
- Meir, S., Philosoph-Hadas, S., Sundaresan, S., Selvaraj, V.K., Burd, S., Kochanek, B., Reid, M.S., Jiang, C., Lers, A. 2010. Microarray analysis of the abscission-related transcriptome in tomato flower abscission zone in response to auxin depletion. Plant Physiology. 154:1929-1956.
- Villalobos-Acuna, M.G., Biasi, W.V., Flores, S., Jiang, C., Reid, M.S., Willits, N.H., Mitcham, E.J. 2011. Effect of maturity and cold storage on ethylene biosynthesis and ripening in �Bartlett� pears treated after harvest with 1-MCP. Postharvest Biology and Technology. 59:1-9.
- Macnish, A.J., Morris, K.L., De Theije, A., Mensink, M.G., Boerrigter, H.A. , Reid, M.S., Jiang, C., Woltering, E.J. 2010. Sodium hypochlorite: A promising agent for reducing Botrytis cinerea infection on rose flowers. Postharvest Biology and Technology. 58:262-267.
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) Objective 1: Determine the effects of the plant growth regulator TDZ on the quality and display life of cut flowers and potted flowering plants. Objective 2: Develop effective and environmentally-sound treatments to protect cut rose flowers from postharvest loss due to infection by Botrytis cinerea. Sub-objectives: 2a) Determine optimal time for applying treatments to control Botrytis on cut roses; 2b) Evaluate efficacy of anti-fungal GRAS compounds for the control of Botrytis cinerea on cut roses. Objective 3: Determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. Sub-objectives: 3a) Utilize virus-induced gene silencing (VIGS) technology to down-regulate the expression of NAC and MADS-box transcription factor genes and to test the effect of silencing these genes on flower longevity; 3b) Test a range of genes that are associated with floral aging and senescence for use as molecular indicators of freshness. Approach (from AD-416) In Objective 1, we will test TDZ, a non-metabolized cytokinin, for its potential to extend the display life of cut flowers and potted flowering plants. In Objective 2, we will characterize the basic biology of Botrytis-rose flower interactions with a view to developing effective disease control measures. We will evaluate GRAS chemicals as they offer a cost effective and environmentally friendly alternative to current conventional fungicides. In Objective 3, we will identify regulatory genes that mediate retardation or acceleration of petal senescence. This will provide a foundation for the development of diagnostic molecular indicators of 'freshness' for cut flowers and for downstream analysis of the effects of loss of function of these genes on the genetic regulation of the senescence network. The integrated nature of this project will enhance the quality and longevity of flowers, leading to greater industry- wide profitability. Formerly 5306-13210-002-00D (11/08). Postharvest losses and poor quality for floricultural crops usually results from the combination of infection by Botrytis cinerea, earlier leaf and flower senescence and abscission, and germplasm that lacks desirable postharvest qualities. This past year we continued to investigate, develop and implement strategies for improving postharvest performance for floriculture crops. Specific areas advanced included the following: 1) We characterized the efficacy of thidiazuron (TDZ), a compound with plant hormone cytokinin-like activity, to improve longevity and to prevent leaf yellowing in bulb flower tulips. A postharvest spray with TDZ significantly extended the vase life of tulip flowers. Leaves of tulip plants treated with TDZ delayed yellowing for considerable time. 2) We continued our investigation into the potential of Chlorox (sodium hypochlorite) to reduce Botrytis infection on cut rose flowers. We showed Clorox reduced Botrytis infection on rose flowers when applied as a postharvest dip treatment. We determined the efficacy of different bleach solutions to reduce Botrytis on rose flowers and compared the effectiveness of the optimal bleach solution to conventional fungicides. The capacity of household bleach to reduce Botrytis on flowers exposed to commercial shipment also was determined. 3) We developed Virus-Induced Gene Silencing (VIGS) technology in four o�clock plants, a model crop for investigating flower senescence and abscission. We are continuing to investigate a large number of �transcription factors� to identify a �master switch� protein that may be the key to regulate senescence and abscission. VIGS-silencing of genes such as a proline-rich protein and a transcriptional regulator delayed leaf and flower abscission in tomato. 4) We hypothesize that inhibition of protein synthesis or preventing targeted protein degradation at the onset of senescence could extend flower life. Silencing protein synthesis (by silencing a ribosome component) or protein degradation (by silencing a proteasome subunit) significantly extended flower life in transgenic petunia plants. Identification of effective targets for the inhibition of protein synthesis and targeted protein degradation paves the way for further research into the mechanisms and control of floral senescence. 5) Flower senescence is under tight genetic control and involves changes in the transcriptome. To identify a common set of genes up-regulated during floral senescence, in a broad range of cut flower species, we developed a microarray that represents almost all the unique EST's from petunia, tomato and potato. Preliminary results indicate more than a hundred genes with modified expression patterns during floral senescence, including some transcriptional regulators. Accomplishments 01 Treatments with Clorox reduces Botrytis disease in cut rose flowers. Infection with the fungal pathogen Botrytis cinerea reduces the market value of many cut flower species. ARS Scientists in Davis, CA continued investigations into the potential of Clorox (sodium hypochlorite) to reduce Botrytis infection on cut rose flowers and showed that Clorox cou reduce Botrytis infection on rose flowers when applied as a postharvest dip treatment. Given that given that sodium hypochlorite is the active ingredient in household bleach, we determined the efficacy of different bleach solutions to reduce Botrytis on rose flowers. Our results highlig the potential for Clorox use as a simple alternative postharvest treatme for the control of Botrytis on cut rose flowers. Our findings also point to an exciting opportunity to include testing the effectiveness of this benign compound on additional rose varieties and flower species. 02 Application of thidiazuron (TDZ), a non-metabolized cytokinin, extends t life of bulb flower plants. Early wilting and leaf yellowing are significant quality problems in a wide range of ornamental potted and bedding plants. Application of low concentrations of thidiazuron (TDZ) has been shown to be a very effective means of delaying leaf yellowing a flower senescence in alstroemeria, stock, lilies and cyclamen. ARS Researchers in Davis, CA examined the possible use of this compound for delaying leaf yellowing and flower senescence in a range of bulb flower plants, including tulips. Spray treatments with TDZ at the end of the production cycle dramatically delayed leaf yellowing and extended flower longevity. Our results indicate significant potential for TDZ as a tool improve the postharvest life of bulb flower plants. 03 Silencing of a Proteasome Component Delays Floral Senescence. Targeted protein degradation via the ubiquitin/26S proteasome pathway is known to play an important function in many phases of plant growth and developmen In previous research we demonstrated that silencing a putative E3 ubiquitin ligase (a component of the pathway) delayed floral senescence. To further test the function of targeted protein degradation in flower senescence, ARS Researchers in Davis, CA chose to silence an endopeptida component in the 20S core of the 26S proteasome. Petunia hybrida was transformed with a construct allowing for chemically-inducible silencing of this protein. Flowers from transgenic plants treated with the chemic inducer showed doubled vase life than controls (transgenic flowers held water). These results indicate that targeted protein degradation plays important regulatory role in floral senescence.
Impacts
(N/A)
Publications
- Jiang, C., Wu, L., Macnish, A., King, A., Yi, M., Reid, M.S. 2009. Thidiazuron, a non-metablized cytokinin, shows promise in extending the life of potted plants. Acta Horticulturae. 847: 59-65.
- Macnish, A., De Theije, A., Reid, M.S., Jiang, C. 2009. An Alternative postharvest handling strategy for cut flowers-dry handling after harvest. Acta Horticulturae. 847: 215-221.
- Macnish, A.J., Negre-Zakharov, F., Jiang, C., Reid, M.S. 2010. PHYSIOLOGICAL AND MOLECULAR CHANGES DURING OPENING AND SENESCENCE OF NICOTIANA MUTABILIS FLOWERS. Plant Science. 179:267-272.
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