Progress 10/01/11 to 09/30/16
Outputs
Target Audience:The main target audience has been other researchers in the area of postharvest biology and technology. However, efforts were made to communicated to other researchers via published articles in Journals and Proceedings, and to other interested people in the industry via talks at national and international meetings and at national workshops. Changes/Problems:The wound response is rapidly induced and transitory. There qualities make it difficult to study the myriad changes that accomplishes wounding and to identify the specific change of events leading from a wound to a response such as tissue browning. Research should continue to characterize and identify the signal produced by mechanical wounding that leads to altered phenolic metabolism and enhanced browning of fresh-cut fruits and vegetables. What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Results have been communicated to researchers via published articles in Journals and Proceedings, and to other interested people in the industry via talks at national and international meetings and at national workshops. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Research has provided a better understanding of the changes in phenolic metabolism associated with wound-induced responses of fresh-cut fruits and vegetables. Technologies have been developed, e.g., heat-shock, that have been adopted by the industry to improve the quality and safety of fresh-cut lettuce. However, identification of the wound signal that intercedes between the actual wound and the induction of the wound-induced physiological responses remains elusive.
Publications
- Type:
Books
Status:
Published
Year Published:
2016
Citation:
Gross, K.C, Wang, C.Y., Saltveit M.E. (eds). 2016. In: K.C. Gross, C.Y. Wang, M.E. Saltveit (Eds.). Agricultural Handbook 66 - The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Crops. REVISED http://www.ba.ars.usda.gov/hb66/contents.html
- Type:
Book Chapters
Status:
Published
Year Published:
2016
Citation:
Saltveit, M.E. 2016. Respiratory metabolism. In Postharvest Ripening Physiology of Crops. Sunil (ed) CRC Press ISBN 9781498703802
- Type:
Book Chapters
Status:
Published
Year Published:
2016
Citation:
Saltveit, M.E. 2016. Water Loss from Harvested Horticultural Commodities. In Postharvest Ripening Physiology of Crops. Sunil (ed) CRC Press ISBN 9781498703802
- Type:
Book Chapters
Status:
Published
Year Published:
2016
Citation:
Saltveit, M.E. 2016. The three responses of plant tissue to wounding. Acta Hort. (ISHS) 1141:13-20
- Type:
Book Chapters
Status:
Awaiting Publication
Year Published:
2017
Citation:
Saltveit, M.E. Synthesis and Metabolism of Phenolic Compounds In Fruit and Vegetable Phytochemicals (Elhadi M. Yahia, Editor) Wiley publishing Chapter 3
|
Progress 10/01/14 to 09/30/15
Outputs
Target Audience:communicated to researchers via published journal articles, and to other interested people in the industry via talks at national meetings and at national workshops. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?The results have been communicated via talks at national meetings, talks at national workshops, and published articles. What do you plan to do during the next reporting period to accomplish the goals?Research will continue on characterizing and identifying the signal produced by mechanical wounding that leads to altered phenolic metabolism and enhanced browning of fresh-cut fruits and vegetables.
Impacts
What was accomplished under these goals?
Research has provided a better understanding of the changes in phenolic metabolism associated with wound-induced responses of fresh-cut fruits and vegetables. However, identification of the wound signal remains elusive.
Publications
- Type:
Books
Status:
Awaiting Publication
Year Published:
2016
Citation:
Gross, K.C, Wang, C.Y., Saltveit M.E. (eds). 2016. In: K.C. Gross, C.Y. Wang, M.E. Saltveit (Eds.). Agricultural Handbook 66 - The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Crops. REVISED http://www.ba.ars.usda.gov/hb66/contents.html
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Tao,F., L. Zhang, M. McCarthy, D.M. Beckles, M.E. Saltveit Magnetic resonance imaging provides spatial resolution of Chilling Injury in Micro-Tom tomato (Solanum lycopersicum L.) fruit. Postharvest Biology and Technology 97: 62-67.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Cantwell, M. and M. Saltveit. 2015. Tolerance of sugar snap peas to modified atmospheres with high concentrations of carbon dioxide. Proc. XI Int. CA/MA Res. Conf. Acta Hort. 1071: 619-625.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Cantwell, M. and M. Saltveit. 2015. Tolerance of grape tomatoes to controlled atmospheres at low temperature. Proc. XI Int. CA/MA Res. Conf. Act Hort. 1071: 627-634.
|
Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Many fruits and vegetables suffer physiological damage after exposure to chilling temperatures. This is especially true of fresh-cut fruits and vegetables that have been additionally stress by wounding. Identifying the underlying physiological cause of chilling will help devise techniques to ameliorate the deleterious effects of chilling on the quality of fresh-cut fruits and vegetables. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Results have been published. What do you plan to do during the next reporting period to accomplish the goals? Magnetic resonance imaging was used to provide spatial resolution of Chilling Injury in Micro-Tom tomato (Solanum lycopersicum L.) fruit.
Impacts
What was accomplished under these goals?
Magnetic resonance imaging was used to provide spatial resolution of chilling Injury in Micro-Tom tomato (Solanum lycopersicum L.) fruit. This allowed us to identify the chilling susceptible of specific tissue within the fruit so its characteristics can be compared with adjacent, more resistant tissue. A physiological and metabolic analysis of these different tissues should help identify some of the underlying physiological causes of chilling injury.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Tao,F., Lu Zhang, Michael McCarthy, Diane M Beckles, Mikal Saltveit 2014 Magnetic resonance imaging provides spatial resolution of Chilling Injury in Micro-Tom tomato (Solanum lycopersicum L.) fruit. Postharvest Biology and Technology 97: 62-67.
|
Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Postharvest researchers in academia, government, and industry. Changes/Problems: The new technology should allow us to identify the metabolic changes that occur during and after chilling . What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Through publications, and oral and poster presentations at conferences. What do you plan to do during the next reporting period to accomplish the goals? More research on how wound-induced and chilling responses effect the nutritional, quality, and safety of fresh-cut fruits and vegetables.
Impacts
What was accomplished under these goals?
A major problem with fresh-cut fruits and vegetables is quality deterioration after processing. Many fruits and vegetables are sensitive to non-freezing temperatures below around 10C, and therefore must be stored at elevated temperatures rather than at temperatures near 0C. We are developing a technology to measure the immediate effects of chilling nondestructively. This will allow repeated measurement during the time it takes for exposure to chilling temperatures to induce those physiological changes that detrimentally affect the quality of fresh-cut fruits and vegetables.
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2014
Citation:
Fei Tao,, Lu Zhang, Michael McCarthy, Diane M Beckles, Mikal Saltveit 2013 Evaluating the use of magnetic resonance imaging to monitor the effects of low temperature storage in tomato (Solanum lycopersicum L.) cv. MicroTom.
|
Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Develop new strategies to maintain fresh cut product quality. Improve understanding of biochemical, physiological and molecular mechanisms that affect fresh cut product quality. Wounded lettuce leaves obtained from commercial sources are the model systems employed in this research. Inhibitors and substrates for specific reactions were used to dissect the pathway that produces the wound signal in lettuce leaves. The efflux of carbon dioxide from fresh cut tomatoes was used to examine wound-induced increases in respiration. A procedure was developed to induce chilling injury in mature-green Micro-Tom tomatoes. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Discoloration of fresh-cut fruits and vegetables reduces their quality and discourages their consumption. Wounding during fresh-cut preparation induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to loss of flavor and tissue browning. Tissue excised from Romaine lettuce was used as a model system. Inhibitors and substrates were applied to excised mid-rib tissue and their effects on subsequent wound pathways were evaluated. Heat shocks were also employed to modulate the wound response. Further characterization of the 'wound signal' was inconclusive as variable results continued to be observed. These treatments and insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning. Metabolic profiling was done to identify compounds that increased or decreased upon chilling.
Publications
- Kietsuda Luengwilai, M.E. Saltveit, D.M. Beckles. 2012. Metabolite content of harvested Micro-Tom tomato (Solanum lycopersicum L.) fruit is altered by chilling and protective heat-shock treatments as shown by GC-MS metabolic profiling. Postharvest Biology and Technology. 63: 116-122.
- Kietsuda Luengwilai, D.M. Beckles, M.E. Saltveit. 2012. Chilling-injury of harvested tomato (Solanum lycopersicum L.) cv. Micro-Tom fruit is reduced by temperature pre-treatments. Postharvest Biology and Technology. 63: 123-128.
|
Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Develop new strategies to maintain fresh cut product quality. Improve understanding of biochemical, physiological and molecular mechanisms that affect fresh cut product quality. Wounded lettuce leaves obtained from commercial sources are the model systems employed in our research. By supplying inhibitors and substrates for specific reactions we are dissecting the pathway that produces the wound signal in lettuce leaves. A new instrument was constructed to measure the efflux of carbon dioxide from fresh cut tomatoes to examine the wound-induced increase in respiration. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Discoloration of fresh-cut fruits and vegetables reduces their quality and discourages people from eating them. Wounding during preparation induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to tissue browning. Tissue excised from Romaine lettuce was used as a model system. Inhibitors and substrates were applied to excised mid-rib tissue and their effects on subsequent wound pathways were evaluated. Heat shocks were also employed to modulate the wound response. Further characterization of the 'wound signal' was inconclusive as variable results continued to be observed. These treatments and insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning.
Publications
- Kietsuda Luengwilai, M.E. Saltveit, D.M. Beckles. 2012. Metabolite content of harvested Micro-Tom tomato (Solanum lycopersicum L.) fruit is altered by chilling and protective heat-shock treatments as shown by GC-MS metabolic profiling. Postharvest Biology and Technology. 63: 116-122.
- 2012 Kietsuda Luengwilai, D.M. Beckles, M.E. Saltveit . 2012. Chilling-injury of harvested tomato (Solanum lycopersicum L.) cv. Micro-Tom fruit is reduced by temperature pre-treatments. Postharvest Biology and Technology. 63: 123-128.
|
Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Instrumentation and analytical procedures were developed to dissect the various metabolic and physical components that go into producing the transient increase in carbon dioxide evolution from wounded fruits and vegetables. Changes in the partial pressures of internal gases following removal of diffusion barriers accounts for a substantial amount of the increased rate of carbon dioxide evolution from fresh-cut tomatoes. Wound-induced changes in metabolic rates of respiration occur about an hour after wounding and this could provide a period of time during which certain control measures may be effective in mediating this and other wound responses in fresh-cut fruits and vegetables. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Discoloration of fresh-cut fruits and vegetables reduces their visual and taste quality. Wounding during preparation induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to tissue browning. Tissue excised from Romaine lettuce was used as a model system. However, our continued efforts to isolate and characterize the chemical wound signal have proven to be inconclusive as variable results continued to be observed. These treatments and insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning.
Publications
- No publications reported this period
|
Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Develop new strategies to maintain fresh cut product quality. Improve understanding of biochemical, physiological and molecular mechanisms that affect fresh cut product quality. Wounded lettuce leaves obtained from commercial sources are the model systems employed in our research. By supplying inhibitors and substrates for specific reactions we are dissecting the pathway that produces the wound signal in lettuce leaves. A new instrument was constructed to measure the efflux of carbon dioxide from fresh cut tomatoes to examine the wound-induced increase in respiration. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Discoloration of fresh-cut fruits and vegetables reduces their quality and discourages people from eating them. Wounding during preparation induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to tissue browning. Tissue excised from Romaine lettuce was used as a model system. Inhibitors and substrates were applied to excised mid-rib tissue and their effects on subsequent wound pathways were evaluated. Heat shocks were also employed to modulate the wound response. Further characterization of the 'wound signal' was inconclusive as variable results continued to be observed. These treatments and insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning.
Publications
- Saltveit, M.E., L.C. Qin. 2008. Heating the ends of leaves cut during coring of whole heads of lettuce reduces subsequent phenolic accumulation and tissue browning. Postharvest Biology and Technology. 47: 255-259.
- Milczarek, R.R., M.E. Saltveit, T.C. Garvey, M.J. McCarthy. 2009. Assessment of tomato pericarp mechanical damage using multivariate analysis of magnetic resonance images. Postharvest Biology and Technology. 52: 189-195.
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Wounding during preparation of fresh-cut salads induces the synthesis and accumulation of compounds that contribute to tissue browning and reduced quality and shelf-life. This project studies how the physical act of cutting causes these physiological changes. Develop new strategies to maintain fresh cut product quality. Improve understanding of biochemical, physiological and molecular mechanisms that affect fresh cut product quality. Wounded lettuce leaves obtained from commercial sources are the model systems employed in our research. By supplying inhibitors and substrates for specific reactions we are dissecting the pathway that produces the wound signal in lettuce leaves. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Discoloration of fresh-cut fruits and vegetables reduces their quality and discourages people from eating them. Wounding during preparation induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to tissue browning. Tissue excised from Romaine lettuce was used as a model system. Inhibitors and substrates were applied to excised mid-rib tissue and their effects on subsequent wound pathways were evaluated. Heat shocks were also employed to modulate the wound response. Further characterization of the wound signal was inconclusive as variable results continued to be observed. These treatments and the insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning.
Publications
- No publications reported this period
|
Progress 01/01/07 to 12/31/07
Outputs
Discoloration of fresh-cut fruits and vegetables reduces their quality and discourages people from eating the fresh-cut fruits and vegetables. Wounding during preparation of fresh-cut salads induces many physiological changes that include enhanced respiration and phenolic metabolism which contribute to tissue browning. Heads of iceberg and Romaine lettuce were used as model systems in our research. Inhibitors and substrates were applied to cut surfaces and their effects of subsequent wound pathways were evaluated. Heat shocks were also employed to modulate the wound response. These studies help us understand the biochemical, physiological and molecular mechanisms that affect fresh cut product quality.
Impacts
We continued our examination of carboxylates as modulators of the wound response in lettuce. Unlike the n-alcohols we previously reported on, carboxylates did not appear to interfere with the generation of the wound signal, but with subsequent metabolic reactions which lead to the formation of those phenolic compounds that participate in tissue browning. We identified compounds and ranges of concentrations and duration of application that would reduce tissue browning without inducing deleterious effects of fresh-cut lettuce quality. Coring of lettuce in the field increases the weight available for processing. However, it also produces a wound response at the cut end of the leaves which induced the synthesis and accumulation of phenolic compounds that contribute to subsequent tissue browning. We developed a method to heat-shock cored lettuce that reduced the synthesis and accumulation of those phenolic compounds. We have identified and devised practical treatments to
reduce tissue browning brought about by wound-induced increases in phenolic metabolism. These treatments and the insight we gained by their development will allow the production of better quality fresh-cut lettuce and by extension other fresh-cut fruit and vegetables that are prone to wound-induced tissue browning.
Publications
- Mikal E. Saltveit, Young-Jun Choi. 2007 Aromatic- and di-carboxylates inhibit wound-induced phenolic accumulation in excised lettuce (Lactuca sativa L.) leaf tissue. Postharvest Biology and Technology, Volume 46, Issue 3, December 2007, Pages 222-229
- Mikal E. Saltveit, Liangchun Qin. 2007 Heating the ends of leaves cut during coring of whole heads of lettuce reduces subsequent phenolic accumulation and tissue browning. Postharvest Biology and Technology, In Press, Corrected Proof, Available online 12 September 2007
|
Progress 01/01/06 to 12/31/06
Outputs
A wound signal originates at the site of injury in lettuce (Lactuca sativa L) leaf tissue and propagates into adjacent tissue where it induces the de novo synthesis of phenylalanine ammonia lyase (PAL), the synthesis and accumulation of soluble phenolic compounds, and subsequent tissue browning. Exposing excised mid-rib leaf tissue to n-alcohols and other inhibitors inhibited this wound-induced browning by 40 percent and 60 percent. This research indicates that the oxylipin pathway that culminates in the production of jasmonic acid may be involved in the production of the wound signal that is responsible for increased wound-induced PAL activity, phenolic accumulation and browning in fresh-cut lettuce leaf tissue. Exposure of excised 5-mm mid-rib segments of romaine lettuce leaf tissue to inhibitors of reaction in the oxylipin pathway inhibited the increase in wound-induced PAL activity, phenolic accumulation and browning in fresh-cut lettuce leaf tissue. Exposing
these segments to non-inhibited lettuce tissue or extracts of lettuce tissue partially overcame the inhibition. We are currently using this bioassay of the wound pathway to further characterize the wound signal and hopefully identify its chemical structure.
Impacts
Many physiological changes are induced in harvested fruits and vegetables by mechanical wounds imparted by the act of harvesting or by intentional segmentation or processing of the produce into a fresh-cut product. The changes detrimentally affect quality by increasing phenolic metabolism, accumulation phenolic compounds, and tissue browning. Knowing how wounding is transduced into a physiological response allowed us to devise postharvest treatments that mitigate deleterious wounding effects on the quality of fresh-cut fruits and vegetables.
Publications
- Saltveit, M.E. 2006. Wound-induced Physiological Changes in Fresh-cut Produce. Acta Hortic. (In Press).
|
Progress 01/01/05 to 12/31/05
Outputs
A wound signal originates at the site of injury in lettuce (Lactuca sativa L) leaf tissue and propagates into adjacent tissue where it induces the de novo synthesis of phenylalanine ammonia lyase (PAL), the synthesis and accumulation of soluble phenolic compounds, and subsequent tissue browning. Exposing excised mid-rib leaf tissue to vapors or aqueous solutions of n-alcohols inhibited this wound-induced browning by 40% and 60%, respectively. Effectiveness of the alcohol increased linearly from ethanol to the seven-carbon heptanol, and then was lost for the longer n-alcohols 1-octanol and 1-nonanol. The 2- and 3-isomers of the effective alcohols did not significantly reduce wound-induced phenolic accumulation at optimal 1-alcohol concentrations, but significant reductions did occur at much higher concentrations of the 2-, and 3-isomers. The active n-alcohols were maximally effective when applied during the first 2 h after excision, and were ineffective if applied 12 h
after excision. Phospholipase D (PLD) and its products linolenic acid (LA) and phosphatidic acid (PA) are thought to initiate the oxylipin pathway that culminates in the production of jasmonic acid, and PLD is specifically inhibited by 1-butanol, but not by 2-, or 3-butanol. These results suggest that PLD, LA, PA, and the oxylipin pathway may be involved in producing the wound signal responsible for increased wound-induced PAL activity, phenolic accumulation and browning in fresh-cut lettuce leaf tissue. Exposure of excised 5-mm mid-rib segments of romaine lettuce leaf tissue to vapors or aqueous solutions of mono-carboxylic acids or their salts inhibited wound-induced phenolic accumulation (WIPA) and subsequent tissue browning. The decline in phenolic content followed a quadratic curve with increasing concentration, reaching a maximum inhibition of 74% after 60 min for 50 mM sodium acetate (2 carbons, C2), and 91% for 20 mM sodium decanoate (capric acid, C10). Carbon dioxide
production was unaffected by concentrations of formic, acetic, or propionic acids that reduced WIPA or that increase ion leakage from the tissue into an isotonic mannitol solution. WIPA was suppressed 70% by 20 mM acetate that did not increase ion leakage over that of water controls. Various acetate salts (i.e., ammonium, calcium, magnesium, sodium) all produced the same level of inhibition. The effectiveness of the compounds increased with increasing number of carbons in the molecule from 1 to 10, but was unaffected by whether the carbons were a straight chain or branched, or whether the treatment was delayed by up to 6 h. The effectiveness of butyrate (C4) in reducing WIPA (27% reduction at 20 mM) was less than that predicted from the response of the two adjacent mono-carboxylates similarly applied; propionate (C3) (62%) and valerate (C5) (73%). It appears that, unlike the n-alcohols, mono-carboxylates are not interfering with the synthesis or propagation of a wound signal, but are
interfering with subsequent steps in the production and accumulation of wound-induced phenolic compounds.
Impacts
Wounding induces physiological changes that can detrimentally affect quality by increasing phenolic metabolism, accumulation phenolic compounds, and tissue browning. Knowing how wounding is transduced into a physiological response allowed us to devise postharvest treatments that mitigate deleterious wounding effects on the quality of fresh-cut fruits and vegetables.
Publications
- Saltveit, M.E., R. Campos-Vargas, H. Nonogaki, and T. Suslow. 2005. Characterization of phenylalanine ammonia-lyase (PAL) gene in wounded lettuce tissue. U.S. Patent No. 6,897,357
- Saltveit, M.E., Y.J. Choi, and F. A. Tomas-Barberan. 2005. Involvement of components of the phospholipid signaling pathway in wound-induced phenylpropanoid metabolism in lettuce (Lactuca sativa L.) leaf tissue. Physiologia Plantarum (In Press).
- Kang, H.M., K.W. Park, and M.E. Saltveit. 2005. Chilling tolerance of cucumber (Cucumis sativus L.) seedling radicles is affected by radicle length, seedling vigor, and induced osmotic- and heat-shock proteins. Physiologia Plantarum (In Press)
- Saltveit, M.E. 2005. Influence of heat shocks on the kinetics of chilling-induced ion leakage from tomato pericarp discs. Postharvest Biology and Technology. 36: 87-92.
- Choi, Y,J., F. A. Tomas-Barberan, and M.E. Saltveit 2005. Wound-induced browning in lettuce (Lactuca sativa L.) leaf tissue in reduced by exposure to n-alcohols. Postharvest Biology and Technology. 37: 47-55.
|
Progress 01/01/04 to 12/31/04
Outputs
Exposing whole heads or leaves of iceberg lettuce (Lactuca sativa L., Iceberg) to 1-methylcyclopropene (1-MCP) significantly decreased the accumulation of phenolic compounds (absorbance of methanol tissue extract at 320 nm) and subsequent tissue discoloration induced by exposure to 1.0 micro L L-1 ethylene in air at 5C. The 0.5 mirco L L-1 concentration of 1-MCP was just as effective as 1.0 micro L L-1, and a 3 h exposure was just as effective as a 24 h exposure at 5C. In contrast, exposure to 1-MCP either before or after excision of mid-rib tissue did not interfere with the wound-induced increase in phenolic content of the tissue. It appears that wounding and ethylene act independently in the induction of phenylpropanoid metabolism and the accumulation of those phenolic compounds that contribute to browning of mechanically injured (e.g., fresh-cut) iceberg lettuce. Phenylalanine ammonia-lyase (PAL) catalyzes the first step controlling the rate of phenylpropanoid
metabolism. Wounding is a ubiquitous stress in nature and in the harvesting and preparation of fruits and vegetables that induces an increase in PAL activity, an accumulation of phenolic compounds and subsequent tissue browning. A wound-inducible PAL gene (LsPAL1) was isolated from Romaine lettuce by RT-PCR. The putative protein encode by LsPAL1 is similar to predictive polypeptides sequences for other PALs. The kinetics of PAL mRNA accumulation is similar to those of induced PAL enzyme activity, with enzyme activity following mRNA accumulation by 12 h. Wound-induced PAL transcripts accumulated in cells close to the wound sites. Tissue printing showed that PAL mRNA was associated with tissue next to the epidermis and vascular bundles. A heterologous PAL protein was expressed in E.coli and was found to show significant PAL activity. Heat-shock treatments may have significant physiological effects on the response of tissue to other stresses, not because of the specific genes they induce
or repress, or the products they cause to be synthesized, but by their secondary action of influencing the synthesis of other proteins (e.g., PAL) by the suppression of non-hsps protein synthesis. A brief heat-shock at 45C reduced wound-induced PAL, accumulation of phenolic compounds, and tissue browning. Western-blot analyses of proteins isolated from wounded and heat-shocked Iceberg and Romaine lettuce mid-rib leaf tissue showed that only those heat-shock treatments that were effective at inducing the synthesis of hsp 23 were effective in reducing the activity of PAL induced by wounding. The preferential synthesis of hsps over that of wound-induced PAL, rather than the presence of hsps, may be responsible for the ability of a heat-shock treatment to reduce the wound-induced increase in PAL activity. Our results support this novel concept.
Impacts
Wounding induces physiological changes that can detrimentally effect quality by increasing phenolic metabolism, accumulation phenolic compounds, and tissue browning. Knowing how wounding is transduced into a physiological response allowed us to devise postharvest treatments that mitigate deleterious wounding effects on the quality of fresh-cut fruits and vegetables.
Publications
- Campos-Vargas, Reinaldo, Hiroyuki Nonogaki, Trevor Suslow and Mikal E. Saltveit. 2004. Isolation and characterization of a wound inducible phenylalanine ammonia-lyase gene (LsPAL1) from Romaine lettuce leaves. Physiologia Plantarum 121: 429-438.
- Saltveit, M.E. 2004. Effect of 1-methylcyclopropene (1-MCP) on phenylpropanoid metabolism, the accumulation of phenolic compounds, and browning of whole and fresh-cut 'Iceberg' lettuce. . Postharvest Biology and Technology 34: 75-80.
- Campos-Vargas, Reinaldo, Hiroyuki Nonogaki, Trevor Suslow and Mikal E. Saltveit. 2004. Heat shock treatments delay the increase in wound-induced phenylalanine ammonia-lyase activity by altering its expression, not its induction in Romaine lettuce (Lactuca sativa) tissue. Physiologia Plantarum (IN PRESS)
- Saltveit, M.E. 2004. Aminoethoxyvinylglycine (AVG) reduces ethylene and protein biosynthesis in excised discs of mature-green tomato pericarp tissue. Postharvest Biology and Technology. (IN PRESS)
- Saltveit, M.E., Campos-Vargas, R., Nonogaki, H., Suslow, T. 2004. Characterization of phenylalanine ammonia-lyase (PAL) gene in wounded lettuce tissue. U.S. Patent No. BEING ISSUED
|
Progress 01/01/03 to 12/31/03
Outputs
Hypocotyl elongation of seedlings from an ethyl methanesulfonate treated lettuce population was used to select lines that were less sensitive to ethylene (Saltveit et al, 2003). Selection for ethylene insensitivity at the seedling stage did not produce mature plants that were consistently less sensitive to ethylene-induced increases in PAL activity or carbon dioxide production. Mutants differed from the wild type in at least 3 of the 7 phenotypes measured, while one line differed in all the measured phenotypes. The apparent random distribution of induced changes observed in the mutant lines suggests that screening additional mutants may identify lines that combine a number of useful horticultural traits. Preparation of 5-mm segments of celery petioles induced PAL activity, and tissue browning potential (Loaiza-Velarde et al,. 2003). Heat-shocking petiole segments (e.g., 50 C for 90 sec) reduced wound-induced PAL and browning. Pithiness was not enhanced by the
treatments. As storage life was extended, however, decay and the protrusion of vascular bundles from the cut ends of the segments became important factors limiting shelf-life. Heat-shock treatments may have significant physiological effects on the response of tissue to other stresses, not because of the specific genes they induce or repress, or the products they cause to be synthesized, but by their secondary action of influencing the synthesis of other proteins (e.g., PAL) by the suppression of non-hsps protein synthesis (Kang and Saltveit 2003). A brief heat-shock at 45 C reduced wound-induced PAL, accumulation of phenolic compounds, and tissue browning. Western-blot analyses of proteins isolated from wounded and heat-shocked Iceberg and Romaine lettuce mid-rib leaf tissue showed that only those heat-shock treatments that were effective at inducing the synthesis of hsp 23 were effective in reducing the activity of PAL induced by wounding. The preferential synthesis of hsps over that
of wound-induced PAL, rather than the presence of hsps, may be responsible for the ability of a heat-shock treatment to reduce the wound-induced increase in PAL activity. Our results support this novel concept. Ethylene production was measured from excised 10-mm apical and sub-apical root segments from 50 cultivars in 19 species of 7 families (Roberto and Saltveit 2003). The many different responses in magnitude and kinetics of wound-induced ethylene production among the species, cultivars and tissues should provide interesting and useful systems with which to study wound responses and induced ethylene production.
Impacts
Wounding induces physiological changes that can detrimentally effect quality by increasing phenolic metabolism, accumulation phenolic compounds, and tissue browning. Knowing how wounding is transduced into a physiological response allowed us to devise postharvest treatments that mitigate deleterious wounding effects on the quality of fresh-cut fruits and vegetables.
Publications
- KANG, H., SALTVEIT, M.E. 2003. Wound-induced increases in phenolic content of fresh-cut lettuce is reduced by a short immersion in aqueous hypertonic solutions. Postharvest Biology and Technology. 29: 271-277
- KANG, H., SALTVEIT, M.E. 2003. Wound-induced PAL activity is suppressed by heat-shock treatments that induce the synthesis of heat-shock proteins. Physiologia Plantarum 119: 450-455
- CABRERA, R.M., SALTVEIT, M.E. 2003 Survey of ethylene evolution from excised root segments. Physiologia Plantarum 119: 203-210
- SALTVEIT, M.E. 2003. Is it possible to find an optimum CA? Postharvest Biology and Technology. 27: 3-13.
- SALTVEIT, M.E., MICHELMORE, R., OCHOA, O., CAMPOS-VARGAS, R. 2003. Mature lettuce plants grown from seedlings selected for ethylene insensitivity were not insensitivity to ethylene. Postharvest Biology and Technology. 27: 277-283.
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Progress 01/01/02 to 12/31/02
Outputs
Preparation of 5-mm segments of celery petioles induced an increase in the activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), and subsequent tissue browning potential. The level of constitutive and wound-induced PAL activity was higher in vascular than in cortex tissue, and lowest in epidermal tissue. Heat-shocking excised petiole segments (e.g., 50 C for 90 sec) significantly reduced the rise in wound-induced PAL and browning potential. Pithiness of the petiole segments did not alter the effectiveness of the heat-shock treatments. As storage life was extended, however, decay and the protrusion of vascular bundles from the cut ends of the segments became important factors in limiting shelf-life. Cutting leaves of Romaine lettuce produces a wound signal that induces the synthesis of phenylalanine ammonia lyase (PAL) and the accumulation of phenolic compounds in cells up to 2 cm from the site of injury, and the browning of tissue near the site of injury. The
response of leaves within a head of Romaine lettuce to putative chemical wound signals (ABA, JA, MeJA, SA) differed significantly with leaf age. Exposure of harvested lettuce to ABA, JA, MeJA, or SA did not induce changes in PAL activity, the concentration of phenolic compounds or browning in mature leaf tissue similar to the level induced by wounding. Methyl jasmonate applied as vapor, or as an aqueous spray or dip at 5 or 10 C did not produce an effect on PAL activity or browning that differed significantly from the untreated controls. In contrast, JA, MeJA and SA did induce elevated levels of PAL activity, the accumulation of phenolic compounds and tissue browning in younger leaves. The levels induced were far lower than those induced by wounding. Wound induced phenolic metabolism in mature leaves appears to be induced by different signals than those functioning in young leaves. Wounding induced the accumulation of phenolic compounds in Iceberg and Romaine lettuce leaf tissue.
Phenolic concentrations were quantified after holding the leaf tissue at 10 C for 48 h as the absorbance of a methanol extract at 320 nm, and by the Folin-Ciocalteu method. Heat-shock treatments applied by immersing tissue in 45 C water for 2 min before or after wounding reduced the accumulation of phenolic compounds. Compared to the non-wounded, non-heat-shocked controls, these and other wounding and heat-shock treatments produced leaf tissue with a 4-fold range in phenolic content. The antioxidant capacity of the tissue, measured as DPPH-radical scavenging activity, or as ferric-reducing antioxidant power (FRAP), increased after wounding. The increase was linearly correlated with the increase in phenolic compounds in Iceberg and in Romaine lettuce leaf tissue. Increased consumption of diets rich in phenolic antioxidants may contribute to reducing human diseases. Treatments that reduce the browning of wounded lettuce leaf tissue by preventing the oxidation of the accumulated
wound-induced phenolic compounds may produce a healthier fresh-cut product than treatments that prevent the wound-induced synthesis and accumulation of phenolic compounds with antioxidant properties.
Impacts
Wounding during the preparation of fresh-cut fruits and vegetables induces physiological changes that often result in detrimental effects on quality; foremost of which is tissue browning. Wounding lettuce and celery induces increases in phenolic metabolism, the accumulation of phenolic compounds, and subsequent tissue browning. Lettuce and celery are usually low in the phenolic compounds that contribute to tissue browning. Our research on how wounding is transduced into a physiological response has allowed us to devise postharvest treatments that mitigate wounding's deleterious effects on the quality of fresh-cut fruits and vegetables.
Publications
- Campos-Vargas, R. and M.E. Saltveit. 2002. Involvement of putative chemical wound signals in the induction of phenolic metabolism in wounded lettuce. Physiologia Plantarum 114: 73-84.
- Julio G. Loaiza-Velarde, Mary E. Mangrich, Reinaldo Campos-Vargas and Mikal E. Saltveit 2002. Heat-shock Reduces Browning of Fresh-cut Celery Petioles. Postharvest Biology and Technology (In Press).
- Kang, Ho-Min and M.E. Saltveit. 2002. Antioxidant capacity of lettuce leaf tissue increases after wounding. Journal of Agricultural and Food Chemistry (In Press).
- Pilar Jaime and Mikal E. Saltveit. 2002. Postharvest changes in broccoli and lettuce during storage in argon, helium, and nitrogen atmospheres containing 2
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