Progress 10/01/98 to 09/30/03
Outputs
Objective 1. Elucidate fundamental mechanisms underlying seed development and germination. Expression of genes of the SNF1-related protein kinase (SnRK) complex was characterized during tomato (LYCOPERSICON ESCULENTUM) seed development and germination. The regulatory component of this complex (LeSNF4) was highly expressed in developing and dormant seeds, but was down-regulated following germination. It was also induced by ABA and repressed by GA, while expression of other genes of this complex (LeSNF1, LeGAL83) were relatively unaffected by these factors. The developmental and hormonal regulation of LeSNF4 could alter the activity of the kinase to shift seed metabolism from a developmental and dormancy mode to a germinative and mobilization mode. The substrates for the kinase remain to be identified. The expression of a class I chitinase (Chi9) in tomato seeds was regulated by wounding and methyl jasmonate, while a class I O-1,3-glucanase was not induced by these
factors. Although these genes are often expressed in concert, hormonal regulation of these genes differed depending upon the tissue location. A different class of chitinase was also expressed in germinating muskmelon (CUCUMIS MELO) seeds. These enzymes could be involved in defense mechanisms against pathogens and saprophytes, or they may have other physiological functions during germination. Objective 2. Develop methods for improving seeds as genetic delivery systems. An analysis of enabling technologies in agricultural biotechnology contributed to the formation of an initiative to pool public-sector intellectual property for plant genetic engineering. This may facilitate utilization of biotechnology to improve specialty and humanitarian crops. An extension bulletin was published describing the utilization of plants and seeds for the production of pharmaceutical proteins. Application of the hydrothermal time model to seed vigor testing was described in a publication targeted to
commercial seed analysts. Modified drying techniques following priming resulted in somewhat greater longevity of lettuce (LACTUCA SATIVA) seeds in storage. Objective 3. Define the ecological interactions of seeds with their environment. A genetic analysis of seed germination and vigor in lettuce identified quantitative trait loci (QTL) associated with several traits, including high temperature germination and sensitivity to light. Near-isogenic lines are being constructed to further map and characterize these QTL.
Impacts
Knowledge of genes involved in the mechanisms of germination and plant defense will lead to methods for enhancing germination and health of crop seeds. Pooled management of public-sector intellectual property may facilitate engineering of improved crop varieties. Understanding the physiological and genetic basis of seed responses to environmental factors can lead to improved seed performance.
Publications
- WU, C.T., AND BRADFORD, K.J. 2003. Class I chitinase and 0-1,3-glucanase are differentially regulated by wounding, methyl jasmonate, ethylene and gibberellin in tomato seeds and leaves. Plant Physiol. 133: 263-273.
- NICOLAS, G., BRADFORD, K.J., COME, D., AND PRITCHARD, H.W., eds. 2003. The Biology of Seeds: Recent Research Advances, CAB International, Wallingford, U.K.
- NONOGAKI, H., BRADFORD, K.J. 2003. Tissue printing for localization of mRNA expression in seeds. In Nicolas, G., Bradford, K.J., Come, D., and Pritchard, H.W., eds., The Biology of Seeds: Recent Research Advances, CAB International, Wallingford, U.K. pp. 171-179.
- SCHWEMBER, A.R. 2003. Effects of post-priming treatments on potential longevity of lettuce seeds. M.S. Thesis. University of California, Davis, 64 pp.
- DOWNIE, B., GURUSINGHE, S., DAHAL, P., THACKER, R.R., SNYDER, J.C., NONOGAKI, H., YIM, K., FUKANAGA, K., ALVARADO, V., BRADFORD, K.J. 2003. Expression of a galactinol synthase gene in tomato is stress induced by an ABA-independent mechanism that is differentially responsive to cold in tomato seeds and leaves. Plant Physiology: 131: 1347-1359 [In press last report]
- THOMAS, B.R., VAN DEYNZE, A., AND BRADFORD, K.J. 2002. Production of therapeutic proteins in plants. University of California, Division of Agriculture and Natural Resources, Agricultural Biotechnology in California Series, Publication 8078.
- BRADFORD, K.J., DOWNIE, A.B., GEE, O.H., ALVARADO, V.Y., YANG, H., DAHAL, P. 2003. Abscisic acid and gibberellin differentially regulate expression of genes of the SNF1-related kinase complex in tomato seeds. Plant Physiol. 132: 1560-1576.
- GRAFF, G.D., CULLEN, S.E., BRADFORD, K.J., ZILBERMAN, D., BENNETT, A.B. 2003. The public-private structure of intellectual property ownership in agricultural biotechnology. Nature Biotechnology 21: 989-995.
- WHITMER, X., NONOGAKI, H., BEERS, E.P., BRADFORD, K.J., WELBAUM, G.E. 2003. Characterization of chitinase activity and gene expression in muskmelon seeds. Seed Sci. Res. 13: 167-178.
- BRADFORD, K.J., AND STILL, D.W. 2004. Applications of hydrotime analysis in seed testing. Seed Technology: in press.
- Patents DOWNIE, A.B., ZHAO, T.Y., MEELEY, R., BRADFORD, K.J. Stress-responsive genes, regulatory elements, and methods of use for same. US Provisional patent application, Serial No. 60/458,339, filing date March 28, 2003.
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Progress 01/01/02 to 12/31/02
Outputs
Objective 1. Elucidate fundamental mechanisms underlying seed development and germination. Expression of a galactinol synthase (LeGolS-1, Accession #AF311943) gene was further characterized during tomato (LYCOPERSICON ESCULENTUM) seed development and germination. The gene was demonstrated to encode a functional galactinol synthase. The mRNA of this gene was first expressed during tomato seed development at 35 days after flowering, coinciding with the completion of dry weight accumulation and the appearance of the reserve oligosaccharide planteose. Chilling and other stress conditions can induce the expression of LeGolS-1 through a mechanism that is independent of abscisic acid. The expression of a class I chitinase (Chi9) in tomato seeds following imbibition was shown to be induced by wounding or methyl jasmonate, while a class I B-1,3-glucanase was not induced by these factors. Ethylene, salicylic acid, and abscisic acid were ineffective in inducing either gene in
seeds, but ethylene was highly effective in leaves. In contrast, gibberellin induced both genes in seeds but not in leaves. Hormonal regulation of specific genes can be altered depending upon the tissue location. Chitinase and glucanase expression in germinating seeds may be involved in a defense mechanism against fungal pathogens or saprophytes. Objective 2. Develop methods for improving seeds as genetic delivery systems. Methods were developed utilizing moisture content reduction and high temperature incubation to extend the storage life of hydrated and dried (primed) seeds. Heat-shock and chaperone proteins (BiP) were expressed in treatments that successfully extended storage life. Slow drying after seed priming effectively extended storage life of lettuce (LACTUCA SATIVA) seeds. Studies on the roles of cell cycle initiation and DNA integrity in seed longevity were continued. Objective 3. Define the ecological interactions of seeds with their environment. The hydrothermal time
model was applied to explain the physiological basis of the cardinal temperatures for seed germination. At sub-optimal temperatures, thermal time (degree-days) determines germination rate, while at supra-optimal temperatures, changes in the threshold water potential are responsible for delaying and inhibiting germination. Shifts in the threshold water potential also are responsible for the alleviation of dormancy by afterripening, chilling or hormonal treatments. The hydrothermal time model provides a framework for analyzing and quantifying seed dormancy and seed responses to environmental factors.
Impacts
Knowledge of genes and proteins involved in the mechanism of germination will lead to methods for enhancing germination of crop seeds or inhibiting germination of weed seeds. Extending the longevity of seeds contributes to the preservation of valuable crop germplasm. Understanding the effects of the environment on seed germination is important in modeling the ecology of native or invasive species.
Publications
- CHEN, F., NONOGAKI, H., AND BRADFORD, K.J. 2002. A gibberellin-regulated xyloglucan endotransglycosylase gene is expressed in the endosperm cap during tomato seed germination. Journal of Experimental Botany 53: 215-223. (in press last report)
- BRADFORD, K.J. 2002. Applications of hydrothermal time to quantifying and modeling seed germination and dormancy. Weed Science 50: 248-260. (in press last report)
- ALVARADO, V., AND BRADFORD, K.J. 2002. A hydrothermal time model explains the cardinal temperatures for seed germination. Plant Cell and Environment 25: 1061-1069.
- GURUSINGHE, S; POWELL, A.L.T., AND BRADFORD, K.J. 2002. Enhanced expression of BiP is associated with treatments that extend storage longevity of primed tomato seeds. Journal of the American Society for Horticultural Science 127: 528-534.
- BRADFORD, K.J. AND BEWLEY, J.D. 2002. Seeds: Biology, Technology and Role in Agriculture. Chapter 9 in M.J. Chrispeels and D.E. Sadava, eds., Plants, Genes and Crop Biotechnology, 2nd Edition, Jones and Bartlett, Boston. Pp. 210-239.
- SUSLOW, T.V., B.R. THOMAS AND K.J. BRADFORD. 2002. Biotechnology provides new tools for plant breeding. University of California, Division of Agriculture and Natural Resources, Agricultural Biotechnology in California Series, Publication 8043.
- SUNDSTROM, F.J., WILLIAMS, J., VAN DEYNZE, A., AND BRADFORD, K.J. 2002. Identity preservation of agricultural commodities. University of California, Division of Agriculture and Natural Resources, Agricultural Biotechnology in California Series, Publication 8077.
- DOWNIE, B., GURUSINGHE, S., DAHAL, P., THACKER, R.R., SNYDER, J.C., NONOGAKI, H., YIM, K., FUKANAGA, K., ALVARADO, V., BRADFORD, K.J. 2003. Expression of a galactinol synthase gene in tomato is stress induced by an ABA-independent mechanism that is differentially responsive to cold in tomato seeds and leaves. Plant Physiology: In press.
- KWONG, F., STODOLSKI, L., MARI, J., GURUSINGHE, S.H. AND BRADFORD, K.J. 2001. Viability constants for delphinium and salvia seeds. Seed Technology 23: 113-125. (in press last report)
- BRADFORD, K.J., P. DAHAL, H. YANG, M. COOLEY, B. DOWNIE AND O. GEE. Regulation of source-sink relationships and responses to stress conditions in plants. U.S. Patent No. 6,342,656 issued January 29, 2002.
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Progress 01/01/01 to 12/31/01
Outputs
Objective 1. To elucidate fundamental mechanisms underlying seed development and germination. In continuing studies of genes expressed during tomato (LYCOPERSICON ESCULENTUM) seed germination, the patterns of expression of two expansin genes (LeEXP8 and LeEXP10, Accession #AF184232 and AF184233) in tomato embryos was characterized. LeEXP8 is expressed specifically in the cortical tissue near the embryonic radicle tip, while LeEXP10 is expressed more generally throughout the embryo. LeEXP8 is not expressed during seed development, while LeEXP10 is abundant during the period when embryo growth occurs during seed development, then declines during seed maturation. A xyloglucan endotransglycosylase (XET; LeXET4, Accession #AF186777) is expressed specifically in the endosperm cap tissue. Coordinated action of XET, expansin and other cell wall hydrolases such as mannanase may be required for weakening of the endosperm tissue enclosing the radicle to allow radicle
penetration. Microcalorimetry was used to measure both heat emission and respiration rates of imbibed seeds under various conditions. This method allowed inferences to be made regarding the types of respiratory substrates utilized during early imbibition and germination. Objective 2. Develop methods for improving seeds as genetic delivery systems. Methods were developed utilizing moisture content reduction and high temperature incubation to extend the storage life of hydrated and dried (primed) seeds. Studies were conducted to identify optimal conditions for such treatments in diverse species. Changes in sugar and oligosaccharide contents during priming and post-priming treatment were not correlated with longevity of tomato and impatiens (IMPATIENS BALSAMINA) seeds. Studies were conducted on whether the expression of heat-shock proteins might be involved in the extension of longevity by post-priming treatments. Seed viability constants defining potential storage lifetime under
different conditions were developed for salvia and delphinium seeds. Objective 3. Define the ecological interactions of seeds with their environment. Applications of the hydrothermal time model to seed germination continue to expand and were reviewed for weed scientists and seed ecologists. At sub-optimal temperatures, thermal time (degree-days) determines germination rate, while at supra-optimal temperatures, changes in the threshold water potential are responsible for delaying and inhibiting germination. Shifts in the threshold water potential also are responsible for the alleviation of dormancy by afterripening, chilling or hormonal treatments.
Impacts
Knowledge of genes and proteins involved in the mechanism of germination will lead to methods for enhancing germination of crop seeds or inhibiting germination of weed seeds. Extending the longevity of seeds contributes to the preservation of valuable crop germplasm. Understanding the effects of the environment on seed germination is important in modeling the ecology of native or invasive species.
Publications
- GURUSINGHE, S., AND BRADFORD, K.J. 2001. Galactosyl-sucrose oligosaccharides and potential longevity of primed seeds. Seed Science Research 11: 121-133. [reported as in press last year]
- WU, C.T., LEUBNER-METZGER, G., MEINS, F. JR. AND BRADFORD K.J. 2001. Class I Beta-1,3-glucanase and chitinase are expressed specifically in the micropylar endosperm of tomato seeds prior to radicle emergence. Plant Physiology 126: 1299-1313.
- EDELSTEIN, M., BRADFORD, K.J. AND BURGER, D.W. 2001. Metabolic heat and CO2 production rates during germination of melon (Cucumis melo L.) seeds measured by microcalorimetry. Seed Science Research 11: 265-272.
- CHEN, F., DAHAL, P., AND BRADFORD, K.J. 2001. Two tomato expansin genes show divergent expression and localization in embryos during seed development and germination. Plant Physiology 127 : 928-936.
- KWONG, F., STODOLSKI, L., MARI, J., GURUSINGHE, S.H. AND BRADFORD, K.J. 2001. Viability constants for delphinium and salvia seeds. Seed Technology: in press.
- CHEN, F., NONOGAKI, H., AND BRADFORD, K.J. 2002. A gibberellin-regulated xyloglucan endotransglycosylase gene is expressed in the endosperm cap during tomato seed germination. Journal of Experimental Botany 53: in press.
- BRADFORD, K.J. 2002. Applications of hydrothermal time to quantifying and modeling seed germination and dormancy. Weed Science, in press.
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Progress 01/01/00 to 12/31/00
Outputs
Objective 1. To elucidate fundamental mechanisms underlying seed development and germination. Germination of tomato (LYCOPERSICON ESCULENTUM) seeds requires weakening of endosperm cap tissues enclosing the radicle. The endosperm cell walls contain 60% mannose, and a cDNA encoding an endo-b-mannanase (LeMAN2, Accession #AF184238) was cloned from imbibed tomato seeds. The corresponding gene is expressed specifically in the endosperm cap, while a distinct mannanase gene (LeMAN1, Accession #AAB87859) is expressed in the remaining endosperm after radicle emergence. Similarly, several expansin genes encoding proteins involved in cell wall expansion or disassembly were cloned from imbibed tomato seeds. One of these (LeEXP4, Accession #AF059488) is expressed specifically in the endosperm cap, while two others (LeEXP8 and LeEXP10, Accession #AF184232 and AF184233) are localized to the embryo. A xyloglucan endotransglycosylase (XET) gene was also cloned (LeXET4, Accession
#AF186777) and is expressed specifically in the endosperm cap tissue. Coordinated action of mannanase, XET and expansin may be required for endosperm cap weakening. The genomic promoter for LeEXP8 was used to construct a non-destructive reporter gene using firefly luciferase. This was transformed into ARABIDOPSIS THALIANA, and allowed repeated monitoring of promoter activity in single seeds during germination under various conditions. Extension of these studies will assist in determining how different factors influence gene expression and ultimately seed germination. Objective 2. Develop methods for improving seeds as genetic delivery systems. Methods were developed utilizing moisture content reduction and high temperature incubation to extend the storage life of hydrated and dried (primed) seeds. Changes in sugar and oligosaccharide contents during priming and post-priming treatment were not correlated with longevity of tomato and impatiens (IMPATIENS BALSAMINA) seeds. However,
expression of a heat-shock responsive endoplasmic reticulum luminal binding protein (BiP) was correlated with extension of longevity by heat and chemical treatments. Heat-shock proteins may play a role in preservation or recovery of cellular integrity during dehydration, storage and imbibition. Objective 3. Define the ecological interactions of seeds with their environment. The hydrothermal time model provided a physiological explanation of the cardinal temperatures for germination of potato (SOLANUM TUBEROSUM) seeds. At sub-optimal temperatures, thermal time (degree-days) determines germination rate, while at supra-optimal temperatures, changes in the threshold water potential are responsible for delaying and inhibiting germination. Shifts in the threshold water potential also are responsible for the alleviation of dormancy by afterripening, chilling or hormonal treatments. Applications of the hydrothermal time model to seed germination continue to expand.
Impacts
Knowledge of genes and proteins involved in the mechanism of germination will lead to methods for enhancing germination of crop seeds or inhibiting germination of weed seeds. Extending the longevity of seeds contributes to the preservation of valuable crop germplasm. Understanding the effects of the environment on seed germination is important in modeling the ecology of native or invasive species.
Publications
- NONOGAKI, H., GEE, O.H., AND BRADFORD, K.J. 2000. A germination-specific endo-beta-mannanase gene is expressed in the micropylar endosperm cap of tomato seeds. Plant Physiology 123 (4): 1235-1245.
- CHEN, F., AND BRADFORD, K.J. 2000. Expression of an expansin is associated with endosperm weakening during tomato seed germination. Plant Physiology 124 (3): 1265-1274.
- GURUSINGHE, S., AND BRADFORD, K.J. 2001. Galactosyl-sucrose oligosaccharides and potential longevity of primed seeds. Seed Science Research, in press.
- BRADFORD, K.J., CHEN, F., COOLEY, M.B., DAHAL, P., DOWNIE, B., FUKUNAGA, K.K., GEE, O.H., GURUSINGHE, S., MELLA, R.A., NONOGAKI, H., WU, C.-T., AND YIM, K.-O. 2000. Gene expression prior to radicle emergence in imbibed tomato seeds. In: M. Black, K.J. Bradford, and J. Vazquez-Ramos, eds., Seed Biology: Advances and Applications, CAB International, Wallingford, U.K., pp. 231-251 [reported as in press last year].
- ALVARADO, V., NONOGAKI, H., AND BRADFORD, K.J. 2000. Expression of endo-b-mannanase and SNF-related protein kinase genes in true potato seeds in relation to dormancy, gibberellin and abscisic acid. In J.-D. Viemont and J. Crabbe, ed., Dormancy in Plants: From Whole Plant Behavior to Cellular Control, CAB International, Wallingford, U.K., pp. 347-364 [reported as in press last year].
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Progress 01/01/99 to 12/31/99
Outputs
Objective 1. To elucidate fundamental mechanisms underlying seed development and germination. Cell wall hydrolases are associated with germination of tomato (LYCOPERSICON ESCULENTUM) seeds. A cDNA encoding an endo-b-mannanase was cloned from imbibed tomato seeds. The corresponding gene is expressed specifically in the endosperm cap enclosing the radicle tip. Similarly, a single member of an expansin gene family is also expressed in the same tissue. Both mannanase and expansin are likely to be involved in tissue weakening to allow radicle emergence during germination. Tomato proteins having sequence homology to three subunits of a yeast protein kinase complex involved in sugar sensing (termed SNF1-related kinases) were demonstrated by the yeast two-hybrid technique to physically interact. Both mutant complementation and protein interactions were differentially affected by the sugar source. This kinase complex may be involved in regulating reserve mobilization during
seed germination. Objective 2. Develop methods for improving seeds as genetic delivery systems. Methods were developed utilizing moisture content reduction and high temperature incubation to extend the storage life of hydrated and dried (primed) seeds. The role of an endoplasmic reticulum luminal binding protein (BiP) in this response is under investigation. Objective 3. Define the ecological interactions of seeds with their environment. The hydrothermal time model was applied to explain the differing germination responses of potato (SOLANUM TUBEROSUM) seeds at sub-optimal versus supra-optimal temperatures. At sub-optimal temperatures thermal time (degree-days) determines germination rate, while at supra-optimal temperatures changes in the threshold water potential are responsible for delaying and inhibiting germination.
Impacts
Knowledge of enzymes and proteins involved in the mechanism of germination will lead to methods for enhancing germination of crop seeds or inhibiting germination of weed seeds. Extending the longevity of seeds contributes to the preservation of valuable crop germplasm. Understanding the effects of temperature on seed germination is important in modeling the ecology of native or invasive species.
Publications
- COOLEY, M.B., YANG, H., DAHAL, P. MELLA, R.A., DOWNIE, B., HAIGH, A.M., AND BRADFORD, K.J. 1999. Vacuolar H+-ATPase is expressed in response to gibberellin during tomato seed germination. Plant Physiology 121: 1339-1347.
- SITRIT, Y., HADFIELD, K.A., BENNETT, A.B., BRADFORD, K.J., AND DOWNIE, B. 1999. Expression of a polygalacturonase associated with tomato seed germination. Plant Physiology 121: 419-428.
- VOSS, R.E., MURRAY, M., BRADFORD, K.J., MAYBERRY, K.S., AND MILLER, I. 1999. Onion seed production in California. University of California, Division of Agriculture and Natural Resources, Publication 8008.
- DOWNIE, B., GURUSINGHE, S., AND BRADFORD, K.J. 1999. Internal anatomy of individual tomato seeds: relationship to abscisic acid and germination physiology. Seed Science Research 9: 117-128.
- CHENG, Z., AND BRADFORD, K.J. 1999. Hydrothermal time analysis of tomato seed germination responses to priming treatments. Journal of Experimental Botany 50: 89-99.
- GURUSINGHE, S.H., CHENG, Z., AND BRADFORD, K.J. 1999. Cell cycle activity during seed priming is not essential for germination advancement in tomato. Journal of Experimental Botany 50: 101-106.
- BRADFORD, K.J., CHEN, F., COOLEY, M.B., DAHAL, P., DOWNIE, B., FUKUNAGA, K.K., GEE, O.H., GURUSINGHE, S., MELLA, R.A., NONOGAKI, H., WU, C.-T., AND YIM, K.-O. 2000 Gene expression prior to radicle emergence in imbibed tomato seeds. In: M. Black, K.J. Bradford, and J. Vazquez-Ramos, eds., Seed Biology: Advances and Applications, CAB International, Wallingford, U.K., in press.
- ALVARADO, V., NONOGAKI, H., AND BRADFORD, K.J. 2000. Expression of endo-b-mannanase and SNF-related protein kinase genes in true potato seeds in relation to dormancy, gibberellin and abscisic acid. In J. Crabbe, ed., Proceedings of the Second International Symposium on Plant Dormancy, CAB International, Wallingford, U.K., in press.
- Patents and Inventions (1999): BRADFORD, K.J., DAHAL, P., YANG, H., COOLEY, M.B., DOWNIE, B., GEE, O.H. Regulation of source-sink relationships and responses to stress conditions in plants. Application serial number 09/359,161, filed 7/21/99, pending. BRADFORD, K.J., CHEN, F., DAHAL, P., DOWNIE, B., NONOGAKI, H. Genes expressed in germinating seeds and their uses. Application serial number 09/410,191, filed 9/30/99, pending.
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Progress 01/01/98 to 12/31/98
Outputs
Objective A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. Genes associated with germination or dormancy of tomato (LYCOPERSICON ESCULENTUM) seeds include cell wall hydrolases (exo-polygalacturonase, cellulases, and arabinosidase), pathogenesis-related proteins (.-1,3-glucanase and chitinase) and novel expansins that are specifically expressed in the micropylar endosperm prior to radicle emergence. Tomato genes having sequence homology to two subunits of a yeast protein kinase complex involved in sugar sensing were demonstrated by mutant complementation to be functional homologs of the yeast genes. The two genes are differentially expressed under various conditions of germination, dormancy and environmental stress. Transgenic plants modifying the expression of these germination-associated genes or reporting their expression patterns are being developed. Objective B. To develop environmentally sound
methods to produce, assess, enhance and preserve seed quality and improve seed performance. Raffinose family oligosaccharides (RFOs) are being studied in relation to seed longevity. Galactinol synthase, a key enzyme in the synthesis of RFOs, was cloned from tomato and its expression patterns are being examined. Treatments that extend longevity of pre-hydrated seeds have been identified, but are not accompanied by changes in sugar contents.
Impacts
(N/A)
Publications
- STILL, D.W. and BRADFORD, K.J. 1998. Using hydrotime and ABA-time models to quantify seed quality of brassicas during development. J. Amer. Soc. Hort. Sci. 123: 692-699.
- BRADFORD, K.J. and COHN, M.A. 1998. Seed biology and technology: At the crossroads and beyond. Seed Sci. Res. 8: 153-160.
- TAYLOR, A.G., ALLEN, P.S., BENNETT, M.A., BRADFORD, K.J., BURRIS, J.S. and MISRA, M.K. 1998. Seed enhancements. Seed Sci. Res. 8:
- WELBAUM, G.E., BRADFORD, K.J., YIM, K.-O., BOOTH, D.T., and OLUOCH M.O. 1998. Biophysical, physiological and biochemical processes regulating seed germination. Seed Sci. Res. 8: 161-172.
- DOWNIE, B., DIRK, L.M.A., HADFIELD, K.A., WILKINS, T.A., BENNETT, A.B. and BRADFORD, K.J. 1998. A gel diffusion assay for quantification of pectin methylesterase activity. Anal. Biochem. 164:
- DOWNIE, B., GURUSINGHE, S., PLOPPER, C., BRADFORD, K.J., GREENWOOD, J.S., and BEWLEY, J.D. 1997. Elongated cells adhering to the megagametophyte and sheathing the radicle of white spruce following completion of germination are derived from the embryo root cap. Internatl. J. Plant Sci. 158: 738-746. (in press last report)
- WU, C.-T., BRADFORD, K.J., LEUBNER-METZGER, G. and MEINS, F. JR. 1998. Class I beta-1,3-glucanase and chitinase are expressed in the endosperm caps of tomato seeds prior to radicle emergence. Plant Biology '98, American Society of Plant Physiologists, Madison,
- CHEN, F. and BRADFORD, K.J. 1998. Expansin genes are expressed in tomato seeds in association with germination. Plant Biology '98, American Society of Plant Physiologists, Madison, Wisconsin, June
- DAHAL, P., DOWNIE, B., MELLA, R.A., YIM, K.-O. and BRADFORD, K.J. 1998. A GA-stimulated transcript (GAST) is expressed during tomato seed germination. Plant Biology '98, American Society of Plant Physiologists, Madison, Wisconsin, June 27-July1, 1998. Abstract #
- GURUSINGHE, S. and BRADFORD, K.J. 1998. Changes in disaccharides and oligosaccharides in seeds during imbibition and priming: relationship to seed longevity. Plant Biology '98, American Society of Plant Physiologists, Madison, Wisconsin, June 27-July1, 1998. Abstract #
- DOWNIE, B., GURUSINGHE, S., DAHAL, P. and BRADFORD, K.J. 1998. A galactinol synthase gene is up-regulated in tomato seeds when germination is prevented by various factors, but does not respond to ABA. Plant Biology '98, American Society of Plant Physiologists, Madison, Wisconsin, June 27-July1, 1998. Abstract # 61.
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Progress 01/01/97 to 12/01/97
Outputs
Objective A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. Genes associated with germination or dormancy of tomato (LYCOPERSICON ESCULENTUM) seeds were isolated and characterized. Full-length cDNAs for a number of mRNAs that are differentially expressed in germinating versus non-germinating tomato seeds were obtained from tomato seed cDNA libraries. Vacuolar H+-ATPase mRNA and protein expression is enhanced during imbibition in wild type seeds and is induced by gibberellin (GA) in GA-deficient mutant seeds. A cDNA has been isolated that exhibits sequence similarity with a subunit of a protein kinase complex known in yeast to regulate catabolite repression in association with sugar sensing. Expression of the mRNA and protein of this gene is down-regulated by GA and is maintained by conditions that prevent completion of germination (dormancy, low water potential, abscisic acid, low temperature).
b-1,3-glucanase and chitinase mRNAs and enzyme activities were detected specifically in the endosperm cap region in association with germination. Expression of expansin mRNA has been detected specifically in the endosperm cap region of tomato seeds prior to radicle emergence. Objective B. To develop environmentally sound methods to produce, assess, enhance and preserve seed quality and improve seed performance. The role of sugars, particularly raffinose family oligosaccharides (RFOs), in seed longevity is being investigated. A gene encoding galactinol synthase, a key enzyme in the synthesis of RFOs, has been cloned.
Impacts
(N/A)
Publications
- DOWNIE, B., GURUSINGHE, S., PLOPPER, C., BRADFORD, K.J., GREENWOOD, J. S., and BEWLEY, J.D. 1997. Elongated cells adhering to the megagametophyte and sheathing the radicle of white spruce following completion of germination are derived.
- BRADFORD, K.J. 1997. The hydrotime concept in seed germination and dormancy. In R.H. Ellis, M. Black, A.J. Murdoch, and T.D. Hong, eds., Basic and Applied Aspects of Seed Biology: Proceedings of the Fifth International Workshop on Seeds,.
- DAHAL, P., NEVINS, D.J., and BRADFORD, K.J. 1997. Relationship of endo-B-mannanase activity and cell wall hydrolysis in tomato endosperm to germination rates. Plant Physiol. 113: 1243-1252 (in
- CHENG, Z., S. GURUSINGHE, and BRADFORD, K.J. 1997. Hydrothermal time and cell cycle activity during priming of tomato seeds. In Proceedings, Fifth National Symposium on Stand Establishment,
- YANG, H., DAHAL, P., DOWNIE, B., YIM, K., CHENG, Z., ABE, H., BRADFORD, K.J. 1997. Regulation of expression of a SNF4-like protein kinase-related gene in tomato seeds. International Symposium on Information Processing Systems in Plants:.
- YANG, H., DAHAL, P., CHENG, Z., ABE, H., BRADFORD, K.J. 1997. Expression of a SNF4-like protein kinase-related gene in tomato seeds. Plant Physiol. (Suppl.) 114: 270, abstract #1398.
- DOWNIE, B., GURUSINGHE, S., BRADFORD, K.J. 1997. Variation in germination behavior among individual sitiens tomato seeds is correlated with seed anatomy. Plant Physiol. (Suppl.) 114: 46,
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Progress 01/01/96 to 12/30/96
Outputs
Objective A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. In tomato (LYCOPERSICON ESCULENTUM), the cell walls of the endosperm tissue enclosing the embryo weaken to allow radicle emergence. We have isolated and characterized genes that may be involved in germination or dormancy in tomato endosperm caps. Differential cDNA display methods were used to identify a number of mRNA fragments that are differentially expressed in germinating versus non-germinating seeds. cDNA libraries were constructed and full-length cDNA clones of several of these messages have been isolated and sequenced, including ones encoding homologs to a vacuolar H+-ATPase subunit, a protein kinase, a pectinase, and a GA-stimulated transcript of unknown function (GAST1). Expression of these transcripts in relation to germination is being characterized using tissue prints to quantify and localize expression on a single-seed basis.
Hydrolase activity associated with endosperm weakening in lettuce (LACTUCA SATIVA) was also characterized. Objective B. To develop environmentally sound methods to produce, assess, enhance and preserve seed quality and improve seed performance. We developed and applied a hydrothermal time model of seed germination rates to describe germination and dormancy behavior across a wide range of conditions. Prehydration (priming) treatments that can speed subsequent germination rates were characterized on a hydrothermal time basis.
Impacts
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Publications
- BRADFORD, K.J. 1997. The hydrotime concept in seed germination and dormancy. In R.H. Ellis, M. Black, A.J. Murdoch, and T.D. Hong, eds., Basic and Applied Aspects of Seed Biology: Proceedings of the Fifth International Workshop on Seeds,.
- DAHAL, P., NEVINS, D.J, and BRADFORD, K.J. 1997. Relationship of endo-B -mannanase activity and cell wall hydrolysis in tomato endosperm to germination rates. Plant Physiol. in press.
- DUTTA, S., BRADFORD, K. J., and NEVINS, D.J. 1997. Endo-B -mannanase activity present in cell wall extracts of lettuce endosperm prior to radicle emergence. Plant Physiol. 113: 155-161.
- STILL, D. W., DAHAL, P., and BRADFORD, K.J. 1997. A single seed assay for endo-B -D-mannanase activity from tomato endosperm and radicle tissues. Plant Physiol. 113: 13-20.
- STILL, D. W., and BRADFORD, K.J. 1997. Endo-B -D-mannanase activity from individual tomato endosperm tissues in relation to germination. Plant Physiol. 113: 21-29.
- BRADFORD, K.J. 1996. Population-based models describing seed dormancy behaviour:implications for experimental design and interpretation. In G.A. Lang, ed., Plant Dormancy: Physiology, Biochemistry and Molecular Biology. CAB International,.
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Progress 01/01/95 to 12/30/95
Outputs
Objective A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. In tomato (LYCOPERSICON ESCULENTUM), the cell walls of the endosperm tissue enclosing the embryo weaken to allow radicle emergence. We are characterizing genes that may be specific for germination or dormancy in tomato endosperm caps. Differential cDNA display methods were used to identify approximately 25 mRNAs that are differentially expressed in germinating versus nongerminating seeds. Characterization of the expression of these genes and sequencing of clones are in progress. The involvement of cell wall hydrolases in endosperm weakening is also under investigation. In other studies, prehydration (priming) treatments can speed subsequent germination rates, but seed longevity in storage is often shortened. Reduced storage life of seeds following priming treatments may be related to progress of meristematic cells into the cell cycle, increasing
nuclear DNA content. Cell cycle activity during priming was highly correlated with rapid germination rates, but loss of potential longevity occurred well before cell cycle activity was initiated in tomato radicle meristems. Objective B. To develop environmentally sound methods to produce, assess, enhance and preserve seed quality and improve seed performance. We developed a hydrotime model of seed germination rates to describe germination and dormancy behavior across a wide range of conditions.
Impacts
(N/A)
Publications
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Progress 01/01/94 to 12/30/94
Outputs
Objective A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. Endosperm weakening is involved in regulation of seed germination and dormancy in many species. In tomato (LYCOPERSICON ESCULENTUM), mannanase enzyme activity is thought to weaken the endosperm cell walls, allowing emergence of the embryonic radicle. However, endosperm mannanase activity per se was not highly correlated with germination rates. Extremely wide variation (over 1000-fold) in mannanase activity among individual seeds in a seed lot suggests that single-seed analyses of seed populations may be required to identify mechanisms controlling germination. Efforts are underway to characterize cDNA clones that may be specific for germination or dormancy in tomato endosperm caps. Prehydration treatments can speed subsequent germination rates, but seed longevity in storage is often shortened. Reduced storage life of seeds following prehydration
treatments may be related to progress of meristematic cells into the cell cycle, increasing nuclear DNA content from 2C to 4C. Increased nuclear DNA content following imbibition was highly correlated with both rapid germination rates and rapid deterioration in tomato seeds. Objective B. To develop environmentally sound methods to produce, assess, enhance and preserve seed quality and improve seed performance.
Impacts
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Publications
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Progress 01/01/93 to 12/30/93
Outputs
A. To investigate the biological mechanisms underlying seed development, germination, dormancy and deterioration. The relationships of abscisic acid (ABA) accumulation and maturity to seed quality during development were evaluated in BRASSICA species. Sensitivity of germination to inhibition by ABA and water potential decreased coordinately during seed maturation. Respiratory rates at different temperatures, water potentials and oxygen levels were determined with respect to corresponding germination rates. Enzymatic processes involved in endosperm hydrolysis which regulates tomato (LYCOPERSICON ESCULENTUM) seed germination is being evaluated in individual seeds according to a population-based model. The possible role of Maillard products in seed deterioration was tested. Fluoresence assays currently used to measure Maillard products are unsatisfactory. B. To develop environmentally sound methods to produce, assess, enhance and preserve seed quality and improve seed
performance. A hydrotime model of seed germination rates is being extened for use as a seed quality index. A similar model to quantify losses of seed quality during aging will be tested with additional species.
Impacts
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Publications
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Progress 01/01/92 to 12/30/92
Outputs
Objective 1: Develop improved methods to assess seed quality. Based upon a "hydrothermal" time model, seed quality can be described in terms of the temperature and water potential thresholds allowing germination, and the time constants relating these factors to germination rate. The same approach has been used to determine maximum potential lifetimes of seeds during storage and to relate aging period to germination timing and viability. Use of a single model to describe seed germination rates and viability loss provides a common basis for quantitating seed quality. Objective 2: Study the physiology and biochemistry of seed quality. Studies on germination of mutant tomato (LYCOPERSICON ESCULENTUM) seeds deficient in either abscisic acid or gibberellin have shown that endogenous growth regulators alter threshold water potential distributions. The regulation and developmental expression of cell wall hydrolyizing enzymes responsible for determining the water potential
thresholds of individual seeds are under investigation. The development of desiccation tolerance and germinability of wild rice (ZIZANIA PALUSTRIS var INTERIOR) and paddy rice (ORYZA SATIVA) seeds was characterized relative to the accumulation of abscisic acid, maturation proteins and sugars in the embryos. Objective 3: Study how production factors affect seed quality. The effect of seed maturity on seed quality of BRASSICA species was evaluated under field and growth chamber conditions using the hydrotime model.
Impacts
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Publications
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Progress 01/01/91 to 12/30/91
Outputs
Objective 1: Develop improved methods to assess seed quality. A "hydrothermal"time model to describe germination responses to temperature and water potential was developed and evaluated. The model accounted for about 70% of the variation in germination times of tomato (LYCOPERSICON ESCULENTUM) at different temperatures and water potentials, but responses to the two factors were not independent. This model also accounted well for the advancement of germination rates after a period of incubation at low water potential (seed priming). Controlled deterioration was used to evaluate the effects of priming on lettuce (LACTUCA SATIVA) seed longevity. Priming reduced longevity to only 20% of that of control seeds. A model was developed to describe the effect of seed aging duration on the time to germination. Objective 2: Study the physiology and biochemistry of seed quality. Interactions between water potential, abscisic acid and gibberellin in regulating seed germination
rates were analyzed by a quantitative mathematical model. Studies on germination of mutant seeds deficient in either abscisic acid or gibberellin have confirmed that endogenous growth regulators act through changes in threshold water potential distributions. Objective 3: Study how production factors affect seed quality. The development of germination capacity and desiccation tolerance was evaluated in wild rice (ZIZANIA PALUSTRIS var. INTERIOR) and paddy rice (ORYZA SATIVA).
Impacts
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Publications
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Progress 01/01/90 to 12/30/90
Outputs
Objective 1: Develop improved methods to assess seed quality. A water relations analysis (see Objective 2) was applied to seed lots of tomato, pepper and sweet corn to determine whether quantitative parameters derived from it would correlate with other seed quality indices. Good correlations were obtained from sweet corn during development, but none of the vigor indices used were highly correlated for tomato and pepper seed lots. Objective 2: Study the physiology and biochemistry of seed quality. A quantitative model was developed to analyze and predict germination responses to temperature, water potential and plant growth regulators. This model accounts not only for the mean response, but also for the population distribution of responses among individual seeds. A theoretical basis for the concept of "hydrotime," or an effect of water potential on the rates of physiological processes analogous to that of temperature or "thermal time" has been developed. A physiological
explanation for the cucurbit seed disorder termed, "fishmouth," characterized by splitting of the seed coat, was also identified. Objective 3: Study how production factors affect seed quality. Muskmelon seed development and maturity were studied in relation to a number of quality factors. Seed quality and vigor continued to improve after seeds became fully germinable, on the basis of increased tolerance to reduced water potential, more rapid germination and less sensitivity to inhibitors (abscisic acid).
Impacts
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Progress 01/01/89 to 12/30/89
Outputs
Objective 1. Develop improved methods to assess seed quality. Vigor tests and priming treatments of pepper (Capsicum annuum L.) seed were evaluated in laboratory and field trials. New methods to quantify seed germination responses to water potential were developed and are under evaluation. Objective 2. Study the physiology and biochemistry of seed quality. A water relations model of seed germination rates was developed to relate seed germination to physiological parameters such as turgor and yield threshold. It was applied to investigate how various factors, such as temperature, hormones, priming, aging and genotype, affect seed germination rates. In tomato (Lycopersicon esculentum Mill.), the rate-limiting processes in germination at both low temperature and reduced water potential are in the endosperm, not in the embryo. Seed imbibition or priming treatments were found to markedly shorten seed longevity in storage. In a study investigating possible mechanisms
underlying the intolerance of wild rice (Zizania palstris L.) seeds to desiccation, the role of sugars in stabilizing membranes and proteins is being studied, as well as the possibility that membrane lipid phrase transitions contribute to desiccation injury. Objective 3. Study how production factors affect seed quality. A two-year study of the relationship between seed maturity (moisture content) at harvest and seed quality of rice (Oryza sativa L.) was completed.
Impacts
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Progress 01/01/88 to 12/30/88
Outputs
Objective 1. Develop practical methods of measuring seed health, putirty, and viability. Methods of breaking dormancy and determining viability were studied in wild rice (Zizania palustris var interior). Dehulling, scarification, and chemical treatments were compared to the tetrazolim test as indicators of viability. No method to overcome the requirement for stratification has yet been found. Objective 2. Evaluate methods of assessing seedling vigor and enhancing field performance. The effects of priming and aging on tomato (Lycopersicon esculentum Mill.), seed vigor and deterioration were investigated. Priming improved the rate of germination, while aging decreased it. Longevity was severely reduced by priming. The resistance to deterioration of seeds is reduced by priming treatments. The water relations of tomato, muskmelon (Cucumis melo L.) and lettuce (Lacuca sativa L.) seed germination with respect to temperature, water potential, and genotype are under study with
respect to a model adapted from plant cell growth. Objective 3. Ascertain the effects of cultural practices and environmental influences on seed quality. Seed vigor (root length test) of muskmelon continued to increase during development after maximum dry weight and germinability had been achieved. In studies on the relationship between seed moisture content at harvest and seed quality in rice (Oryza sativa L.), no improvement in quality occurred below 22% moisture content.
Impacts
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Publications
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Progress 01/01/87 to 12/30/87
Outputs
Contributions were made to two objectives in Regional Research Project W-168: Objective 2 - Evaluate methods of assessing seedling vigor and enhancing field performance. A second year of field and laboratory trials was completed on priming of pepper (Capsicum annuum) seed to improve the rate of field emergence. The average time (33 seed lots) to 50% emergence was reduced by 73% in the laboratory and 26% in the field. The inheritance of a non-dormancy trait in wild lettuce (Lactuca sativa) line (Pl 251245) is being determined for possible incorporation into cultivars. Seed priming can alleviate thermodormancy in lettuce. We have shown that this effect is not due to endosperm weakening or to solute accumulation in the embryo. Other hypotheses are under investigation. Objective 3 - Ascertain the effects of cultural practices and environmental influences on seed quality. Planting density was found to influence seed yield in carrot (Daucus carota), but had no effect
on seed quality. Seed yield and quality were correlated with the harvest index. A water potential disequilibrium was measured between the seed and the fruit during muskmelon (Cucumis melo) development. Low water potentials inside the fruit prevent precocious germination. Moisture content/seed quality relationships are being studied in rice (Oryza sativa) and wild rice (Zizania palustris).
Impacts
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Publications
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Progress 01/01/86 to 12/30/86
Outputs
Investigations were conducted on seed production or quality in pepper (Caspicum annuum L.), lettuce (Lactuca sativa L.), carrot (Daucus carota L.) and cantaloupe (Cucumis melo L.). Pepper. The effectiveness of seed priming in improving the rate of seedling emergence was demonstrated in field tests of 50 seed lots of varying initial vigor. The pretreatment reduced the time to 50% emergence by 33% when averaged across all lots. Lettuce. The inheritance of germination ability at high temperature (nondormancy) was studied by F(3) analysis of an F(2) population of a cross between P1 251245 (nondormant) and 'Vanguard' (dormant). The nondormant trait is inherited quantitively and studies are in progress to estimate the number of genes involved. Carrot. Decreasing between-plant spacing from 30 to 5 cm increased the proprotion of the total seed yield contributed by primary umbels. The quality of seed decreased as umbel order decreased. Higher yields and better quality
can be achieved in carrot seed production by utilizing high plant populations. Cantaloupe. Seed development was studied in relation to germination and vigor. Maximum seed dry weight was achieved 35 days after flowering, but maximum germination and vigor were delayed by 10 and 20 days, respectively. Seeds developed the ability to germinate at lower water potentials and higher abscisic acid levels as they matured. Low fruit water potential and possibly chemical inhibitors prevent precocious germination of melon seed.
Impacts
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Progress 01/01/85 to 12/30/85
Outputs
Studies on cotyledon cracking of snap bean (Phaseolus vulgaris L.) seeds were concluded. No significant involvement of seed mineral content in the disorder was found. Studies on the effects of seed priming on germination and emergence of lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.) and cantaloupe (Cucumis melo L.) were continued. Priming can be beneficial in improving stand establishment, but the effects are dependent upon soil and weather conditions. Storage experiments with primed tomato seeds indicate that the beneficial effects on germination rate can be retained for at least one year under good storage conditions. An investigation of seed development in cantaloupe was initiated to characterize the factors controlling germination during development and maturation. The water relations of acid development within the fleshy fruit will be emphasized.
Impacts
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Publications
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Progress 01/01/84 to 12/30/84
Outputs
Objective I. To develop practical methods of measuring seed health, purity and viability. Under this objective, isozyme variation among single-gene isolines of tomato were being investigated. Differences were detected, but were judged not to be suitable for further development as isoline markers. Continuation of work on this objective is not anticipated. Objective II. To evaluate methods of assessing seedling vigor and enhancing field performance. Osmotic priming is being tested as a means of enhancing seed performance under adverse field conditions. Earlier emergence or greater percentage emergence have been obtained with lettuce, tomatoes and melons due to priming treatments. In tomatoes, growth advantages due to earlier emergence were documented as well. Emphasis is now being placed on evaluating vigor tests which can be used to predict the field performance of primed seeds. Objective III. to ascertain the effect of cultural practices and environmental
influences on seed quality. Ethephon, an ethylene-releasing compound, is sometimes used to accelerate fruit ripening in processing tomatoes. The effect of this ractice on seed quality was evaluated in field trials. Ethephon treatment significantly reduced seed vigor and viability when applied at high rates 10 days before harvest. The influence of calcium on transverse cotyledon cracking in beans was also studied.
Impacts
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