Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2007
Publication Date: N/A
Technical Abstract: Prolonged high temperatures during soybean seed development can impact seed quality. High temperature occurs frequently during soybean seed development and maturity, especially in the Southern USA, and have been reported to have a considerable effect on soybean yields, seed composition and seed vigor. The effects of a high temperature (37/30ºC) treatment on the proteome were investigated using developing (R5-days 1 and 4, and R7-days 1 and 4) and mature seeds harvested from plants grown in environment-controlled chambers. High temperature treatment decreased seed quality resulting in a greater proportion of abnormal seeds and reduced seed germination. No significant change in total seed protein concentration was detected when seed developed under high temperature conditions. Proteomic comparisons of developing and mature embryos treated with high temperature, versus the control, detected functional proteins that were differentially accumulated. Seven subunits of seed storage proteins account for the majority of the proteins detected and 11S glycinin and 7S beta-conglycinin were the major storage proteins. Among the remaining protein spots we identified those responding to abiotic stresses or having a function in respiration: i) sucrose binding protein (SBP), ii) Class III acidic endochitinase, iii) heat shock protein (HSP22), iv) late embryo abundant protein (EM), v) Bowman-Birk proteinase inhibitor, and vi) formate dehydrogenase (FDH). A decrease in the amount of SBP precursor was observed in seeds developed under the high temperature treatment, relative to the control temperature. The SBP is associated with plasma membranes and is a vehicle for sucrose transport across the plasma membrane. Our contention is that high temperature inhibited the synthesis of sucrose and SBP of seed developing under our experimental temperature regime. Seeds that developed under the high temperature treatment produced less FDH compared to the control. It has been reported that the amount of FDH transcripts and proteins are positively associated to environmental stresses in mature seed; i.e., SBP, FDH, HSP22, EM, chitinase and BBI. Information on the relationship of any of these six proteins to seed germination and vigor has not been discovered, but functions in germination and post-germinative growth for some could be rationalized. A decrease of seed SBP may reduce sucrose transportation through the plasma membrane and in turn inhibit fatty acid digestion and nutrient supply to the radicle, slowing germination and seedling growth. A decrease of seed FDH directly reduces respiration activities and energy supply for germination and seedling growth. An increase of one type of seed BBI may disturb temporal proteolysis after imbibition, disrupting the amino nutrient supply for germination and post-germinative growth.