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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #204820
Title: Effect of temperature on microsomal omega-3 linoleate desaturase gene expression and linolenic acid content in developing soybean seeds

Author
item BYFIELD, GRACE - NC STATE UNIVERSITY
item Upchurch, Robert

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2007
Publication Date: 7/30/2007
Citation: Byfield, G., Upchurch, R.G. 2007. Effect of temperature on microsomal omega-3 linoleate desaturase gene expression and linolenic acid content in developing soybean seeds. Crop Science, 47:2445-2452.

Interpretive Summary: Linolenic acid content in soybean oil is critical since high levels cause the oil to oxidize, become rancid, and lose quality. Previous research has show that linolenic acid content in soybean seeds is a heritable trait and significantly the result of the action of the three omega-3 fatty acid desaturase genes present in soybean. Omega-3 fatty acid desaturases (GmFAD3s) catalyze the insertion of a third double bond into the linoleic acid to produce linolenic acid. In addition, the environmental factor, growth temperature, interacts with plant genotype and most likely influences linolenic acid accumulation in seed as well. The present investigation was conducted to determine to what extent omega-3 fatty acid desaturase gene expression changes in developing soybean seeds in response to changes in growth temperature and how these changes are associated with linolenic acid content in soybean seeds. At 35 days after flowering, expression of GmFAD3A decreased by 5-15 fold, GmFAD3B by 4-9 fold, and GmFAD3C by 2-3 fold in seeds that developed in a warm (D/N=30/26 degrees C) versus a cool (D/N=22/18 degrees C) environment. At this stage of seed development, decreased omega-3 desaturase gene expression levels were positively associated with decreased linolenic acid content in the seed that developed in the warm environment. The reductions in linolenic acid content (39-50 %) measured in seed developing in the warm environment were substantial when compared to the reductions (27-67 %) reported for linolenic acid content measured in the mature seed of omega-3 desaturase soybean mutants.

Technical Abstract: The mechanism of temperature adaptation in plants, including the formation of polyunsaturates in seed storage lipids, most likely involves transcriptional as well as post-translational regulation of fatty acid desaturase activity. The present investigation was conducted to measure changes in the transcript accumulation among the three members of the soybean microsomal omega-3 fatty acid desaturase gene family in response to altered growth temperature during seed development. Microsomal omega-3 fatty acid desaturases (FAD3s) catalyze the insertion of a third double bond into the linoleic (C18:2) acid to produce linolenic (C18:3) acid. At 35 days after flowering (DAF), transcript accumulation (normalized for soybean actin) of GmFAD3A decreased by 5-15 fold, GmFAD3B by 4-9 fold, and GmFAD3C by 2-3 fold in seeds that developed in a warm (D/N=30/26 degrees C) versus a cool (D/N=22/18 degrees C) environment. At this stage of seed development, decreased omega-3 desaturase gene expression levels were positively associated with decreased linolenic acid content in the seed that developed in the warm environment. The reductions in linolenic acid content (39-50 %) measured in seed developing in the warm environment were substantial when compared to the reductions (27-67 %) reported for linolenic acid content measured in the mature seed of omega-3 desaturase soybean mutants.