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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Temperature on Delta-9 Stearoyl-Acp and Microsomal Omega-6 Desaturase Gene Expression and Fatty Acid Content in Developing Soybean Seeds

Authors
item Byfield, Grace - NCSU
item Upchurch, Robert

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2006
Publication Date: July 1, 2007
Citation: Byfield, G.E., Upchurch, R.G. 2007. Effect of temperature on delta-9 stearoyl-acp and microsomal omega-6 desaturase gene expression and fatty acid content in developing soybean seeds. Crop Science, 47:1698-1704.

Interpretive Summary: The Delta-9 stearoyl-ACP desaturase enzymes (SACPDs) convert stearic (18:0) to oleic acid (18:1) and are important for the acclimation of plants, including soybean, to low temperatures. Since these enzymes carry out the important life functions involved in cell membrane synthesis and maintenance, they are under constitutive control, but may also be supplemented by fine regulation at both the transcriptional and post-transcriptional levels. We measured the expression (transcript accumulation) of SACPD-A and -B in developing soybean seeds across cold (22/18 degrees C) normal (26/22 degrees C), and warm (30/26 degrees C) temperatures. The expression of both SACPD genes decreased by up to 69% with increasing temperature in cultivars Dare, A6 (a high stearate line), and N01-3544 (a mid-oleic line). Stearic acid content of A6 was inversely related to the level of SACPD-A and -B expression at the warm and cold temperatures, as might be expected, but the stearic acid content of N01-3544 and Dare did not appear to be affected by temperature despite dynamic changes in the expression levels of the SACPD genes in these lines. This suggests that in these two lines stearate does not accumulate with higher temperature because it may be metabolically reclaimed as it is synthesized. Similarly, but unexpectedly, the oleic acid content of all three lines was inversely related to the levels of SACPD gene expression at the warm and cold temperatures. This suggests that transcription control of the SACPDs is not a crucial factor regulating oleic acid content in soybean seed.

Technical Abstract: The Delta-9 stearoyl-ACP desaturases (SACPDs) are important enzymes for the acclimation of organisms, including soybean, to low temperatures. Since these enzymes carry out important housekeeping functions such as lipid membrane biosynthesis they are under constitutive control, but may also be supplemented by fine regulation at both the transcriptional and post-transcriptional levels. We measured the transcript accumulation of SACPD-A and –B genes in developing soybean seeds across cold (22/18 degrees C) normal (26/22 degrees C), and warm (30/26 degrees C) temperatures by quantitative RT-PCR. Transcript accumulation of SACPD-A and -B decreased by up to 69% with increasing temperature in cultivars Dare, A6 (a high stearate line), and N01-3544 (a mid-oleic line). Stearic acid content of A6 was inversely related to the level of SACPD-A and -B gene expression at the warm and cold temperatures, as might be expected, but the stearic acid content of N01-3544 and Dare did not appear to be affected by temperature despite dynamic changes in the expression levels of the SACPDs in these lines. This suggests that in these two lines stearate does not accumulate with higher temperature because it may be metabolically reclaimed as it is synthesized. Similarly, but unexpectedly, the oleic acid content of all three lines was inversely related to the levels of SACPD expression at the warm and cold temperatures. This suggests that transcription control of SACPD is not a crucial factor for regulating oleic acid content in soybean.

Last Modified: 12/22/2014
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