Discovery of a new mechanism for regulation of plant triacylglycerol metabolism: The peanut diacylglycerol acyltransferase-1 gene family transcriptome is highly enriched in alternative splicing variants

Authors: ZHENG, LING - Shandong Academy Of Agricultural Sciences; Shockey, Jay; GUO, FENG - Shandong Academy Of Agricultural Sciences; LINGMIN, SHI - Shandong Academy Of Agricultural Sciences; LI, XINGUO - Shandong Academy Of Agricultural Sciences; SHAN, LEI - Shandong Academy Of Agricultural Sciences; WAN, SHUBO - Shandong Academy Of Agricultural Sciences; PENG, ZHENYING - Shandong Academy Of Agricultural Sciences

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2017
Publication Date: 12/1/2017
Citation: Zheng, L., Shockey, J., Guo, F., Shi, L., Li, X., Shan, L., Wan, S., Peng, Z. 2017. Discovery of a new mechanism for regulation of plant triacylglycerol metabolism: The peanut diacylglycerol acyltransferase-1 gene family transcriptome is highly enriched in alternative splicing variants. Journal of Plant Physiology. 219:62-70.

Interpretive Summary: Peanuts are a major commodity oilseed crop grown in many areas around the world, including in China and the southeastern United States. Peanut oil is highly prized for its attractive taste and compatibility with high-temperature cooking processes. Little is currently known about how peanuts control the fatty acid composition of the seed oils. This study describes the analysis of several related forms of a gene that likely exerts strong influence over peanut oil production in seeds. We found that unlike most other related enzymes from other oilseeds, the peanut gene family is controlled by a novel process.

Technical Abstract: Triacylglycerols (TAGs) are the most important energy storage form in oilseed crops. Diacylglycerol acyltransferase (DGAT) catalyzes the rate-limiting step of the Kennedy pathway of TAG biosynthesis. To date, little is known about the regulation of DGAT activity in peanut (Arachis hypogaea), an agronomically important oilseed crop that is cultivated in many parts of the world. In this study, seven distinct forms of type 1 DGAT (AhDGAT1.1-AhDGAT1.7) were identified, cloned, and characterized. Comparisons of the nucleotide sequences and gene structures revealed many different splicing isoforms of AhDGAT1, some of which displayed different organ-specific expression patterns. A representative gene (AhDGAT1.1) was transformed into wild-type tobacco and was shown to increase seed fatty acid (FA) content by 14.7%-20.9%. All seven AhDGAT1s were expressed in TAG-deficient Saccharomyces cerevisiae strain H1246; the five longest AhDGAT1 isoforms generated high levels of acyltransferase activity and complimented the free fatty acid lethality phenotype in this strain. The alternative splicing that gives rise to AhDGAT1.2 and AhDGAT1.4 creates predicted protein C-terminal truncations. These protein isoforms were not active and did not complement the fatty acid sensitivity in H1246. These results were verified by visualization of intracellular lipid droplets using Nile Red staining. Collectively, the results presented here represent the first comprehensive analysis of the peanut DGAT1 gene family, which unlike in other published plant DGAT1 sequences, shows widespread alternative splicing that affects the expression patterns and enzyme activities of many members of the gene family.