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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #326183

Research Project: Increasing the Value of Cottonseed

Location: Commodity Utilization Research

Title: Variant amino acid residues alter the enzyme activity of peanut type 2 Diacylglycerol Acyltransferases

item ZHENG, LING - Shandong Academy Of Agricultural Sciences
item Shockey, Jay
item BIAN, FEI - Shandong Academy Of Agricultural Sciences
item CHEN, GAO - Shandong Academy Of Agricultural Sciences
item SHAN, LEI - Shandong Academy Of Agricultural Sciences
item LI, XINGUO - Shandong Academy Of Agricultural Sciences
item WAN, SHUBO - Shandong Academy Of Agricultural Sciences
item PENG, ZHENYING - Shandong Academy Of Agricultural Sciences

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 10/16/2017
Citation: Zheng, L., Shockey, J., Bian, F., Chen, G., Shan, L., Li, X., Wan, S., Peng, Z. 2017. Variant amino acid residues alter the enzyme activity of peanut type 2 diacylglycerol acyltransferases. Frontiers in Plant Science. 8:1751.

Interpretive Summary: Recent research from various laboratories around the world, including our own, has helped to cement the idea that diacylglycerol acyltransferases (DGATs) are integral components for seed oil production in oilseed crops. At least three types of DGATs are known, but the overall contribution each of the three types makes to shaping the size and composition of the seed oil pool in each plant species is still not well known. Peanut is an economically important oilseed crop; peanut oil is one of the major forms of vegetable oil produced globally each year. Very little is known about the DGAT enzymes in peanut. This study thoroughly investigates the type-2 (DGAT2) gene family size in peanut, and explores the biochemical and physiological properties of peanut DGAT2 when expressed in transgenic tobacco plants and yeast cells.

Technical Abstract: Diacylglycerol acyltransferase (DGAT) catalyzes the final, rate-limiting step in triacylglycerol (TAG) biosynthesis via the acyl-CoA-dependent acylation of diacylglycerol. In this study, type-2 DGAT2 genes were cloned from eleven peanut cultivars. Sequence analysis revealed at least eight peanut DGAT2 genes (designated AhDGAT2a-h). A representative full-length cDNA clone (AhDGAT2a) was characterized in detail; it contained 1232 bp, including a 5’-untranslated region (UTR) of 52 bp, a 1005 bp open reading frame (ORF), and a 175-bp 3’-UTR. Sequence alignments revealed 21 nucleotide differences, but only six predicted amino acid differences. The biochemical effects of altering the sequence of AhDGAT2a to include single variant amino acid residues followed by functional complementation assays in transgenic yeast. Substitution A26P appeared to slightly increased enzyme activity, all other mutations decreased activity. However, these five substitutions altered substrate specificity, as shown by substantial growth rate changes on media containing monounsaturated versus polyunsaturated fatty acids. Like most other plant DGAT2 genes, AhDGAT2 is strongly expressed in immature seeds, but is also expressed in all other plant organs analyzed, including leaves and flowers. Over-expression of AhDGAT2a in tobacco substantially increased the fatty acid (FA) content of transformed tobacco seeds and significantly altered steady-state transcript levels of endogenous lipid metabolic genes.