Abstract
Diacylglycerol acyltransferases (DGATs) play a key role in plant triacylglycerol (TAG) biosynthesis. Two type 1 and 2 DGATs from soybean were characterized for their functions in TAG biosynthesis and physiological roles. GmDGAT1A is highly expressed in seeds while GmDGAT2D is mainly expressed in flower tissues. They showed different expression patterns in response to biotic and abiotic stresses. GmDGAT2D was up-regulated by cold and heat stress and ABA signaling, and repressed by insect biting and jasmonate, whereas GmDGAT1A show fewer responses. Both GmDGAT1A and GmDGAT2D were localized to the endoplasmic reticulum and complemented the TAG deficiency of a yeast mutant H1246. GmDGAT2D-transgenic hairy roots synthesized more 18:2- or 18:1-TAG, whereas GmDGAT1A prefers to use 18:3-acyl CoA for TAG synthesis. Overexpression of both GmDGATs in Arabidopsis seeds enhanced the TAG production; GmDGAT2D promoted 18:2-TAG in wild-type but enhanced 18:1-TAG production in rod1 mutant seeds, with a decreased 18:3-TAG. However, GmDGAT1A enhanced 18:3-TAG and reduced 20:1-TAG contents. The different substrate preferences of two DGATs may confer diverse fatty acid profiles in soybean oils. While GmDGAT1A may play a role in usual seed TAG production and GmDGAT2D is also involved in usual TAG biosynthesis in other tissues in responses to environmental and hormonal cues.
Highlights
Donors and different glycerol backbones as acceptors
It is concluded that GmDGAT2D is a highly active type 2 Diacylglycerol acyltransferases (DGATs) involved in regular soybean TAG biosynthesis
Since most reported plant DGAT2s are involved in biosynthesis of unusual TAG with hydroxy fatty acids (FAs), this soybean GmDGAT2D is different from these plant DGAT2s, but more close to animal, fungal or algae DGAT2s, which have potential for enhancing oil production and improve oil compositions in crops[7,28,38]
Summary
Donors and different glycerol backbones as acceptors. acyltransferases conduct the acyl editing on DAG and eventual product TAGs in the ER, and manipulation of these acyltransferases leads to increased TAG production in plants[7]. We report the functional comparison study on type 1 and 2 soybean diacylglycerol acyltransferases, GmDGAT1A and GmDGAT2D. The expression of both GmDGAT1A and GmDGAT2D restored the in vivo synthesis of TAG in yeast strain Saccharomyces cerevisiae H1246. GmDGAT2D expression in soybean hairy roots and Arabidopsis lead to similar function in regular TAG production like fungal and animal DGAT2, but differ from other known plant DGAT2s, which synthesize unusual TAGs with hydroxy FAs. Our study suggests that GmDGAT1A and 2D are differentially regulated by jasmonate during insect and wounding responses and ABA for cold and heat stress response, indicating their different functions in soybean stress responses
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