Genome-wide analysis and functional characterization of Acyl-CoA:diacylglycerol acyltransferase from soybean identify GmDGAT1A and 1B roles in oil synthesis in Arabidopsis seeds

Acyl-CoA:diacylglycerol acyltransferase (DGAT) is a key enzyme in the Kennedy pathway of triacylglycerol (TAG) synthesis. It catalyzes the acyl-CoA-dependent acylation of sn-1, 2-diacylglycerol to form TAG. DGATs in soybean (Glycine max) have been reported, but their functions are largely unclear. Here we cloned three members of DGAT1 and four members of DGAT2 family from soybean, named GmDGAT1A to GmDGAT1C, and GmDGAT2A to GmDGAT2D, respectively. GmDGAT1A and GmDGAT1C were expressed at a high level in immature seeds, GmDGAT2B in mature seeds, and GmDGAT2C in older leaves. The seven genes were transformed into the H1246 quadruple mutant yeast strain, in which GmDGAT1A, GmDGAT1B, GmDGAT1C, GmDGAT2A, and GmDGAT2B had the ability to produce TAG. Six genes were transformed into Arabidopsis respectively, and constitutive expression of GmDGAT1A and GmDGAT1B resulted in an increase in oil content at the cost of reduced protein content in seeds. Overexpression of GmDGAT1A produced heavier weight of individual seed, but did not affect the weight of total seeds from a plant. Our results reveal the functions of soybean DGATs in seed oil synthesis using transgenic Arabidopsis. The implications for the biotechnological modification of the oil contents in soybeans by altering DGAT expression are discussed.