Different DGAT1s show different TAG synthesis abilities and a specific amino acid substitution enhances oil accumulation

Abstract

Triacylglycerols (TAGs) are the major component of plant storage lipids. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step of the Kennedy pathway, and responsible for plant oil accumulation. We previously found DGAT activity of Vernonia galamensis DGAT1 was distinctively higher than that of Arabidopsis thaliana DGAT1 and soybean DGAT1 in a yeast microsome assay. In this study, the DGAT1 cDNAs of Arabidopsis, Vernonia, soybean, and castor were introduced into Arabidopsis (ecotype Col-0). All Vernonia DGAT1 expressing lines showed a significantly higher oil content (average 49% relative increase compared to the wild type) followed by soybean, and castor. Most Arabidopsis DGAT1 over-expressing lines did not show a significant increase. In addition to these four DGAT1s, sunflower, Jatropha and sesame DGAT1 genes were introduced into the TAG biosynthesis defective yeast mutant (H1246). In the yeast expression culture, DGAT1s from Arabidopsis, castor, and soybean only slightly increased TAG content, however, DGAT1s from Vernonia, sunflower, Jatropha, and sesame remarkably increased TAG content more than 10 times higher than the former three DGAT1s. Three amino acid residues were characteristically common in the latter four DGAT1s. Using soybean DGAT1, these amino acid substitutions by site-directed mutagenesis was performed and analyzed. These substitutions substantially increased the TAG content. HighlightDGAT1s from several plant species were tested their TAG accumulation promotion in Arabidopsis and yeast. They were divided into high and low function and single amino acid substitution enhanced function