LAUSR

Triacylglycerols (TAGs) are the major component of plant storage lipids such as oils. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step of the Kennedy pathway, and is mainly responsible for plant oil accumulation. We previously found that the DGAT activity of Vernonia DGAT1 was distinctively higher than that of Arabidopsis DGAT1 and soybean DGAT1 in a yeast microsome assay. In this study, the DGAT1 cDNAs of Arabidopsis, Vernonia, soybean, and castor bean were introduced into Arabidopsis. All Vernonia DGAT1 expressing lines showed a significantly higher oil content (49% mean increase compared to wild-type) followed by soybean and castor bean. 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 a TAG biosynthesis defective yeast mutant. In the yeast expression culture, DGAT1s from Arabidopsis, castor bean, and soybean only slightly increased the TAG content; however, DGAT1s from Vernonia, sunflower, Jatropha, and sesame increased TAG content more than 10 times than the former three DGAT1s. Three amino acid residues were characteristically common in the latter four DGAT1s. Using soybean DGAT1, these amino acid substitutions were performed by site-directed mutagenesis and substantially increased the TAG content.