Increasing seed oil content and altering oil quality of Brassica napus L. by over-expression of diacylglycerol acyltransferase 1 (SsDGAT1) from Sapium sebiferum (L.) Roxb.

摘要

Sapium sebiferum (L.) Roxb. [S. sebiferum] is one of the most important woody oil trees and traditional herbal medicines in China. Diacylglycerol acyltransferases (DGATs) esterify sn-1,2-diacylglycerol with a long-chain fatty acyl-CoA acting as a key enzyme at the last and rate-limiting step of triacylglycerol (TAG) biosynthesis in eukaryotic organisms. Although at least 61 DGAT1 sequences from 48 organisms have been identified, until now there have been almost no reports on the DGAT1 gene in S. sebiferum (SsDGAT1). In an attempt to clarify SsDGAT1's function, we cloned the CDS (coding sequence) of SsDGAT1 by RACE (rapid amplification of cDNA ends) technology. The full-length CDS of SsDGAT1 contains 1524 bp, encoding a protein of 507 amino acids. Even recombinant SsDGAT1 was able to restore TAG biosynthesis in the yeast strain S. cerevisiae H1246 TAG-deficient mutant. Moreover, when SsDGAT1 was placed under the control of 35S promoter in Brassica napus L. W10, the total oil content of transgenic rape plants showed an increase of 12.3-14.7 % compared with the wild type. In addition, the transgenic rapeseed with heterologous expression of SsDGAT1 showed an alteration in seed oil composition overall: a significant decrease in oleic acid levels but a tendency towards an increase in linolenic acid levels. The result confirmed that SsDGAT1 may be involved in flux control of oil biosynthesis and could be used specifically to manipulate and improve oil content and composition in plants. These experimental findings suggest that we might be able to develop a plant high in industrial oils by over-expression of SsDGAT1 in S. sebiferum.