Expression analysis of VfDGAT2 in various tissues of the tung tree and in transgenic yeast

The tung tree (Vernicia fordii Hemsl.; Vf) has great potential as an industrial crop owning to its seed oil that has multiple uses. Diacylglycerol acyltransferases (DGATs) catalyze the last and most committed step of triacylglycerol (TAG) biosynthesis. In order to examine the physiological role of the VfDGAT2 gene in the tung tree, we characterized its expression profiles in different tung tissues/organs and seeds at different developmental stages. Oil content and α-eleostearic acid production during seed development were also examined. Expression studies showed that VfDGAT2 was expressed in all tissues tested, with the highest expression in developing seeds where the expression was about 19-fold more than that in leaves. VfDGAT2 showed temporal-specific expression during seed development and maturation. Notably, the expression of VfDGAT2 in developing seeds was found to be consistent with tung oil accumulation and α-eleostearic acid production. The expression level of VfDGAT2 was lower in the early stages of oil accumulation and α-eleostearic acid biosynthesis, rapidly increased during the peak periods of fatty acid synthesis in August, and then decreased during completion of the accumulation period at the end of September. When the VfDGAT2 gene was transferred to the oleaginous yeast Rhodotorula glutinis, its expression was detected along with fatty acid products. The results showed that VfDGAT2 was highly expressed in transgenic yeast clones, and the total fatty acid content in one of these clones, VfDGAT2-3, was 7.8-fold more than that in the control, indicating that VfDGAT2 contributed to fatty acid accumulation into TAG and might be a target gene for improving tung oil composition through genetic engineering.