Abstract
The transcription factor WRINKLED1 (WRI1) has been considered as a master regulator regulating fatty acid biosynthesis in oilseeds. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step of triacylgrycerol (TAG) synthesis, and is mainly responsible for plant oil accumulation. It has been reported that co-expression of these genes in the transient leaf expression system resulted in TAG levels exceeding those expected from an additive effect and this was considered as a “synergistic effect”. Our purpose is to verify that this effect would be found in TAG accumulating organ, such as seeds, and then to improve a TAG synthesis ability in oilseeds. WRI1 genes from Arabidopsis (AtWRI1) and castor bean (RcWRI1) were cloned and introduced into wild-type Arabidopsis ecotype Col-0 under the control of seed-specific promoter or constitutive promoter. A slight increase in seed oil content was observed in both WRI1-expressing lines compared to the wild-type Arabidopsis. When the AtWRI1 or RcWRI1 genes were introduced into wild-type Arabidopsis under the control of a constitutive promoter, the increase in seed oil contents was higher than using a seed-specific promoter although growth defects were observed frequently. Furthermore, Vernonia DGAT1 (VgDGAT1A)-expressing line was crossed with AtWRI1- or RcWRI1-expressing lines to produce double transformants. We measured the seed oil content of the double transformants of VgDGAT1A and AtWRI1 or RcWRI1 to investigate whether a “synergistic effect” was observed or not. There was no significant difference between the double transformants and VgDGAT1A single introduced lines. According to our previous study, transformants introduced with VgDGAT1A alone showed a significant increase in seed oil content. It was suggesting that VgDGAT1A introduction was strong enough to increase TAG accumulation, therefore the “synergistic effect” by co-expression with WRI1 might not be observed.
