The transcription factor CeWRI3 functions in TAG accumulation through activating CeOLE2 in Cyperus esculentus

A WRI-like gene (CeWRI3) homologous to AtWRI3/4 was isolated from oil-rich Cyperus esculentus tubers, which was shown to function in TAG accumulation through activating CeOLE2. In oilseeds, WRI1 has proven to be a master regulator in the transcriptional control of genes involved in fatty acid biosynthesis. By contrast, no evidence is available for WRI1 and its homologs in regulating genes associated with triacylglycerol (TAG) biosynthesis. In this study, we present the characterization of a WRINKLED (WRI)-like gene from tigernut (Cyperus esculentus L., Cyperaceae), a rare example accumulating high levels of TAGs in underground tubers. This gene was named CeWRI3 for its homology to AtWRI3/-4 in Arabidopsis thaliana. Subcellular localization analysis in Nicotiana benthamiana and transactivation assay in yeast revealed that CeWRI3 indeed functions as a transcription factor with nuclear localization and transcriptional activation activity. Further qRT-PCR analysis showed that CeWRI3 exhibits a constitutive expression pattern and its transcripts are positively correlated with TAG accumulation during tuber development. Moreover, transient overexpression of CeWRI3 in N. benthamiana leaves could significantly enhance the TAG content, implying its contribution to TAG accumulation in tigernut tubers. Correspondingly, yeast one-hybrid and dual-luciferase reporter assays revealed that CeWRI3 could activate CeOLE2, but not CeOLE5 and CeDGAT2b, another two key genes related to TAG biosynthesis. Our findings emphasize the potential application of CeWRI3 in improving oil production of vegetative tissues.