WRINKLED1 homologs highly and functionally express in oil-rich endosperms of oat and castor

Abstract Oat ( Avena sativa ) and castor ( Ricinus communis ) accumulate a large amount of lipids in their endosperms, however the molecular mechanism remains unknown. In this study, differences in oil regulators between oat and wheat ( Triticum aestivum ) as well as common features between oat and castor were tested by analyzing their transcriptomes with further q-PCR analysis. Results indicated that WRINKLED1 ( WRI1 ) homologs and their target genes highly expressed in the endosperms of oat and castor, but not in the starchy endosperms of wheat. Expression pattern of WRI1 s was in agreement with that of oil accumulation. Three AsWRI1 s ( AsWRI1a , AsWRI1b and AsWRI1c ) and one RcWRI1 were identified in the endosperms of oat and castor, respectively. AsWRI1c lacks VYL motif, which is different from the other three WRI1s. Expressions of these four WRI1 s all complemented the phenotypes of Arabidopsis wri1-1 mutant. Overexpression of these WRI1 s in Arabidopsis and tobacco BY2 cells increased oil contents of seeds and total fatty acids of the cells, respectively. Moreover, this overexpression also resulted in up-regulations of WRI1 target genes, such as PKp-β1 . Taken together, our results suggest that high and functional expression of WRI1 play a key role in the oil-rich endosperms and the VYL motif is dispensable for WRI1 function.