Genome-Wide Profiling of Soybean WRINKLED1 Transcription Factor Binding Sites Provides Insight into the Regulation of Fatty Acid and Triacylglycerol Biosynthesis Program in Seeds

Abstract

ABSTRACTUnderstanding the regulatory mechanisms controlling seed lipid accumulation provides opportunities for the development of new crops with enhanced oil levels. The WRINKLED1 transcription factor (WRI1 TF) is a central regulator of lipid biosynthesis in many plant species. We characterized the genome-wide binding profile of soybean (Gm)WRI1 and showed that the TF directly regulates many genes required for the fatty acid and triacylglycerol biosynthesis pathway. We showed that GmWRI1 binds primarily to regions downstream of target gene transcription start sites. Regions bound by GmWRI1 were enriched for its canonical DNA binding element, the AW Box (CNTNGNNNNNNNCG), and another DNA element, the CNC Box (CNCCNCC), that shows some similarity to other characterized DNA motifs. Functional assays showed that both DNA elements are required to mediate transcriptional activation by GmWRI1. Comparison of genes targeted directly by GmWRI1 and by GmLEC1, a central regulator of the maturation phase of seed development, revealed that the two TFs act in a positive feedback subcircuit to control fatty acid and triacylglycerol biosynthesis. Our results provide new insights into the genetic circuitry by which GmWRI1 regulates fatty acid and triacylglycerol biosynthetic genes, and provides evidence that GmWRI1 contributes to establishing the regulatory state of the soybean embryo to promote oil accumulation.