Molecular Basis of Plant Oil Biosynthesis: Insights Gained From Studying the WRINKLED1 Transcription Factor

Abstract

Most plant species generate and store triacylglycerol (TAG) in their seeds, serving as a core supply of carbon and energy to support seedling development. Plant seed oils have a wide variety of applications, from being essential for human diets to serving as industrial renewable feedstock. WRINKLED1 (WRI1) transcription factor plays a central role in the transcriptional regulation of plant fatty acid biosynthesis. Since the discovery of Arabidopsis WRI1 gene (AtWRI1) in 2004, the function of WRI1 in plant oil biosynthesis has been studied intensively. In recent years, the identification of WRI1 co-regulators and deeper investigations of the structural features and molecular functions of WRI1 have advanced our understanding of the mechanism of the transcriptional regulation of plant oil biosynthesis. These advances also help pave the way for novel approaches that will better utilize WRI1 for bioengineering oil production in crops.

Keywords: WRI1; intrinsically disordered region; plant oil biosynthesis; post-translational modifications; protein stability; protein–protein interaction; transcription factor.

Figure 1

AtWRI1 structural characteristics and molecular mechanism of AtWRI1-regulated gene expression. (A) Schematic diagram of AtWRI1. AtWRI1 protein comprises of two AP2 domains, three intrinsically disordered regions (IDRs), a functional motif of “VYL”, the transactivation domain (TAD), the 14-3-3 and E3 ligase adaptor (BPM) binding motifs, the PEST motif, the ubiquitination sites, and the KIN10 phosphorylation sites. (B) Regulatory mechanism of AtWRI1 target genes. LEC1, LEC2, and FUS3 are positive regulators which mediate AtWRI1 expression. MYB89 acts as a negative regulator of AtWRI1 expression. At the protein level, AtWRI1 is regulated by post-translational modifications (such as phosphorylation and ubiquitination) and AtWRI1-interacting regulators, such as 14-3-3s, mediator subunit 15 (MED15), BPMs, and kinase KIN10. In the perception of environmental or developmental signals, the regulators fine-tune the protein stability and transcriptional activity of AtWRI1, through protein complex assembly and modifications, leading to mediation of the expression of AtWRI1 target genes.