Phase separation of MYB73 regulates seed oil biosynthesis in Arabidopsis

MYB family transcription factors (TFs) play crucial roles in plant development, metabolism, and responses to various stresses. However, whether MYB TFs are involved in regulating fatty acid biosynthesis in seeds remains largely elusive. Here, we demonstrated that transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing MYB73 exhibit altered FATTY ACID ELONGATION1 (FAE1) expression, seed oil content, and seed fatty acid composition. Electrophoretic mobility shift assays showed that FAE1 is a direct target of MYB73, and functional assays revealed that MYB73 represses FAE1 promoter activity. Transcriptomic analysis of the MYB73-overexpressing plants detected significant changes in the expression of genes involved in fatty acid biosynthesis and triacylglycerol assembly. Furthermore, MYB73 expression was responsive to abscisic acid (ABA), and ABA-responsive element binding factor 2 directly bound to the ABA-responsive element in the MYB73 promoter to activate its expression. Additionally, we determined that MYB73 exhibits the hallmarks of an intrinsically disordered protein and forms phase-separated condensates with liquid-like characteristics, which are important in regulating target gene expression. Together, our findings suggest that MYB73 condensate formation likely fine-tunes seed oil biosynthesis.