The transcription factors PIF4 and PIF5 interact with WRINKLED1 to modulate fatty acid biosynthesis during seed maturation

Abstract PHYTOCHROME-INTERACTING FACTORS (PIFs), members of the basic helix-loop-helix (bHLH) transcription factor (TF) family, regulate various developmental processes in Arabidopsis (Arabidopsis thaliana). However, their involvement in fatty acid biosynthesis and seed maturation is largely unknown. WRINKLED1 (WRI1) is a pivotal TF regulating plant fatty acid biosynthesis. In this study, we identified WRI1 as an interacting partner of PIF4 and PIF5. PIF4 and PIF5, similar to WRI1, are expressed during seed maturation. Over-expressing PIF4 or PIF5 triggers increased seed fatty acid biosynthesis, while loss-of-function pif4 and pif5 mutants exhibit reduced seed fatty acid biosynthesis and delayed seed maturation. Further analysis revealed that PIF4 and PIF5 promote WRI1-dependent expression of fatty acid biosynthesis genes. Together, our findings suggest that PIF4 and PIF5 interact with WRI1, thereby promoting fatty acid biosynthesis gene expression and increasing fatty acid biosynthesis. This study reports a previously uncharacterized regulatory mechanism that fine-tunes seed fatty acid biosynthesis and seed maturation.