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

This article focuses on the regulatory role of PHYTOCHROME-INTERACTING FACTORS 4 and 5 (PIF4 and PIF5), members of the basic helix-loop-helix transcription factor family, in seed fatty acid biosynthesis and maturation in Arabidopsis thaliana. The study demonstrates that PIF4 and PIF5 physically interact with WRINKLED1 (WRI1), a key APETALA2 transcription factor regulating fatty acid biosynthesis, enhancing WRI1's transcriptional activity on target genes involved in fatty acid synthesis. Genetic analyses reveal that over-expression of PIF4 or PIF5 increases seed fatty acid content and seed size, while loss-of-function mutants show reduced fatty acid accumulation and delayed seed maturation, effects that are dependent on WRI1 function. Chromatin immunoprecipitation assays indicate that PIF4 and PIF5 are recruited to WRI1 target gene promoters in a WRI1-dependent manner, acting as co-activators to promote fatty acid biosynthesis gene expression. This study uncovers a previously uncharacterized mechanism by which PIF4 and PIF5 fine-tune seed oil accumulation and maturation through interaction with WRI1.