Mechanistic insights into WRKY transcription factor-mediated regulation of fruit pigmentation.

WRKY transcription factors are key regulators of plant transcriptional networks and have emerged as important modulators of fruit pigmentation. This review summarizes recent advances in understanding the molecular mechanisms by which WRKY transcription factors regulate the biosynthesis, degradation, and interconversion of major fruit pigments, including carotenoids, chlorophylls, anthocyanins, and betalains, primarily through W-box-dependent transcriptional regulation of target genes. WRKY proteins function as integrators of multiple signaling pathways, linking environmental cues such as light, temperature, water status, and nutrient availability with endogenous signals, including hormone signaling and reactive oxygen species (ROS), thereby modulating pigment metabolism during fruit development and ripening. In addition, WRKY transcription factors interact with key regulatory proteins, particularly MYB and bHLH transcription factors, forming transcriptional networks that fine-tune pigment biosynthesis. These regulatory processes are further shaped by MAPK signaling cascades, protein-protein interactions, and feedback regulatory loops. Collectively, WRKY transcription factors act as important components of integrated signaling and transcriptional networks governing fruit pigment metabolism, providing mechanistic insights into the coordination of physiological processes and metabolic regulation.