CaLWD1 forms an MBW complex with CaAMS and CaMS188 to regulate pollen exine formation in pepper

Pollen wall formation is essential for male reproduction in flowering plants. Although several core regulators of pollen wall development have been identified, whether WD40 proteins, which often act as protein interaction scaffolds, contribute to this process remains unclear. Here, we identified CaLWD1 (LIGHT-REGULATED WD 1), a WD40 gene highly expressed during early anther development in pepper (Capsicum annuum). CaLWD1 transcripts accumulated mainly in the tapetum and microspores. Silencing CaLWD1 disrupted the outer exine structure and resulted in male sterility. Transcriptomic and metabolomic analyses showed that CaLWD1 silencing significantly reduced the expression of genes involved in fatty acid metabolism and sporopollenin biosynthesis and decreased the accumulation of fatty acid metabolites. CaLWD1 interacted with CaAMS and CaMS188 to form a MYB-bHLH-WD40 (MBW) complex and enhanced CaAMS- and CaMS188-mediated transcriptional activation of CaFAR2 and CaCYP703A2. CaLWD1 was also directly regulated by CaMS188, and this regulation was further strengthened by the CaAMS-CaMS188 interaction, forming a feed-forward module. These findings reveal a CaLWD1-mediated regulatory module controlling pepper exine formation and define a role for WD40 proteins and MBW complexes in pollen wall development.