A role for OVATE FAMILY PROTEIN1 (OFP1) and OFP4 in a BLH6-KNAT7 multi-protein complex regulating secondary cell wall formation in Arabidopsis thaliana.

Formation of secondary walls is a complex process that requires the coordinated and developmentally regulated expression of secondary wall biosynthetic genes. In Arabidopsis thaliana, a transcriptional network orchestrates the biosynthesis and deposition of the main SCW components in xylem and fiber cells. It was recently reported that interacting TALE homeodomain proteins BEL-LIKE HOMEODOMAIN6 (BLH6) and KNOTTED ARABIDOPSIS THALIANA7 (KNAT7) negatively regulate secondary cell wall formation in the interfascicular fibers of Arabidopsis inflorescence stems. Members of the Arabidopsis OVATE FAMILY PROTEIN (OFP) family of transcriptional regulators have been shown to physically interact in yeast with various KNAT and BLH proteins, forming a proposed TALE-OFP protein interaction network. This study presents molecular and genetic data indicating that OFP1 and OFP4, previously reported to interact with TALE homeodomain proteins, enhance the repression activity of BLH6, supporting a role for these OFPs as components of a putative multi-protein transcription regulatory complex containing BLH6 and KNAT7.