Master-Switches of Secondary Cell Wall Formation in Flax (Linum usitatissimum L.).

All vital processes in plants are regulated by a complex network of transcription factors. The formation of the cell wall, one of the key structures of plant cells that determines plant development and function, is tightly controlled. In particular, the main target genes regulated by transcription factors encode enzymes involved in polysaccharide metabolism, specifically their biosynthesis and modification. The transcriptional network governing secondary cell wall formation comprises the bulk of vascular and mechanical tissues, which together constitute a general component of wood. Despite overlapping main components, secondary cell walls in fibers and vessels are controlled by distinct master regulators. Flax phloem fibers form a tertiary cell wall composed mainly of cellulose and a small portion of pectins, with an absence of xylan and lignin. Formation of the tertiary cell wall requires the deposition of even a thin layer of secondary cell wall. For the first time, a comprehensive revision of VNS genes, belonging to the NAC family of transcription factors, has been performed in flax. The NST group of NAC transcription factors, potentially involved in secondary cell wall formation in both phloem and xylem fibers, has been identified. These genes represent valuable targets for both fundamental studies on cell wall biogenesis and molecular-genetic manipulation aimed at improving plant quality.