Abstract
Secondary cell walls in fibers and tracheary elements constitute the most abundant biomass on the land. While a number of genes involved in the biosynthesis of secondary cell wall components have been identified so far, little is known about the molecular mechanisms underlying the coordinated expression of these genes. Here, we identified the Arabidopsis NAC domain protein, SND1 (for secondary wall–associated NAC domain protein), which is a key transcriptional activator regulating secondary cell wall synthesis in fibers. SND1 is expressed specifically in interfascicular fibers and xylary fibers in stems and dominant repression of SND1 causes a drastic reduction in the secondary wall thickening of fibers. Ectopic overexpression of SND1 results in activation of the expression of secondary cell wall biosynthetic genes, leading to massive deposition of secondary cell walls in non-fiber cells.
