The ability to make secondary cell walls was a pivotal step for vascular plants in their conquest of dry land. Here, we review recent molecular and genetic studies that reveal that a group of Arabidopsis (Arabidopsis thaliana) secondary wall-associated NAC domain transcription factors are master switches regulating a cascade of downstream transcription factors, leading to activation of the secondary wall biosynthetic program. Close homologs of the Arabidopsis secondary wall NACs and their downstream transcription factors exist in diverse taxa of vascular plants and some are functional orthologs of their Arabidopsis counterparts. There is evidence to suggest that the secondary wall NAC-mediated transcriptional regulation of secondary wall biosynthesis is a conserved mechanism throughout vascular plants.
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