Transcriptional activator that binds DNA to the AC cis-elements 5'-ACCTACC-3', 5'-ACCAACC-3' and 5'-ACCTAAC-3' of promoters and specifically activates lignin biosynthetic genes during secondary wall formation mediated by SND1. Expressed in leaves (PubMed:9839469). Specifically expressed in fibers and vessels undergoing secondary wall thickening, especially in inflorescence stems (PubMed:19122102). In nonelongating internodes, highly expressed in interfascicular fibers and xylem cells but not in parenchymatous pith cells. In elongating internodes, predominantly expressed in protoxylem vessels. Slightly induced by light (PubMed:9839469). Regulated by the SND1 close homologs NST1, NST2, VND6, and VND7 and their downstream targets MYB46 and MYB83 (PubMed:19122102, PubMed:22197883). Reduction in secondary wall thickening and lignin content.