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 at low levels in stems, roots and siliques (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 interfascicular fibers. Accumulates in the developing secondary xylem of roots. Slightly induced by UV light (PubMed:9839469). Triggered by salicylic acid and jasmonic acid (PubMed:16463103). 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.