Transcription activator that binds to the secondary wall NAC binding element (SNBE), 5'-(T/A)NN(C/T)(T/C/G)TNNNNNNNA(A/C)GN(A/C/T)(A/T)-3', in the promoter of target genes (e.g. genes involved in secondary wall biosynthesis, cell wall modification such as xylan accumulation, and programmed cell death) (PubMed:20935069, PubMed:20488898, PubMed:22037706, PubMed:21284754). Involved in xylem formation in roots and shoots, especially regulating protoxylem vessel differentiation by promoting immature xylem vessel-specific genes expression (PubMed:16103214, PubMed:18445131, PubMed:20488898, PubMed:21498679, PubMed:21284754). Can activate the expression of several genes including XCP1, MYB46, NAC010/SND3, MYB103, MYB58, MYB63, MYB83, KNAT7, ASL19 and ASL20 (PubMed:17890373, PubMed:19088331, PubMed:18952777, PubMed:19122102, PubMed:19808805, PubMed:20935069, PubMed:21284754). Required for the soilborne fungal pathogen Verticillium longisporum-induced transdifferentiation of chloroplast-containing bundle sheath cells to functional xylem elements leading to stunted growth, vein clearing, and leaf chloroses, as well as xylem hyperplasia within the vasculature of leaves, hypocotyls, and roots due to reinitiation of cambial activity and transdifferentiation of xylem parenchyma cells. This developmental reprogramming mediates also an increased drought stress tolerance. Forms homodimer and heterodimers with other VND proteins (e.g. NAC037/VND1, NAC076/VND2 and NAC105/VND3) via their N-termini (PubMed:18445131). Interacts with NAC083/VNI2 (PubMed:20388856). Expressed in developing protoxylems in roots and shoots (PubMed:16103214, PubMed:16581911, PubMed:17565617, PubMed:18952777). Detected in root protoxylem poles and in vessels of protoxylems, outermost metaxylems, inner metaxylems, shoots and hypocotyls. Expressed in roots, hypocotyls, cotyledons and leaves (PubMed:18445131). Accumulates in the xylem but not in interfascicular fibers or pith cells in inflorescence stems. Present in developing vessels of the secondary xylem in roots undergoing secondary growth (PubMed:18952777). Predominantly expressed in immature xylem vessels, only in some cells just beside xylem vessels. Also present in various vascular cells of older part of the roots, near the location of emergence of the lateral roots. By brassinosteroids (e.g. brassinolide BL), auxin (e.g. 2,4-dichlorphenoxyacetic acid 2,4-D) and cytokinin (e.g. kinetin), with a synergistic effect (PubMed:16103214, PubMed:22345435). Up-regulated in a feed-back loop by ASL20 (PubMed:19088331). Levels are monitored by proteasome-mediated degradation (PubMed:18445131). Repressed by WEE1 upon replication stress to prevent premature tracheary element differentiation (PubMed:21498679). Accumulates during infection by the soilborne fungal pathogen Verticillium longisporum, especially in tissues undergoing de novo xylem formation (PubMed:23023171). The NAC domain includes a DNA binding domain and a dimerization domain. Defects in protoxylem vessel formation in seedling roots. Belongs to the plant vascular related NAC-domain protein family.