Transcription factor involved in the regulation of tiller bud outgrowth, but does not seems to regulate tiller bud initiation (PubMed:17888111). Possesses transactivation activity in yeast (PubMed:17888111). Involved in the regulation of plant architecture and grain yield (PubMed:29365136). Acts as negative regulator of plant height and flowering time (PubMed:25754802). Regulates directly key genes of the gibberellin (GA) pathway by binding to their promoters (PubMed:25754802). Positively regulates leaf senescence in an age-dependent manner (PubMed:28500268). Activates directly the expression of the chlorophyll degradation genes SGR and NYC3 (PubMed:28500268). Regulates positively the level of abscisic acid (ABA) by directly up-regulating the expression of the ABA biosynthetic genes NCED3 and ZEP, and down-regulating the ABA catabolic gene CYP707A5/ABA8OX1 (PubMed:28500268). Promotes salt-induced cell death accompanied by the loss of plasma membrane integrity, nuclear DNA fragmentation, and changes of caspase-like activity (PubMed:29436050). Targets genes that encoded a reactive oxygen species (ROS) scavenger COX11 and a caspase-like protease AP37 (PubMed:29436050). Activates the potassium efflux channels GORK and SKOR (PubMed:29436050). Acts as positive regulator of drought and salt tolerance through ABA-mediated pathways (PubMed:31637532). Acts as negative regulator of root growth (PubMed:31389120). Functions as an upstream integrator of auxin and cytokinin signals that affect CROWN ROOTLESS (CRL) and cyclin-dependent protein kinase (CDK) genes to regulate cell division during root development (PubMed:31389120). Binds directly to the promoters of the auxin inactivation-related genes GH3.6 and GH3.8, the auxin signaling-related gene ARF25, and the cytokinin oxidase gene CKX4 (PubMed:31389120). Activates directly the expressions of the 1-aminocyclopropane-1-carboxylate oxidase genes ACO1 and ACO3, enhancing ethylene synthesis, and then retarding seedling establishment (PubMed:34367219). Expressed in roots, tiller buds, stems, leaves, lamina joints and the young husks (PubMed:17888111). Expressed in embryos, coleoptiles, radicles, leaf pulvinus, ligules, panicles, palea and lemma, anthers, and the internode of the peduncles (PubMed:25754802). Expressed in young leaves, root meristems, florescence meristems and young spikelets (PubMed:25754802). In 5-day-old seedling, expressed in the maturation zone of roots, and later in the whole root tip. In 9- to 13-day-old plants, expressed mainly in the elongation zone of roots. In 14-day-old plants, expressed in the whole root tip, the apex and base of lateral roots, the lateral root primordia and crown roots. Up-regulated during leaf senescence (PubMed:28500268). Induced by salt stress (PubMed:29436050). The NAC domain includes a DNA binding domain and a dimerization domain. The gain-of-function mutant plants Ostil1 (T-DNA activation tagging) exhibit increased tiller number, enlarged tiller angle and semidwarf phenotype (PubMed:17888111). Overexpression of NAC4 shortens plant height (PubMed:25754802). Plants overexpressing NAC4 exhibit early leaf senescence (PubMed:28500268). Truncated N-terminus.