Required for secondary wall formation in fibers, especially in short days conditions. Promotes indole metabolism and transport (e.g. tryptophan, neoglucobrassicin and auxin (indole-3-acetic acid)). May prevent salicylic-acid (SA) accumulation. Also detected in transvacuolar strands. Mostly expressed in stems and hypocotyls, also present in seedlings, root, leaves, flowers and siliques. Ubiquitous, mostly expressed in vascular tissues and secondary wall-forming cells, including developing xylem vessels and fibers. In stems, defect in cell elongation resulting in dwarf and bushy plants with altered mechanical properties, as well as little to no secondary cell walls in fibers, including xylary and interfascicular fibers; these symptoms are partly reversed by continuous light conditions. At the flowering stage, red, dry and bent downwards stem apices. General repression of indole metabolism, including tryptophan, neoglucobrassicin and auxin (indole-3-acetic acid). Broad-spectrum resistance to vascular pathogens, including the bacteria Ralstonia solanacearum and Xanthomonas campestris pv. campestris, and the fungi Verticillium dahliae and Verticillium albo-atrum in a salicylic-acid- (SA-) dependent manner. SA accumulation in roots. Belongs to the drug/metabolite transporter (DMT) superfamily. Plant drug/metabolite exporter (P-DME) (TC 2.A.7.4) family.