Xylan acetyltransferase required for 2-O- and 3-O-monoacetylation of xylosyl residues in xylan (PubMed:23659919, PubMed:30083810, PubMed:32354790). Catalyzes the 2-O-acetylation of xylan, followed by nonenzymatic acetyl migration to the O-3 position, resulting in products that are monoacetylated at both O-2 and O-3 positions (PubMed:32354790). Is necessary for the formation of the functional xylem, which is required for water transport to aerial tissues (PubMed:21408051, PubMed:23340742). Acts as negative regulator of cold acclimation (PubMed:17316173). Involved in water economy as well as salt tolerance (PubMed:19061521, PubMed:19054354). Regulated at the transcriptional level by NAC012/SND1 (Probable). Expressed in roots, young seedlings, leaves, stems, flowers and developing siliques. Specifically expressed in secondary wall-forming cells, xylem and interfascicular fibers. Not induced during cold acclimation. Strong constitutive freezing tolerance. Altered vascular apparatus morphology, and reduced xylan acetylation and secondary wall thickening. Reduced rosette-leaf growth and inflorescence size. Contains 2 motifs that are conserved in esterases, but it is unlikely that this protein belongs to the catalytically active pectin esterases. Belongs to the PC-esterase family. TBL subfamily.