Probable O-acetyltransferase involved in the acetylation of cell wall polymers (both pectic and nonpectic polysaccharides) and of xylan during secondary wall biosynthesis. Catalyzes the O-acetylation of xyloglucan. Seems required for infection by the necrotrophic fungal pathogen Botrytis cinerea. Expressed in cells undergoing secondary wall thickeningin a SND1-dependent manner, such as xylem cells. Slightly elevated in the inflorescence stems (PubMed:21673009). Mainly observed in leaves and inflorescence stem tops, but present ubiquitously (PubMed:21212300). Decreased levels of acetylated cell wall polymers and lower amounts of acetic acid in single mutant. Increased tolerance toward the necrotrophic fungal pathogen Botrytis cinerea (PubMed:21212300). Severe growth phenotypes (e.g. dwarf and abnormal flower organs) associated with reduction in the secondary wall thickening and the stem mechanical strength in the quadruple mutant rwa1 rwa2 rwa3 rwa4 and characterized by reduced xylan acetylation and altered ratio of non-methylated to methylated glucuronic acid side chains. Absence of interfascicular fibers and xylem cells differentiation (PubMed:21673009, PubMed:24019426). The double mutant rwa2 rwa4 and triple mutants rwa2 rwa3 rwa4, rwa1 rwa2 rwa3 and rwa1 rwa2 rwa4 are also dwarfs with abnormal morphology. Altered O-acetylated xyloglucans (XyG) oligosaccharides (XyGOs) composition (PubMed:24019426). Belongs to the PC-esterase family. CASD1 subfamily.