PT - JOURNAL ARTICLE AU - Gille, Sascha AU - de Souza, Amancio AU - Xiong, Guangyan AU - Benz, Monique AU - Cheng, Kun AU - Schultink, Alex AU - Reca, Ida-Barbara AU - Pauly, Markus TI - <em>O</em>-Acetylation of <em>Arabidopsis</em> Hemicellulose Xyloglucan Requires AXY4 or AXY4L, Proteins with a TBL and DUF231 Domain AID - 10.1105/tpc.111.091728 DP - 2011 Nov 01 TA - The Plant Cell PG - 4041--4053 VI - 23 IP - 11 4099 - http://www.plantcell.org/content/23/11/4041.short 4100 - http://www.plantcell.org/content/23/11/4041.full SO - Plant Cell2011 Nov 01; 23 AB - In an Arabidopsis thaliana forward genetic screen aimed at identifying mutants with altered structures of their hemicellulose xyloglucan (axy mutants) using oligosaccharide mass profiling, two nonallelic mutants (axy4-1 and axy4-2) that have a 20 to 35% reduction in xyloglucan O-acetylation were identified. Mapping of the mutation in axy4-1 identified AXY4, a type II transmembrane protein with a Trichome Birefringence-Like domain and a domain of unknown function (DUF231). Loss of AXY4 transcript results in a complete lack of O-acetyl substituents on xyloglucan in several tissues, except seeds. Seed xyloglucan is instead O-acetylated by the paralog AXY4like, as demonstrated by the analysis of the corresponding T-DNA insertional lines. Wall fractionation analysis of axy4 knockout mutants indicated that only a fraction containing xyloglucan is non-O-acetylated. Hence, AXY4/AXY4L is required for the O-acetylation of xyloglucan, and we propose that these proteins represent xyloglucan-specific O-acetyltransferases, although their donor and acceptor substrates have yet to be identified. An Arabidopsis ecotype, Ty-0, has reduced xyloglucan O-acetylation due to mutations in AXY4, demonstrating that O-acetylation of xyloglucan does not impact the plant’s fitness in its natural environment. The relationship of AXY4 with another previously identified group of Arabidopsis proteins involved in general wall O-acetylation, reduced wall acetylation, is discussed.