Glycosyl transferases in family 61 mediate arabinofuranosyl transfer onto xylan in grasses

Anders, N., Wilkinson, M. D., Lovegrove, A., Freeman, J., Tryfona, T., Pellny, T. K., Weimar, T., Mortimer, J. C., Stott, K., Baker, J. M., Defoin-Platel, M., Shewry, P., Dupree, P. and Mitchell, R. A. C. (2012) Glycosyl transferases in family 61 mediate arabinofuranosyl transfer onto xylan in grasses. Proceedings of the National Academy of Sciences, 109 (3). pp. 989-993. ISSN 0027-8424 doi: 10.1073/pnas.1115858109

Abstract/Summary

Xylan, a hemicellulosic component of the plant cell wall, is one of the most abundant polysaccharides in nature. In contrast to dicots, xylan in grasses is extensively modified by alpha-(1,2)- and alpha-(1,3)-linked arabinofuranose. Despite the importance of grass arabinoxylan in human and animal nutrition and for bioenergy, the enzymes adding the arabinosyl substitutions are unknown. Here we demonstrate that knocking-down glycosyltransferase (GT) 61 expression in wheat endosperm strongly decreases alpha-(1,3)-linked arabinosyl substitution of xylan. Moreover, heterologous expression of wheat and rice GT61s in Arabidopsis leads to arabinosylation of the xylan, and therefore provides gain-of-function evidence for alpha-(1,3)-arabinosyltransferase activity. Thus, GT61 proteins play a key role in arabinoxylan biosynthesis and therefore in the evolutionary divergence of grass cell walls.