Glycosyl transferases in family 61 mediate arabinofuranosyl transfer onto xylan in grasses.
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 α-(1,2)- and α-(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 α-(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 α-(1,3)-arabinosyltransferase activity. Thus, GT61 proteins play a key role in arabinoxylan biosynthesis and therefore in the evolutionary divergence of grass cell walls.
Department of Biochemistry,  University of Cambridge, Cambridge CB2 1QW,  United Kingdom.
Nadine
N
Anders
Mark D
MD
Wilkinson
Alison
A
Lovegrove
Jacqueline
J
Freeman
Theodora
T
Tryfona
Till K
TK
Pellny
Thilo
T
Weimar
Jennifer C
JC
Mortimer
Katherine
K
Stott
John M
JM
Baker
Michael
M
Defoin-Platel
Peter R
PR
Shewry
Paul
P
Dupree
Rowan A C
RA
Mitchell
D001089:Arabinose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D056625:Endosperm / Q000378:metabolism; D016695:Glycosyltransferases / Q000378:metabolism*; D006720:Homozygote; D030821:Plants, Genetically Modified; D006109:Poaceae / Q000201:enzymology*; D034622:RNA Interference; D014990:Xylans / Q000737:chemistry / Q000378:metabolism*
D014990:Xylans; C431714:arabinofuranose; D001089:Arabinose; D016695:Glycosyltransferases