Identification and evolution of a plant cell wall specific glycoprotein glycosyl transferase, ExAD

S.R. MOELLER, X. YI, S.M. VELÁSQUEZ, S. GILLE, P.L. MUNKE HANSEN, CHRISTIAN POULSEN, CARL ERIK OLSEN, M. REJZEK, H. PARSONS, Y. ZHANG, H.H. WANDALL, H. CLAUSEN, R. A. FIELD, M. PAULY, J.M. ESTEVEZ, J. HARHOLT, P. ULVSKOV, B. LARSEN PETERSEN

Scientific Reports

Nature

Lugar: London; Año: 2017

2045-2322

Extensins are plant cell wall glycoproteins that act as scaffolds for the deposition of the mainwall carbohydrate polymers, which are interlocked into the supramolecular wall structurethrough intra- and inter-molecular iso-di-tyrosine crosslinks within the extensin backbone. Inthe conserved canonical extensin repeat, Ser-Hyp4, serine and the consecutive C4-hydroxyprolines (Hyps) are substituted with an α-galactose and 1-5 β- or α-linkedarabinofuranoses (Arafs), respectively. These modifications are required for correct extendedstructure and function of the extensin network. Here, we identified a single Arabidopsisthaliana gene, At3g57630, in clade E of the inverting Glycosyltransferase family GT47 as acandidate for the transfer of Araf to Hyp-arabinofuranotriose (Hyp-β1,4Araf-β1,2Araf-β1,2Araf) side chains in an α-linkage, to yield Hyp-Araf4 which is exclusively found inextensins. T-DNA knock-out mutants of At3g57630 showed a truncated root hair phenotype,as seen for mutants of all hitherto characterized extensin glycosylation enzymes; both roothair and glycan phenotypes were restored upon reintroduction of At3g57630. At3g57630 wasnamed Extensin Arabinose Deficient transferase, ExAD, accordingly. The occurrence ofExAD orthologs within the Viridiplantae along with its? product, Hyp-Araf4, point to ExADbeing an evolutionary hallmark of terrestrial plants and charophyte green algae.