Analysis of the Arabidopsis IRX9/IRX9-L and IRX14/IRX14-L Pairs of Glycosyltransferase Genes Reveals Critical Contributions to Biosynthesis of the Hemicellulose Glucuronoxylan

• Published in: Plant physiology (Bethesda) Vol. 153; no. 2; pp. 542 - 554
• Main Authors: Wu, Ai-Min, Hörnblad, Emma, Voxeur, Aline, Gerber, Lorenz, Rihouey, Christophe, Lerouge, Patrice, Marchant, Alan
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01-06-2010; Oxford University Press ; American Society of Plant Biologists
• Subjects: Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biosynthesis; Botanik; Botany; Cell Wall - chemistry; Cell walls; DNA, Bacterial - genetics; Enzymes; Exons; FOCUS ISSUE ON PLANT CELL WALLS; Genes; Genes, Plant; Genetic Complementation Test; Genetics; Genetik; Life Sciences; Mathematical functions; Mutagenesis, Insertional; Mutation; Pentosyltransferases - genetics; Pentosyltransferases - metabolism; Phenotypes; Plant cells; Plants; Xylans; Xylans - biosynthesis
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.110.154971

The hemicellulose glucuronoxylan (GX) is a major component of plant secondary cell walls. However, our understanding of GX synthesis remains limited. Here, we identify and analyze two new genes from Arabidopsis (Arabidopsis thaliana), IRREGULAR XYLEM9-LIKE (IRX9-L) and IRX14-LIKE (IRX14-L) that encode glycosyltransferase family 43 members proposed to function during xylan backbone elongation. We place IRX9-L and IRX14-L in a genetic framework with six previously described glycosyltransferase genes (IRX9, IRX10, IRX10-L, IRX14, FRAGILE FIBER8 [FRA8], and FRA8 HOMOLOG [F8H]) and investigate their function in GX synthesis. Double-mutant analysis identifies IRX9-L and IRX14-L as functional homologs of IRX9 and IRX14, respectively. Characterization of irx9 irx10 irx14 fra8 and irx9-L irx10-L irx14-L f8h quadruple mutants allows definition of a set of genes comprising IRX9, IRX10, IRX14, and FRA8 that perform the main role in GX synthesis during vegetative development. The IRX9-L, IRX10-L, IRX14-L, and F8H genes are able to partially substitute for their respective homologs and normally perform a minor function. The irx14 irx14-L double mutant virtually lacks xylan, whereas irx9 irx9-L and fra8 f8h double mutants form lowered amounts of GX displaying a greatly reduced degree of backbone polymerization. Our findings reveal two distinct sets of four genes each differentially contributing to GX biosynthesis.