title: Analysis of the Arabidopsis IRX9/IRX9-L and IRX14/IRX14-L pairs of glycosyltransferase genes reveals critical contributions to biosynthesis of the hemicellulose glucuronoxylan.
abstract: 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.
authors.affiliation: School of Biological Sciences, University of Southampton, Boldrewood Campus, Southampton SO16 7PX, United Kingdom.
authors.forename: Ai-Min
authors.initials: AM
authors.lastname: Wu
authors.forename: Emma
authors.initials: E
authors.lastname: Hörnblad
authors.forename: Aline
authors.initials: A
authors.lastname: Voxeur
authors.forename: Lorenz
authors.initials: L
authors.lastname: Gerber
authors.forename: Christophe
authors.initials: C
authors.lastname: Rihouey
authors.forename: Patrice
authors.initials: P
authors.lastname: Lerouge
authors.forename: Alan
authors.initials: A
authors.lastname: Marchant
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D017343:Genes, Plant; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D009154:Mutation; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism*; D014990:Xylans / Q000096:biosynthesis*
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; D014990:Xylans; C038910:glucuronoxylan; C521260:IRX9 protein, Arabidopsis; D010430:Pentosyltransferases