title: The Arabidopsis irregular xylem8 mutant is deficient in glucuronoxylan and homogalacturonan, which are essential for secondary cell wall integrity.
abstract: The secondary cell wall in higher plants consists mainly of cellulose, lignin, and xylan and is the major component of biomass in many species. The Arabidopsis thaliana irregular xylem8 (irx8) mutant is dwarfed and has a significant reduction in secondary cell wall thickness. IRX8 belongs to a subgroup of glycosyltransferase family 8 called the GAUT1-related gene family, whose members include GAUT1, a homogalacturonan galacturonosyltransferase, and GAUT12 (IRX8). Here, we use comparative cell wall analyses to show that the irx8 mutant contains significantly reduced levels of xylan and homogalacturonan. Immunohistochemical analyses confirmed that the level of xylan was significantly reduced in the mutant. Structural fingerprinting of the cell wall polymers further revealed that irx8 is deficient in glucuronoxylan. To explore the biological function of IRX8, we crossed irx8 with irx1 (affecting cellulose synthase 8). The homozygous irx1 irx8 exhibited severely dwarfed phenotypes, suggesting that IRX8 is essential for cell wall integrity during cellulose deficiency. Taken together, the data presented show that IRX8 affects the level of glucuronoxylan and homogalacturonan in higher plants and that IRX8 provides an important link between the xylan polymer and the secondary cell wall matrix and directly affects secondary cell wall integrity.
authors.affiliation: Carnegie Institution, Stanford, California 94305, USA.
authors.forename: Staffan
authors.initials: S
authors.lastname: Persson
authors.forename: Kerry Hosmer
authors.initials: KH
authors.lastname: Caffall
authors.forename: Glenn
authors.initials: G
authors.lastname: Freshour
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Hilley
authors.forename: Stefan
authors.initials: S
authors.lastname: Bauer
authors.forename: Patricia
authors.initials: P
authors.lastname: Poindexter
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.forename: Debra
authors.initials: D
authors.lastname: Mohnen
authors.forename: Chris
authors.initials: C
authors.lastname: Somerville
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D002458:Cell Fractionation; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D003433:Crosses, Genetic; D005964:Glucosyltransferases / Q000235:genetics / Q000502:physiology; D016695:Glycosyltransferases / Q000235:genetics* / Q000502:physiology; D007150:Immunohistochemistry; D009154:Mutation; D010368:Pectins / Q000378:metabolism*; D010641:Phenotype; D018547:Plant Stems / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014990:Xylans / Q000378:metabolism*; D052584:Xylem / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D014990:Xylans; C038910:glucuronoxylan; D010368:Pectins; D016695:Glycosyltransferases; C502807:Irx8 protein, Arabidopsis; C420969:CESA8 protein, Arabidopsis; D005964:Glucosyltransferases; C003181:polygalacturonic acid