title: Loss of Arabidopsis GAUT12/IRX8 causes anther indehiscence and leads to reduced G lignin associated with altered matrix polysaccharide deposition.
abstract: GAlactUronosylTransferase12 (GAUT12)/IRregular Xylem8 (IRX8) is a putative glycosyltransferase involved in Arabidopsis secondary cell wall biosynthesis. Previous work showed that Arabidopsis irregular xylem8 (irx8) mutants have collapsed xylem due to a reduction in xylan and a lesser reduction in a subfraction of homogalacturonan (HG). We now show that male sterility in the irx8 mutant is due to indehiscent anthers caused by reduced deposition of xylan and lignin in the endothecium cell layer. The reduced lignin content was demonstrated by histochemical lignin staining and pyrolysis Molecular Beam Mass Spectrometry (pyMBMS) and is associated with reduced lignin biosynthesis in irx8 stems. Examination of sequential chemical extracts of stem walls using 2D (13)C-(1)H Heteronuclear Single-Quantum Correlation (HSQC) NMR spectroscopy and antibody-based glycome profiling revealed a reduction in G lignin in the 1 M KOH extract and a concomitant loss of xylan, arabinogalactan and pectin epitopes in the ammonium oxalate, sodium carbonate, and 1 M KOH extracts from the irx8 walls compared with wild-type walls. Immunolabeling of stem sections using the monoclonal antibody CCRC-M138 reactive against an unsubstituted xylopentaose epitope revealed a bi-lamellate pattern in wild-type fiber cells and a collapsed bi-layer in irx8 cells, suggesting that at least in fiber cells, GAUT12 participates in the synthesis of a specific layer or type of xylan or helps to provide an architecture framework required for the native xylan deposition pattern. The results support the hypothesis that GAUT12 functions in the synthesis of a structure required for xylan and lignin deposition during secondary cell wall formation.
authors.affiliation: Department of Plant Biology, University of Georgia Athens, GA, USA ; Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Zhangying
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Utku
authors.initials: U
authors.lastname: Avci
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tan
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; Department of Chemistry, University of Georgia Athens, GA, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Glushka
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Pattathil
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Eberhard
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA.
authors.forename: Tipton
authors.initials: T
authors.lastname: Sholes
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; Department of Biology, Lawrence University Appleton, WI, USA.
authors.forename: Grace E
authors.initials: GE
authors.lastname: Rothstein
authors.affiliation: Department of Plant Biology, University of Georgia Athens, GA, USA.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lukowitz
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; Department of Chemistry, University of Georgia Athens, GA, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Orlando
authors.affiliation: Department of Plant Biology, University of Georgia Athens, GA, USA ; Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia Athens, GA, USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory Oak Ridge, TN, USA ; Department of Biochemistry and Molecular Biology, University of Georgia Athens, GA, USA.
authors.forename: Debra
authors.initials: D
authors.lastname: Mohnen
keywords: anther dehiscence; lignin; pectin; secondary cell walls; wall glycan epitopes; xylan