title: XTH31, encoding an in vitro XEH/XET-active enzyme, regulates aluminum sensitivity by modulating in vivo XET action, cell wall xyloglucan content, and aluminum binding capacity in Arabidopsis.
abstract: Xyloglucan endohydrolase (XEH) and xyloglucan endotransglucosylase (XET) activities, encoded by xyloglucan endotransglucosylase-hydrolase (XTH) genes, are involved in cell wall extension by cutting or cutting and rejoining xyloglucan chains, respectively. However, the physiological significance of this biochemical activity remains incompletely understood. Here, we find that an XTH31 T-DNA insertion mutant, xth31, is more Al resistant than the wild type. XTH31 is bound to the plasma membrane and the encoding gene is expressed in the root elongation zone and in nascent leaves, suggesting a role in cell expansion. XTH31 transcript accumulation is strongly downregulated by Al treatment. XTH31 expression in yeast yields a protein with an in vitro XEH:XET activity ratio of >5000:1. xth31 accumulates significantly less Al in the root apex and cell wall, shows remarkably lower in vivo XET action and extractable XET activity, has a lower xyloglucan content, and exhibits slower elongation. An exogenous supply of xyloglucan significantly ameliorates Al toxicity by reducing Al accumulation in the roots, owing to the formation of an Al-xyloglucan complex in the medium, as verified by an obvious change in chemical shift of (27)Al-NMR. Taken together, the data indicate that XTH31 affects Al sensitivity by modulating cell wall xyloglucan content and Al binding capacity.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xiao Fang
authors.initials: XF
authors.lastname: Zhu
authors.forename: Yuan Zhi
authors.initials: YZ
authors.lastname: Shi
authors.forename: Gui Jie
authors.initials: GJ
authors.lastname: Lei
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Fry
authors.forename: Bao Cai
authors.initials: BC
authors.lastname: Zhang
authors.forename: Yi Hua
authors.initials: YH
authors.lastname: Zhou
authors.forename: Janet
authors.initials: J
authors.lastname: Braam
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.forename: Xiao Yan
authors.initials: XY
authors.lastname: Xu
authors.forename: Chuan Zao
authors.initials: CZ
authors.lastname: Mao
authors.forename: Yuan Jiang
authors.initials: YJ
authors.lastname: Pan
authors.forename: Jian Li
authors.initials: JL
authors.lastname: Yang
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
authors.forename: Shao Jian
authors.initials: SJ
authors.lastname: Zheng
mesh_terms: D000535:Aluminum / Q000633:toxicity*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D002614:Chelating Agents / Q000032:analysis / Q000378:metabolism; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000032:analysis / Q000378:metabolism*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009928:Organ Specificity; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D011134:Polysaccharides / Q000032:analysis / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D014990:Xylans / Q000032:analysis / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002614:Chelating Agents; D005936:Glucans; D011134:Polysaccharides; D011993:Recombinant Fusion Proteins; D014990:Xylans; C029353:xyloglucan; C007916:hemicellulose; D000535:Aluminum; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase