title: AtBGAL10 is the main xyloglucan β-galactosidase in Arabidopsis, and its absence results in unusual xyloglucan subunits and growth defects.
abstract: In growing cells, xyloglucan is thought to connect cellulose microfibrils and regulate their separation during wall extension. In Arabidopsis (Arabidopsis thaliana), a significant proportion of xyloglucan side chains contain β-galactose linked to α-xylose at O2. In this work, we identified AtBGAL10 (At5g63810) as the gene responsible for the majority of β-galactosidase activity against xyloglucan. Xyloglucan from bgal10 insertional mutants was found to contain a large proportion of unusual subunits, such as GLG and GLLG. These subunits were not detected in a bgal10 xyl1 double mutant, deficient in both β-galactosidase and α-xylosidase. Xyloglucan from bgal10 xyl1 plants was enriched instead in XXLG/XLXG and XLLG subunits. In both cases, changes in xyloglucan composition were larger in the endoglucanase-accessible fraction. These results suggest that glycosidases acting on nonreducing ends digest large amounts of xyloglucan in wild-type plants, while plants deficient in any of these activities accumulate partly digested subunits. In both bgal10 and bgal10 xyl1, siliques and sepals were shorter, a phenotype that could be explained by an excess of nonreducing ends leading to a reinforced xyloglucan network. Additionally, AtBGAL10 expression was examined with a promoter-reporter construct. Expression was high in many cell types undergoing wall extension or remodeling, such as young stems, abscission zones, or developing vasculature, showing good correlation with α-xylosidase expression.
authors.affiliation: Departamento de Fisiología Vegetal, Universidad de Santiago, Santiago de Compostela 15782, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Sampedro
authors.forename: Cristina
authors.initials: C
authors.lastname: Gianzo
authors.forename: Natalia
authors.initials: N
authors.lastname: Iglesias
authors.forename: Esteban
authors.initials: E
authors.lastname: Guitián
authors.forename: Gloria
authors.initials: G
authors.lastname: Revilla
authors.forename: Ignacio
authors.initials: I
authors.lastname: Zarra
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000201:enzymology / Q000235:genetics; D004789:Enzyme Activation; D035264:Flowers / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D005936:Glucans / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010802:Phylogeny; D010843:Pichia / Q000235:genetics; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D018547:Plant Stems / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D011401:Promoter Regions, Genetic; D014990:Xylans / Q000378:metabolism*; D014995:Xylosidases / Q000235:genetics* / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; D014990:Xylans; C029353:xyloglucan; C488782:XYL1 protein, Arabidopsis; D014995:Xylosidases; D001616:beta-Galactosidase