AtBGAL10 Is the Main Xyloglucan β-Galactosidase in Arabidopsis, and Its Absence Results in Unusual Xyloglucan Subunits and Growth Defects
AtBGAL10 Is the Main Xyloglucan β-Galactosidase in Arabidopsis, and Its Absence Results in Unusual Xyloglucan Subunits and Growth Defects
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DOI：
10.1104/pp.111.192195
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发表时间：
2012-03-01
期刊：
影响因子：
7.4
通讯作者：
Zarra, Ignacio
中科院分区：
文献类型：
--
作者：
Sampedro, Javier;Gianzo, Cristina;Zarra, Ignacio
在生长的细胞中，木葡聚糖被认为连接纤维素微纤维并在壁延伸期间调节它们的分离。在拟南芥（Arabidopsis thaliana）中，显著比例的木葡聚糖侧链含有在O2处与α-木糖连接的β-半乳糖。在这项工作中，我们确定了AtBGAL 10（At 5g 63810）作为负责大部分β-半乳糖苷酶对木葡聚糖的活性的基因。发现来自bgal 10插入突变体的木葡聚糖含有大比例的不寻常亚基，如GLG和GLLG。这些亚基没有检测到bgal 10 xyl 1双突变体，缺乏β-半乳糖苷酶和α-木糖苷酶。来自bgal 10 xyl 1植物的木葡聚糖反而富集在XXLG/XLXG和XLLG亚基中。在这两种情况下，木葡聚糖组成的变化较大的内切葡聚糖酶可访问的部分。这些结果表明，在野生型植物中，作用于非还原性末端的糖苷酶消化大量的木葡聚糖，而缺乏这些活性的植物积累部分消化的亚基。在bgal 10和bgal 10 xyl 1中，角果和萼片较短，这一表型可以通过导致增强的木葡聚糖网络的过量非还原性末端来解释。此外，AtBGAL 10表达用启动子-报告基因构建体检查。在经历壁延伸或重塑的许多细胞类型中表达高，例如年轻的茎、分离区或发育中的脉管系统，显示出与α-木糖苷酶表达的良好相关性。
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 beta-galactose linked to alpha-xylose at O2. In this work, we identified AtBGAL10 (At5g63810) as the gene responsible for the majority of beta-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 beta-galactosidase and alpha-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 alpha-xylosidase expression.