Elucidation of molecular mechanism by which plant constructs cell-type specific cell-wall architecture

木葡聚糖内切转葡糖基酶/水解酶（XTH）是涉及纤维素/木葡聚糖框架的构建和重构的一类酶。在拟南芥基因组中发现了XTH基因家族的33个成员，但它们的作用仍不清楚。在这项研究中，我们分析了组织特异性和生长阶段依赖的启动子：：GUS融合构建的四个拟南芥XTH基因，AtXTH 17，-18，-19，和-20，这是一个植物遗传学上密切相关的另一个表达谱。AtXTH 17和AtXTH 18在根伸长和分化区的所有细胞类型中表达，而AtXTH 19在顶端分裂和伸长区以及分化区中表达，并受到生长素的上调。AtXTH 20在根的基部成熟区域的维管组织中特异性表达。该表达分析还公开了在表达水平上保守的顺式调节序列。 ...更多信息 在四个基因中，并负责根特异性表达谱。接下来，我们检查了其中每个拟南芥XTH基因被破坏的突变体的表型，以鉴定该基因家族的每个成员的作用。这是使用反向遗传方法进行的，并公开了AtXTH 27基因的两个功能丧失突变体，xth 27 -1和xth 27 -2。第一叶的第三脉中出现了短形的导管分子，减少了第一叶的第三脉数量。在该突变体的成熟莲座状叶片中，还观察到黄色的类似病变的斑点。pXTH 27：：GUS融合基因在莲座叶未成熟的导管分子中广泛表达。AtXTH 27 mRNA在莲座叶中的表达水平最高，在叶扩展过程中观察到，当导管元件伸长。这些发现表明AtXTH 27在拟南芥莲座叶中的导管元件的产生过程中起着至关重要的作用。这些结果表明，四个XTH基因，这是由基因复制产生的，已经多样化的表达谱在这样一种方式，以负责特定的生理作用，在细胞壁动力学的根。少

Xyloglucan endotransglucosylase/hydrolases (XTHs) are a class of enzymes that are implicated in the construction and restructuring of the cellulose/xyloglucan framework. Thirty-three members of the XTH gene family are found in the genome of Arabidopsis thaliana, but their roles remain unclear. In this research we have analyzed the tissue-specific and growth stage-dependent expression profiles of promoter::GUS fusion constructs for four Arabidopsis XTH genes, AtXTH17, -18, -19, and -20, which are phylogenetically closely related to one another. AtXTH17 and AtXTH18 were expressed in all cell types in the elongating and differentiating region of the root, while AtXTH19 was expressed in the apical dividing and elongating regions, as well as in the differentiation zone, and was up-regulated by auxin. In contrast, AtXTH20 was specifically expressed in vascular tissues in the basal mature region of the root. This expression analysis also disclosed cis-regulatory sequences that are conserved a … More mong the four genes, and are responsible for the root-specific expression profile. Next, we examined phenotypes of mutants in which each of the Arabidopsis XTH genes was disrupted, to identify the role of each member of this gene family, This was undertaken using a reverse genetic approach, and disclosed two loss-of-function mutants for the AtXTH27 gene, xth27-1 and xth27-2. These exhibited short-shaped tracheary elements in tertiary veins, and reduced the number of tertiary veins in the first leaf. In mature rosette leaves of the mutant, yellow lesion-mimic spots were also observed. Extensive expression of the pXTH27::GUS fusion gene was observed in immature tracheary elements in the rosette leaves. The highest level of AtXTH27 mRNA expression in the rosette leaves was observed during leaf expansion, when the tracheary elements were elongating. These findings indicate that AtXTH27 plays an essential role during the generation of tracheary elements in the rosette leaves of Arabidopsis. These results indicate that the four XTH genes, which were generated by gene duplication, have diversified their expression profile within the root in such a way to take responsibility for particular physiological roles in the cell wall dynamics. Less