Roles of the XTH protein family in the expanding cell
Roles of the XTH protein family in the expanding cell
复制标题
DOI：
10.1007/7089_2006_072
复制
发表时间：
2006
期刊：
影响因子：
--
通讯作者：
K. Nishitani;K. Vissenberg
中科院分区：
文献类型：
--
作者：
K. Nishitani;K. Vissenberg
由于木葡聚糖被认为是细胞壁中重要的结构多糖， 使相邻的纤维素微纤丝相互连接，在细胞膨胀期间修饰木葡聚糖的酶 这个过程受到很多关注。其中一种酶是木葡聚糖内切转葡糖基酶/水解酶（XTH）， 糖苷水解酶家族16的一个亚组。迄今为止检测的XTH蛋白显示内糖基转移酶 (XET)、水解酶（XEH）或对木葡聚糖的这两种活性。几种模式植物的基因组测序 物种的研究表明，XTH蛋白由大的多基因家族编码。综合分析 XTH基因表达的研究，以及基于功能缺失突变体的功能分析，提供了 支持这一假设的证据，即这些多基因家族的每个成员都有自己的作用。这 通过几个个体成员的不同底物特异性和pH依赖性来反映。表达 这些基因中的每一个都受到各种激素以及环境信号的精确调节。一些 这些成员似乎在促进细胞壁扩张中是关键的并且因此对于细胞扩张是必需的， 而其它的则需要用于在已经完成膨胀过程的细胞中构建细胞壁。
Since xyloglucan is believed to be an important structural polysaccharide in the cell wall, possibly interconnecting adjacent cellulose microfibrils, enzymes that modify xyloglucan during the cell expansion process receive much attention. One of the enzymes is xyloglucan endotransglucosylase/hydrolase (XTH), a subgroup of glycoside hydrolase family 16. XTH proteins examined so far display endotransglycosylase (XET), hydrolase (XEH), or both activities towards xyloglucans. Genome sequencing of several model plant species has revealed that XTH proteins are encoded by large multigene families. Comprehensive analyses of XTH gene expression, together with functional analyses based on loss-of-function mutants, have provided evidence in support of the hypothesis that each member of these multigene families has its own role. This is reflected by different substrate specificities and pH dependencies of several individual members. Expression of each of these genes is precisely regulated by various hormones as well as by environmental signals. Some members appear to be critical in promoting cell wall expansion and are therefore essential for cell expansion, whereas others are required for construction of cell walls in cells that have completed the expansion process.