The cotton β-galactosyltransferase 1 (GalT1) that galactosylates arabinogalactan proteins participates in controlling fiber development
The cotton β-galactosyltransferase 1 (GalT1) that galactosylates arabinogalactan proteins participates in controlling fiber development
复制标题
棉花 β-半乳糖基转移酶 1 (GalT1) 可半乳糖基化阿拉伯半乳聚糖蛋白，参与控制纤维发育
DOI：
10.1111/tpj.13434
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发表时间：
2017-03-01
期刊：
影响因子：
7.2
通讯作者：
Li, Xue-Bao
中科院分区：
文献类型：
--
作者：
Qin, Li-Xia;Chen, Yun;Li, Xue-Bao
阿拉伯半乳聚糖蛋白（AGPs）是一种高度糖基化的蛋白，在植物的多种发育过程中起关键作用。ii型AG聚糖，主要与蛋白质骨架的羟脯氨酸残基o键连接，占AGP的95% w/w，但其功能仍不清楚。棉纤维是种子表皮上的极长单细胞毛状体；然而，对纤维细胞发育调控的分子基础知之甚少。在这里，我们鉴定了CAZy糖基转移酶31 （GT31）家族成员GhGalT1在棉纤维发育中的作用。过表达GhGalT1的转基因棉花的纤维长度比野生型短，而GhGalT1沉默系的纤维长度比野生型明显增加。GhGalT1转基因棉花纤维中AGPs的碳水化合物部分发生了改变。与野生型相比，GhGalT1过表达纤维中AG聚糖的半乳糖：阿拉伯糖比例较高，而GhGalT1沉默系中AG聚糖的半乳糖：阿拉伯糖比例较低。GhGalT1的过表达上调了一系列细胞壁相关基因的转录水平，尤其是fasiclin样AGP （FLA）骨干基因。酶活性分析表明，GhGalT1是一种β -1,3-半乳糖基转移酶（β -1,3- galt），参与AGPs ii型AG聚糖的β -1,3-半乳糖主链的生物合成。我们还发现GhGalT1可以与其他棉花GT31家族成员形成同源和异源二聚体，以促进AGPs的AG聚糖组装。因此，我们的数据表明GhGalT1通过控制agp的糖基化来影响棉纤维的发育，特别是FLAs。
Arabinogalactan proteins (AGPs) are highly glycosylated proteins that play pivotal roles in diverse developmental processes in plants. Type-II AG glycans, mostly O-linked to the hydroxyproline residues of the protein backbone, account for up to 95% w/w of the AGP, but their functions are still largely unclear. Cotton fibers are extremely elongated single-cell trichomes on the seed epidermis; however, little is known of the molecular basis governing the regulation of fiber cell development. Here, we characterized the role of a CAZy glycosyltransferase 31 (GT31) family member, GhGalT1, in cotton fiber development. The fiber length of the transgenic cotton overexpressing GhGalT1 was shorter than that of the wild type, whereas in the GhGalT1-silenced lines there was a notable increase in fiber length compared with wild type. The carbohydrate moieties of AGPs were altered in fibers of GhGalT1 transgenic cotton. The galactose: arabinose ratio of AG glycans was higher in GhGalT1 overexpression fibers, but was lower in GhGalT1-silenced lines, compared with that in the wild type. Overexpression of GhGalT1 upregulates transcript levels of a broad range of cell wall-related genes, especially the fasciclin-like AGP (FLA) backbone genes. An enzyme activity assay demonstrated that GhGalT1 is a beta-1,3-galactosyltransferase (beta-1,3-GalT) involved in biosynthesis of the beta-1,3-galactan backbone of the type-II AG glycans of AGPs. We also show that GhGalT1 can form homo-and heterodimers with other cotton GT31 family members to facilitate AG glycan assembly of AGPs. Thus, our data demonstrate that GhGalT1 influences cotton fiber development via controlling the glycosylation of AGPs, especially FLAs.