National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Biomass & Bioenergy Research Centre, Huazhong Agricultural University, Wuhan, 430070, China.
Sci Rep. 2020 Feb 28;10(1):3726. doi: 10.1038/s41598-020-60593-3.
Leaf chlorophyll content is an important physiological indicator of plant growth, metabolism and nutritional status, and it is highly correlated with leaf nitrogen content and photosynthesis. In this study, we report the cloning and identification of a xylan glucuronosyltransferase gene (OsGUX1) that affects relative chlorophyll content in rice leaf. Using a set of chromosomal segment substitution lines derived from a cross of wild rice accession ACC10 and indica variety Zhenshan 97 (ZS97), we identified numerous quantitative trait loci for relative chlorophyll content. One major locus of them for relative chlorophyll content was mapped to a 10.3-kb region that contains OsGUX1. The allele OsGUX1 from ACC10 significantly decreases nitrogen content and chlorophyll content of leaf compared with OsGUX1 from ZS97. The overexpression of OsGUX1 reduced chlorophyll content, and the suppression of this gene increased chlorophyll content of rice leaf. OsGUX1 is located in Golgi apparatus, and highly expressed in seedling leaf and the tissues in which primary cell wall synthesis occurring. Our experimental data indicate that OsGUX1 is responsible for addition of glucuronic acid residues onto xylan and participates in accumulation of cellulose and hemicellulose in the cell wall deposition, thus thickening the primary cell wall of mesophyll cells, which might lead to reduced chlorophyll content in rice leaf. These findings provide insights into the association of cell wall components with leaf nitrogen content in rice.
叶片叶绿素含量是植物生长、代谢和营养状况的一个重要生理指标，它与叶片氮含量和光合作用高度相关。在本研究中，我们报告了一个木聚糖葡萄糖醛酸基转移酶基因（OsGUX1）的克隆和鉴定，该基因影响水稻叶片的相对叶绿素含量。利用来自野生稻ACC10和籼稻品种珍汕 97（ZS97）杂交的一组染色体片段替换系，我们鉴定了许多影响相对叶绿素含量的数量性状位点。其中一个主要的相对叶绿素含量位点被映射到一个包含 OsGUX1 的 10.3kb 区域。与 ZS97 的 OsGUX1 相比，ACC10 的 OsGUX1 等位基因显著降低了叶片的氮含量和叶绿素含量。OsGUX1 的过表达降低了叶绿素含量，而该基因的抑制增加了水稻叶片的叶绿素含量。OsGUX1 位于高尔基体中，在幼苗叶片和初生细胞壁合成发生的组织中高度表达。我们的实验数据表明，OsGUX1 负责将葡萄糖醛酸残基添加到木聚糖上，并参与细胞壁沉积中纤维素和半纤维素的积累，从而使叶肉细胞的初生细胞壁变厚，这可能导致水稻叶片中叶绿素含量降低。这些发现为细胞壁成分与水稻叶片氮含量的关联提供了新的见解。
