The cell wall is a complex polysaccharide network structure composed of cellulose, hemicellulose, and pectin, and it is also the material basis for plant growth to drive cell growth. Rice cell wall research is of great significance for the improvement of agronomic traits such as lodging resistance and rice plant morphology. In addition to cellulose being synthesized on the plasma membrane, plant cell wall polysaccharides are mainly synthesized in Golgi. The required substrates and various nucleotide sugars are mainly synthesized in the cytoplasm and need to be transported across the membrane to the Golgi body through the nucleoside transporter to participate in polysaccharide synthesis. Studies have shown that defects in substrate synthesis can affect cell wall synthesis, so it is speculated that nucleoside sugar transporters have an important effect on cell wall synthesis. However, this hypothesis has been controversial due to lack of genetic evidence.
In the latest study, the research group of Zhou Yihua of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, discovered a wild-type gene encoding Golgi-localized uridine diphosphate-glucose (UDP-Glucose) transport by identifying a new rice brittle stalk mutant bc14 Son is involved in cell wall polysaccharide synthesis. A detailed phenotypic analysis of the bc14 mutant found that the gene mutation caused abnormal secondary wall structure and decreased cellulose content, resulting in a significant decrease in mechanical strength and growth and development defects. Gene cloning and complementary experiments found that the mutant phenotype was caused by a missense mutation in the nucleotide sugar transporter (Oryza sativa Nucleotide Sugar Transporter1) gene. Rice protoplasts expressed the BC14 / OsNST1 fusion fluorescent protein vector and found that the protein was localized in the Golgi apparatus. In vitro enzyme activity experiments proved that the transporter has uridine diphosphate-glucose transport activity. Detailed analysis of the cell wall components confirmed that the glucose content in the mutant matrix polysaccharides decreased significantly.
This study confirms the important role of the Golgi-localized nucleoside transporter in the synthesis of cell wall polysaccharides, provides key evidence for the analysis of the biochemical and biological mechanisms of cell wall biosynthesis, and solves a long-standing outstanding problem in this field .
This work was published online on March 7 in the Proceedings of the National Academy of Sciences (PNAS) (DOI: /10.1073/pnas.1016144108). Zhou Yihua's research group Zhang Baocai, Liu Xiangling and Qian Qian, a researcher at the Rice Research Institute of the Chinese Academy of Agricultural Sciences, are co-first authors of the paper. The research was supported by the National Transgenic Project and the Knowledge Innovation Direction Project of the Chinese Academy of Sciences.
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