State Key Laboratory of Tea Plant Biology and Utilization , Anhui Agricultural University , Hefei , Anhui 230036 , China.
School of Life Science , Anhui Agricultural University , Hefei , Anhui 230036 , China.
J Agric Food Chem. 2018 Jul 11;66(27):7139-7149. doi: 10.1021/acs.jafc.8b01870. Epub 2018 Jun 29.
UDP-Rhamnose synthase (RHM), the branch-point enzyme controlling the nucleotide sugar interconversion pathway, converts UDP-d-glucose into UDP-rhamnose. As a rhamnose residue donor, UDP-l-rhamnose is essential for the biosynthesis of pectic polysaccharides and secondary metabolites in plants. In this study, three CsRHM genes from tea plants ( Camellia sinensis) were cloned and characterized. Enzyme assays showed that three recombinant proteins displayed RHM activity and were involved in the biosynthesis of UDP-rhamnose in vitro. The transcript profiles, metabolite profiles, and mucilage location suggest that the three CsRHM genes likely contribute to UDP-rhamnose biosynthesis and may be involved in primary wall formation in C. sinensis. These analyses of CsRHM genes and metabolite profiles provide a comprehensive understanding of secondary metabolite biosynthesis and regulation in tea plants. Moreover, our results can be applied for the synthesis of the secondary metabolite rhamnoside in future studies.
UDP-鼠李糖合酶（RHM）是一种分支点酶，控制核苷酸糖互变途径，将 UDP-D-葡萄糖转化为 UDP-鼠李糖。作为鼠李糖残基供体，UDP-L-鼠李糖是植物中果胶多糖和次生代谢物生物合成所必需的。本研究从茶树（ Camellia sinensis）中克隆并鉴定了三个 CsRHM 基因。酶活性测定表明，三个重组蛋白均具有 RHM 活性，可在体外参与 UDP-鼠李糖的生物合成。转录谱、代谢谱和黏液定位分析表明，三个 CsRHM 基因可能参与 UDP-鼠李糖的生物合成，并可能参与茶树初生壁的形成。这些 CsRHM 基因和代谢谱的分析为茶树次生代谢物的生物合成和调控提供了全面的认识。此外，我们的研究结果可应用于今后鼠李糖苷等次生代谢物的合成。
