Li Pan, Lei Kang, Li Yanjie, He Xingrui, Wang Shuo, Liu Renmin, Ji Lusha, Hou Bingkai
College of Pharmacy, Liaocheng University, Liaocheng, 252000, Shandong, China.
College of Life Science, Shandong University, Qingdao, 250000, Shandong, China.
Rice (N Y). 2019 Mar 29;12(1):19. doi: 10.1186/s12284-019-0279-9.
Cytokinins are one of the five major hormones families in plants and are important for their normal growth and environmental adaptability. In plants, cytokinins are mostly present as glycosides in plants, and their glycosylation modifications are catalyzed by family 1 glycosyltransferases. Current research on cytokinin glycosylation has focused on the biochemical identification of enzymes and the analysis of metabolites in Arabidopsis. There are few studies that examine how cytokinin glycosylation affects its synthesis and accumulation in plants. It is particularly important to understand these processes in food crops such as rice (Oryza sativa); however, to date, cytokinin glycosyltransferase genes in rice have not been reported.
In this study, we identified eight rice genes that were functionally homologous to an Arabidopsis cytokinin glycosyltransferase gene. These genes were cloned and expressed in a prokaryotic system to obtain their purified proteins. Through enzymatic analysis and liquid chromatography-mass spectrometry, a single rice glycosyltransferase, Os6, was identified that glycosylated cytokinin in vitro. Os6 was overexpressed in Arabidopsis, and the extraction of cytokinin glycosides showed that Os6 is functionally active in planta.
The identification and characterization of the first cytokinin glycosyltransferase from rice is important for future studies on the cytokinin metabolic pathway in rice. An improved understanding of rice cytokinin glycosyltransferases may facilitate genetic improvements in rice quality.
细胞分裂素是植物中五大主要激素家族之一，对植物的正常生长和环境适应性至关重要。在植物中，细胞分裂素大多以糖苷形式存在，其糖基化修饰由1类糖基转移酶催化。目前关于细胞分裂素糖基化的研究主要集中在拟南芥中酶的生化鉴定和代谢产物分析。很少有研究探讨细胞分裂素糖基化如何影响其在植物中的合成和积累。了解水稻等粮食作物中的这些过程尤为重要；然而，迄今为止，水稻中的细胞分裂素糖基转移酶基因尚未见报道。
在本研究中，我们鉴定出8个与拟南芥细胞分裂素糖基转移酶基因功能同源的水稻基因。这些基因被克隆并在原核系统中表达以获得其纯化蛋白。通过酶促分析和液相色谱 - 质谱联用，鉴定出一种单一的水稻糖基转移酶Os6，它能在体外使细胞分裂素糖基化。Os6在拟南芥中过表达，细胞分裂素糖苷的提取表明Os6在植物体内具有功能活性。
水稻中首个细胞分裂素糖基转移酶的鉴定和表征对未来水稻细胞分裂素代谢途径的研究具有重要意义。对水稻细胞分裂素糖基转移酶的深入了解可能有助于水稻品质的遗传改良。
