State Key Laboratory of Rice Biology and Key Laboratory for Zhejiang Super Rice Research, China National Rice Research Institute, Hangzhou 310006, China.
Int J Mol Sci. 2019 Apr 29;20(9):2107. doi: 10.3390/ijms20092107.
Pyrimidine nucleotides are important metabolites that are building blocks of nucleic acids, which participate in various aspects of plant development. Only a few genes involved in pyrimidine metabolism have been identified in rice and the majority of their functions remain unclear. In this study, we used a map-based cloning strategy to isolate a gene in rice, encoding the UMP kinase that phosphorylates UMP to form UDP, from a recessive mutant with pale-green leaves. In the mutant, UDP content always decreased, while UTP content fluctuated with the development of leaves. Mutation of reduced chlorophyll contents and decreased photosynthetic capacity. In the mutant, transcription of plastid-encoded RNA polymerase-dependent genes, including , , and , was significantly reduced, whereas transcription of nuclear-encoded RNA polymerase-dependent genes, including , , , and , was elevated. The expression of was significantly induced by various stresses, including cold, heat, and drought. Increased sensitivity to cold stress was observed in the mutant, based on the survival rate and malondialdehyde content. High accumulation of hydrogen peroxide was found in the mutant, which was enhanced by cold treatment. Our results indicate that the UMP kinase gene plays important roles in regulating chloroplast development and stress response in rice.
嘧啶核苷酸是重要的代谢物，是核酸的组成部分，参与植物发育的各个方面。在水稻中，只有少数参与嘧啶代谢的基因被鉴定出来，它们的大多数功能仍不清楚。在这项研究中，我们使用基于图谱的克隆策略，从一个叶色浅绿的隐性突变体中分离出一个编码 UMP 激酶的基因，该激酶将 UMP 磷酸化形成 UDP。在突变体中，UDP 含量总是降低，而 UTP 含量随叶片的发育而波动。突变导致叶绿素含量降低，光合作用能力下降。在突变体中，质体编码 RNA 聚合酶依赖性基因，包括 、 、 和 ，的转录显著降低，而核编码 RNA 聚合酶依赖性基因，包括 、 、 和 ，的转录升高。在各种胁迫下，包括冷、热和干旱， 的转录明显被诱导。突变体对冷胁迫的敏感性增加，表现在存活率和丙二醛含量上。在突变体中发现了过氧化氢的高积累，冷处理增强了这种积累。我们的结果表明，UMP 激酶基因在调控水稻叶绿体发育和应激反应中发挥重要作用。
