摘要:活性氧(reactive oxygen species，ROS)是一类具有高反应活性的氧衍生物，包括超氧阴离子(·O2-)、羟自由基(·OH)、过氧羟自由基(·HO2)以及过氧化氢(H2O2)等。植物在进行有氧代谢或遭遇生物与非生物胁迫时会产生ROS，它不仅仅是有氧代谢的有毒副产物，同时能作为信号分子调节体内代谢过程，对抗外界环境。豆科植物形成根瘤时同样会产生ROS，这种ROS的变化区别于病原体入侵，而是作为一种信号物质参与结瘤过程。结瘤因子(nod factor，NF)诱导下ROS的产生参与了浸染线形成时细胞壁的重建、植物基质糖蛋白(matrix glycoprotein，MGP)的交联和肌动蛋白微丝的成核和延长过程。细胞质膜NADPH氧化酶(respiratory burst oxidase homologue，RBOHs)是共生过程中ROS产生的主要途径，Rboh基因的过表达会促进根瘤菌浸染和根瘤形成，同时根瘤中的共生微粒体数量增加，固氮效率提高，而表达受抑制后会减少ROS的产生，同时下调结瘤相关基因RIPs、NIN、ENOD2的表达，抑制固氮酶活性。此外，ROS时空上的变化与Ca2+相关联，协同调控根系结瘤。ROS的产生是植物与微生物早期的识别信号，通过认识ROS在早期结瘤过程中的作用有助于我们进一步理解共生关系建立的特异性。本文就ROS在早期结瘤过程中的产生及其发挥的作用做了综述，指出ROS通过直接或间接作用诱导结瘤基因的表达，是豆科植物根瘤形成以及功能固氮的重要信号分子。
关键词:活性氧/
结瘤信号/
根瘤形成/
固氮/
豆科作物
Abstract:Research on the production and function of reactive oxygen species (ROS) formed during early nodulation in legumes was reviewed. The ROS are highly reactive oxygen derivatives, including superoxide anion (·O2-), hydroxyl radical (·OH), hydroperoxyl radical (·HO2), and hydrogen peroxide (H2O2). These radicals were produced during aerobic metabolism and when plants were under biotic and abiotic stresses. While toxic, these compounds serve as signalers that can trigger metabolism regulations to combat adverse environments. The ROS are produced during nodulation in legumes, induced by the nod factor (NF), to participate in infection formation, contributing to cell wall reconstruction, cross-linking of matrix glycoprotein (MGP), and actin microfilament nucleation and branching. Symbiotic production of ROS is primarily through cytoplasmic membrane NADPH respiratory burst oxidase homologue (RBOHs). Overexpression of Rboh stimulates rhizobia infection and nodule formation, resulting in increased number of symbiotic microsomes and nitrogen fixation efficiencies. Conversely, inhibition of Rboh decreases the production of ROS and down-regulates the expression of related RIPs, NIN, and ENOD2. The ROS regulate nodulation also in conjunction with Ca2+ through spatial and temporal alterations. In conclusion, ROS in legumes are a group of signaler molecules that function to regulate nodulation through genes expression.
Key words:ROS/
Nodulation signal/
Nodulation/
Nitrogen fixation/
Legume
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