高温胁迫下水稻光温敏核不育系开颖和雌蕊受精障碍的机理与调控

The harm of high temperature stress (HTS) to spikelet-opening and pistil fertilization of photoperiod-thermo-sensitive genic male sterile (PTSGMS) rice lines has become a serious problem in the “two-line-method” hybrid rice production. The information on its mechanism and regulation, however, is not available. Using typical PTSGMS rice lines as materials and subjected to HTS treatments during the period of meiosis, heading and flowering, this proposed project aims to investigate (1) changes in the content of jasmonic acid (JA) and methyl jasmonate (MeJA), expression of the genes involved in JA and MeJA biosynthesis, reactive oxygen species (ROS) production, activity of antioxidant enzymes (AOE) in the lodicules, and ultrastructure of lodicule cells during heading and flowering and their relationship with lodicule activity and spikelet-opening, (2) changes in the content of 24-epibrassinolide (24-EBL) and 28-homobrassinolide, expression of the genes related to the signal transduction of brassinosteroids, ROS production, and AOE activity and their relationship with pistil activity and fertilization, and (3) the effect of MeJA or 24-EBL application and irrigation regimes on spikelet-opening and pistil fertilization and its mechanism. It is expected that the proposed project can reveal the mechanism in which HTS impairs spikelet-opening and pistil fertilization of PTSGMS rice lines, explore regulatory approaches to reduce the harm of HTS to spikelet-opening and pistil fertilization and understand their mechanism, and provide theoretical and practical guidance to the selection and breeding of PTSGMS rice lines with strong thermo-tolerance and the mitigation in the harm of HTS to PTSGMS rice lines through chemical and cultural regulation.

高温胁迫危害水稻光温敏核不育系开颖和雌蕊受精已成为“两系法”杂交水稻生产上的一个突出问题，但对其机理和调控途径缺乏研究。本项目以代表性水稻光温敏核不育系为材料并在减数分裂和抽穗开花期进行高温胁迫处理，重点研究：(1)花期浆片中茉莉酸和茉莉酸甲酯(MeJA)含量及其合成途径中相关基因的表达、活性氧 (ROS)产生、抗氧化酶(AOE)活性和浆片细胞超微结构变化特点及其与浆片活性和开颖的关系；(2)雌蕊中24-表油菜素内酯(24-EBL)和28-高油菜素内酯含量、油菜素甾醇信号传导相关基因的表达、ROS产生和AOE活性变化特点及其与雌蕊活性和受精的关系；(3)外源MeJA、24-EBL和灌溉方式对开颖和雌蕊受精的调节作用及其原理。揭示水稻光温敏核不育系开颖和雌蕊受精的高温危害机制，探明减轻高温危害的调控途径与原理，为耐高温水稻光温敏核不育系的选育与减轻高温危害的化学和栽培调控提供理论与实践指导。

高温胁迫危害水稻光温敏核不育系(PTSGMS)开颖和雌蕊受精已成为“两系法”杂交水稻生产上的一个突出问题，本项目研究了高温危害PTSGMS开颖和雌蕊受精的机理与减轻高温危害的调控途径，获得了重要结果。(1)发现PTSGMS浆片中茉莉酸类(JAs)对开颖有重要调控作用。在开花期高温胁迫下，PTSGMS在开花前和开花时浆片中JAs含量低是导致开颖障碍的重要原因。JAs通过增强PTSGMS浆片抗氧化能力，增加细胞内线粒体和核糖体数目，降低活性氧水平，减轻开花期高温胁迫引起的开颖障碍，提高PTSGMS的开颖率。(2)发现PTSGMS雌蕊中油菜素甾醇(BRs)对雌蕊活性和受精能力有重要调控作用。在开花期高温胁迫下，PTSGMS雌蕊中BRs含量的降低是导致其雌蕊受精障碍的重要原因。BRs可抑制雌蕊中乙烯和活性氧的产生，增强抗氧化能力，减轻高温胁迫对PTSGMS雌蕊的伤害。(3)提出了减轻PTSGMS高温危害的调控途径和技术。发现浆片中JAs或雌蕊中BRs含量在PTSGMS间差异很大，培育或选用在高温胁迫下浆片中JAs、雌蕊中BRs含量高的PTSGMS，可提高其耐高温能力，减轻开花期高温胁迫引起的开颖障碍和雌蕊受精障碍；在开花期高温条件下，喷施100μM茉莉酸甲酯或100μM茉莉酸，可增强PTSGMS浆片中JAs生物合成相关基因的表达，促进开颖；喷施1μM 24-表油菜素内酯或1μM 28-高油菜素内酯，可增强雌蕊中BRs信号传导相关基因的表达，提高雌蕊活性；当雌雄蕊分化期和抽穗始期植株含氮量分别低于2.5%和2.2%，施用氮素保花肥或氮素粒肥或采用无水层湿润灌溉技术(土壤饱和含水量的95%-100%)，可减轻高温胁迫对PTSGMS开花受精的伤害，提高其杂交制种的结实率和产量。(4)本项目已发表SCI论文10篇，获国家授权发明专利2件，培养博士后1名和研究生3名。