茉莉酸参与稗草对除草剂产生抗性的调控机理

Barnyardgrass (Echinochloa crus-galli) with herbicide resistance threatens the safety of rice production seriously in our country. The molecular mechanism underlying herbicide resistance in barnyardgrass is a major concern of weed scientists. Jasmonic acid (JA) plays important roles in plant growth, development and defense. It has been found that the content of JA can be induced by the application of quinclorac and their contents in resistant (R) and sensitive (S) biotypes are significantly different. However, little is known about the function of JA on the resistance mechanism in barnyardgrass. This project intends to use resistant and sensitive barnyardgrass as research objects to study the effects of JA on plants after the application of quinclorac. Physiological characteristic parameters and hormone levels will be detected and compared among different materials. Key genes in JA synthesis and signaling (AOS, OPR and MYC) are cloned and their expressions and activities of relative enzymes are quantified. CRISPR/Cas9 system will be used to verify the function of AOS, OPR and MYC gene in resistance to quinclorac. The results of these studies could be important to reveal the regulatory function of JA on quinclorac resistence in barnyardgrass and elucidate the new mechanism of weed resistance. It will provide scientific theoretical basis for the green governance of resistant weeds and has fantastic application prospects.

抗性稗草是持续严重威胁我国水稻产量与品质的恶性杂草之一。项目申请者前期研究发现，二氯喹啉酸能诱导稗草中茉莉酸的积累，且稗草抗性生物型中茉莉酸的含量与敏感性生物型间存在显著差异，但是目前有关茉莉酸参与稗草对除草剂产生抗性的调控机理，还知之甚少。本项目拟以遗传背景完全一致的稗草抗二氯喹啉酸生物型和敏感性生物型为研究材料，研究茉莉酸对经二氯喹啉酸胁迫后稗草生理特征参数、激素水平的影响；克隆稗草茉莉酸合成与信号转导关键基因AOS、OPR和MYC，探索茉莉酸对经二氯喹啉酸胁迫后稗草关键基因的表达量和相关酶的活性影响；利用CRISPR/Cas9技术分别靶向敲除AOS、OPR和MYC基因，验证其在稗草对二氯喹啉酸产生抗性过程中的调节功能。研究成果可揭示茉莉酸在稗草抵抗除草剂过程中的调控功能，挖掘杂草产生抗性的新机理，为抗性杂草的绿色治理提供科学的理论依据，应用前景广阔。

以遗传背景一致的抗二氯喹啉酸型和敏感型稗草为供试材料，分析了经外源茉莉酸甲酯(MeJA)预处理后，稗草种群间应对二氯喹啉酸胁迫的抗性水平及4种内源激素含量的变化。进行转录组分析，挖掘在外源MeJA对抗、敏稗草抗性差异影响这一过程中发挥作用的关键通路与基因。分析了植物激素合成与信号转导通路及关键基因对除草剂和外源MeJA的响应，并通过反转录定量PCR对关键基因的表达量进行了验证。结果显示，外源MeJA处理可显著提高抗性稗草对二氯喹啉酸的抗性，而对敏感稗草的抗性影响不显著。供试材料间植株体内生长素(IAA)、脱落酸(ABA)、水杨酸(SA)和茉莉酸(JA)的含量及其变化幅度存在显著差异。二氯喹啉酸处理显著增加了稗草ABA、SA和JA的含量，且敏感稗草ABA和JA含量升高幅度明显高于抗性稗草；外源MeJA预处理能显著增强二氯喹啉酸对稗草ABA和JA含量的诱导，且敏感稗草变化幅度较大。表明敏感稗草较快的激素变化不利于其应对除草剂胁迫，抗性稗草相对平缓的激素变化赋予了其对除草剂的适应性，且MeJA处理增强了其对二氯喹啉酸的抗性。稗草植株体内植物激素信号在其抵抗二氯喹啉酸胁迫过程中可能发挥重要的生物学功能。本研究初步揭示了外源MeJA对抗、敏稗草抗性差异影响的分子机制，以及植物激素在稗草对二氯喹啉酸产生抗性过程中的调节功能。