【作者】 李常保；

【导师】 张春庆； 李传友；

【作者基本信息】 山东农业大学 ， 农学， 2006， 博士

【摘要】 高等植物在长期的进化过程中形成了复杂而精细的抗性反应机制以抵抗昆虫的侵害。深入认识植物对昆虫抗性的分子机理将会为利用植物自身的抗性建立环境友好的控制农业害虫的策略提供理论依据。本实验室以番茄为模式系统,建立了用正向遗传学方法研究植物对昆虫抗性机理的研究体系。前期工作证明植物激素茉莉酸作为一种可以长距离运动的信号分子在植物对昆虫侵害的系统性抗性中起核心调控作用。在此基础上,本研究对以往的遗传筛选体系进行了改进,使之适合从全基因组范围内大规模鉴定番茄抗性缺失突变体。本研究中的spr6是新获得的番茄抗性缺失突变体,机械受伤和外施系统素不能诱导蛋白酶抑制剂II(PI-II)的表达,但茉莉酸能够以剂量依赖的方式诱导PI-II的表达。对spr6中JA含量测定表明,突变并没有影响JA的基础含量,但是部分破坏了受伤诱导的JA的积累。遗传学研究证明,该抗性缺失性状是由单隐性基因控制。利用图位克隆技术将相应基因Spr6定位在第5号染色体IL5-3相应区段,通过候选基因法策略证明Spr6基因是LeCOI1基因单碱基突变形成的一个等位基因。spr6突变体育性正常并对JA的反应具有剂量效应,为研究茉莉酸信号传导提供了一个非常有价值的工具。本研究中Spr6基因的快速分离证明了基于遗传连锁分析的候选基因法策略的成功,而且随着更多的系统素/茉莉酸信号途径相关基因/突变位点在番茄遗传连锁图上被定位,这方面的优势会更加明显。更多还原

【Abstract】 Higher plant has established the complicated and elaborate defense mechanism against insect attack during the long-term evolution. Having deeper understanding of the molecular mechanism of plant resistance to herbivores will provide theoretical evidence to establish the environment-friendly agricultural herbivores management by employing the resistance ability of plant itself. We set up a research system to explore the mechanism of plant resistance to pest by forward chemical genetics approach with tomato as a model system. The past efforts demonstrated that phytohormone jasmonate plays pivotal role in plant systemic resistance to herbivores attack as a long-distance mobile signal. Base on this knowledge, we are initiating a screening project to isolate more tomato defenseless mutants at large-scale at the whole-genome level with some improvement on the basis of the traditional genetic screen.In this study, spr6, a new JA-signaling mutant, failed to accumulate proteinase inhibitors (PI-II) in response to mechanical wounding and exogenous systemin, but was fully responsive to exogenous JA in a dose-dependent manner. GC-MS assay indicates that even though the spr6 mutation does not affect the maintenance of basal JA levels in leaf tissues, it slightly damaged the wound-induced JA accumulation. Genetic characterization suggests that the mutant phenotype is defined by a single recessive nuclear gene. The results of Map-based cloning indicated that Spr6 located on the chromosome region defined by IL5-3. Using a candidate gene approach based on genetic linkage, we demonstrate that spr6 is allelic to jai1-1, which is a loss of function allele of the tomato homolog of CORONATIN-INSENSITIVE1 (COI1), an F-box protein that is required for JA-signaled processes in Arabidopsis. The spr6 which displays normal fertility and seed set, and responses to exogenous JA in a dose-dependent manner provides a valuable tool to dissect JA signaling in tomato.The gene identification process of Spr6 we described herein represents an example showing the convenience of a candidate gene approach, based on genetic linkage, to identify gene functions of genetic loci defined by tomato wound response mutants. As more genes and mutant loci are mapped, the probability for identifying genes corresponding to functionally characterized loci will increase. We speculate this candidate gene approach will be helpful to our long-term goal in genetic dissection of the systemin/JA-signaled defense responses in tomato.更多还原