【作者】 龙海；

【导师】 徐建华；

【作者基本信息】 南京农业大学 ， 植物病理学， 2006， 博士

【摘要】 根结线虫(Meloidogyne spp．)是世界范围内的重要植物病原物，在中国，根结线虫从南到北都有分布，侵染多种作物品种，造成的损失高达70％。目前，防治根结线虫的主要手段有，农药防治和抗性基因的筛选和应用。已经从多种植物中鉴定到了抗根结线虫的基因。其中最有效的抗性基因是Mi基因，它可以有效地抗三种主要的根结线虫，花生根结线虫(M．arenaria)、南方根结线虫(M．incognita)和爪哇根结线虫(M．javanica)。抗性的表型是在线虫侵入点附近产生过敏性坏死反应。Mi基因是从野生番茄品种Lycopersicon peruvianum中得到的，目前国外种植的抗性番茄品种都含有这一抗性基因。但是随着栽种面积的不断扩大和时间的积累，逐渐出现了能克服抗性基因的毒性根结线虫群体。目前，对于其中的分子机理研究的很少。 在植物和微生物中，分支酸变位酶位于莽草酸代谢途径的末端，催化分支酸转化成预石炭酸盐，为苯丙氨酸和酪氨酸的合成提供前体。分支酸是许多复合物(Chorismate-derived complexes，CDCs)的前体，包括和植物防卫相关的水杨酸，芳香族氨基酸，吲哚乙酸和许多次级代谢产物。线虫的分支酸变位酶对这些生理途径的干扰可能会破坏一般的植物防卫反应，改变CDCs的水平，如水杨酸或吲哚乙酸，甚至破坏植物细胞壁的结构。 第一个动物源的分支酸变位酶(Mj-cm-1)来自爪哇根结线虫(M．javanica)，它在线虫的食道腺中表达。在大豆的须根中表达MJ-CM-1蛋白，限制维管束细胞的分化和侧根的形成，但是具体机制尚不明了。源自大豆胞囊线虫(Heterodera glycines)的分支酸变位酶Hg-cm-1显示出和毒性相关的多态性。研究表明，Hg-cm-1等位基因帮助大豆胞囊线虫适应特定的大豆寄主。最近，分别从南方根结线虫，大豆胞囊线虫和马铃薯胞囊线虫(Globodera rostochiensis)中克隆到了分支酸变位酶。但是目前尚无有关花生根结线虫分支酸变位酶的研究报道，分支酸变位酶在植物寄生线虫和寄主互作中的具体作用尚未得到清楚的阐明。 鉴于以上所述原因，本文主要开展了以下研究工作。 1．利用抑制差减杂交(Suppression Subtractire Hybridization，SSH)方法分离致病相关基因 以一对M．arenaria无毒和毒性近等基因系(near-isogenic lines，NIL)为材料，用抑制差减杂交技术(Suppression Subtractive Hybridization，SSH)建立更多还原

【Abstract】 Root-knot nematodes (Meloidogyne spp.) are economically important pests for agricultural crops worldwide. These root endoparasites are widely distributed from the tropical south to the temperate north in China, infecting many crops species and causing crop losses up to 70%. Due to the current restriction in the use of chemical nematicides, host resistance is being considered as the most efficient method to control root-knot nematodes. Resistance genes against root-knot nematodes have been characterized in many plant species. In particular, the tomato Mi gene, which confers effective resistance to the three major root-knot nematode species M. arenaria, M. incognita and M. javanica, is, so far, one of the best-identified resistance genes. Resistance is mediated by a hypersensitive response (HR) consisting of a local necrosis of root cells around the invading nematode. Mi resistance was identified in the wild tomato species Lycopersicon peruvianum. Up to now, all the available tomato cultivars with resistance to Meloidogyne spp. included the Mi gene. However, use of this resistance could be hampered by the occurrence of resistance-breaking virulent populations of root-knot nematodes. In fact, natural Meloidogyne biotypes virulent against the tomato Mi gene have been described from a number of recent reports. So far, the molecular mechanisms involved in virulence or avirulence to plant resistance genes are largely unknown in nematodes.In plants and microorganisms, chorismate mutase catalyses the conversion of chorismate to prephenate, providing the precursors for the biosynthesis of phenylalanine and tyrosine at the final step of the shikimate pathway, which is a primary metabolic route found in plants and microbes. Moreover, chorismate (or prephenate) is a precursor for a range of compounds including plant defense-related salicylic acid, aromatic amino acids, the phytohormone, indole-3-acetic acid, and a great number of other secondary metabolites. Therefore these chorismate-derived compounds (CDCs) play crucial roles in plant growth, development, defence and interactions with other organisms. Interference in these plant pathways by a nematode chorismate mutase could potentially disrupt general plant defenses,更多还原