LOXD调控番茄根结线虫病的作用机理研究

Root knot nematode (RKN) is the one of most destructive diseases in the world, which leads to severe losses of economy of global agriculture. In the pursuit of high profits, protected vegetable is year-circle production that results in successive cropping obstacle. As the abolishment of utilization of methyl bromide to the control RKN, the prevention of RKN disease becomes more and more difficult. Jasmonic acid (JA) modulates the innate immunity system of plants and enhances the resistance to stresses. Recently, the effects of JA in preventing RKN diseases attract many researchers’ attention. Based on our previous research, we take LOXD overexpression (LOXD-oe), LOXD mutant (spr8) and wild type tomato plants as the materials. After RKN inoculation, we observe the number of galls and disease index, identify the difference of root exudates, and analyze the influences of different tomato plants to RKN, eg. chemotaxis and development, explore the expression pattern of genes in JA pathway, and investigate the localization of LOXD in tissue and subcellular level. We attempt to screen interacting protein of LOXD to preliminarily illuminate the effects of LOXD in RKN resistance. The elucidation of these problems will decipherthe natural immune system of RKN resistance modulated by (JA) and provide the theoretical basis for the application in agriculture.

根结线虫已成为全球危害最大的病害之一，对农业经济造成很大损失。设施蔬菜的周年生产引起连作障碍严重，造成根结线虫病大面积爆发。溴甲烷防治的全球性取消与根结线虫发生的隐蔽性，使得根结线虫病的防治困难增加。茉莉酸（Jasmonate, JA）可以调控植物的天然免疫系统，增强其对逆境的抵抗能力。近年来，JA在根结线虫防治中的作用备受关注。本研究在前期研究的基础上，以LOXD过表达番茄株系（JA合成途径关键基因）、LOXD突变体Spr8及其野生型为试材，接种根结线虫二龄幼虫，观测根系根结数、病情指数，鉴定差异根系分泌物，分析不同株系对根结线虫趋化、发育的影响机理，探索JA途径关键基因的表达模式，研究LOXD在不同器官组织及细胞内的定位，通过酵母双杂筛选LOXD互作的蛋白，以期阐明LOXD在番茄抗根结线虫的作用，为利用JA途径调控植物的天然免疫系统及其在农业中的应用提供可靠的科学理论依据。

番茄是我国设施内栽培面积最大的蔬菜作物，连作导致根结线虫病发生严重。研究表明茉莉酸可以提高番茄对根结线虫的抗性，然而其潜在机理尚不清楚。本项目利用茉莉酸合成通路关键基因LoxD的过表达和突变体（spr8）株系，从根系分泌物角度入手，证明高內源JA的LoxD过表达株系的根系分泌物能够排斥或抑制根结线虫。通过代谢组学等手段，证明根系分泌物中的山萘酚能够抑制根结线虫。结合转录学分析，证明LoxD过表达激活了山萘酚合成通路中的CHI、F3H、FLS基因的表达。获得FLS基因过表达番茄株系，过表达株系中黄酮醇物质-山萘酚和槲皮素含量都明显升高，并且其根结线虫抗性显著提高。最终，我们提出，JA正调控FLS等基因的表达，影响番茄根系分泌物中的山萘酚含量，进而提高了番茄对根结线虫的抗性。该研究结果，有助于我们初步了解JA调控的番茄对根结线虫的抗性机制，为深入研究其中分子机制奠定了基础。