在模式植物番茄中，过表达系统素前体基因Prosystemin的转基因植物（35S::PS）组成型地激活茉莉酸响应基因的表达，表明多肽信号分子系统素(Systemin)和植物激素茉莉酸(Jasmonic acid, JA)通过共同的信号转导途径调控植物对害虫的免疫反应。深入研究这一信号转导途径对于建立环境友好型的害虫防控策略具有重要意义。

　　中科院遗传所李传友研究组长期利用遗传学解析系统素/茉莉酸介导的免疫反应信号途径。最近，李传友研究组与中科院动物研究所康乐研究组，北京农林科学院李常保研究组合作，通过对番茄免疫反应缺失突变体spr8 (suppressor of prosystemin-mediated response 8)的系统研究发现了在植物免疫反应中起重要作用的功能基因Spr8/TomLoxD。

   spr8突变体表现出一系列免疫反应缺陷的表型，包括对机械伤害不敏感、表皮毛分泌的萜类代谢物减少、对咀嚼式害虫棉铃虫和腐生型病原菌抗性降低等。图位克隆的结果表明Spr8编码脂氧化酶TomLoxD，是受伤诱导的茉莉酸合成途径的限速酶。

   ChIP与EMSA的实验结果表明，TomLoxD基因的表达受JA信号途径中的转录因子SlMYC2的正反馈调控。遗传操作发现超表达Spr8/TomLoxD可以显著提高植物对害虫和腐生型病原菌的抗性。

   重要的是，这一研究发现过表达Spr8/TomLoxD特异性地提高了植物的免疫性而对生长发育没有不良影响，这与已经报道的茉莉酸途径的其它基因显著不同。这项工作表明Spr8/TomLoxD在植物保护方面有重要的应用前景。 

　　该研究结果已于2013年12月12日在线发表于PLoS Genetics (DOI: 10.1371/journal.pgen.1003964)。李传友实验室的博士研究生闫留华是该论文的共同第一作者。该研究得到农业部、科技部和北京自然科学基金委的资助。

原文摘要：

Role of Tomato Lipoxygenase D in Wound-Induced Jasmonate Biosynthesis and Plant Immunity to Insect Herbivores

In response to insect attack and mechanical wounding, plants activate the expression of genes involved in various defense-related processes. A fascinating feature of these inducible defenses is their occurrence both locally at the wounding site and systemically in undamaged leaves throughout the plant. Wound-inducible proteinase inhibitors (PIs) in tomato (Solanum lycopersicum) provide an attractive model to understand the signal transduction events leading from localized injury to the systemic expression of defense-related genes. Among the identified intercellular molecules in regulating systemic wound response of tomato are the peptide signal systemin and the oxylipin signal jasmonic acid (JA). The systemin/JA signaling pathway provides a unique opportunity to investigate, in a single experimental system, the mechanism by which peptide and oxylipin signals interact to coordinate plant systemic immunity. Here we describe the characterization of the tomato suppressor of prosystemin-mediated responses8 (spr8) mutant, which was isolated as a suppressor of (pro)systemin-mediated signaling. spr8 plants exhibit a series of JA-dependent immune deficiencies, including the inability to express wound-responsive genes, abnormal development of glandular trichomes, and severely compromised resistance to cotton bollworm (Helicoverpa armigera) and Botrytis cinerea. Map-based cloning studies demonstrate that the spr8 mutant phenotype results from a point mutation in the catalytic domain of TomLoxD, a chloroplast-localized lipoxygenase involved in JA biosynthesis. We present evidence that overexpression of TomLoxD leads to elevated wound-induced JA biosynthesis, increased expression of wound-responsive genes and, therefore, enhanced resistance to insect herbivory attack and necrotrophic pathogen infection. These results indicate that TomLoxD is involved in wound-induced JA biosynthesis and highlight the application potential of this gene for crop protection against insects and pathogens.

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