PDF(Pubmed)
Abstract：
BACKGROUND: Early blight and brown leaf spot are often cited as the most problematic pathogens of tomato in many agricultural regions. Their causal agents are Alternaria spp., a genus of Ascomycota containing numerous necrotrophic pathogens. Breeding programs have yielded quantitatively resistant commercial cultivars, but fungicide application remains necessary to mitigate the yield losses. A major hindrance to resistance breeding is the complexity of the genetic determinants of resistance and susceptibility. In the absence of sufficiently resistant germplasm, we sequenced the transcriptomes of Heinz 1706 tomatoes treated with strongly virulent and weakly virulent isolates of Alternaria spp. 3 h post infection. We expanded existing functional gene annotations in tomato and using network statistics, we analyzed the transcriptional modules associated with defense and susceptibility.
RESULTS: The induced responses are very distinct. The weakly virulent isolate induced a defense response of calcium-signaling, hormone responses, and transcription factors. These defense-associated processes were found in a single transcriptional module alongside secondary metabolite biosynthesis genes, and other defense responses. Co-expression and gene regulatory networks independently predicted several D clade ethylene response factors to be early regulators of the defense transcriptional module, as well as other transcription factors both known and novel in pathogen defense, including several JA-associated genes. In contrast, the strongly virulent isolate elicited a much weaker response, and a separate transcriptional module bereft of hormone signaling.
CONCLUSIONS: Our findings have predicted major defense regulators and several targets for downstream functional analyses. Combined with our improved gene functional annotation, they suggest that defense is achieved through induction of Alternaria-specific immune pathways, and susceptibility is mediated by modulating hormone responses. The implication of multiple specific clade D ethylene response factors and upregulation of JA-associated genes suggests that host defense in this pathosystem involves ethylene response factors to modulate jasmonic acid signaling.
RESULTS: The induced responses are very distinct. The weakly virulent isolate induced a defense response of calcium-signaling, hormone responses, and transcription factors. These defense-associated processes were found in a single transcriptional module alongside secondary metabolite biosynthesis genes, and other defense responses. Co-expression and gene regulatory networks independently predicted several D clade ethylene response factors to be early regulators of the defense transcriptional module, as well as other transcription factors both known and novel in pathogen defense, including several JA-associated genes. In contrast, the strongly virulent isolate elicited a much weaker response, and a separate transcriptional module bereft of hormone signaling.
CONCLUSIONS: Our findings have predicted major defense regulators and several targets for downstream functional analyses. Combined with our improved gene functional annotation, they suggest that defense is achieved through induction of Alternaria-specific immune pathways, and susceptibility is mediated by modulating hormone responses. The implication of multiple specific clade D ethylene response factors and upregulation of JA-associated genes suggests that host defense in this pathosystem involves ethylene response factors to modulate jasmonic acid signaling.
摘要：
背景：早疫病和褐色叶斑病通常被认为是许多农业地区番茄中最成问题的病原体。它们的致病因子是链格孢菌属。,子囊属的一个属，含有许多坏死性病原体。育种计划已经产生了定量抗性的商业品种，但杀菌剂的应用仍然是必要的，以减轻产量损失。抗性育种的主要障碍是抗性和易感性的遗传决定因素的复杂性。在缺乏足够抗性的种质的情况下，我们对亨氏1706番茄的转录组进行了测序，这些番茄用链格孢菌的强毒力和弱毒力分离株处理。感染后3小时。我们扩展了番茄中现有的功能基因注释，并使用网络统计，我们分析了与防御和易感性相关的转录模块.
结果：诱导的反应非常不同。弱毒力分离株诱导了钙信号的防御反应，激素反应，和转录因子。这些与防御相关的过程与次级代谢产物生物合成基因一起存在于单个转录模块中，和其他防御反应。共表达和基因调控网络独立预测了几个D进化枝乙烯反应因子是防御转录模块的早期调节因子，以及在病原体防御中已知和新颖的其他转录因子，包括几个JA相关基因。相比之下,强毒力分离株引起的反应要弱得多，和一个单独的转录模块失去了激素信号传导。
结论：我们的发现预测了主要的国防监管机构和下游功能分析的几个目标。结合我们改进的基因功能注释，他们认为防御是通过诱导链格孢菌特异性免疫途径来实现的，易感性是通过调节激素反应介导的。多个特定进化枝D乙烯反应因子和JA相关基因的上调的含义表明，该病理系统中的宿主防御涉及乙烯反应因子来调节茉莉酸信号传导。
结果：诱导的反应非常不同。弱毒力分离株诱导了钙信号的防御反应，激素反应，和转录因子。这些与防御相关的过程与次级代谢产物生物合成基因一起存在于单个转录模块中，和其他防御反应。共表达和基因调控网络独立预测了几个D进化枝乙烯反应因子是防御转录模块的早期调节因子，以及在病原体防御中已知和新颖的其他转录因子，包括几个JA相关基因。相比之下,强毒力分离株引起的反应要弱得多，和一个单独的转录模块失去了激素信号传导。
结论：我们的发现预测了主要的国防监管机构和下游功能分析的几个目标。结合我们改进的基因功能注释，他们认为防御是通过诱导链格孢菌特异性免疫途径来实现的，易感性是通过调节激素反应介导的。多个特定进化枝D乙烯反应因子和JA相关基因的上调的含义表明，该病理系统中的宿主防御涉及乙烯反应因子来调节茉莉酸信号传导。
