Functional Analysis of Plant Defense Suppression and Activation by the Xanthomonas Core Type III Effector XopX.
Functional Analysis of Plant Defense Suppression and Activation by the Xanthomonas Core Type III Effector XopX.
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DOI：
10.1094/mpmi-09-14-0263-r
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发表时间：
2015-02
期刊：
影响因子：
--
通讯作者：
Mudgett MB
中科院分区：
文献类型：
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作者：
Stork W;Kim JG;Mudgett MB
许多植物病原性III型分泌效应物（T3Es）已显示靶向和抑制植物免疫信号传导，但T3Es对植物免疫系统的干扰也可引起植物应答。XopX是黄单胞菌T3E的“核心”，其在番茄黄单胞菌（Xanthomonaseuvesicatoria）感染期间有助于生长和症状发展，但其功能作用尚未确定。我们测试了XopX对植物免疫信号传导的几个方面的影响。XopX促进乙烯生产和植物细胞死亡（PCD）在感病番茄和烟草本塞姆氏瞬时表达试验，这是符合其发展的Xe诱导的疾病症状的要求。此外，虽然XopX抑制鞭毛蛋白诱导的活性氧，但它促进了模式触发免疫（PTI）基因转录物的积累。令人惊讶的是，XopX与其他PCD诱导子的共表达导致延迟的PCD，表明XopX依赖性PCD与其他PCD途径之间的拮抗作用。然而，我们发现没有证据表明XopX有助于抑制效应触发的免疫在Xe番茄相互作用，这表明XopX的主要毒力作用是调节PTI。这些结果突出了核心黄单胞菌T3E在同时抑制和激活植物防御反应中的双重作用。
Many phytopathogenic type III secretion effectors (T3Es) have been shown to target and suppress plant immune signaling, but perturbation of the plant immune system by T3Es can also elicit a plant response. XopX is a “core” Xanthomonas T3E that contributes to growth and symptom development during Xanthomonas euvesicatoria (Xe) infection of tomato, but its functional role is undefined. We tested the effect of XopX on several aspects of plant immune signaling. XopX promoted ethylene production and plant cell death (PCD) during Xe infection of susceptible tomato and in transient expression assays in Nicotiana benthamiana, which is consistent with its requirement for the development of Xe-induced disease symptoms. Additionally, although XopX suppressed flagellin-induced reactive oxygen species, it promoted the accumulation of pattern-triggered immunity (PTI) gene transcripts. Surprisingly, XopX co-expression with other PCD elicitors resulted in delayed PCD, suggesting antagonism between XopX-dependent PCD and other PCD pathways. However, we found no evidence that XopX contributed to the suppression of effector-triggered immunity during Xe-tomato interactions, suggesting that XopX’s primary virulence role is to modulate PTI. These results highlight the dual role of a core Xanthomonas T3E in simultaneously suppressing and activating plant defense responses.