The Type III Effector AvrBs2 in Xanthomonas oryzae pv. oryzicola Suppresses Rice Immunity and Promotes Disease Development
The Type III Effector AvrBs2 in Xanthomonas oryzae pv. oryzicola Suppresses Rice Immunity and Promotes Disease Development
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米黄单胞菌 pv 中的 III 型效应器 AvrBs2。
DOI：
10.1094/mpmi-10-14-0314-r
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发表时间：
2015-08-01
影响因子：
3.5
通讯作者：
Sun, Wenxian
中科院分区：
文献类型：
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作者：
Li, Shuai;Wang, Yanping;Sun, Wenxian
水稻白稻瘟病菌（oryzicola）是水稻上最重要的细菌性病原菌之一，是水稻细菌性条斑病的病原菌。然而，关于个体的III型效应子在X的毒力和致病性中的功能，目前还知之甚少。oryzaepv.稻生菌属在这里，我们检测了23个假定的非转录激活子样效应基因的突变对X。oryzaepv.稻瘟菌毒力。敲除avrBs2的突变体对水稻的毒力显著降低。相反，xopAA缺失导致对水稻品种的致病性增强。研究还表明，XopN、XopX、XopA、XopY、XopF1和AvrBs2等6个效应子可引起烟草非寄主叶片的过敏反应。通过转基因技术进一步证实了AvrBs2的毒力功能。在表达AvrBs2的转基因水稻品系中，病原体相关的分子模式触发的免疫应答，包括活性氧的产生和发病相关基因的表达被强烈抑制。尽管不能抑制flg22诱导的促分裂原活化蛋白激酶的活化，但异源表达AvrBs2极大地促进了水稻中由两种重要的细菌病原体X.稻瘟病菌稻和稻生菌。这些结果表明，AvrBs2是X. oryzaepv.通过抑制防御反应和促进细菌增殖来抑制稻瘟病菌的毒力。
Xanthomonas oryzae pv. oryzicola, the causal agent of bacterial leaf streak, is one of the most important bacterial pathogens in rice. However, little is known about the functions of individual type III effectors in virulence and pathogenicity of X. oryzae pv. oryzicola. Here, we examined the effect of the mutations of 23 putative nontranscription activator-like effector genes on X. oryzae pv. oryzicola virulence. The avrBs2 knock-out mutant was significantly attenuated in virulence to rice. In contrast, the xopAA deletion caused enhanced virulence to a certain rice cultivar. It was also demonstrated that six putative effectors, including XopN, XopX, XopA, XopY, XopF1, and AvrBs2, caused the hypersensitive response on nonhost Nicotiana benthamiana leaves. Virulence function of AvrBs2 was further confirmed by transgenic technology. Pathogen-associated molecular pattern-triggered immune responses including the generation of reactive oxygen species and expression of pathogenesis-related genes were strongly suppressed in the AvrBs2-expressing transgenic rice lines. Although not inhibiting flg22-induced activation of mitogen-activated protein kinases, heterologous expression of AvrBs2 greatly promotes disease progression in rice caused by two important bacterial pathogens X. oryzae pvs. oryzae and oryzicola. Collectively, these results indicate that AvrBs2 is an essential virulence factor that contributes to X. oryzae pv. oryzicola virulence through inhibiting defense responses and promoting bacterial multiplication in monocot rice.