Strong host resistance targeted against a viral suppressor of the plant gene silencing defence mechanism
Strong host resistance targeted against a viral suppressor of the plant gene silencing defence mechanism
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DOI：
10.1093/emboj/18.10.2683
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发表时间：
1999-05-17
期刊：
影响因子：
11.4
通讯作者：
Ding, SW
中科院分区：
文献类型：
--
作者：
Li, HW;Lucy, AP;Ding, SW
黄瓜花叶黄瓜病毒（Cmv2b）编码的2b蛋白通过抑制转录后基因沉默（PTGS），作为一个重要的毒力决定因素，PTGS是植物对病毒的天然防御机制。我们在此报道，番茄aspermy cucumovirus 2b蛋白（Tav2b）从不相关的烟草花叶烟叶病毒（TMV） RNA基因组中表达，激活烟草宿主对TMV的强烈抗性反应，这是典型的基因对基因的抗病机制。Cmv2b与Tav2b之间的结构域交换揭示了Tav2b中对引发病毒抗性和超敏细胞死亡至关重要的功能结构域。此外，用Cmv2b中相同位置的氨基酸Lys21—>Val和Arg28—>Ser取代Tav2b中的两个氨基酸，可以消除诱导超敏细胞死亡和病毒抗性的能力。然而，在与烟草相关的benthamiana中，Tav2b作为毒力决定因子并抑制PTGS，因此，宿主基因沉默防御机制的病毒抑制因子是另一种独立的宿主抗性机制的靶标。我们的研究结果为病毒及其宿主防御、反防御和反反防御的复杂分子策略提供了新的见解。
The 2b protein encoded by cucumber mosaic cucumovirus (Cmv2b) acts as an important virulence determinant by suppressing post-transcriptional gene silencing (PTGS), a natural plant defence mechanism against viruses. We report here that the tomato aspermy cucumovirus 2b protein (Tav2b), when expressed from the unrelated tobacco mosaic tobamovirus (TMV) RNA genome, activates strong host resistance responses to TMV in tobacco which are typical of the gene-for-gene disease resistance mechanism. Domain swapping between Cmv2b, which does not elicit these responses, and Tav2b, revealed functional domains in Tav2b critical for triggering virus resistance and hypersensitive cell death. Furthermore, substitution of two amino acids from Tav2b by those found at the same positions in Cmv2b, Lys21-->Val and Arg28-->Ser, abolished the ability to induce hypersensitive cell death and virus resistance. However, in Nicotiana benthamiana, a species related to tobacco, Tav2b functions as a virulence determinant and suppresses PTGS, Thus, a viral suppressor of the host gene silencing defence mechanism is the target of another independent host resistance mechanism, Our results provide new insights into the complex molecular strategies employed by viruses and their hosts for defence, counter-defence and counter counter-defence.