Self-interaction of the cucumber mosaic virus 2b protein plays a vital role in the suppression of RNA silencing and the induction of viral symptoms.
Self-interaction of the cucumber mosaic virus 2b protein plays a vital role in the suppression of RNA silencing and the induction of viral symptoms.
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DOI：
10.1111/mpp.12051
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发表时间：
2013-10
影响因子：
4.9
通讯作者：
Aixia Xu;Zhijing Zhao;Wenhu Chen;Hengmu Zhang;Qiansheng Liao;Jishuang Chen;J. Carr;Z. Du
中科院分区：
文献类型：
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作者：
Aixia Xu;Zhijing Zhao;Wenhu Chen;Hengmu Zhang;Qiansheng Liao;Jishuang Chen;J. Carr;Z. Du
黄瓜花叶病毒(CMV)2b蛋白是一种RNA沉默抑制蛋白，也可以在症状诱导中发挥直接和间接作用。前人的工作表明，用Rad35-CMV株系的2b基因替换FNY-CMV株的2b基因而产生的杂交病毒FRad35(2b)-CMV(这里改名为CMV-FRad2b-Pro)对烟草的致病力明显低于FNY-CMV。然而，CMV-FRad2b-Pro(Rad2b-Pro)2b蛋白第55位的亮氨酸替换产生了一种引起严重症状的病毒(CMV-FRad2b-Leu)。侵染介导抗病毒RNA沉默的Dicer样内切核酸酶2和4表达缺陷的拟南芥突变体，以及dcl3和dcl2/3/4三重突变植株，表明Rad2b-Pro是一种比Rad2b-Leu蛋白更弱的RNA沉默抑制因子。通过农业渗透试验证实了这一点，表明与Rad2b-Leu或Fny2b蛋白相比，Rad2b-Pro在抑制绿色荧光蛋白报告基因的局部或系统沉默方面无效。RAD2b-Leu的转基因表达，而不是RAD2b-Pro的转基因表达，诱导了症状表型，并挽救了2b缺失突变体FNY-CMVΔ2b的积累。双分子荧光互补实验表明，在植物中，Rad2b-Leu，而不是Rad2b-Pro，是自我作用的。因此，自身相互作用对于2b蛋白抑制沉默和诱导症状样表型的能力至关重要，并且取决于55位残基的性质。
The cucumber mosaic virus (CMV) 2b protein is an RNA silencing suppressor protein that can also play direct and indirect roles in symptom induction. Previous work has shown that a hybrid virus, FRad35(2b) -CMV (renamed here as CMV-FRad2b-Pro), generated by replacement of the 2b gene of strain Fny-CMV with that from Rad35-CMV, displays markedly lower pathogenicity than Fny-CMV on Nicotiana species. However, the replacement of proline with leucine at position 55 of the 2b protein of CMV-FRad2b-Pro (protein Rad2b-Pro) created a virus (CMV-FRad2b-Leu) that induced severe symptoms. Infection of Arabidopsis thaliana mutants defective in the expression of DICER-like (DCL) endoribonucleases 2 and 4, which mediate antiviral RNA silencing, as well as of dcl3 and dcl2/3/4 triple-mutant plants, indicated that Rad2b-Pro was a weaker RNA silencing suppressor than the protein Rad2b-Leu. This was confirmed in Nicotiana benthamiana using agroinfiltration assays, showing that, compared with either Rad2b-Leu or the Fny2b protein, Rad2b-Pro was ineffective at inhibiting local or systemic silencing of expression of a green fluorescent protein reporter gene. Transgenic expression of Rad2b-Leu, but not of Rad2b-Pro, in Arabidopsis induced symptom-like phenotypes and rescued the accumulation of the 2b-deletion mutant Fny-CMVΔ2b. Bimolecular fluorescent complementation indicated that, in planta, Rad2b-Leu, but not Rad2b-Pro, self-interacts. Thus, self-interaction is crucial to the ability of the 2b protein to suppress silencing and induce a symptom-like phenotype, and is dependent on the properties of the residue at position 55.