Brassica yellows virus P0 protein impairs the antiviral activity of NbRAF2 in Nicotiana benthamiana
2018
Sun, Qian | Li, Yuan-Yuan | Wang, Ying | Zhao, Hang-Hai | Zhao, Tian-Yu | Zhang, Zong-Ying | Li, Da-Wei | Yu, Jia-Lin | Wang, Xian-Bing | Zhang, Yong-Liang | Han, Cheng-Gui
In interactions between poleroviruses and their hosts, few cellular proteins have been identified that directly interact with the multifunctional virus P0 protein. To help explore the functions of P0, we identified a Brassica yellows virus genotype A (BrYV-A) P0ᴮʳᴬ-interacting protein from Nicotiana benthamiana, Rubisco assembly factor 2 (NbRAF2), which localizes in the nucleus, cell periphery, chloroplasts, and stromules. We found that its C-terminal domain (amino acids 183–211) is required for self-interaction. A split ubiquitin membrane-bound yeast two-hybrid system and co-immunoprecipitation assays showed that NbRAF2 interacted with P0ᴮʳᴬ, and co-localized in the nucleus and at the cell periphery. Interestingly, the nuclear pool of NbRAF2 decreased in the presence of P0ᴮʳᴬ and during BrYV-A infection, and the P0ᴮʳᴬ-mediated reduction of nuclear NbRAF2 required dual localization of NbRAF2 in the chloroplasts and nucleus. Tobacco rattle virus-based virus-induced gene silencing of NbRAF2 promoted BrYV-A infection in N. benthamiana, and the overexpression of nuclear NbRAF2 inhibited BrYV-A accumulation. Potato leafroll virus P0ᴾᴸ also interacted with NbRAF2 and decreased its nuclear accumulation, indicating that NbRAF2 may be a common target of poleroviruses. These results suggest that nuclear NbRAF2 possesses antiviral activity against BrYV-A infection, and that BrYV-A P0ᴮʳᴬ interacts with NbRAF2 and alters its localization pattern to facilitate virus infection.
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