State Key Laboratory for Agro-biotechnology and Ministry of Agriculture Key Laboratory for Plant Pathology, China Agricultural University, Beijing 100193, P, R, China.
Virol J. 2013 Nov 1;10:325. doi: 10.1186/1743-422X-10-325.
Rice black-streaked dwarf virus (RBSDV), a member of the genus Fijivirus within the family Reoviridae, causes severe damage to cereal crops in South East Asia. The protein P7-2, encoded by the second open reading frame of segment S7, is conserved among most plant-infecting fijiviruses, but its function is still obscure.
In this study, P7-2 was used as bait in two-hybrid screens of a cDNA library expressing Zea mays proteins. It was found that there is a strong interaction between P7-2 and Z. mays SKP1 (SKP1Maize), a core subunit of the multicomponent SCF (SKP1/Cullin1/F-box/Rbx1) E3 ubiquitin ligase. The interaction was then confirmed in leaf epidermal cells of Nicotiana benthamiana by bimolecular fluorescence complementation assay. Further investigations indicated that P7-2 also interacts with SKP1 proteins from other plants, including Arabidopsis thaliana, N. benthamiana,Oryza sativa and Saccharum sinense. The C-terminal fragment of SKP1Maize (residues 97-176) and the middle fragment of P7-2 (residues 79-214) are necessary to sustain the interaction, while the C-terminal putative α-helix domain spanning residues 214-295 of P7-2 greatly facilitates the interaction. Agrobacterium-mediated transient suppression assay showed that P7-2 has no obvious activity to suppress local RNA silencing.
Taken together, our results indicated that RBSDV P7-2 can interact with SKP1 proteins from different plants. This is the first report linking a Fijivirus protein to a component of the ubiquitin proteasome system. P7-2 might be a potential F-box protein encoded by RBSDV and involved in the plant-virus interaction through ubiquitination pathway.
水稻黑条矮缩病毒（RBSDV），呼肠孤病毒科斐济病毒属的一种成员，对东南亚的谷类作物造成严重损害。由 S7 段第二个开放阅读框编码的蛋白 P7-2，在大多数侵染植物的斐济病毒中是保守的，但它的功能仍不清楚。
在本研究中，P7-2 被用作 cDNA 文库表达 Zea mays 蛋白的双杂交筛选的诱饵。发现 P7-2 与 Z. mays SKP1（SKP1Maize）之间存在强烈的相互作用，SKP1Maize 是多成分 SCF（SKP1/Cullin1/F-box/Rbx1）E3 泛素连接酶的核心亚基。通过双分子荧光互补测定，在 Nicotiana benthamiana 的叶表皮细胞中进一步证实了这种相互作用。进一步的研究表明，P7-2 还与包括拟南芥、N. benthamiana、水稻和甜高粱在内的其他植物的 SKP1 蛋白相互作用。SKP1Maize 的 C 端片段（残基 97-176）和 P7-2 的中间片段（残基 79-214）是维持相互作用所必需的，而 P7-2 的 C 端假定的 α-螺旋结构域（残基 214-295）极大地促进了相互作用。农杆菌介导的瞬时抑制试验表明，P7-2 没有明显的抑制局部 RNA 沉默的活性。
综上所述，我们的结果表明，RBSDV P7-2 可以与不同植物的 SKP1 蛋白相互作用。这是首次将一种斐济病毒蛋白与泛素蛋白酶体系统的一个组成部分联系起来。P7-2 可能是 RBSDV 编码的潜在 F-box 蛋白，通过泛素化途径参与植物-病毒相互作用。
