BACKGROUND In Raphanus sativus (Japanese radish), strain D8 of cucumber mosaic virus (CMV-D8) establishes a systemic infection and induces mild mosaic on upper, non-inoculated leaves, whereas strain Y of CMV (CMV-Y) causes only a local infection in the inoculated leaves. Here, we further analyzed the specific viral factor(s) of CMV-D8 that is (are) indispensable for systemic infection in Japanese radish. METHODS To identify which genomic RNA(s) is (are) involved in systemic infection in radish, we carried out a pseudorecombination analysis between CMV-D8 and CMV-Y. With recombination analyses between CMV-D8 and CMV-Y using mutant/recombinant RNA2s, chimeric and point-mutated RNA3s, we identified viral factors that are indispensable for systemic infection. RESULTS Viral RNA2 and RNA3 of CMV-D8 facilitated efficient virus spread into the upper, non-inoculated plant tissues of radish (cv. Tokinashi), but not those of CMV-Y. Recombinant RNA2s demonstrated that the 2b protein (2b) and the C-terminus of the 2a protein (2a) of CMV-D8 have a crucial role in systemic infection. In addition, we used chimeric and point-mutated RNA3s to that Pro17 and Pro129 in the coat protein (CP) of CMV-D8 are involved in efficient systemic infection and that Ser51 in the 3a protein (3a) of CMV-D8 has positive effects on systemic spread. The results suggested that these viral factors facilitate systemic infection of CMV-D8 in Japanese radish. CONCLUSION The C-terminal region of 2a, the entire region of 2b, and supplementary function of either Ser51 in 3a or Pro17/Pro 129 in CP confer systemic infectivity on CMV-D8 in radish. These results further elucidate the complex interaction of viral proteins of CMV to complete systemic infection as a host-specific manner.

中文翻译：

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2b蛋白和2a蛋白的C末端区域必不可少地促进黄瓜花叶病毒在萝卜中的系统运动，并具有3a或外壳蛋白的补充功能。

背景技术在萝卜萝卜中，黄瓜花叶病毒D8株（CMV-D8）建立全身感染并在未接种的上部叶片上引起轻度花叶病，而CMV Y株（CMV-Y）仅引起局部接种叶片感染。在这里，我们进一步分析了CMV-D8的特定病毒因子，这对于日本萝卜的全身感染是必不可少的。方法为了确定哪些基因组RNA参与了萝卜的全身感染，我们在CMV-D8和CMV-Y之间进行了伪重组分析。通过使用突变体/重组RNA2，嵌合和点突变RNA3在CMV-D8和CMV-Y之间进行重组分析，我们确定了全身感染必不可少的病毒因子。结果CMV-D8的病毒RNA2和RNA3促进了病毒高效传播到上部，未接种的萝卜植物组织（Tokinashi品种），而不是CMV-Y的组织。重组RNA2s证明CMV-D8的2b蛋白（2b）和2a蛋白（2a）的C末端在全身感染中起关键作用。此外，我们使用嵌合和点突变RNA3来证明CMV-D8的外壳蛋白（CP）中的Pro17和Pro129参与有效的全身感染，而CMV-D8的3a蛋白（3a）中的Ser51具有积极作用在全身扩散。结果表明，这些病毒因素促进了CMV-D8在萝卜中的全身感染。结论2a的C末端区域，2b的整个区域以及3a中的Ser51或CP中的Pro17 / Pro 129的补充功能赋予萝卜CMV-D8全身性感染力。