Department of Plant Pathology, Ohio State University, Wooster, OH, 44691, USA.
USDA-ARS Corn Soybean and Wheat Quality Research Unit, Wooster, OH, 44691, USA.
Virology. 2022 May;570:96-106. doi: 10.1016/j.virol.2022.02.003. Epub 2022 Mar 23.
Marafiviruses, including maize rayado fino virus (MRFV) and oat blue dwarf virus (OBDV), encode two carboxy co-terminal coat proteins, CP1 and CP2, which encapsidate the genome to form icosahedral virions. While CP2 expression is expected to be solely driven from a second start codon of a subgenomic RNA under a marafibox promoter sequence, the larger CP1 with an in-frame N-terminal extension relative to CP2 could potentially be expressed either by proteolytic release from the MRFV polyprotein or from subgenomic RNA translation. We examined MRFV CP expression strategy with a series of mutations in the CP coding region and identified mutants viable and nonviable for systemic plant infection. Polyprotein expression of MRFV CP1 was minimal. Mutants blocking CP2 expression failed to establish systemic infection, while mutants depleted in CP1 exhibited systemic infection and formation of virus-like particles but lost leafhopper transmissibility, indicating that CP1 is required for leafhopper transmission.
马纳菲病毒属，包括玉米线条病毒（MRFV）和燕麦蓝矮病毒（OBDV），编码两个羧基末端的衣壳蛋白 CP1 和 CP2，它们包裹基因组形成二十面体病毒粒子。虽然 CP2 的表达预计仅由亚基因组 RNA 的第二个起始密码子驱动，在马纳菲盒启动子序列下，但相对于 CP2 具有框内 N 末端延伸的较大 CP1 可能通过从 MRFV 多蛋白的蛋白水解释放或从亚基因组 RNA 翻译表达。我们通过在 CP 编码区的一系列突变检查了 MRFV CP 的表达策略，并鉴定了对系统植物感染具有生存力和非生存力的突变体。MRFV CP1 的多蛋白表达最小。阻断 CP2 表达的突变体无法建立系统感染，而耗尽 CP1 的突变体表现出系统感染和形成病毒样颗粒，但丧失了叶蝉传播性，表明 CP1 是叶蝉传播所必需的。
