State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
Hainan Institute, Zhejiang University, Sanya 572025, China.
Viruses. 2022 Aug 19;14(8):1821. doi: 10.3390/v14081821.
Umbraviruses are a special class of plant viruses that do not encode any viral structural proteins. Here, a novel umbravirus that has been tentatively named chlorosis yellow virus (PSCYV) was discovered through RNA-seq in plants showing leaf chlorosis and yellowing symptoms. The PSCYV genome is a 4301 nt positive-sense, single strand RNA that contains four open reading frames (ORFs), i.e., ORF1-4, that encode P1-P4 proteins, respectively. Together, ORF1 and ORF2 are predicted to encode an additional protein, RdRp, through a -1 frameshift mechanism. The P3 protein encoded by ORF3 was predicted to be the viral long-distance movement protein. P4 was determined to function as the viral cell-to-cell movement protein (MP) and transcriptional gene silencing (TGS) suppressor. Both P1 and RdRp function as weak post-transcriptional gene silencing (PTGS) suppressors of PSCYV. The PVX-expression system indicated that all viral proteins may be symptom determinants of PSCYV. Phylogenetic analysis indicated that PSCYV is evolutionarily related to members of the genus in the family . Furthermore, a cDNA infectious clone of PSCYV was successfully constructed and used to prove that PSCYV can infect both and plants through mechanical inoculation, causing leaf chlorosis and yellowing symptoms. These findings have broadened our understanding of umbraviruses and their host range.
类菌病毒是一类特殊的植物病毒，它们不编码任何病毒结构蛋白。本研究通过 RNA-seq 在表现叶片褪绿和黄化症状的植物中发现了一种新型类菌病毒，暂命名为褪绿黄化病毒（PSCYV）。PSCYV 基因组是一条 4301nt 的正链单链 RNA，包含四个开放阅读框（ORF），即 ORF1-4，分别编码 P1-P4 蛋白。ORF1 和 ORF2 共同通过-1 移码机制预测编码一个附加蛋白 RdRp。ORF3 编码的 P3 蛋白被预测为病毒的长距离移动蛋白。P4 被确定为病毒的细胞间运动蛋白（MP）和转录基因沉默（TGS）抑制子。P1 和 RdRp 均作为 PSCYV 的弱转录后基因沉默（PTGS）抑制子发挥功能。PVX 表达系统表明，所有病毒蛋白可能都是 PSCYV 的症状决定因子。系统发育分析表明，PSCYV 与家族 属的成员进化相关。此外，成功构建了 PSCYV 的 cDNA 感染性克隆，并用于证明 PSCYV 可以通过机械接种感染 和 植物，引起叶片褪绿和黄化症状。这些发现拓宽了我们对类菌病毒及其宿主范围的认识。
