Fei Shifang, Yu Jiaping, Zhou Yali, Xie Yi, Xie Li, Fu Shuai, Wu Jianxiang
Hainan Institute of Zhejiang University, Sanya, 572025, China; State Key Laboratory of Rice Biology, Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
Hainan Institute of Zhejiang University, Sanya, 572025, China.
Virol Sin. 2025 Feb;40(1):71-79. doi: 10.1016/j.virs.2024.11.003. Epub 2024 Nov 12.
Ligularia jaluensis is an important medicinal and ornamental plant in China. However, the viruses capable of infecting Ligularia jaluensis remains unknown. Here, we identified a novel carlavirus, tentatively named ligularia jaluensis carlavirus (LJCV), as well as a known iris severe mosaic virus (ISMV), in L. jaluensis plants displaying chlorosis and yellow ring spot symptoms, using RNA-seq analysis. The LJCV genome consists of an 8497 nt positive-sense, single-stranded RNA [excluding the poly(A) tail], and contains six open reading frames (ORFs). Phylogenetic analyses based on the full-length genome and RNA-dependent RNA polymerase (RdRp) amino acid (aa) sequences revealed that LJCV clusters within an evolutionary branch alongside known viruses in the Carlavirus genus. The RdRp protein encoded by ORF1 of LJCV shared 45.38%-67.41% identity with the corresponding proteins of eight closely related carlaviruses. ORFs 2-4 constitute the triple gene block (TGB), with TGBp1 and TGBp3 localized in the endoplasmic reticulum (ER), while TGBp2 is localized at plasmodesmata (PD) and facilitates viral intercellular movement, as demonstrated by its ability to complement the potato virus X with movement-deficient mutant (PVX-Δp25-GFP). Additionally, ORF6 encodes a cysteine-rich protein (CRP) that is localized in the chloroplast and functions as a viral pathogenicity factor, inducing severe viral symptoms in the heterologous PVX expression system. Furthermore, we successfully constructed an infectious cDNA clone of LJCV, and found that it can infect Nicotiana benthamiana plants through mechanical inoculation or agrobacterium-mediated infiltration of the LJCV infectious clone. These findings enhance our understanding of the characteristics and host range of carlaviruses, as well as the viruses capable of infecting L. jaluensis.
东北橐吾是中国一种重要的药用和观赏植物。然而，能够感染东北橐吾的病毒仍然未知。在此，我们通过RNA测序分析，在表现出黄化和黄环斑症状的东北橐吾植株中鉴定出一种新型香石竹潜隐病毒，暂命名为东北橐吾香石竹潜隐病毒（LJCV），以及一种已知的鸢尾严重花叶病毒（ISMV）。LJCV基因组由一个8497个核苷酸的正链单链RNA组成（不包括poly(A)尾），并包含六个开放阅读框（ORF）。基于全长基因组和RNA依赖的RNA聚合酶（RdRp）氨基酸序列的系统发育分析表明，LJCV聚集在香石竹潜隐病毒属内与已知病毒的一个进化分支中。LJCV的ORF1编码的RdRp蛋白与八种密切相关的香石竹潜隐病毒的相应蛋白具有45.38%-67.41%的同一性。ORF2-4构成三联基因块（TGB），TGBp1和TGBp3定位于内质网（ER），而TGBp2定位于胞间连丝（PD）并促进病毒细胞间移动（通过其互补马铃薯X病毒运动缺陷突变体（PVX-Δp25-GFP）的能力证明）。此外，ORF6编码一种富含半胱氨酸的蛋白（CRP），其定位于叶绿体并作为病毒致病因子发挥作用，在异源PVX表达系统中诱导严重的病毒症状。此外，我们成功构建了LJCV的感染性cDNA克隆，并发现它可以通过机械接种或农杆菌介导的LJCV感染性克隆浸润感染本氏烟草植株。这些发现增进了我们对香石竹潜隐病毒以及能够感染东北橐吾的病毒的特征和宿主范围的理解。
