Allexiviruses may have acquired inserted sequences between the CP and CRP genes to change the translation reinitiation strategy of CRP
Allexiviruses are economically important garlic viruses that are involved in garlic mosaic diseases. In this study, we characterized the allexivirus cysteine-rich protein (CRP) gene located just downstream of the coat protein (CP) gene in the viral genome. We determined the nucleotide sequences of the CP and CRP genes from numerous allexivirus isolates and performed a phylogenetic analysis. According to the resulting phylogenetic tree, we found that allexiviruses were clearly divided into two major groups (group I and group II) based on the sequences of the CP and CRP genes. In addition, the allexiviruses in group II had distinct sequences just before the CRP gene, while group I isolates did not. The inserted sequence between the CP and CRP genes was partially complementary to garlic 18S rRNA. Using a potato virus X vector, we showed that the CRPs affected viral accumulation and symptom induction in Nicotiana benthamiana, suggesting that the allexivirus CRP is a pathogenicity determinant. We assume that the inserted sequences before the CRP gene may have been generated during viral evolution to alter the termination-reinitiation mechanism for coupled translation of CP and CRP.
We thank Dr. David Baulcombe for providing the PVX vector. We are also grateful to Dr. Katsunori Murota for his technical assistance in the in vitro translation experiment.
Compliance with ethical standards
Conflicts of interest
The authors declare no conflicts of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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