Allexiviruses may have acquired inserted sequences between the CPand CRP genes to change the translation reinitiation strategy of CRP

Abstract

AbstractAllexiviruses are economically important garlic viruses that are involved in garlic mosaic diseases. In this study, we characterizedthe allexivirus cysteine-rich protein (CRP) gene located just downstream of the coat protein (CP) gene in the viralgenome. We determined the nucleotide sequences of the CP and CRP genes from numerous allexivirus isolates and performeda phylogenetic analysis. According to the resulting phylogenetic tree, we found that allexiviruses were clearly divided intotwo major groups (group I and group II) based on the sequences of the CP and CRP genes. In addition, the allexiviruses ingroup II had distinct sequences just before the CRP gene, while group I isolates did not. The inserted sequence between theCP and CRP genes was partially complementary to garlic 18S rRNA. Using a potato virus X vector, we showed that theCRPs affected viral accumulation and symptom induction in Nicotiana benthamiana, suggesting that the allexivirus CRP isa pathogenicity determinant. We assume that the inserted sequences before the CRP gene may have been generated duringviral evolution to alter the termination-reinitiation mechanism for coupled translation of CP and CRP