Abstract
Recombination drives evolution of single-stranded RNA viruses and contributes to virus adaptation to new hosts and environmental conditions. Intraspecific recombinants are common in potyviruses, the largest family of single-stranded RNA viruses, whereas interspecific recombinants are rare. Here, we report an interspecific recombination event between papaya ringspot potyvirus (PRSV) and zucchini tigre mosaic potyvirus (ZTMV), two potyviruses infecting cucurbit crops and sharing similar biological characteristics and close phylogenetic relationship. The PRSV-ZTMV recombinants were detected through small RNA sequencing of viruses infecting cucurbit samples from Guangxi and Henan provinces of China. The complete nucleotide (nt) sequences of the interspecific recombinant viruses were determined using overlapping RT-PCR. Multiple sequence alignment, recombination detection analysis and phylogenetic analysis confirmed the interspecific recombination event, and revealed an additional intraspecific recombination event among ZTMV populations in China. The symptoms and host ranges of two interspecific recombinant isolates, KF8 and CX1, were determined through experimental characterization using cDNA infectious clones. Surveys in 2017 and 2018 indicated that the incidences of the interspecific recombinant virus were 16 and 19.4%, respectively, in cucurbits in Kaifeng of Henan province. The identified interspecific recombinant virus between PRSV and ZTMV and the novel recombination pattern with the recombination site in HC-pro in potyvirid provide insights into the prevalence and evolution of ZTMV and PRSV in cucurbits.
Highlights
Cucurbits including watermelon (Citrullus lanatus), melon (Cucumis melo), cucumber (Cucumis sativus), zucchini (Cucurbita pepo), and pumpkin (Cucurbita moschata) are economically important fruit and vegetable crops worldwide
Zucchini tigre mosaic potyvirus is a member of the genus Potyvirus, containing genomic RNA of ~10.3 kb in length, which encodes two ORFs, the pretty interesting potyvirus open reading frame (ORF; encoding protein PIPO) and a single major polyprotein that is cleaved into 10 mature proteins: protein 1 (P1), helper component-protease (HC-Pro), protein 3 (P3), 6-kDa peptide 1 (6K1), Cylindrical Inclusion protein (CI), 6-kDa peptide 2 (6K2), Viral Protein genome-linked (VPg), Nuclear inclusion A-protease (Nla-pro), Nuclear inclusion B (Nlb), and Coat protein (King et al, 2011; Romay et al, 2014)
Zucchini tigre mosaic potyvirus has been detected in cucurbit crops grown in Asia, Europe, and America, as well as some Caribbean and Indian Ocean islands (Romay et al, 2014; Xiao et al, 2016; Desbiez et al, 2017; Abdalla and Ali, 2018; Wang et al, 2019); to date only seven complete genome sequences of zucchini tigré mosaic virus (ZTMV) are available in GenBank (Figure 3)
Summary
Cucurbits including watermelon (Citrullus lanatus), melon (Cucumis melo), cucumber (Cucumis sativus), zucchini (Cucurbita pepo), and pumpkin (Cucurbita moschata) are economically important fruit and vegetable crops worldwide. 15 potyviruses, one of the largest groups of plant viruses, have been reported to naturally infect cucurbits: Algerian watermelon mosaic virus (AWMV), clover yellow vein virus (ClYVV), cucurbit vein banding virus (CVBV), melon vein-banding mosaic virus (MVBMV), Moroccan watermelon mosaic virus (MWMV), papaya ringspot virus (PRSV), Sudan watermelon mosaic virus (SuWMV), turnip mosaic virus (TuMV), watermelon leaf mottle virus (WLMV), watermelon mosaic virus (WMV), wild melon vein banding virus (WMVBV), zucchini yellow fleck virus (ZYFV), zucchini yellow mosaic virus (ZYMV), zucchini tigré mosaic virus (ZTMV), and zucchini shoestring virus (ZSSV; Lecoq and Desbiez, 2012; Romay et al, 2014; Ibaba et al, 2016; Perotto et al, 2018; Moury and Desbiez, 2020). Two ZTMV isolates infecting wax gourd (Benincasa hispida) under accession number MN267689 and bitter melon (Momordica charantia) under accession number LC371337 have been detected in Guangdong and Taiwan provinces, respectively
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