Construction and biological characterization of an Agrobacterium-mediated infectious cDNA of squash mosaic virus

Squash mosaic virus (SqMV), a member of the species Squash mosaic virus in the genus Comovirus (family Comoviridae), is an important seed-borne virus that causes serious economic losses in cucurbit crops. Here, we constructed infectious cDNA clones of SqMV genomic RNAs (RNA1 and RNA2) under the control of the cauliflower mosaic virus (CaMV) 35S promoter by Gibson assembly. The infectious cDNA clones of SqMV could infect zucchini squash (Cucurbita pepo) plants systemically by agrobacterium-mediated inoculation. The virus progeny from the infectious clones showed no difference from the wild type in terms of pathogenicity and symptom induction. It could be mechanically transmitted to zucchini squash (Cucurbita pepo), pumpkin (Cucurbita moschata), cucumber (Cucumis sativus), and muskmelon (Cucumis melo) but not watermelon (Citrullus lanatus) or Nicotiana benthamiana. This is the first report of construction of a SqMV infection clone and will facilitate the investigation of viral pathogenesis and host interactions.