Development of a full-length infectious clone of sunflower chlorotic mottle virus (SuCMoV)

Rapid Construction of Stable Infectious Full-Length cDNA Clone of Papaya Leaf Distortion Mosaic Virus Using In-Fusion Cloning

Papaya leaf distortion mosaic virus (PLDMV) is becoming a threat to papaya and transgenic papaya resistant to the related pathogen, papaya ringspot virus (PRSV). The generation of infectious viral clones is an essential step for reverse-genetics studies of viral gene function and cross-protection. In this study, a sequence- and ligation-independent cloning system, the In-Fusion^® Cloning Kit (Clontech, Mountain View, CA, USA), was used to construct intron-less or intron-containing full-length cDNA clones of the isolate PLDMV-DF, with the simultaneous scarless assembly of multiple viral and intron fragments into a plasmid vector in a single reaction. The intron-containing full-length cDNA clone of PLDMV-DF was stably propagated in Escherichia coli.In vitro intron-containing transcripts were processed and spliced into biologically active intron-less transcripts following mechanical inoculation and then initiated systemic infections in Carica papaya L. seedlings, which developed similar symptoms to those caused by the wild-type virus. However, no infectivity was detected when the plants were inoculated with RNA transcripts from the intron-less construct because the instability of the viral cDNA clone in bacterial cells caused a non-sense or deletion mutation of the genomic sequence of PLDMV-DF. To our knowledge, this is the first report of the construction of an infectious full-length cDNA clone of PLDMV and the splicing of intron-containing transcripts following mechanical inoculation. In-Fusion cloning shortens the construction time from months to days. Therefore, it is a faster, more flexible, and more efficient method than the traditional multistep restriction enzyme-mediated subcloning procedure.

Construction of infectious clones of tomato torrado virus and their delivery by agroinfiltration

The first biologically active infectious clones of tomato torrado virus (ToTV) were generated and delivered into Nicotiana benthamiana and Solanum lycopersicum plants via Agrobacterium tumefaciens. The engineered constructs consisted of PCR-amplified complementary DNAs derived from the ToTV RNA1 and RNA2 components, individually inserted into an engineered pGreen binary vector between the CaMV 35S promoter and nopaline synthase terminator. These constructs were introduced into the plant hosts by means of A. tumefaciens-mediated infiltration. In the presence of the progeny virus, typical symptoms of ToTV infection developed in N. benthamiana and S. lycopersicum. Moreover, the virus was sap-transmissible when isolated from agroinfiltrated plants and induced symptoms similar to those caused by the wild-type virus. The presence of viral particles and viral genetic material was confirmed by electron microscopy and re-inoculation to S. lycopersicum and N. benthamiana, as well as by reverse transcription polymerase chain reaction and high-resolution melt analysis.