Construction and Biological Characterization of Papaya Leaf Curl Guangdong Virus Infectious cDNA Clone

Papaya leaf curl Guangdong virus (PaLCuGDV), a member of the genus Begomovirus, poses a significant threat to passion fruit (Passiflora edulis) cultivation. A recent field survey in the Rongjiang area of Guizhou Province revealed a high natural infection rate of PaLCuGDV (90.1%; 209/232 plants). From a naturally infected passion fruit plant, the complete genome of a PaLCuGDV isolate was cloned and sequenced. The obtained genome, designated PaLCuGDV-GZ (GenBank OP901623.1), comprises 2732 nucleotides and shows > 90% similarity to other Chinese PaLCuGDV isolates based on BLAST analysis. To experimentally investigate its pathogenicity, an infectious clone containing a 1.4-mer of the viral genome was constructed. Agroinoculation using this clone demonstrated that PaLCuGDV infection induced mild leaf wrinkling, curling, and chlorosis in Nicotiana benthamiana, whereas it caused severe leaf curl and mosaic symptoms in passion fruit. The average experimental infection rate reached 46.7% in P. edulis, while it was 96.7% in N. benthamiana at 4 weeks post-inoculation. Furthermore, transmission electron microscopy of N. benthamiana leaves infected with the infectious clone revealed two key findings: purified virions exhibited a unique "twin icosahedral" structure, and infected cells showed a significant reduction in chloroplast number along with abnormal chloroplast morphology. In summary, this study reports the prevalence of PaLCuGDV in the field and successfully establishes an infectious clone, which provides an essential tool for future research into the gene function, pathogenicity, and virus-host interactions of this economically important virus.