Agroinfection of tobacco by croton yellow vein mosaic virus and designing of a replicon vector for expression of foreign gene in plant.

Croton yellow vein mosaic virus (CYVMV, genus Begomovirus family Geminiviridae) is a proliferating begomovirus in the Indian sub-continent. The infectious constructs in binary vector was developed against the CYVMV genome and its associated betasatellite. Agroinoculation of the genomic construct of CYVMV produced leaf curl symptoms alone in three species of tobacco, Nicotiana tabacum, N. benthamiana and N. glutinosa. Co-inoculation of betasatellite enhanced the severity of the disease and reduced the incubation time. Based on the infectious clone, a replicon vector pCro, with only the ability to replicate inside the plant was developed. In pCro vector, CP and V2 ORFs from genome of CYVMV was deleted, which resulted localised replication of the molecule with no visible symptoms. Besides the partial CYVMV genome, pCro also has a cassette containing a double 35S promoter, multiple cloning sites and a NOS terminator to overexpress any foreign protein in plant. Episomal release of the replicon from the binary vector backbone after agroinoculation was detected by PCR. A GFP gene was cloned in pCro vector (pCro-GFP) and agroinoculated to N. tabacum resulted in localized expression of GFP at 5 dpi. The CYVMV replicon vector will be a useful tool for studying functional genomics, vaccine expression and gene silencing in plant.