COMPARISON OF THE COAT PROTEIN OF A SOUTH INDIAN STRAIN OF PRSV WITH OTHER STRAINS FROM DIFFERENT GEOGRAPHICAL LOCATIONS
M.V. Hema, D.T. Prasad
Papaya ring spot virus (PRSV) causes major diseases in papaya and cucurbits in the Indian sub-continent that result in significant yield losses. Molecular characterization of the coat protein (CP) gene of a South Indian strain (INP-UAS) of PRSV-P revealed an open reading frame of 849 bp that encoded the putative coat protein of 283 amino acids (GenBank Acc No. AF528190). The DAG triplet associated with aphid transmissibility and the potential protease cleavage site Q/S, located in the N-terminus of the INP-UAS CP, were conserved, as has been reported for other PRSV coat proteins. The sequence had a deletion of 24 nucleotides that corresponded to eight amino acids in the N-terminal region of the CP. A comparison of the amino acid sequence of the INP-UAS CP with those reported for other PRSV isolates showed that the N-termini were variable and suggested that the distinctiveness of INP-UAS was linked to its geographical location. Phylogenetic analysis also showed that the INP-UAS strain coat protein gene was relatively divergent from those of other PRSV-P isolates as it formed a separate and distinct group. The implications of sequence variability for the use of CPgenes in the development of transgenic plants for viral resistance are discussed.