Molecular Characterization of a Carla virus Infecting Eggplant the Role of Virus Proteins in Pathogenesis

Abstract

Present study is the first report of complete genome sequence and host range study of eggplant infecting Carlavirus Pepper virus A from India. We report the complete RNA genome sequence of 8669 nucleotides, excluding poly (A) tail of eggplant infecting Carlavirus (IND-SHM) isolate originating from Telangana State of India. Host range study showed that this virus is restricted to eggplant and tomato, causing mild to severe mosaic and mottling symptoms. The phylogenetic and sequence analysis revealed that replicase and coat protein of this isolate share 88% and 92% similarity respectively, at amino acid level with hot pepper infecting Pepper virus A (KU726694). Genome sequence similarity and phylogenetic analysis suggests that IND-SHM isolate is the strain of Pepper virus A. Complete genome sequence of eggplant infecting Carlavirus IND-SHM isolate is deposited in GenBank (accession no. MH725809). Total 13 CP sequences of eggplant (12) and tomato (1) was deposited in NCBI GenBank. Virus transmission study showed that the eggplant infecting Pepper virus A was transmitted through sap, grafting and whitefly. RNA silencing suppressor screening in present investigation revealed that the ORF5 of Pepper virus A exhibits a local RNA silencing suppression activity and ORF6 has showed local as well as systemic RNA silencing suppression activity when co-infiltrated with GFP in 16C line. Study highlighted the eggplant infecting Pepper virus A encodes more than one RNA silencing suppressors viz. ORF5 and ORF6. Pathogenesis study using Potato virus X as heterologus expression system showed that ORF5 of Pepper virus A infiltrated N. benthamiana caused severe mosaic and mottling of the leaves. Whereas the ORF6 of Pepper virus A infiltrated plants showed severe mosaic initially and in later stage of infection caused leaf and stem necrosis. It indicates that ORF6 of Pepper virus A plays an important role in pathogenicity determination. Based on our findings, we conclude that ORF6 plays dual role viz. strong RNA silencing suppressor a