Eggplant mild leaf mottle virus (EMLMV), a new putative member of the genus Ipomovirus that harbors an HC-Pro gene

Abstract

Since 2003, a new viral disease of eggplant (Solanum melongena L.) has been spreading in fields in the Jordan and Arava Valleys, Israel. The symptoms of this disease include mild leaf mottling and varying degrees of fruit distortion. This disease can be transmitted by mechanical sap inoculation, as well as by the whitefly Bemisia tabaci (Homoptera, Aleyrodidae) and has been tentatively named eggplant mild leaf mottle virus (EMLMV). Our study aimed to determine the complete sequence and genome organization of EMLMV. The extracted viral RNA was subjected to SOLiD next-generation sequence analysis and used as a template for reverse transcription synthesis, which was followed by ds-cDNA synthesis or PCR amplification. The ssRNA genome of EMLMV includes 9,280 nucleotides, excluding a 3' terminal poly-adenylated tail. The genome includes a putative single, large open reading frame (ORF) that encodes a polyprotein of 3,011 amino acids, a short overlapping ORF of PIPO protein comprised of 71 amino acids and 5' and 3' non-coding regions of 108 and 136 nucleotides, respectively. The deduced amino acid sequence of the EMLMV polyprotein is relatively close to that of sweet potato mild mottle virus (SPMMV), with 37% shared sequence identity. Among the four ipomoviruses, only SPMMV and the putative genus member EMLMV contain a helper component-proteinase (HC-Pro) gene. Like SPMMV-HC-Pro, EMLMV-HC-Pro also contains the highly conserved PTK domain that is thought to be involved in the aphid-assisted transmission of potyviruses.