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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #322630
Title: Cucumis melo endornavirus: Genome organization, host range and codivergence with the host

Author
item SABANADAZOVIC, SEAD - Mississippi State University
item Wintermantel, William - Bill
item VALVERDE, RODRIGO - Louisiana State University
item McCreight, James - Jim
item ABOUGHANEM-SABANADAZ, NINA - Mississippi State University

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2016
Publication Date: 1/22/2016
Citation: Sabanadazovic, S., Wintermantel, W.M., Valverde, R.A., McCreight, J.D., Aboughanem-Sabanadaz, N. 2016. Cucumis melo endornavirus: Genome organization, host range and codivergence with the host. Virus Research. 214:49-58.

Interpretive Summary: A high molecular weight, double stranded RNA (dsRNA) was isolated from a melon (Cucumis melo) plant (referred to as“CL01”) of an unknown cultivar and sequenced, which showed similarities with members of the Endornaviridae, a group of double-stranded RNA viruses transmitted through pollen that infect but do not cause disease of the plants they infect. The name Cucumis melo endornavirus (CmEV) is proposed. Analysis of the putative CmEV-encoded polyprotein revealed a unique genome organization, that suggested endornaviruses may be acquired by plants through multiple horizontal gene transfer events from different sources, primarily bacteria. Phylogenetic analyses of a key region of the virus genome (RdRp domain) showed that CmEV belongs to a specific lineage within the family Endornaviridae that includes exclusively plant-infecting members. There was a high incidence of CmEV among melon germplasm accessions (> 92% of tested melon samples). Analyses of partial genome sequences of CmEV isolates from 28 melon genotypes suggests adaptation and co-divergence with the host. CmEV infects plants belonging to four different genera of the family Cucurbitaceae. Such a wide host range is not reported for any known endornaviruses infecting plants, fungi or oomycetes, suggesting a long history of CmEV association with cucurbits predating their speciation.

Technical Abstract: A high molecular weight dsRNA was isolated from a Cucumis melo plant (referred to as“CL01”) of an unknown cultivar and completely sequenced. Sequence analyses showed similarities with members of the Endornaviridae. The name Cucumis melo endornavirus (CmEV) is proposed. The genome of CmEV-CL01 consist of 15,078 nt, and contains a single ORF of 4,939 amino acids that terminates with a stretch of 10 cytosine residues. Comparison of the putative CmEV-encoded polyprotein with available reference sequences in protein databases revealed a unique genome organization characterized by the presence of the following domains: viral helicase Superfamily 1 (Hel-1), two copies of putative capsular polysaccharide synthetases (CPS-1 and -2), a putative C_28_Glycosyltransferase (C28_GTS), and an RNA-dependent RNA polymerase (RdRp). The presence of three glycome-related domains of different origin makes the genome organization of CmEV-CL unique among endornaviruses and suggests their acquisition via multiple horizontal gene transfer events from different sources, primarily bacteria. Furthermore, pair-wise comparisons with related endornaviruses revealed the presence of a ‘cysteine rich region’ (CRR) previously reported in other endornaviruses as a possible domain of yet unknown function. Phylogenetic analyses of viral RdRp domains showed that CmEV belongs to a specific lineage within the family Endornaviridae that includes exclusively plant-infecting members. A RT-PCR based survey demonstrated a high incidence of CmEV among melon germplasm accessions (> 92% of tested melon samples). Analyses of partial genome sequences of 28 CmEV isolates from different melon genotypes suggests adaptation and co-divergence with the host. Finally, results of the present study revealed that CmEV infects plants belonging to four different genera of the family Cucurbitaceae. Such a wide host range is not reported for any known endornaviruses infecting plants, fungi or oomycetes, suggesting a long history of CmEV association with cucurbits predating their speciation.