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Title: Create the genus Pelarspovirus in the family Tombusviridae

item SCHEETS, KAY - Oklahoma State University
item Jordan, Ramon
item WHITE, ANDY - York University
item HERNANDEZ, CARMEN - Polytechnic University Of Valencia (UPV)

Submitted to: Electronic Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2015
Publication Date: 7/24/2016
Citation: Scheets, K., Jordan, R.L., White, A., Hernandez, C. 2016. Create the genus Pelarspovirus in the family Tombusviridae. Electronic Publication.

Interpretive Summary: A significant factor in the continued growth of the ornamentals industry is the introduction of new plant species and varieties to the trade; however the introduction of new plant materials also brings the risk of new viral diseases as new crops are introduced or grown in new areas. Over the past several years, research on established and new or emerging viruses of geranium and roses has revealed that several of these viruses posses unique biochemical and genomic features that differentiate them from other related viruses. This contribution is the final publication in the process of establishing a new plant virus genus in the Family Tombusviridae. The International Committee on the Taxonomy of Viruses (ICTV) is charged with the task of developing, refining and maintaining a universal virus taxonomy. Viruses, including those that are pathogens of plants, are mainly classified by phenotypic characteristics, such as the size and shape of the virus, nucleic acid size and type (DNA or RNA), genome organization, mode of replication, host(s), and the type of disease they cause. The creation or elimination, (re)naming, and (re)assignment of a virus species, genus, (sub)family, or order are all taxonomic acts that require public scrutiny and debate, leading to formal approval by the full membership of the ICTV. The first step in our process of establishing a new plant virus genus was to create four new unassigned virus species in the family Tombusviridae. The second step was to formally publish the scientific evidence of the key distinguishing characteristics of at least six viruses to be included in this new genus and the rational for its establishment. This report is the final proposal to ICTV demonstrating that there is sufficient molecular and phylogenetic support for the creation of the new genus Pelarspovirus in family Tombusviridae.

Technical Abstract: In 2014 we submitted a proposal to create this new genus with six members. The Executive Committee (EC) of the ICTV did not support its creation at that time due to the placement of the pelarspovirus genus branch within a larger monophyletic lineage of many of the members of the carmovirus genus which have very similar genome organizations. The EC suggested that we revise that original proposal to one to create four new unassigned species in the family Tombusviridae. The EC also suggested a revision of the family with particular emphasis on the carmovirus genus, and the Tombusviridae Study Group (SG) is submitting a separate proposal that divides the current carmovirus genus into three new genera (Alphacarmovirus, Betacarmovirus, and Gammacarmovirus). Additionally, the genus demarcation criteria have been revised in the carmovirus proposal to include translational characteristics and to emphasize that the complete RNA-dependent RNA polymerase (RdRp) is the most useful protein for providing phylogenetic trees that define the genera. The division of carmovirus and the revised demarcation criteria provide a new framework for examining the creation of genus Pelarspovirus. Revised genus demarcation criteria in the family Tombusviridae include structural criteria - spherical virions with either a smooth or granular appearance; genomic criteria - genome organization, number of genome segments, size of genome, translation characteristics; polymerase criteria - gene interrupted by a termination codon or a -1 ribosomal frameshifting element that is periodically read through; and differential branching of phylogenetic trees based on the complete RdRp. Phylogenetic analysis of the predicted Pelarspovirus proteins indicate that they always cluster as a separate group from the other Tombusviridae members, including alpha-, beta-, and gammacarmoviruses. Suggested species demarcation criteria in the new Pelarspovirus genus include <75% amino acid sequence identity in RdRp proteins and <75% identity in coat proteins. Pelargonium line pattern virus is the well-characterized member and is designated as type species. The origin of the new genus name is the sigla from Pelargonium ringspot virus, the first of these viruses to be named and described.