Family Level Phylogenies Reveal Relationships of Plant Viruses within the Order Bunyavirales

Abstract

Bunyavirales are negative-sense segmented RNA viruses infecting arthropods, protozoans, plants, and animals. This study examines the phylogenetic relationships of plant viruses within this order, many of which are recently classified species. Comprehensive phylogenetic analyses of the viral RNA dependent RNA polymerase (RdRp), precursor glycoprotein (preGP), the nucleocapsid (N) proteins point toward common progenitor viruses. The RdRp of Fimoviridae and Tospoviridae show a close evolutional relationship while the preGP of Fimoviridae and Phenuiviridae show a closed relationship. The N proteins of Fimoviridae were closer to the Phasmaviridae, the Tospoviridae were close to some Phenuiviridae members and the Peribunyaviridae. The plant viral movement proteins of species within the Tospoviridae and Phenuiviridae were more closely related to each other than to members of the Fimoviridae. Interestingly, distal ends of 3′ and 5′ untranslated regions of species within the Fimoviridae shared similarity to arthropod and vertebrate infecting members of the Cruliviridae and Peribunyaviridae compared to other plant virus families. Co-phylogeny analysis of the plant infecting viruses indicates that duplication and host switching were more common than co-divergence with a host species.

A Look into Bunyavirales Genomes: Functions of Non-Structural (NS) Proteins

“…The Phenuiviridae family includes animal, plant, insect, and human pathogens [ 11 , 19 ]. Human pathogens are generally transmitted by ticks or phlebotomus sandflies, although RVFV, a notable human pathogen, is an outlier transmitted by Aedes and Culex mosquitos [ 19 ].…”

“…RVFV and other Phenuiviridae human pathogens, including Severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), Punta Toro virus (PTV), and Toscana virus (TOSV) share a similar genomic organization of structural and NS proteins. While the genomic L and M segments are of negative polarity [ 11 ], the S segment is uniquely ambisense, encoding the NP and an antigenomic NSs ( Figure 3 ) [ 19 ]. Interestingly, while the NSs is weakly conserved across Phenuiviridae in amino acid sequence, its function as an interferon (IFN) antagonist is highly conserved [ 19 ].…”

“…The NSs protein of the Phenuiviridae members RVFV and SFTSV are among the most well studied NS proteins of the Bunyavirales order. The NSm, preceding the Gn and Gc in the M segment ORF ( Figure 3 ), is not as extensively studied but is thought to play a role in maintaining infection in viral vectors [ 11 ].…”

“…Across the order, genomes consist of two to six segments and this can vary even within specific families. For example, viruses in the Arenaviridae , Wupedeviridae , and Unassigned families typically have bi-segmented genomes, while viruses in Fimoviridae and the Phenuiviridae subfamily tenuivirus can have four to six [ 6 , 7 , 8 , 9 , 10 , 11 ]. However, generally bunyaviruses have three genomic segments: the small (S) segment of ~1–2kb, medium (M) segment of ~3.7–5kb, and the large (L) segment varying from ~6.8–12kb [ 12 , 13 ] ( Figure 2 and Figure 3 ).…”

Introduction to Special Issue of Plant Virus Emergence

“…Torrance and Talianksly make the case for research that integrates phylogenetic analyses and high-throughput next-generation sequencing for the detection, identification, and surveillance of new virus strains. Along these lines, Herath et al present, in “ Family Level Phylogenies Reveal Relationships of Plant Viruses within the Order Bunyavirales ” [ 9 ], the importance of phylogenetics in consideration of emergence negative-sense segmented RNA viruses infecting arthropods, protozoans, plants, animals, and humans. Comprehensive phylogenetic analyses of the four “hallmark” genes demonstrated the relatedness of virus species across host eukaryotic species, herein reinforcing the similar emergence phenomena that occur in both plant and animal systems.…”