Cladistic analysis of Tospovirus using molecular characters

Area of Science:

• Plant Virology
• Molecular Phylogenetics
• Virus Taxonomy

Background:

• The genus Tospovirus was historically considered to comprise only the tomato spotted wilt virus (TSWV).
• Recent serological and molecular data suggest the existence of at least four distinct Tospovirus species.
• Previous classification efforts relied on global sequence similarities of the N gene and N protein, potentially misrepresenting evolutionary relationships.

Purpose of the Study:

• To re-evaluate the classification of the Tospovirus genus using a more robust phylogenetic approach.
• To investigate the evolutionary history and genealogical relationships among Tospovirus isolates.
• To incorporate new Argentinean isolates into the Tospovirus phylogenetic framework.

Main Methods:

• Cladistic analysis using parsimony was employed to analyze RNA sequences.
• A 450-nucleotide region of the N gene was sequenced from 14 new Argentinean and 4 previously described Tospovirus isolates.
• Representatives from the Bunyaviridae family, Rift Valley Fever Virus (Phlebovirus) and Bunyamwera (Bunyavirus), were used as outgroups for phylogenetic reconstruction.

Main Results:

• Phylogenetic analysis based on cladistics provided a refined classification of the Tospovirus genus.
• The study identified distinct evolutionary lineages within the Tospovirus group, challenging previous classifications.
• The inclusion of new Argentinean isolates contributed to a more comprehensive understanding of Tospovirus diversity.

Conclusions:

• Cladistic analysis offers a more accurate representation of Tospovirus genealogy compared to analyses based solely on global sequence similarities.
• The findings support the expansion of the Tospovirus genus beyond TSWV, with evidence for multiple distinct species.
• This study provides a refined phylogenetic framework for Tospovirus classification and understanding their evolutionary dynamics.