Abstract
Tomato spotted wilt virus (TSWV) is a generalist pathogen with one of the broadest known host ranges among RNA viruses. To understand how TSWV adapts to different hosts, we experimentally passaged viral populations between two alternate hosts, Emilia sochifolia and Datura stramonium, and an obligate vector in which it also replicates, western flower thrips (Frankliniella occidentalis). Deep sequencing viral populations at multiple time points allowed us to track the evolutionary dynamics of viral populations within and between hosts. High levels of viral genetic diversity were maintained in both plants and thrips between transmission events. Rapid fluctuations in the frequency of amino acid variants indicated strong host-specific selection pressures on proteins involved in viral movement (NSm) and replication (RdRp). While several genetic variants showed opposing fitness effects in different hosts, fitness effects were generally positively correlated between hosts indicating that positive rather than antagonistic pleiotropy is pervasive. These results suggest that high levels of genetic diversity together with the positive pleiotropic effects of mutations have allowed TSWV to rapidly adapt to new hosts and expand its host range.
Highlights
Tomato spotted wilt virus (TSWV) is a generalist pathogen with one of the broadest known host ranges among RNA viruses
While little is known about the realized host range of any particular genotype of TSWV in nature, TSWV vectors like western flower thrips (Frankliniella occidentalis) feed on hundreds of plant species[5], making it highly probable that a single viral lineage may move between multiple crop and wild host species over the course of a single growing season and overwinter in another perennial h ost[12]
Single nucleotide variant (SNV) frequencies were highly correlated between the paired sequencing replicates (Fig. 2), suggesting that our sequencing protocol introduced little sampling variance and that the sequence data accurately reflects the genetic composition of the original viral populations
Summary
Tomato spotted wilt virus (TSWV) is a generalist pathogen with one of the broadest known host ranges among RNA viruses. While little is known about the realized host range of any particular genotype of TSWV in nature, TSWV vectors like western flower thrips (Frankliniella occidentalis) feed on hundreds of plant species[5], making it highly probable that a single viral lineage may move between multiple crop and wild host species over the course of a single growing season and overwinter in another perennial h ost[12]. The genome encodes for two genes that likely reflect specific adaptations to plants and insects: the silencing suppressor NSs, which helps counteract host antiviral RNA silencing, and the movement protein NSm, which is involved in both cell-to-cell and long-distance movement in plants[13]. In a positive-sense orientation while the other three are in a negative-sense orientation and must first be transcribed by RdRp into viral mRNAs before translation of the full set of proteins required for infection can occur
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
