Elucidating complex interactions between viruses and vectors: Virus impacts on biology and behavior
Kerry Mauck: University of California, Riverside
<div>Dependence on vectors for transmission shapes the evolution of plant virus adaptations for facilitating acquisition, retention, and inoculation. Until recently, it was hypothesized that these adaptations are limited to virus proteins that enable virion binding to vector mouthparts or invasion of internal tissues. However, we now have evidence that viruses can manipulate host plant phenotypes in ways that enhance transmission by vectors. Viruses influence vector behavior through alteration of plant cues that mediate vector orientation, feeding, and dispersal behaviors. These cues include tactile and visual aspects, odors, defenses, secondary metabolites, sugars, and free amino acids. Effects are not uniform, but exhibit convergence depending on the specific frequency and duration of probing and feeding required to transmit distinct types of plant viruses. The induction of similar phenotypes by phylogenetically divergent viruses transmitted via the same sequences of vector behavior supports the hypothesis that virus effects are not just by-products of infection. Instead, effects are purportedly induced by multifunctional proteins that, in addition to primary roles in host plant exploitation, have evolved secondary functions as effectors of host phenotypes. The question of whether viruses can evolve manipulative functions in natural or agricultural settings is central to our understanding of the ecological and epidemiological importance of host and vector manipulation. To address this question, we synthesized available literature to identify patterns in virus effects among pathogens with shared transmission mechanisms. Results are discussed in the context of molecular and environmental constraints on virus evolution, limitations of existing studies, and prospects for future research.</div>
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