New research horizons in vector-transmission of plant viruses.

Understanding the mechanisms controlling vector-transmission of plant viruses requires integrating information from at least three different viewpoints: virus-vector interactions, plant-vector interactions and virus-plant interactions. While some of these aspects have been covered by past and present investigations, others have been bypassed completely, because of technical bottlenecks or conceptual lacunas. Here, we highlight recent advances and needs in hitherto poorly documented aspects of vector transmission, such as characterization of the vector molecules responsible for initial viral recognition, and the role of vector saliva in inoculation and initial onset of infection in a new plant. We also propose and discuss some novel conceptual and complementary questions that are opening up fascinating new horizons in this field. We explore the possible existence of viral morphs with specific properties that facilitate acquisition by vectors, and discuss the dynamics/genetics of such viral subpopulations, which could differentiate and specialize in different host compartments.