Genetic Basis of Coleopteran Vectorial Capacity for Bean pod mottle virus Transmission

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Why do some leaffeeding arthropods transmit plant pathogens while others do not? Moreover, why typically are only a small minority of individuals within a vector species proficient at transmitting a particular pathogen? A considerable number of coleopteran beetles transmit viruses that cause disease to economically important vegetables and crops. However, the degree of variation within and among beetle species in their ability to harbor and transmit pathogens is remarkable (i.e. their vector competence). The genetic makeup of the vector undoubtedly contributes significantly to its susceptibility to pathogen infection and transmission, yet characterization of specific genes that influence vector competence has proven elusive. The longterm goal of the proposed research is to understand the genetic interactions and mechanisms of pathogen transmission by insects. Identifying genes that disrupt vector-mediated pathogen transmission will lead to novel and promising avenues for disease control. The proposed research will harness the unique attributes of a soybean pathosystem, consisting of three beetle species that exhibit individual and species level variation in their ability to vector a soybean virus that is prevalent in North America, Bean pod mottle virus (BPMV). My previous research strongly suggested that the genetic key' to BPMV transmission capability lies in the beetle's own regurgitant, which is deposited at leaf wounding sites during feeding. Given the role of insect effector genes in encoding proteins that alter plant defenses, I hypothesized that the complement of effectors secreted in the beetle's regurgitant also impacts host plant susceptibility to insectborne pathogen invasion. To explore this, the proposed research will integrate comparisons of beetle regurgitant transcriptomes and data on vector competence and genomic variability to identify, and then test candidate effectors for their influence on vector competence. Objective 1. Characterize interspecific and intraspecific differences in the regurgitant composition of effector genes. Objective 2. Develop RNAibased tools to functionally characterize the role of candidate effectors identified in Objective 1. Objective 3. Determine the extent of variation in BPMV transmission rates and candidate gene sequence polymorphism in natural populations.I expect to identify and functionally implicate a subset of genes that contribute to the differences in BPMV vectorial capacity within and among beetle species. Further, the proposed work will lead to a better understanding of the genetic, evolutionary and environmental factors that drive insect-vectored disease transmission.