We are interested in three broad research areas: i) ecology of emerging diseases, ii) pathogen transmission biology, and iii) insect-microbe interactions. We currently use two research systems to address questions of interest, the xylem-limited leafhopper-transmitted bacterium Xylella fastidiosa, and the mealybug-borne grapevine leafroll virus complex. We have worked with other systems and are open to the possibility of exploring new emerging diseases. Below is a brief discussion of each of these areas of interest.
Ecology of emerging insect-borne plant diseases
We are interested in understanding the factors driving the emergence of new diseases by studying different aspects of pathogen and disease ecology. We incorporate approaches used in molecular ecology and evolutionary biology to vector-borne pathogens by exploring the genetic structure of microbes to infer the history of epidemics and potential evolutionary trajectories of emerging pathogens. For example, a study we did with collaborators in Brazil used a multi-locus sequencing approach to determine the structure of a bacterium causing two diseases, which we found to be in fact to caused by two genetically and biologically different strains of this organism. Interestingly, although these strains were found to be recombining, they were diverging from each other sympatrically. In another study, we used a molecular approach to study the spread of an introduced plant virus in Hawaii, and were able to demonstrate that all the events leading to the invasion of new islands were associated with the first infected island, suggesting anthropogenic spread of infected plant material as a driving factor of that epidemic. We are also interested in testing other hypotheses aimed at explaining what are the ecological factors driving emerging diseases.
Transmission of insect-borne plant pathogens
An essential component to any research on insect-borne diseases is a good understanding of how vectors acquire the pathogen from an infected host and later inoculate it into a susceptible one (i.e. transmission process). It is also important to identify what organism is the vector and the relationships between vector and pathogen taxa. We use two model systems to address questions of relevance to other vector-borne plant pathogens. A lot of research on this topic involves classical transmission experiments.
Insect symbiosis is a thriving field of biological sciences. We use two systems to study insect symbiotic relationships (not necessarily mutualisms), one is a leafhopper-borne plant pathogenic bacterium (Xylella fastidiosa) and another are stink bug (pentatomid) gut symbionts. For X. fastidiosa, we are interested in how this bacterium attaches to the cuticular lining of the foregut of leafhoppers. We are now exploring new ideas aimed at blocking pathogen adhesion to vectors, which would disrupt the transmission process. Our other system focuses on bacteria that colonize the midgut of stink bugs. We showed that a group of bacteria colonize the gut of several stink bug species analyzed, but they are polyphyletic rather than having a common ancestor like most other vertically transmitted bacterial symbionts. In addition, vertical transmission occurs when newly hatched nymphs probe on the surface of eggs, onto which females smeared the symbionts.