Aspartyl protease in the secretome of honey bee trypanosomatid parasite contributes to infection of the host

Exoproteome represents the proteome consisting of all secreted proteins and proteins derived from the cell surface and lysed cell. The exoproteome of the trypanosomatid parasite should interact with the host cells and the associated microbiota; however, the roles of infecting insect hosts are not yet understood. To uncover the functions of exoproteome, we identified the exoproteome of honey bee trypanosomatid parasite, Lotmaria passim, and found that approximately 28 % are shared with that common between Leishmania spp. It demonstrates a core exoproteome with conserved functions exists in the Leishmaniinae lineage. The bioinformatic characterization suggests that L.passim exoproteome may interact with the host and its microbiota as well as their metabolites. Deletion of genes encoding two secretome proteins revealed that an aspartyl protease but not chitinase affects the development of L. passim under the culture condition and is necessary for the efficient infection in the honey bee gut. Our results demonstrate that the exoproteome represents a resource to uncover the mechanisms of trypanosomatid parasites to infect the insect host by interacting with the gut environment.