Assistant Professor University of Tennessee Knoxville, Tennessee
Insect-associated microbes impact host phenotypes like resistance to pathogens. Eukaryotic pathogens also ‘host’ microbes, and emerging evidence shows that bacteria within pathogenic fungi can affect virulence. Insect and pathogen microbial communities likely both contribute to host resistance. Further, how these associations evolve is relevant to threats pathogens pose to humans, agriculture, and biodiversity. The fungal pathogen Pandora neoaphidis infects pea aphids (Acyrthisiphon pisum), a pest of legume crops, and is a tractable system for studying microbial symbiont effects on host-pathogen interactions. In 2021-2022, we collected 851 pea aphids from wild legume plants and recorded whether each aphid became infected by Pandora. We screened aphids for facultative bacterial symbionts including Regiella insecticola and Rickettsia sp. which are hypothesized to increase aphid resistance to pathogen infection compared to symbiont-free aphids. One in six aphids (149 of 851) succumbed to Pandora infection resulting in a sporulating cadaver. Aphids harboring Rickettsia sp. were less likely to be killed by Pandora than aphids without the symbiont. The presence of Regiellainsecticola, however, was not associated with protection from Pandora. Further investigation revealed that Regiella samples were genetically variable and distinguished into two clades, with the dominant clade (clade 2) representing 213 of 228 samples. Whole genome sequencing in the future will further characterize our population of Regeilla and if genetic variability explains pathogen “breakthroughs” in protection. 16S amplicon sequencing of Pandora spores will assess how the pathogen’s bacterial microbiome contributes to breakthrough infections.
