Genetic underpinnings of host manipulation by Ophiocordyceps as revealed by comparative transcriptomics

The ant-infecting Ophiocordyceps fungi are globally distributed, host manipulating, specialist parasites that drive aberrant behaviors in infected ants, at a lethal cost to the host. An apparent increase in activity and wandering behaviors precedes a final summiting and biting behavior on to vegetation, positioning the manipulated ant in a site beneficial for fungal growth and transmission. Notably, across Ophiocordyceps species and other known host manipulators, the molecular mechanisms underlying behavioral changes remain largely unclear.

We explored possible genetic underpinnings of host manipulation by: (i) producing a hybrid assembly of the Ophiocordyceps camponoti-floridani genome, (ii) conducting laboratory infections coupled with RNAseq of both O. camponoti-floridani and its host, Campontous floridanus, and (iii) using these data for a comparative analysis to similar work performed in Ophiocordyceps kimflemingiae and Camponotus castaneus.

We propose differentially expressed genes tied to ant neurobiology, odor response, circadian rhythms, and foraging behavior may be the result of putative fungal effectors such as enterotoxins, aflatrem, and mechanisms disrupting nutrition-sensing or caste-identity pathways.