Project description:Parasites with complex life cycles often manipulate the phenotype of their intermediate hosts to increase the probability of transmission to their definitive hosts. Infection with Anomotaenia brevis, a cestode that uses Temnothorax nylanderi ants as intermediate hosts, leads to a multiple-fold extension of host lifespan and to changes in behaviour, morphology and colouration. The mechanisms behind these changes are unknown, as is whether the increased longevity is achieved through parasite manipulation. Here, we demonstrate that the parasite releases proteins into its host with functions that might explain the observed changes. These parasitic proteins make up a substantial portion of the proteome of the hosts' haemolymph, and thioredoxin peroxidase and superoxide dismutase, two antioxidants, exhibited the highest abundances among them. The largest part of the secreted proteins could not be annotated, indicating they are either novel or severely altered during recent coevolution to function in host manipulation. We also detected shifts in the hosts' proteome with infection, in particular an overabundance of vitellogenin-like A in infected ants, a protein that regulates division of labour in Temnothorax ants, which could explain the observed behavioural changes. Our results thus suggest two different strategies that might be employed by this parasite to manipulate its host: secreting proteins with immediate influence on the host's phenotype and altering the host's translational activity. Our findings highlight the intricate molecular interplay required to influence the phenotype of a host and point to potential signalling pathways and genes involved in parasite-host communication.
Project description:Caffeine, a widely occurring plant alkaloid, has been shown to exhibit antimicrobial properties and influence insect behaviour. This study investigates the potential of caffeine to mitigate the effects of the fungal pathogen Beauveria bassiana in colonies of the ant Formica fusca. Using field-collected colonies, we examined the impact of a naturally relevant caffeine concentration (100 ppm) on ant survival, foraging behaviour, and gene expression under fungal exposure. Caffeine consumption delayed peak mortality and altered foraging dynamics in exposed ants, although it did not prevent fungal spore germination at the tested concentration. Transcriptomic analysis revealed significant upregulation of immune- and metabolism-related genes in exposed ants, alongside changes in genes linked to feeding behaviour and symbiotic interactions. While caffeine was a deterrent to sham-treated ants, exposed ants did not exhibit avoidance/preference. Additionally, caffeine demonstrated antifungal activity at higher concentrations, suggesting potential disruption of fungal development. These findings highlight the complex interplay between dietary compounds, pathogen defence, and ant behaviour, emphasizing the role of plant secondary metabolites in shaping insect-pathogen interactions.
Project description:<p>One of the main challenges of the socially parasitic mode of life is bypassing the host's recognition ability, which ensures that altruistic behaviour is directed towards related individuals. Various chemical strategies have evolved to achieve this goal. The most widespread, used also by the obligate slave-making ants, is camouflage or mimicry of colony odour encoded in cuticular hydrocarbon (CHC) composition. However, recent studies have shown that facultative slave-makers employ a different strategy: they manipulate the slaves' recognition labels to make them resemble the parasite's CHC profile. We examined the limitations of this strategy by focusing on incipient F. sanguinea colonies, where slaves are the majority. Our study revealed that callow F. sanguinea ants initially suppress their species-specific odour profile, which develops gradually over time accompanied by an increase of CHC amount per surface area in slave-maker workers. This allows the slaves to familiarise themselves with the parasite's CHC. We found that callow ants produce lower amounts of CHC, and the relative abundance of certain compounds differs from what is observed in older ants. Additionally, preimaginal stages of F. sanguinea ants acquire CHC from the slaves, which are later incorporated into the imagines’ recognition labels. These findings support the proposition that the parasite's manipulation strategy is limited by the slaves' learning capacity, which is necessary to maintain colony cohesion. They also shed light on the selective pressures that might have led to the evolution of chemical mimicry in mature obligate slave-maker colonies.</p>
Project description:The biting behavior observed in Carpenter ants infected by the specialized fungus Ophiocordyceps unilateralis s.l. is an example of a complex host behavioral manipulation by parasite. Though parasitic manipulation of host behavior is generally assumed to be due to the parasite’s gene expression, few studies have set out to test this. We experimentally infected Carpenter ants to collect tissue from both parasite and host during the time period when manipulated biting behavior is experienced. Upon observation of synchronized biting, samples were collected and subjected to RNA-Seq analyses. We also sequenced and annotated the O. unilateralis s.l. genome as a reference for the fungal reads. Our mixed transcriptomics approach, together with a comparative genomics study, shows that the majority of the fungal genes that are up-regulated during manipulated biting behavior are unique to the O. unilateralis s.l. genome. This study furthermore reveals that the fungal parasite might be regulating immune- and neuronal stress responses in the host during manipulated biting, as well as impairing its chemosensory communication and causing apoptosis. Moreover, we found genes up-regulated during manipulation that putatively encode for proteins with reported effects on behavioral outputs, proteins involved in various neuropathologies, and proteins involved in the biosynthesis of secondary metabolites such as alkaloids.
Project description:Female larvae of the honeybee (Apis mellifera) develop into either queens or workers depending on nutrition during larval development. This nutritional stimulus triggers different developmental trajectories, resulting in adults that differ in physiology, behaviour and life-span. To understand how these developmental trajectories are established we have undertaken a comprehensive analysis of differential gene expression throughout larval development.