Abstract:
Apoptosis is not only pivotal for development, but also for pathogen defence in multicellular
organisms. Although numerous intracellular pathogens are known to interfere with the
host’s apoptotic machinery to overcome this defence, its importance for host-parasite
coevolution has been neglected. We conducted three inoculation experiments to investigate
in the apoptotic respond during infection with the intracellular gut pathogen Nosema
ceranae, which is considered as potential global threat to the honeybee (Apis mellifera) and
other bee pollinators, in sensitive and tolerant honeybees. To explore apoptotic processes
in the gut epithelium, we visualised apoptotic cells using TUNEL assays and measured the
relative expression levels of subset of candidate genes involved in the apoptotic machinery
using qPCR. Our results suggest that N. ceranae reduces apoptosis in sensitive honeybees
by enhancing inhibitor of apoptosis protein-(iap)-2 gene transcription. Interestingly, this
seems not be the case in Nosema tolerant honeybees. We propose that these tolerant honeybees
are able to escape the manipulation of apoptosis by N. ceranae, which may have
evolved a mechanism to regulate an anti-apoptotic gene as key adaptation for improved
host invasion.
