Evolutionary ecology of parasitic fungi and their host insects

Abstract

Abstract The coevolution of parasites and their hosts is accompanied by rapid reciprocal adaptations. Recent studies focusing on the evolutionary ecology of parasitic fungi and their host insects have revealed an unexpectedly complex molecular arms race. Insects recognize the presence of invading fungi when molecular patterns associated with the fungal cell wall bind to host receptors and respond by inducing the synthesis of proteinase inhibitors and antifungal peptides such as metchnikowin. Parasitic fungi can in turn sense the presence of these host-derived defense molecules and respond by synthesizing chymotrypsin and metalloproteases to digest them. As a counter-response, insects have evolved the ability to perceive the presence of microbial metalloproteinases, inducing the synthesis of further antimicrobial peptides and the insect metalloproteinase inhibitor to regulate these virulence-associated fungal proteinases. These specific responses and counter-responses indicate that coevolution has resulted in communication between fungal parasites and their insect hosts, which was recently shown to involve transcriptional reprogramming controlled by histone acetylation/deacetylation and DNA methylation. Consequently, the reciprocal adaptations associated with host–parasite coevolution can be expanded beyond the genetic level to encompass epigenetic mechanisms.