Can Insects Develop Resistance to Insect Pathogenic Fungi?

Abstract

Microevolutionary adaptations and mechanisms of fungal pathogen resistance were explored in a melanic population of the Greater wax moth, Galleria mellonella. Under constant selective pressure from the insect pathogenic fungus Beauveria bassiana, 25th generation larvae exhibited significantly enhanced resistance, which was specific to this pathogen and not to another insect pathogenic fungus, Metarhizium anisopliae. Defense and stress management strategies of selected (resistant) and non-selected (susceptible) insect lines were compared to uncover mechanisms underpinning resistance, and the possible cost of those survival strategies. We hypothesize that the insects developed a transgenerationally primed resistance to the fungus B. bassiana, a costly trait that was achieved not by compromising life-history traits but rather by prioritizing and re-allocating pathogen-species-specific augmentations to integumental front-line defenses that are most likely to be encountered by invading fungi. Specifically during B. bassiana infection, systemic immune defenses are suppressed in favour of a more limited but targeted repertoire of enhanced responses in the cuticle and epidermis of the integument (e.g. expression of the fungal enzyme inhibitor IMPI, and cuticular phenoloxidase activity). A range of putative stress-management factors (e.g. antioxidants) is also activated during the specific response of selected insects to B. bassiana but not M. anisopliae. This too occurs primarily in the integument, and probably contributes to antifungal defense and/or helps ameliorate the damage inflicted by the fungus or the host’s own immune responses.

Highly specific host-pathogen interactions influence Metarhizium brunneum blastospore virulence against Culex quinquefasciatus larvae

“…Some studies reported a possible positive correlation between melanisation, PO activity, and tolerance to parasites and pathogens such as B. bassiana and M. anisopliae [59,60]. In our electron microscopy studies of the head region, we found that infection of M. brunneum blastospores triggers a melanisation response by Cx.…”

Coevolution of parasitic fungi and insect hosts

“…This defense mechanism is found naturally (Dubovskiy et al, 2013a) or can be the outcome of experimental coevolution (Dubovskiy et al, 2013b), indicating that natural melanism in this species may have evolved as a heritable response to fungal infection.…”

“…To determine whether the insects could evolve to acquire resistance to the fungi, experimental coevolution was carried out using G. mellonella and B. bassiana (Dubovskiy et al, 2013b). A melanic G. mellonella population was selected over 25 generations for increased resistance towards B. bassiana.…”

Control of Mahanarva fimbriolata (Stl) (Hemiptera: Cercopidae) with entomopathogenic fungus and insecticides using two sampling methods on sugarcane fields

“…However, although generalizations cannot be made, the cumulative effect is controlled by the weather, the active constituent of the insecticide, the chemical mode of action, and the M. anisopliae isolated to control M. fimbriolata (Dinardo-Miranda et al, 2004a;Loureiro et al, 2005). On other hand, the genetic constitution of the pest population (Quinelato et al, 2012), adaptations and mechanisms of insect resistance (Dubovskiy et al, 2013) may influence the efficiency of the control techniques.…”