Dodecanol, metabolite of entomopathogenic fungus Conidiobolus coronatus, affects fatty acid composition and cellular immunity of Galleria mellonella and Calliphora vicina

Michalina Kazek,Agata Kaczmarek,Anna Katarzyna Wrońska,Mieczysława Irena Boguś

doi:10.1038/s41598-021-95440-6

Michalina Kazek, Agata Kaczmarek + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-95440-6

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Abstract

One group of promising pest control agents are the entomopathogenic fungi; one such example is Conidiobolus coronatus, which produces a range of metabolites. Our present findings reveal for the first time that C. coronatus also produces dodecanol, a compound widely used to make surfactants and pharmaceuticals, and enhance flavors in food. The main aim of the study was to determine the influence of dodecanol on insect defense systems, i.e. cuticular lipid composition and the condition of insect immunocompetent cells; hence, its effect was examined in detail on two species differing in susceptibility to fungal infection: Galleria mellonella and Calliphora vicina. Dodecanol treatment elicited significant quantitative and qualitative differences in cuticular free fatty acid (FFA) profiles between the species, based on gas chromatography analysis with mass spectrometry (GC/MS), and had a negative effect on G. mellonella and C. vicina hemocytes and a Sf9 cell line in vitro: after 48 h, almost all the cells were completely disintegrated. The metabolite had a negative effect on the insect defense system, suggesting that it could play an important role during C. coronatus infection. Its high insecticidal activity and lack of toxicity towards vertebrates suggest it could be an effective insecticide.

Highlights

In their natural environment, insects have to cope with a variety of microorganisms, and as such, have developed a complex and efficient defense system
The quantitative profiles of the dodecanol produced by C. coronatus were found to depend on the type of culture medium: C. coronatus cultured in MM medium produced significantly more dodecanol than that propagated in rich LB medium—twice the amount was observed during the three-week incubation (Student’s t-test p < 0.001) and 1.4 times the amount during the four-week incubation (Student’s t-test p = 0.001) (Supplementary Table 1)
Our present findings indicate that a metabolite of C. coronatus, dodecanol, is secreted into the medium in which the fungus grows; it kills G. mellonella imagoes, prevents most C. vicina larvae from successfully completing metamorphosis and reaching the imago stage, has a negative impact on the hemocytes of G. mellonella and C. vicina, as well as the Sf9 cell line, and alters the cuticular free fatty acid (FFA) profiles of both species

Summary

Introduction

Insects have to cope with a variety of microorganisms, and as such, have developed a complex and efficient defense system. Successful penetration of the host body is followed by the death of the host, either by mechanical damage of the internal organs, the action of toxic metabolites or exhaustion of nutrients Due to their ability to infect and kill insects, entomopathogenic fungi offer great potential as biological control agents. C. coronatus produces two key insecticidal proteins: cronatin-1 (36 kDa), showing both elastolytic and chitinolytic activities, and coronatin-2 (14.5 kDa), which does not appear to demonstrate any enzymatic activity Both proteins are toxic to G. mellonella hemocytes, being known to disintegrate the nets formed by granulocytes and plasmatocytes by rapid degranulation of granulocytes, and to cause extensive vacuolization of plasmatocytes accompanied by cytoplasm expulsion and cell d isintegration[19,25]

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