Differential potency of drosomycin to Neurospora crassa and its mutant: implications for evolutionary relationship between defensins from insects and plants

Drosomycin, the first inducible antifungal peptide isolated from Drosophila, belongs to the superfamily of CSalphabeta-type defensins. In the present study we report a modified approach for high-level expression of drosomycin, which allows us to evaluate its differential potency on the filamentous fungus Neurospora crassa WT (wild type) and N. crassa MUT16, a specific resistance mutant strain to plant defensins, by using different approaches. The results presented here show for the first time that N. crassa MUT16 is resistant to our recombinant drosomycin. Differential survival rates of Drosophila larvae infected by N. crassa WT and MUT16 further confirm the key antifungal role of drosomycin in vivo. The absence of activity against MUT16 suggests a mechanical commonality between drosomycin and plant defensins, which provides additional evidence in favor of their homologous relationship. Furthermore, the existence of drosomycin-like molecules in fungi suggests that all these peptides could originate from a common ancestry rather than horizontal gene transfer between plants and insects, which is further strengthened by the monophyletic origin of these peptides from plants, fungi and insects.