Nematode-derived drosomycin-type antifungal peptides provide evidence for plant-to-ecdysozoan horizontal transfer of a disease resistance gene.

Drosomycin-type antifungal peptides (DTAFPs) are key innate immunity components of Drosophila and plants and confer resistance to fungal infection. Here we report the discovery of a multigene family of DTAFPs, comprising of 15 members (termed cremycin-1 to crymycin-15), in the fruit nematode Caenorhabditis remanei. Cremycins share highly similar amino-acid sequences and identical precursor organization to drosomycins. Of the 15 cremycin genes, 10 are found to be transcriptionally active and 6 are upregulated after fungal challenge. Synthetic cremycin-5 is active on filamentous fungi and a series of clinical isolates of human pathogenic yeasts and exhibits low haemolysis and high serum stability. The specific distribution of DTAFPs in a clade of moulting animals (Ecdysozoa), including Arthropoda, Nematoda and Tardigrada, together with the widespread presence in plants but the absence in fungi and protozoans, provides evidence for horizontal transfer of a disease resistance gene between plants and ecdysozoans.