Insights on KP4 Killer Toxin-like Proteins of Species in Interspecific Interactions.

KP4 killer toxins are secreted proteins that inhibit cell growth and induce cell death in target organisms. In , KP4-like (KP4L) proteins contribute to fungal virulence in wheat seedling rot and are expressed during Fusarium head blight development. However, fungal KP4L proteins are also hypothesized to support fungal antagonism by permeabilizing cell walls of competing fungi to enable penetration of toxic compounds. Here, we report the differential expression patterns of KP4L genes (, , and ) in a competitive interaction, using as the antagonist. The results from dual cultures indicate that and could participate in the recognition at the distance of the antagonist, while all genes were highly activated in the pathogen during the physical interaction of both fungi. Only was up-regulated during the interaction with in wheat spikes. This suggests the KP4L proteins could participate in supporting interspecific interactions, even in living plant tissues. The distribution of KP4L orthologous within the genus revealed they are more represented in species with broad host-plant range than in host-specific species. Phylogeny inferred provides evidence that KP4L genes evolved through gene duplications, gene loss and sequence diversification in the genus .