Abstract

In fungi, cell fusion between genetically unlike individuals triggers a cell death reaction known as the incompatibility reaction. In Podospora anserina, the genes controlling this process belong to a gene family encoding STAND proteins with an N‐terminal cell death effector domain, a central NACHT domain and a C‐terminal WD‐repeat domain. These incompatibility genes are extremely polymorphic, subject to positive Darwinian selection and display a remarkable genetic plasticity allowing for constant diversification of the WD‐repeat domain responsible for recognition of non‐self. Remarkably, the architecture of these proteins is related to pathogen‐recognition receptors ensuring innate immunity in plants and animals. Here, we hypothesize that these P. anserina incompatibility genes could be components of a yet‐unidentified innate immune system of fungi. As already proposed in the case of plant hybrid necrosis or graft rejection in mammals, incompatibility could be a by‐product of pathogen‐driven divergence in host defense genes.