NLR surveillance of essential SEC-9 SNARE proteins induces programmed cell death upon allorecognition in filamentous fungi

Significance NOD-like receptors (NLRs) are fundamental components of plant and animal innate immune systems. Some fungal proteins with NLR-like architecture are involved in an allorecognition process that results in cell death, termed heterokaryon incompatibility. A role for fungal NLR-like proteins in pathogen defense has also been proposed. Here, we show that a fungal NLR-like protein, patatin-like phospholipase-1 (PLP-1), monitors the essential SNARE protein SEC-9 in two distantly related fungal species, Neurospora crassa and Podospora anserina . Both plp-1 and sec-9 are highly polymorphic in fungal populations and show evidence of balancing selection. This study provides biochemical evidence that fungal NLRs function similar to NLRs in plants and animals, indicating that these fundamental players of innate immunity evolved independently in all three kingdoms.