Programmed cell death and heterokaryon incompatibility in filamentous fungi

Abstract

Filamentous fungal hyphal networks can be formed by intercellular interactions within and between fungal colonies. However, intercellular interactions can be restricted by a self/nonself recognition mechanism, such that networks can only be formed between colonies that are identical at all self/nonself recognition (het) loci. Hyphal fusion between fungal colonies that are nonself results in the rapid induction of programmed cell death (PCD) in the fusion compartment and subtending cells. Although PCD in fungi exhibits some morphological similarities with apoptotic cell death, the genetic regulation of PCD appears to be unique. Self/nonself recognition loci have been cloned in the model fungal systems Podospora anserina and Neurospora crassa and have revealed that self/nonself recognition loci often involve both allelic and nonallelic interactions, show evolutionary features consistent with their selection for recognition and have implicated a filamentous fungal-specific protein domain (termed HET) in the induction of PCD.