Somatic Incompatibility in Fungi

Abstract

Somatic recognition, or the ability to distinguish self from nonself, is found in many groups of organisms, including vertebrates, colonial marine invertebrates, and slime molds. In vertebrates, somatic recognition (or historecognition), is limited to rather unusual circumstances, such as the rejection of tissue grafts or organ transplants. In contrast, in colonial invertebrates and fungi, somatic recognition (often called historecognition in marine invertebrates, somatic incompatibility in basidiomycetes, and vegetative or heterokaryon incompatibility in ascomycetes) is a common event, and generally occurs whenever individuals from different incompatibility groups meet on the same substrate. In these taxa, encounters between individuals from the same incompatibility group generally lead to fusion, and may result in the creation of a physiologically connected organism. In contrast, encounters between genotypes recognizing each other as nonself are usually followed by a rejection response that prevents or restricts cytoplasmic or nuclear exchange between the two genotypes, allowing the persistence of each as a discrete genetic and physiological unit.