APPLICATION OF MATING-TYPE GENE TECHNOLOGY TO PROBLEMS IN FUNGAL BIOLOGY

In ascomycetes, the single mating type locus (MAT) controls sexual dev elopment. This locus is structurally unusual because the two alternate forms (''alleles'') are completely dissimilar sequences, encoding dif ferent transcription factors, yet they occupy the same chromosomal pos ition. Recently developed procedures allow efficient cloning of MAT ge nes from a wide array of filamentous ascomycetes, thereby providing MA T-based technology for application to several ongoing issues in fungal biology. This article first outlines the basic nature of MAT genes, t hen addresses the following topics: efficient cloning of MAT genes; th e unusual molecular characteristics of these genes; phylogenetics usin g MAT; the issues of why some fungi are self-sterile, others self-fert ile, and yet others asexual; the long-standing mystery of possible mat ing type switching in filamentous fungi; and finally the evolutionary origins of pathogenic capability.