HETEROLOGOUS EXPRESSION OF MATING-TYPE GENES IN FILAMENTOUS FUNGI

Podospora anserina and Neurospora crassa, two filamentous heterothalli c ascomycetes, have a single mating-type locus with two alternate form s called mat+ and mat- and A and a, respectively. Mating type controls entry into the sexual cycle, events subsequent to fertilization, and, in N. crassa, prevents the formation of mixed mating-type heterokaryo ns. The mating types of these two organisms display similarity in thei r DNA structure and in the encoded polypeptides involved in fertilizat ion. Here we show that this molecular similarity reflects a functional homology with respect to mating identity. Transformation experiments show that the N. crassa mating-type genes can provide the fertilizatio n functions in P. anserina strains devoid of mating specificity as wel l as in mat+ and mat- strains. Reciprocally, the introduction of P. an serina mating-type genes confers mating activity in N. crassa. Functio nal identity between the mating types is not observed for vegetative i ncompatibility or for post-fertilization events such as meiosis and as cosporogenesis.