Isolation of pheromone precursor genes of Magnaporthe grisea

In heterothallic ascomycetes one mating partner serves as the source of fem ale tissue and is fertilized with spermatia from a partner of the opposite mating type. The role of pheromone signaling in mating is thought to involv e recognition of cells of the opposite mating type. We have isolated two pu tative pheromone precursor genes of Magnaporthe grisea. The genes are prese nt in both mating types of the fungus but they are expressed in a mating ty pe-specific manner. The MF1-1 gene, expressed in Mat1-1 strains, is predict ed to encode a 26-amino-acid polypeptide that is processed to produce a lip opeptide pheromone. The MF2-1 gene, expressed in Mat1-2 strains, is predict ed to encode a precursor polypeptide that is processed by a Kex2-like prote ase to yield a pheromone with striking similarity to the predicted pheromon e sequence of a close relative, Cryphonectria parasitica. Expression of the M. grisea putative pheromone precursor genes was observed under defined nu tritional conditions and in field isolates. This suggests that the requirem ent for complex media for mating and the poor fertility of field isolates m ay not be due to limitation of pheromone precursor gene expression. Detecti on of putative pheromone precursor gene mRNA in conidia suggests that phero mones may be important for the fertility of conidia acting as spermatia, (C ) 1999 Academic Press.