A MUTATION IN AN HSP90 GENE AFFECTS THE SEXUAL CYCLE AND SUPPRESSES VEGETATIVE INCOMPATIBILITY IN THE FUNGUS PODOSPORA-ANSERINA

Vegetative incompatibility is widespread in fungi but its molecular me chanism and biological function are still poorly understood. A way to study vegetative incompatibility is to investigate the function of gen es whose mutations suppress this phenomenon. In Podospora anserina, th ese genes are known as mod genes. In addition to suppressing Vegetativ e incompatibility, mod mutations cause some developmental defects. Thi s suggests that the molecular mechanisms of vegetative incompatibility and development pathways are interconnected. The mod-E1 mutation was isolated as a suppressor of the developmental defects of the mod-D2 st rain. We show here that mod-E1 also partially suppresses vegetative in compatibility, strengthening the link between development and vegetati ve incompatibility. mod-E1 is the first suppressor of vegetative incom patibility characterized at the molecular level. It encodes a member o f the Hsp90 family, suggesting that development and vegetative incompa tibility use common steps of a signal transduction pathway. The involv ement of mod-E in the sexual cycle has also been further investigated.