MOLECULAR-GENETIC EVALUATION OF FUNGAL MOLECULES FOR ROLES IN PATHOGENESIS TO PLANTS

Fungus-plant interactions involve complex developmental processes in w hich a variety of fungal and plant molecules are required to determine whether the outcome is a susceptible reaction (successful fungal colo nization of plant tissues) or a resistant reaction (the plant mounts a defence that aborts Fungal invasion). To understand the molecular bas is of fungal disease, it is necessary to identify the fungal molecules that are essential for pathogenic processes, and to distinguish them from molecules that may be present during infection but not critical t o its outcome. Molecular-genetic technology has been developed for fun gal pathogens and used to evaluate the roles of Fungal molecules in fu ngal infection processes. Although the field is in its infancy, severa l molecules have already been proven as essential components of fungal pathogenesis. Some are clearly involved in the adhesion and penetrati on phases of infection, i.e. hydrophobins, melanin, glycerol, cutinase , and components of signal transduction pathways (which mediate coloni zation as well), whereas others are required for colonization of plant tissues after penetration, i.e. toxins that induce susceptibility, to xins that induce resistance, and enzymes that inactivate plant defence mechanisms. Molecular-genetic manipulation has also been used to show that certain candidates for roles in pathogenesis are in fact not inv olved in any detectable way.