Molecular-genetic evaluation of fungal molecules for roles in pathogenesis to plants

Fungus-plant interactions involve complex developmental processes in which a variety of fungal and plant molecules are required to determine whether the outcome is a susceptible reaction (successful fungal colonization of plant tissues) or a resistant reaction (the plant mounts a defence that aborts Fungal invasion). To understand the molecular basis 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 to its outcome. Molecular-genetic technology has been developed for fungal pathogens and used to evaluate the roles of Fungal molecules in fungal infection processes. Although the field is in its infancy, several molecules have already been proven as essential components of fungal pathogenesis. Some are clearly involved in the adhesion and penetration phases of infection, i.e. hydrophobins, melanin, glycerol, cutinase, and components of signal transduction pathways (which mediate colonization as well), whereas others are required for colonization of plant tissues after penetration, i.e. toxins that induce susceptibility, toxins 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 involved in any detectable way.