Two-Component Signaling System in Filamentous Fungi and the Mode of Action of Dicarboximide and Phenylpyrrole Fungicides

Abstract

Elucidating the mode of action of fungicides and the mechanism of fungicide resistance is a promising scientific approach to plant protection. However, the fungicidal mode of action or the mechanism of fungicide resistance has not been elucidated for all new fungicides. Furthermore, the mode of the action has not been fully elucidated for some fungicides that have long been on the market. Dicarboximide fungicides, one of the classes of fungicides dealt with in this paper, have also commercially available for a long time. Several theories have been proposed regarding their mode of action, but their bona fide fungicidal mechanism has not been fully elucidated. Fungi, including phytopathogenic fungi, usually develop thalli and their cells are directly exposed to the environment. The cells inevitably experience several kinds of environmental stresses throughout their life cycles. These stresses include water activity (osmotic) stress and oxidative stress caused by the host response in a host-parasite interaction. To sense and respond to these stresses, fungi possess signal transduction systems and adaptation mechanisms. In the last 10 years, information obtained in the field of genome science on budding yeast (Saccharomyces cerevisiae, a leading model organism in fungal science) has enabled us to elucidate signal transduction systems and adaptation mechanisms in filamentous fungi, and further progress led to the clarification of the mode of action of dicarboximide and phenylpyrrole fungicides. These fungicides are closely involved in an osmotic signaling system in filamentous fungi. The fungicides now constitute an essential tool for studying this system. And as a result, this system has attracted great attention as a target of new antifungal agents. Furthermore, in some fungi, this system is involved in the pathogenicity of their hosts. In this paper, we introduce researches on the mode of action of these fungicides, which lead to the identification of the osmotic signaling system in pathogenic filamentous fungi, and related findings.