Fungal pathogens of plants: deciphering the mechanisms of Fusarium wilt

Fusarium oxysporum (Fo) is among the most dangerous soilborne pathogens, causing Fusarium wilt and root rots in over 100 plant species worldwide. Some pathogen strains can also infect immunocompromised animals and humans. Consequently, studying the molecular mechanisms associated with pathogen virulence and the plant immune response at different stages of disease development is of paramount importance. The process of host recognition by the pathogen and all stages of the infection process involve a wide repertoire of specific signaling molecules, effector proteins, receptor complexes, as well as interconnected and overlapping signaling pathways. Plants, in turn, have evolved a complex defense system to counter this attack: they also possess intricate molecular-level mechanisms that, triggered by pathogen assault, transmit signals to activate a defensive response. In this review, we examine the main currently known molecular mechanisms of Fo-host interaction within the plant-pathogen system: from plant detection and directed hyphal growth driven by chemotropism, to complex interactions at the level of immune response and specific fungal tactics for its suppression. The review includes sections dedicated to the dynamics of plant infection, pathogen genome organization and its genomic diversity, plant immune response and pathogen suppression tactics, as well as an analysis of the main known effector molecules of the pathogen and associated transcription factors. Special emphasis is put on the special form of Fo that infects flax (Linum usitatissimum L.).