Hiroshi Otani

Role of host-specific toxins in the pathogenesis of Alternaria alternata

Host recognition and its specificity in host-parasite interactions are the most attractive subjects in the field of physiological plant pathology. Recently, several models have been proposed as to the mechanisms responsible for determining disease specificity. One of these models comes from studies of host-specific or host-selective toxins (HSTs) produced by fungal pathogens. A mechanism that determines specificity in the diseases involving HST is comprised of three basic processes (Nishimura et al., 1983; Kohmoto et al., 1987, 1989): 1) Spores of a fungal parasite release HST, a host recognition factor, on germination, 2) the released signal factor selectively binds to receptor sites in the host cells, and 3) the accessible state or susceptibility of host cells to possible hyphal invasion is disposed by the signal transduction.