Studies on the Molecular Mechanism in Life-cycle Development and Signal Trnnsduction of Aphanomyces cochlioides, a Cause of Spinach Root Rot

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1.The zoospores of phytopathogenic Oomycete, Aphanomyces cochlioides show clear positive chemotaxis to the host-specific singanl substances. The reputed receptor for the host-specific attractant toward the zoospores of spinach root rot pathogen, A.cochlioides wsa surveyed by using a biotin conjugated azidoflavone as a probe and resulted in 40 and 70 kDa membrane proteins on electropholetic gel plates.2.The events caused by signal transduction regarding the life-cycle development of a Peronosporomycete (Oomycete) Aphanonyres cochlioides has been studied by using microscopic techniques. An interesting difference in F-actin profiles was observe between two kinds of custospores, one developing ahead to hyphal germination and the other rejuvenating to regeneration of zoospores.3.About 150 rhizoplane bacteria were isolated from host and non-host plants, and our dual culture bioassay revealed that more than 5 % of isolates caused severe morphological alterations on phytopathogenic Oomycete Aphanomyces cochlioides and the fungal growth was strongly inhibited. From these results, we proposed that this method is new and effective way to find biological control agents against soilbome phytopathogens.4.Cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) known as the host-specific zoospore attractant for a spinach root rot pathogen has been isolated so far only from Chenopodiaceae plants, spinach, sugar beet, and Chenopodium album, however, in our recent survey of zoospore attractants in Amamthaceae plant, Celosia cristata revealed that one of the active princilpes was indeed cochliophilin A.