Variation in chemotactic preferences of Aphanomyces cochlioides zoospores to flavonoids.
The zoospores of the phytopathogenic Aphanomyces cochlioides are chemotactically attracted by a host-specific flavone, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone), and repelled from the mammalian estrogens or estrogenic compounds. This study further examined the responses of A. cochlioides zoospores to some flavonoids structurally related to cochliophilin A or compounds known as phytoestrogens. The bioassay revealed that some synthetic flavones (such as 6-methyl-4'-methoxyflavone, 3-hydroxy-4'-methoxyflavone, 7-hydroxy-5-methylflavone, 3-hydroxy-4'-methoxy-6-methylflavone) elicited attractant activity at concentrations as low as picomolar (10 pM), which was an 100-fold lower concentration than that of the threshold concentration of the host-specific attractant cochliophilin A. Apparently, a hydrophobic B-ring with an alkylated (methylated) A-ring or a methoxylated B-ring with an unsubstituted A-ring in the flavone skeleton played a significant role in higher attractant activity. On the other hand, all known estrogenic flavonoids (such as equol, 3'- or 8-prenylated naringenins) displayed potent repellent activity toward zoospores. Surprisingly, zoospores were attracted by non-estrogenic 6-prenylated naringenin indicating that repellent activity is linked to the estrogenic activity of the phytoestrogens.
Islam
M Tofazzal
MT
Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan. tofazzalislam@yahoo.com
D044744:Aphanomyces / Q000187:drug effects / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D047309:Flavones / Q000737:chemistry / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D008958:Models, Molecular; D048789:Phytoestrogens / Q000494:pharmacology; D013170:Spores / Q000187:drug effects / Q000502:physiology*
D047309:Flavones; D005419:Flavonoids; D048789:Phytoestrogens; C494663:cochliophilin A