Effects of different classes of attractants, cochliophilin A and N-(E)-feruloyl-4-O-methyldopamine, on the response of Aphanomyces cochlioides zoospores in their chemoattraction and activation of motility linked with intracellular cAMP

Cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone, 1) and N-(E)-feruloyl-4-O-methyldopamine (2) are naturally occurring host-specific chemoattractants for Aphanomyces cochlioides zoospores. In a cross-competition assay, compound 1 (4 fmol) applied to diatomite particles clearly attracted A. cochlioides zoospores in an aqueous solution of excessive compound 2 (1×10^-6 M) that could mask a concentration gradient of 1 dispersed from the particles. Similarly, 2 (40 fmol) on particles also attracted A. cochlioides zoospores in an aqueous solution of 1 (1×10^-6 M). In addition, compound 2 on the particles did not attract the zoospores in an aqueous solution containing 1×10^-6 M NADP⁺, while 1 clearly attracted zoospores in the same solution. These results allowed us to speculate that compounds 1 and 2 do not share receptors. The chemosensory system for 1 is probably for host recognition of A. cochlioides zoospores, while the system for 2 is linked to cell differentiation.