Cell-cell recognition during fertilization in a red alga, Antithamnion sparsum (Ceramiaceae, Rhodophyta)

Abstract

A gamete recognition mechanism in Antithamnion sparsum Tokida is proposed based on experiments using various lectins and carbohydrates. Spermatial binding to trichogynes is inhibited by pre-incubation of spermatia with concanavalin A (ConA) and/or L-fucose, while trichogyne receptors are blocked by the complementary carbohydrate α-methyl D-mannose and'or the lectin Ulex europaeus agglutinin (UeA1). Binding inhibition (40-50%) was observed with 10-50 mM carbohydrates and 25-50μg ml-1 lectins. The inhibitory effects of ConA and UeA 1 is partially reversed (to 80-90% of controls) by addition of α-methyl D-mannose and L-fucose, respectively. Lectin binding to spermatial surfaces was visualized by Fluorescein isothiocyanate (FITC) conjugated ConA, whereas carbohydrate receptors along the trichogyne and spermatium were localized with α-mannosylated-FITC- albumin and L-fucosylated-FITC-albumin, respectively. These results suggest that gamete recognition in Antithamnion sparsum is mediated by a double- docking recognition system consisting of spermatia possessing surface L- fucose receptors and α-methyl D-mannose moiety, and trichogynes possessing the complementary receptors.