CHEMISTRY OF ATTRACTION AND DEFENSE IN MACRO‐ AND MICROALGAE

Abstract

Boland, W. & Pohnert, G.Max‐Planck‐Institut of Chemical Ecology, Carl‐Zeiss‐Promenade 10, 07745 Jena, GermanyA diverse group of brown seaweeds produce bouquets of C11 and C8 metabolites, some of which act as pheromones that trigger gamete release or attract sperm to eggs following release [1]. The same compounds and, especially, their oxidative degradation products frequently and strongly deter feeding by mezograzers (Ampithoe longimana) which often consume seaweed spores, zygotes, and juveniles [2]. Besides macroalgae also several microalgae (ca. 20 Gomphonema spp., Asterionella formosa; Diatomophyceae) produce C11 and C8 hydrocarbons along with a toxic polar compound from the pool of highly unsaturated fatty acids (eicosanoids) [3]. In biosynthetic studies with cell free extracts of the diatom G. parvulum (9S)‐hydroperoxy‐eicosatetraenoic (9S‐HPETE) acid was shown to be converted by a novel type of a lyase into the defensive com‐pound 9‐oxo‐nona‐5Z,7E‐dienoic acid along with cyclic and linear C11 hydrocarbons [4]. If the eicosanoid pre‐cursors are first con‐verted into C‐12 hydroperoxides, subsequent lyase activity produces C8 trienes together with 12‐oxo‐dodeca‐5Z,8Z,10E‐dienoic acid (A. formosa). Both unsaturated acids serve as efficient chemi‐cal defenses against attacking feeders and microorganisms. The reaction cascade is triggered by damage of the diatom, initiating rapid release of the free fatty acid from phospholipids followed by lipoxygenation and oxidative cleavage into the unsaturated hydrocarbon and the oxo acid [5].1. Boland W 1995 Proc. Natl. Acad. Sci. 92:31‐43.2. Hay ME, Piel J, Boland W, Schnitzler I 1998 Chemoecology 8:91‐983. Pohnert G, Boland W 1997 Tetrahedron 53:13681‐13694.4. Hombeck M, Pohnert G, Boland W 1999 J. Chem. Soc., Chem. Commun., 243‐244.5. Pohnert G 2000 Angew. Chem. 112:4506‐4508.