Localisation and surface quantification of secondary metabolites in the red alga Delisea pulchra

Abstract

The localisation of halogenated furanones, the biologically active secondary metabolites from the red alga Delisea pulchra (Greville), was determined by a combination of fluorescence microscopy, culture studies and quantitative chemical analyses. All types of evidence showed that furanones are localised in the central vesicle of gland cells in D. pulchra. These cells release furanones onto the surface of the plant, where they can be quantified using a newly developed surface extraction-technique. Levels of furanones on the surface of the plant were highest near the apical tips (≃100 ng cm−2), and decreased towards the base of the alga. Variation in furanone levels within the plant and variation in the number of gland cells followed a similar pattern. The localisation of furanones within gland cells in D. pulchra and the presence and concentrations of furanones on the surface of the plant are consistent with furanones functioning as antifoulants and in mediating other ecological interactions at the surface of the alga.