Role of ABC Proteins in Secondary Metabolism and Immune (= Defensive) Response in Seaweeds

Laurencia seaweed species synthesize a broad range of secondary metabolites mainly terpenes, such as the elatol exhibiting ecological roles, such as defense against fouling and herbivores. Recently, an intricate cellular machinery was evidenced concerning terpenes biosynthetic pathways, storage inside corps en cerise - CC and regulated exocytosis in these species. But for seaweeds in general, the proteins involved in transmembrane transport of secondary metabolites remains unknown. Assays with Rhodamine-123 and cyclosporine A (CSA) revealed the presence of ABC transporters in CC membrane of Laurencia dendroidea. In vivo incubation assays with CSA resulted in CC morphological changes, reduced intracellular elatol concentrations and increased biofouling cover on the seaweed surface. Cultivation assays in the presence of a marine pathogenic bacteria induced the expression of ABC proteins belonging to the subfamilies ABCB, ABCD, ABCF and ABCG. The later subfamily is known to associated in the transport terpenes in plants. Our results shed new light on the role of ABC proteins in key mechanisms of the defensive system in seaweeds against fouling and herbivory.