The biosynthesis and metabolism of prostaglandins in microalgae

Prostaglandins (Pgs) are hormone-like mediators in many physiological and pathological processes that are present in all vertebrates, in some terrestrial and aquatic invertebrates, and have also been identified in some micro and macroalgae. In mammals, where they were mostly studied, they are key players in a great variety of physiological and pathological processes, playing similar roles in lower organisms, including marine invertebrates. Very recently the Pgs pathway has been identified in some species of marine microalgae, particularly in diatoms and dinoflagellates, suggesting a broad diffusion and conservation of these important pathway, strengthening Pgs importance in living organisms. The expression of the enzymes composing the pathway has been demonstrated in these microalgae, as well as the synthesis and release of the corresponding molecules outside the cells. The phylogenetic analysis of the limiting enzyme, the cyclooxygenase (COX), in diatoms indicated the presence of additional enzyme types related to the oxidative metabolism of fatty acids belonging to the peroxidase-cyclooxygenase superfamily. These findings suggest a more complex evolution and diversity of metabolic pathways leading to the synthesis of lipid mediators in diatoms. The occurrence of prostaglandins in unicellular photosynthetic eukaryotes opens new intriguing perspectives in the evolution and role of these molecules in the marine environment as possible mediators in cell-to-cell signaling, eventually influencing population dynamics in the plankton.