Nitric oxide generation by the unicellular marine green alga

FORESI N, CORREA-ARAGUNDE N, CALÓ G, SALERNO G, LAMATTINA L

Puerto Madryn, Argentina

Congreso; Sociedad Argentina de Bioquimica y Biologia molecular; 2010

Sociedad Argentina de Bioquimica y Biologia molecular

The Prasinophiceae is one of the most ancient groups within the green lineage. O. tauri and O. lucimarinus belong to Prasinophiceae and their genomes have been completely sequenced. O. tauri is a eukaryotic unicellular photosynthetic microalga. Because of its simple physiology, its small genome size and its early branching in the green lineage, O. tauri is an important model for functional studies. NO (nitric oxide) production by algae could be of great importance in view of their occurrence in all biotopes and their contribution of more than 50 % to global NO productivity. The search for a NO Synthase (NOS) sequence in the plant kingdom retrieved two sequences. These correspond to O. tauri and O. lucimarinus. The specific fluorescent NO probe DAF-FMDA detected a rapid increase of NO when the NOS substrate L-arg was added to O. tauri cell culture. NO production was higher in O. tauri growing with 100 µmol m-2 s-1 of light irradiance compared with 40 µmol m-2 s-1. The addition of NOS inhibitors or a NO quencher abolished the signal. One hour of treatment with the photosynthetic electron transport inhibitor Paraquat (PQ) induced NO and ROS production. The nitrate reductase (NR) inhibitor was able to block the PQ-induced NO production. These results suggest the involvement of NR and NOS as NO generating enzymes under different physiological conditions in O. tauri.