Characterization of a nitric oxide synthase from the plant kingdom: NO Generation from the green alga Ostreococcus tauri Is light irradiance and growth phase dependent

N. FORESI; N. CORREA-ARAGUNDE; G. PARISI; G. CALÓ; G.L.. SALERNO; L. LAMATTINA

PLANT CELL

AMER SOC PLANT BIOLOGISTS

Año: 2010 vol. 22 p. 3816 - 3830

1040-4651

Abstract. The search for a Nitric Oxide Synthase (NOS) sequence in the plant kingdom retrieved two sequences. These correspond to the recent published genomes of two species of the green algae Ostreococcus sp. (O. tauri and O. lucimarinus).  In the present study we characterized the sequence, structure, phylogenetic relationships as well as biochemical and expression analysis of NOS from O. tauri (OtNOS). The aminoacid sequence of OtNOS showed 45 % similarity with known human NOSs. Fold assignment methods show that OtNOS could fold as the endothelial NOS isoform. Phylogenetic analysis reveals that OtNOS clusters together with Synechoccocus sp. and Physarum polycephalum NOS as an out-group of a main cluster containing NOS representatives from chordates. Purified recombinant OtNOS is active with a Km for the substrate L-Arginine of 12 ±5 µM. Bacteria expressing recombinant OtNOS have higher levels of NO and cell viability. O. tauri cultures at exponential growing phase have 3-fold more NOS-dependent NO production than those at stationary phase. In O. tauri, NO production increases with high light irradiation and upon L-Arginine addition, suggesting a link between NOS activity and the physiology of microalgae.