Nitric oxide synthase (NOS) from photosynthetic microorganisms: studies linking its transgenic expression in higher plants with nitrogen metabolism

NOELIA FORESI; FIORELLA DEL CASTELLO; NATALIA CORREA-ARAGUNDE; MARTÍN MAYTA; ANABELLA F. LODEYRO; NÉSTOR CARRILLO; LORENZO LAMATTINA

Fox de Iguazú

Congreso; 11th International Congress of Plant Molecular Biology; 2015

International Plant Molecular Biology

Nitric oxide (NO) is a free radical involved in several physiological processes in all living organisms. In plants, NO acts as a growth promoter, mainly favoring the development of roots and positively influencing the formation of plant biomass and productivity. Nitrogen (N) assimilation is essential for growth and development of plants. However, there is not yet enough evidence on the role of NO in response to N deficiency. In animals, NO is mainly synthesized by nitric oxide synthases (NOS) from the substrate L-arginine (L-Arg), while higher plants lack a canonical NOS enzyme. Our laboratory characterized the first NOS belonging to the plant kingdom from the marine unicellular algae Ostreococcus tauri (OtNOS, Foresi et al. 2010). Through bioinformatics analysis, we found a sequence coding a NOS orthologue in another photosynthetic microorganism, the cyanobacterium Synechococcus PCC 7335 (SyNOS). SyNOS possesses high similarity to OtNOS except for a globin domain at the N-terminus. The full length sequence of OtNOS was cloned under the control of the 35S promoter, and Arabidopisis and tobacco transgenic plants were generated. Preliminary results indicate that OtNOS-transgenic tobacco plants growing in N-deficient soil produce higher biomass than WT plants. Furthermore, OtNOS transgenic plants display higher photosynthetic rates and chlorophyll contents. The hypothesis that NOS activity and its product NO improve the fixation/assimilation of N in the transgenic tobacco plants is currently evaluated in our lab.