Expression of NOS enzyme from photosynthetic microorganisms in higher plants: a tool to improve nitrogen use efficiency

FORESI NOELIA; NEJAMKIN ANDRES; CORREA ARAGUNDE NATALIA; DEL CASTELLO FIORELLA; LAMATTINA LORENZO

Salta

Congreso; LV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2019

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Nitrogen (N) is one of the major macronutrients for plants. The massive use of N fertilizers in agricultural production has a negative impact on the environment, biodiversity and human health. The development of strategies to improve the nitrogen use efficiency (NUE) in plants is of relevance in plant biology. Some studies showed that nitric oxide (NO) is a signal for N deficiency in plants as well as a potential source of N, since it can be oxidized to NO3- by phytoglobin. In animals, the enzyme NO synthase (NOS) catalyzes the biosynthesis of NO from the arginine substrate. Some evidences suggest the existence of a putative NOS activity in plants, however NOS sequences were not found in land plant genomes. In recent years, NOS enzymes were identified in photosynthetic microorganisms such as green algae, diatoms and cyanobacteria. In our lab, it was characterized the functionality of the NOS from the cyanobacteria Synechococcus PCC 7335 (SyNOS). SyNOS has a similar structure to animal NOS with both oxygenase and reductase domains, and contains an additional domain in the N terminus which encodes to a globin. It has been demonstrated that the globin domain of SyNOS acts as a NO dioxygenase, oxidizing NO to NO3-. As result, SyNOS is able not only to produce NO from arginine but also to catalyze NO to NO3-. Since arginine is a N storage amino acid in plants, it was hypothesized that the expression of SyNOS in plants may remobilize N from arginine making it more available. We have generated Arabidopsis transgenic lines that express SyNOS under the constitutive ubiquitin promoter. As expected, the transgenic lines display increased NOS activity and less arginine content. Our results show that SyNOS-transgenic plants growing in N deficiency have greater shoot height, shoot branching and seed production compared to the Wt plants. Nitrate content in seeds/plant is higher in the SyNOS lines than in wt. No statistical differences were detected in the fresh weight and area of rosette leaves. Bioassays for cytokinin (CK) showed a high CK content in SyNOS plants respect to wt. Our results suggest that the SyNOS expression would increase NO3- availability and CK levels generating a positive effect in growth and seed production in Arabidopsis plants growing under limiting N conditions.