Expression of Nitric Oxide Synthase from Synechococcus PCC 7335 (SyNOS) in higher plants and its putative involvement in nitrogen metabolism

NEJAMKIN ANDRES; CORREA ARAGUNDE NATALIA; FEINGOLD SERGIO; DECIMA ONETO CECILIA; MASSA GABRIELA; DEL CASTELLO FIORELLA; FORESI NOELIA; LAMATTINA LORENZO

Montevideo

Simposio; COURSE AND SYMPOSIUM: REDOX CHEMISTRY AND BIOLOGY OF THIOLS; 2019

Instituto Pasteur

Nitric oxide (NO) is a radical involved in many physiological processes in all living organisms. In plants, NO acts as a growth regulator, stimulating root development, increasing biomass and productivity, depending on plant physiological conditions and environmental situations. In animals, NO is synthesized by NO synthase (NOS) from the substrate L-arginine, whereas in higher plants no gene, cDNA or protein with homology to NOS has been identified. We have characterized two new NOS from the microalgae Ostreococcus tauri (OtNOS) and from the cyanobacteria Synechococcus PCC 7335 (SyNOS). OtNOS has the canonical NOS architecture whereas SyNOS is different from canonical NOSs, having an unusual globin domain in its amino-terminus. It has been proposed that this globin domain oxidizes NO to nitrate in aerobiosis. The aim of my PhD thesis is to study the heterologous expression of OtNOS and SyNOS in higher plants and its impact on nitrogen (N) metabolism. OtNOS was expressed in tobacco and SyNOS in potato plants under the control of the 35S promoter. Transgenic plants were characterized and presented differential responses to N deficiency. NO is a well-known signal molecule in plants, mainly produced by Nitrate Reductase (NR). NR activity is regulated mainly by nitrate uptake from soil and plant N status. Nonetheless, the regulation of this process is poorly understood. Two transcription factors (TF) NLP7 and TCP20 are master regulators of N signaling. TCP20 has a unique cysteine in its DNA-binding domain. It has been demonstrated that when TCP20 is oxidized or treated with NO donors, the binding of the TF to DNA is blocked. The other TF, NLP7, has 25 Cys and interacts physically with TCP20 to coordinate N signaling and metabolism. I am evaluating the post-translational modifications of those TFs by nitrosation, and how it interferes the DNA binding and/or affects the TCP20-NLP7 interaction. It is imperative to understand the process of N assimilation and metabolism to improve N use efficiency (NUE) in plants. Making plants more efficient in the use of N would help to solve a global pollution problem generated by an excesive N fertilization.