Abstract
Nitric oxide (NO) is a messenger molecule widespread studied in plant physiology. Latter evidence supports the lack of a NO-producing system involving a NO synthase (NOS) activity in higher plants. However, a NOS gene from the unicellular marine alga Ostreococcus tauri (OtNOS) was characterized in recent years. OtNOS is a genuine NOS, with similar spectroscopic fingerprints to mammalian NOSs and high NO producing capacity. We are interested in investigating whether OtNOS activity alters nitrogen metabolism and nitrogen availability, thus improving growth promotion conditions in tobacco. Tobacco plants were transformed with OtNOS under the constitutive CaMV 35S promoter. Transgenic tobacco plants expressing OtNOS accumulated higher NO levels compared to siblings transformed with the empty vector, and displayed accelerated growth in different media containing sufficient nitrogen availability. Under conditions of nitrogen scarcity, the growth promoting effect of the OtNOS expression is diluted in terms of total leaf area, protein content and seed production. It is proposed that OtNOS might possess a plant growth promoting effect through facilitating N remobilization and nitrate assimilation with potential to improve crop plants performance.
Highlights
Crop productivity depends on strong nitrogen (N) fertilization, though plants use only 50% of the supplied nitrogen
We have previously showed that the expression of nitric oxide synthase from Ostreococcus tauri (OtNOS) with the control of a stress-inducible short promoter fragment (SPF) of the sunflower (Helianthus annuus) Hahb-4 gene improved stress tolerance of Arabidopsis (Foresi et al, 2015)
We tested whether a constitutive expression of OtNOS in tobacco plant could generate a benefit on growth parameters
Summary
Crop productivity depends on strong nitrogen (N) fertilization, though plants use only 50% of the supplied nitrogen. Metabolic processes based on protein synthesis and N-containing biomolecules are critical for plant vegetative and reproductive growth and yield, and dependent on the adequate N supply (Sinclair and Rufty, 2012). Improving NUE is a big challenge for plant biotechnology (Masclaux-Daubresse et al, 2010). Both field and laboratory researches have demonstrated that increasing the supply of N fertilizers enhances growth and photosynthesis. The sensitivity for N fertilization is species specific and Abbreviations: NO, nitric oxide; NUE, nitrogen use efficiency; OtNOS, nitric oxide synthase from Ostreococcus tauri
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