Production of N-labeled nitrogen gas tracer for the imaging of nitrogen fixation in soybean nodules

Ishii, Satomi; Igura, Masato*; Yin, Y.-G.; Hung, N. V. P.*; Suzui, Nobuo; Kawachi, Naoki; Koyanagi, Atsushi*; Oyama, Takuji*; Fujimaki, Shu

Nitrogen is the most important nutrient for the plants. Soybean can utilize nitrogen from atmospheric N fixed by nodules which are symbiotic organs of leguminous plants with rhizobia. In the beginning of this research project, we set our methodological goal to visualize and analyze the nitrogen fixation in the nodules and subsequent nitrogen transport to the aerial part in a plant using N and PETIS. Previously, we have developed a method of production of highly purified N-labelled nitrogen gas tracer using gas chromatography and successfully visualized nitrogen fixation in intact nodules. However, the yields of the tracer were only a few ten megabecquerels and too low to visualize the transport of fixed nitrogen to the aerial part. Therefore, we have been trying to improve the production method to gain much higher radioactivity with consideration of the very short half-life of [N]N. In this study, we tested a new technique to turn the main by-product [N]NO into the desired product [N]N directly.