Production of solar driven gas-gas-converting denitrifying plants and their utilization for mitigation of air pollution

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It has been shown for the first time that the capability to convert nitrate (or nitrite) to N_2O is common in various plants with some exceptions. It is also suggested that NO_2 can also be utilized as substrate in the "denitrification" process of plants. There was more than a 58-fold variation in the "N_2O emission" in the 17 plant taxa studied. A negative correlation was obtained for the N_2O emission and NO_2 assimilation. This is the first report that there is a competitive interaction between the activities of plants to assimilate and "dissimilate" nitrogen in plants.The nosZ gene from Pseudomonas stutzeri, a denitrifier, encoding nitrous oxide reductase (N_2OR) was fused to the CaMV 35S promoter and the resulting expression cassette (pIGnosZ) was introduced to roots of Arabidopsis thaliana ecotype C24 by Agrobacterium method. Transgenic plants were selected for hygromycin resistance. Expression of nosZ gene was shown by western blotting analysis using anti-N_2OR antibody. The result indicated that bacterial N_2OR gene was transcribed and translated in plants. The N_2OR enzyme activity in the extracts of T_2 plants was assayed using benzyl viologen as electron donor. To date no positive results showing the enzyme activity in transgenic plants have been obtained.Arabidopsis thaliana and rice genomes have been launched, taking this advantage homology searches for plant genes related to bacterial or fungal denitrification system were done. However, no completely sequenced genes, at least in Arabidopsis and rice genomes, were homologous to those for the gas-gas converting steps of the bacterial or fungal denitrification pathways.Phylogeny and bioinformatics studies revealed that the fungi Fusarium oxysporum and Cylidrocarpon tonkinense cytochrome P-450 (P-450nor) are phylogenetically related to Arabidopsis COX6B and to rice COX6B.