Functional analysis of fusarium oxysporum nitric oxide reductase expressed in plant suspension-cultured cells

The biological function of Reactive Nitrogen Species (RNS) is not well understood, however, they actively contribute to the effect of green house gases. Development of plants that could efficiently denitrify intermediates of the RNS to the dinitrogen (N2) is a rationale that could help amelioration the effect of these gases. Fusarium oxysporum cytochrome P-450 nor gene (Fnor) was constitutively expressed in tobacco BY-2 cells. The gene product functions as nitric oxide reductase (nor), which catalyzes the reduction of nitric oxide (NO) to nitrous oxide (N2O) in the fungal denitrification pathway. Intact transgenic BY-2 cells cultured in 15N-labeled nitrate (15NO3-) actively produced 15N2O gas up to 59 folds higher than the wild-type cells. Activity of the enzyme was also confirmed by an in vitro nor activity assay. Tungstate (a nitrate reductase inhibitor) and cyanide (an inhibitor of the last protein complex of electron transport chain) strongly inhibited 15N2O production. These observations together suggest that Fnor enhanced the reduction of nitrate to N2O in plant cells. This finding indicates that plant cells are capable to tackle the denitrification pathway. © 2009 Asian Network for Scientific Information.