Nitrite accumulation and nitric oxide emission in relation to cellular signaling in nitrite reductase antisense tobacco

An antisense nitrite reductase (NiR, EC 1.7.7.1) tobacco (Nicotiana tabacum L.) transformant (clone 271) was used to gain insight into a possible correlation between nitrate reductase (NR, EC 1.6.6.1)-dependent nitrite accumulation and nitric oxide (NO) production, and to assess the regulation of signal transduction in response to stress conditions. Nitrite concentrations of clone 271 leaves were 10-fold, and NO emission rates were 100-fold higher than in wild type leaves. Increased protein tyrosine nitration in clone 271 suggests that high NO production resulted in increased peroxynitrite (ONOO-) formation. Tyrosine nitration was also observed in vitro by adding peroxynitrite to leaf extracts. As in mammalian cells, NO and derivatives also increased synthesis of proteins like 14-3-3 and cyclophilins, which are both involved in regulation of activity and stability of enzymes.