“…In accordance with its key role in the nitrogen metabolism, C-NaR is highly regulated by complex transcriptional, translational, and posttranslational mechanisms that respond to nitrogen, carbon dioxide, and dioxygen availabilities, pH, temperature, and light. ,− ,, Noteworthy, C-NaR is rapidly degraded in darkness (half-life of 6 h). Besides this well-established role in the reduction of nitrate, C-NaR from different species were shown to also catalyze the subsequent nitrite reduction to NO (eq ), not only in vitro, ,− but also in vivo. The in vivo evidences for C-NaR-dependent NO generation were provided by studies with (i) transgenic plants expressing a permanently active C-NaR, ,,− (ii) C-NaR knockout mutants ( nia 1 and nia 2 genes), ,− (iii) inactive C-NaR (e.g., plants with tungstate supply instead of molybdate), ,,− and (iv) others. ,,,− The nitrite reduction by C-NaR was also studied in silico, and it was found that both nitrate and nitrite are easily reduced (to nitrite and NO, respectively), although, as expected, nitrate is the preferred substrate These two C-NaR activities, nitrate reductase and nitrite reductase, seem to be controlled by the dioxygen concentration.…”