Nitric Oxide –mediated inhibition of OsDHODH1 gene expression is independent to the Cytochrome c Oxidase activity in rice

Nitric oxide (NO) interacts with the plant mitochondrial electron transport chain (ETC) at the cytochrome c oxidase (COX). The plant DHODH links physically de novo pyrimidine biosynthesis pathway to the mitochondrial respiratory chain (MRC) via the ETC. NO was shown to have a high affinity with the CcOX, which is also the primary site for oxygen binding and consumption. A late in vitro enzymatic assay supported that inhibition of the CcOX responsible for reduction of O2 to H2O by NO resulted in indirect suppression of DHODH activity. However, the mechanism underlying the inhibition of the plant DHODH by binding of NO to the CcOX is poorly understood. In this study, we monitored by qPCR the transcriptional level of OsDHODH1 in relation with the activity of two main subunits of the CcOX containing the binuclear center where NO and O2 competitively bind.