In higher plants, only root mitochondria, but not leaf mitochondria reduce nitrite to NO, in vitro and in situ

Abstract

At oxygen concentrations of < or =1%, even completely nitrate reductase (NR)-free root tissues reduced added nitrite to NO, indicating that, in roots, NR was not the only source for nitrite-dependent NO formation. By contrast, NR-free leaf slices were not able to reduce nitrite to NO. Root NO formation was blocked by inhibitors of mitochondrial electron transport (Myxothiazol and SHAM), whereas NO formation by NR-containing leaf slices was insensitive to the inhibitors. Consistent with that, mitochondria purified from roots, but not those from leaves, reduced nitrite to NO at the expense of NADH. The inhibitor studies suggest that, in root mitochondria, both terminal oxidases participate in NO formation, and they also suggest that even in NR-containing roots, a large part of the reduction of nitrite to NO was catalysed by mitochondria, and less by NR. The differential capacity of root and leaf mitochondria to reduce nitrite to NO appears to be common among higher plants, since it has been observed with Arabidopsis, barley, pea, and tobacco. A specific role for nitrite to NO reduction in roots under anoxia is discussed.

Mitochondrial Reactive Oxygen Species. Contribution to Oxidative Stress and Interorganellar Signaling

“…Both the Arg-dependent and the NO 2 -dependent pathways of NO production are located mainly in mitochondria (for review, see Crawford and Guo, 2005). The NO 2 -dependent pathway is stimulated under oxygen deprivation (Gupta et al, 2005), leading to NO accumulation (e.g. Dordas et al, 2003).…”

Regulation of hypoxia adaptation: an overlooked virulence attribute of pathogenic fungi?

“…It has been shown that mitochondria from yeast, rat liver, and plants are capable of nitrite (NO 2 -)-dependent nitric oxide (NO) synthesis (60,(62)(63)(64)(65)(66). This pathway is induced when cells experience hypoxia, and furthermore, Castello et al (60) suggest that mitochondrially produced NO functions in a signaling pathway to the nucleus by reacting with the superoxide produced by hypoxic mitochondria (67) to form peroxynitrite (ONOO -) that promotes protein tyrosine nitration of specific proteins that may be involved in a signaling pathway to the nucleus.…”

Arginase-Negative Mutants of Arabidopsis Exhibit Increased Nitric Oxide Signaling in Root Development

“…Indeed, addition of nitrite to nia1 nia2 leaves restored fluorescence by the intracellular NO trap 3-amino,4-aminomethyl-2#,7#-difluorofluorescein diacetate (DAF FM-DA, herewith designated DAF) and restored the hypersensitive response to an incompatible strain of Pseudomonas syringae (Modolo et al, 2006). Kaiser's group (Gupta et al, 2005;Kaiser et al, 2007) reported that anaerobic mitochondria of roots of several plants reduced nitrite to NO in the presence of NADH via both the cytochrome and alternative oxidase pathways. They reported that there was no NO production by aerobic leaf mitochondria.…”