open access

https://hdl.handle.net/2115/64660

Nitric oxide suppresses the energy transduction of plant mitochondria

英語

oxidative stress

2002-02-01

CSIRO

Proceedings of the 12th International Congress on Photosynthesis

3(1)

S29-007

Plant mitochondria are known to possess two respiratory electron transport pathways, i.e. the cytochrome and alternative pathways. The cytochrome pathway, which ends at cytochrome c oxidase (COX), is almost identical to the respiratory electron transport pathway in animal mitochondria. The alternative pathway, which ends at alternative oxidase (AOX), is unique in plants, fungi and parasitic protozoa. Although thermogenesis has been considered as a possible role for alternative pathway. the physiological significance of this non-energy producing pathways is not fully understood. Millar and Day (1996) have proposed that the alternative pathway may play an important role in preventing oxidative damage induced by nitric oxide (NO). Nitric Oxide (NO) is a free radical that can act as a signal messenger in animal cells (Packer 1996). It has been known that NO sometimes disturbs the energy transduction system in animal mitochondria by inhibiting the activity of COX (Brookes e al. 1999), In contrast to extensive knowledge on biochemistry and physiology on NO in animal systems, the source and role of NO in plants have been not yet confirmed. We have recently revealed that plant nitrate reductase (NR) is capable of converting nitrite to NO in the presence of NADH (Yamasaki, Sakihama 2000; Yamasaki 2000). NR is a key enzyme in nitrate assimilation pathway. By using the NR-catalyzed NO production system, here we demonstrate in vitro effects of NO on the energy transduction system of mitochondria. The results presented in this study provide substantial evidence to confirm that the plant alternative pathway is resistant to NO>

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