Abstract
As one of plant photo-protection systems, it is known that excess reducing equivalents could be exported from chloroplasts and be oxidized by mitochondrial respiratory chain. Alternative oxidase (AOX), the unique respiratory pathway in plant, could dissipate these reducing equivalents efficiently, because the electron flow via AOX is not restricted by the cellular ATP/ADP ratio. In fact, we previously reported that accumulation of reducing equivalents in the chloroplasts caused the synchronized up-regulations of the transport activity of the reducing equivalents and AOX capacity. These results indicate that AOX has an important role for photo-protection, and raised the new question about the messenger for AOX up-regulation. We found that the yellow variegated 2 (var2) mutants induced AOX without the accumulation of the reducing equivalents. The green sector in var2 leaves was suffered from the oxidative stress, implying that the oxidative stress in chloroplasts would transduce some signals for AOX expression.
