Abstract

Transient loss of membrane potential in single plant mitochondria. Mitochondria are common to all complex life. They provide energy by respiration – also in plants. When a plant faces changes in its environment, mitochondrial function is often affected. Mitochondrial bioenergetic status can then change rapidly, not only lowering energy output but also increasing free radical production that can impact on cell signalling. Seeking to understand short term bioenergetic changes in plant mitochondria we have recently discovered spontaneous functional fluctuations in mitochondria in vivo: within a matter of seconds individual mitochondria lose and re-gain their membrane potential. Although those ‘pulses’ happen relatively rarely under physiological conditions they can be strongly induced by a variety of environmental stresses. Studies in isolated mitochondria have revealed that pulsing causes uncoupling of electron transport and is therefore energetically costly. To further dissect the physiological context of pulsing we have been using a combination of novel genetically encoded probes for in vivo measurements of mitochondrial superoxide, glutathione redox state and calcium dynamics. Our results suggest that mitochondrial pulsing is a novel phenomenon in plants and may have an important role in integration, maintenance and signaling of mitochondrial function.