Update: Mitochondrial energy signaling and its role in the low oxygen stress response of plants
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Abstract
Cells of complex organisms typically rely on mitochondria for energy provision. The amount of energy required to sustain cellular activity can vary strongly depending on external conditions. Vice versa, constraints on respiratory activity due to metabolic status or stress insult require mitochondrial signaling to coordinate cellular physiology with the function of the organelle. In this update, we review recent insights into plant mitochondrial energy signaling in the light of their significance to stress acclimation. Firstly, we focus on the characteristic adjustments of the nuclear transcriptome that occur after pharmacological inhibition of the mitochondrial electron transport chain as the output of mitochondrial retrograde signaling. Secondly, we discuss the proteins that have recently been identified as regulators of the transcript responses and the emerging picture of their action as a signaling network. We then pose the question how well our current models of inducing mitochondrial dysfunction relate to conditions that plants face naturally. We reason that low oxygen stress shows striking similarities with electron transport inhibitors with respect to their impact on mitochondrial energy physiology upstream, as well as the cellular transcriptomic response. Finally, we highlight and discuss changes in mitochondrial physiology that are common to both stimuli as candidates for upstream signals. The aim of this update is to better define the physiological context in which mitochondrial signaling operates to provide new directions for future research.
