Abstract
Fluctuations in oxygen (O(2)) availability occur as a result of flooding, which is periodically encountered by terrestrial plants. Plant respiration and mitochondrial energy generation rely on O(2) availability. Therefore, decreased O(2) concentrations severely affect mitochondrial function. Low O(2) concentrations (hypoxia) induce cellular stress due to decreased ATP production, depletion of energy reserves and accumulation of metabolic intermediates. In addition, the transition from low to high O(2) in combination with light changes-as experienced during re-oxygenation-leads to the excess formation of reactive oxygen species (ROS). In this review, we will update our current knowledge about the mechanisms enabling plants to adapt to low-O(2) environments, and how to survive re-oxygenation. New insights into the role of mitochondrial retrograde signaling, chromatin modification, as well as moonlighting proteins and mitochondrial alternative electron transport pathways (and their contribution to low O(2) tolerance and survival of re-oxygenation), are presented.