Reactive Oxygen Species and Alternative Oxidase in Multiple Stress Tolerance

Reactive oxygen species (ROS) are a natural product of metabolism in oxygen-rich environments. Despite their highly reactive nature, ROS can be tolerated in most biological systems and are essential for growth, development and stress responses. Under typical growth conditions, the relative rate of ROS generation remains at, or below, the capacity for ROS processing. However, if a threshold level is breached, ROS amplification may trigger cellular damage. This is known as oxidative stress, with potentially fatal consequences for the cell. Different environmental conditions may initiate different mechanisms of ROS accumulation. Therefore, in the presence of multiple stressors, ROS amplification may change in an additive, or non-additive way. Enhancing components of ROS-prevention or ROS-processing systems can improve plant tolerance to environmental stress. Mitochondrial alternative respiration is one process by which ROS production can be dampened. Several studies have shown that enhancing the expression of mitochondrial alternative respiration components, such as alternative oxidase, can improve tolerance of plants to multiple independent stresses, and in some cases combinations of stresses. There is great potential for enhancing multiple stress tolerance via the optimisation of mitochondrial alternative respiration.