Fig. 1.

The multi-directional role of mitochondria during cold stress. The mitochondria are both the target of cold stress and the central hub that coordinates the cell response to it. During cold stress, the energy metabolism of these organelles changes in order to maintain the functionality of the entire cell. Insects faced with cold stress change their cellular metabolism, which often results in increased accumulation of ROS by mitochondria. Consequently, the mitochondrial antioxidant system during cold stress is modulated to counteract the negative effects of cold-associated ROS formation [37]. It is also increasingly obvious that the mitochondrial integrity and cellular signaling associated with mitochondria are essential for sustaining ion and energetic homeostasis of the cell and its survival [28]. Tight regulation of apoptosis by mitochondrial pathway is essential for survival as the stimulated activity of caspases is not solely the indicator of apoptosis but besides, it demonstrates nonapoptotic functions i.e., control of a cell shape, cell migration or proliferation. Mitochondria may also take part in heat dissipation which is caused by uncoupling of the respiration by these organelles [55]. If these mechanisms fail to adapt the cell to prevail the cold stress and the accumulation of cold-injuries is increasing, the mitochondria commence the processes leading to the programmed cell death pathway via apoptosis to utilize and recycle damaged cells and their components [38]. Green arrows indicate mitochondria regulated processes leading to the cell survival pathway, whereas red arrows processes leading to cell death