Abiotic Stress-Induced Programmed Cell Death in Plants: A Phytaspase Connection

The plants in the course of ontogenesis are frequently exposed to various unfavourable environmental stress factors (such as high and low temperatures, heavy metals, salt and anaerobic stress, biotic stresses, etc.). If extreme, these stress factors can bring about damage of agricultural crops and wild flora causing considerable environmental and economic losses worldwide. In the course of evolution, and also due to targeted selection, many plant species have developed the capacity for adaptation to some extent to these unfavourable stresses. Under these circumstances adaptive processes in plants are aimed on sustainability of the plant cell and thus on survival of the whole organism. It is worth noting that plants have also developed alternative adaptive mechanisms which are aimed at selective death of the cells and tissues under abiotic and biotic stresses rather than on their survival. Such selective programmed cell death (PCD) eventually provides survival benefits for the whole organism under extreme conditions (Drew et al., 2000; Jackson & Armstrong, 1999). This review focuses on abiotic stress-induced PCD in plants and highlights the role of a newly discovered plant protease, phytaspase, in this process. We describe the role of phytaspase in PCD execution, structure and properties of the enzyme, and its intriguing trafficking in response to stress stimuli. Parallels between the mechanisms of PCD in plants and animals are drawn, highlighting both similarities and differences of the apoptotic proteases involved and the strategies to keep them under control.