Organelle Dynamics during Salinity-Induced Programmed Cell Death in Plants

Abstract

Programmed cell death (PCD) is a complex mechanism induced by environmental stress (ePCD) or developmental processes (dPCD). ePCD can be triggered by various types of unfavorable abiotic conditions, including salinity stress. Exposure to high concentrations of salt not only declines the morphological features of plants but also severely affects biochemical and molecular processes. Furthermore, plant activates numerous defense mechanisms, which take place in different organelles in a plant cell. It includes ionic, osmotic and oxidative damage in the plasma membrane, mitochondria, chloroplasts, vacuole and nucleus. Main disturbance in the plasma membrane is characterized by a decline in the transport system, ROS accumulation and Ca2+ influx. Mitochondrial dysfunction is rightly related to high accumulation of ROS, activation of protective pathways such as AOX, UCPs, GABA shunt, and cytochrome c release. Moreover, photosynthetic rate is highly decreased related to a decline in chlorophyll content. Vacuoles integrate osmotic and ionic signals by sequestering Na+ through NHX antiporters and V-ATPase activity, but when this system collapses and Ca2+ converge on the nucleus. Moreover, overproduction of ROS acts as a signal molecule to EXECUTER proteins in chloroplast-nuclear communication. Salinization activates osmotic, ionic and oxidative signals that result in chromatin degradation. Altogether, those interconnected processes lead to the PCD.