Molecular physiology of osmotic stress in plants

Abstract

Osmotic stress apparently reduces growth and productivity of crop plants. When plants are subjected to abiotic stress conditions like drought and salinity stress, most of the affected cellular processes are common and some overlap with cold stress. One important response to osmotic stress is the accumulation of the phytohormone abscisic acid (ABA), which induces several responses to osmotic stress. Osmotic stress signaling consists of an ABA-dependent and an ABA-independent pathway. Osmotic stress also caused increased ROS generation, which in turn elicits various cellular signaling networks resulting into physiological damage to plant cell. Osmotic stress signaling activates specific kinases, including one that belongs to the SNF1-related protein kinase (SnRK) 2 family, which is a plant-specific protein kinase family with 10 members (SnRK2.1-2-10) in Arabidopsis. ABA strongly activates SnRK2.2, 2.3, and 2.6, whereas osmotic stress activate almost all members of SnRK2s. Previous report revealed that SnRK2.2, 2.3, and 2.6 are core components of the ABA pathways whereas SnRK2s are essential kinases for osmotic stress signaling. Though the activation mechanism of SnRK2s in the ABA pathway is elucidated, regulatory mechanisms of SnRK2s in the ABA-independent pathway remain obscure. Thus, further analysis of SnRK2s must be a key study to draw the whole signaling pathways. This chapter is an insight into the molecular physiology of osmotic stress signaling and response in plants.