The chapter discusses the signal transduction pathways in plants that respond to salt and drought stress. These pathways are categorized into three functional categories: ionic and osmotic stress signaling for reestablishing cellular homeostasis, detoxification signaling for controlling and repairing stress damages, and growth control signaling for coordinating cell division and expansion. The SOS pathway, involving the SOS3-SOS2 protein kinase complex, is highlighted as a key mechanism for ion homeostasis and salt tolerance. Osmotic stress signaling is mediated by several protein kinases, including MAP kinases, and phospholipid signaling systems, which generate various messengers like IP3 and DAG. Abscisic acid (ABA) plays a crucial role in water stress tolerance, regulating both osmotic stress induction of ABA accumulation and ABA-dependent gene expression. The chapter also explores the interaction between ABA and other stress signals, such as cold stress, and the potential role of ABA in cold acclimation. Finally, it outlines future prospects for understanding and improving plant stress tolerance through genetic engineering.The chapter discusses the signal transduction pathways in plants that respond to salt and drought stress. These pathways are categorized into three functional categories: ionic and osmotic stress signaling for reestablishing cellular homeostasis, detoxification signaling for controlling and repairing stress damages, and growth control signaling for coordinating cell division and expansion. The SOS pathway, involving the SOS3-SOS2 protein kinase complex, is highlighted as a key mechanism for ion homeostasis and salt tolerance. Osmotic stress signaling is mediated by several protein kinases, including MAP kinases, and phospholipid signaling systems, which generate various messengers like IP3 and DAG. Abscisic acid (ABA) plays a crucial role in water stress tolerance, regulating both osmotic stress induction of ABA accumulation and ABA-dependent gene expression. The chapter also explores the interaction between ABA and other stress signals, such as cold stress, and the potential role of ABA in cold acclimation. Finally, it outlines future prospects for understanding and improving plant stress tolerance through genetic engineering.