The role of signaling pathways such as plant hormonal signaling, mitogen-activated protein kinases (MAPK) signaling, and oxidative stress signaling in plant under stress is of great significance. MAPK molecules are a set of proteins, handling different functions in plant including cell cycling, plant growth and development, plant response to stress, etc. To make plants survive more efficiently under salinity stress, the signaling pathways including the MAPK cascade must be recognized in greater details. Accordingly in this book some of the most recent and important details related to the role of MAPK signaling under stress have been presented.