Role of polyamines in alleviating salt stress

Abstract

Salinity is one of the major abiotic stresses that reduce plant growth and productivity of many crops worldwide. Similarly to other stresses, salinity may cause oxidative stress via production of reactive oxygen species (ROS) which in high concentrations provoke oxidative damages to proteins, DNA, and lipids; disturb plant physiological processes and even lead to plant death. In low concentrations, ROS could activate defense mechanisms or repair programs that help plant cell to overcome the negative stress consequences. The diamine putrescine, triamine spermidine and tetraamine spermine are the major polyamines which are constitutive for all plant species. They are organic low-weight molecules with aliphatic amine structure possessing phytohormone-like features and are involved in various important processes of plant growth and development. Under physiological pH conditions they bear positive charge and may conjugate with other negatively charged molecules like phenolic acids, proteins, phospholipids or DNA. The participation of polyamines in the scavenging of free radicals, antioxidant activity and modulation of plant stress tolerance to various abiotic stresses has been extensively studied. The current review will focus on the recent investigations regarding the involvement of polyamines in plant tolerance to salinity stress. The alterations of the endogenous polyamine levels, the changes in their biosynthetic and catabolic enzymes in salt stressed plants, and the role of polyamine metabolism in alleviation of salinity stress is discussed. Possibilities for application of exogenous polyamines to overcome saline stress injuries and to induce plant salt tolerance are also summarized.