ABSTRACT
Abstract. Salinity stress shows negative impact on agricultural yield throughout the world. Various plants adapt themselves to salinity stress by modulating their growth and development along with diverse physiological and biochemical changes. Biochemically salt stress adaptation requires cellular ion homeostasis, and involves net intracellular toxic ion uptake and subsequent vacuolar compartmentalization without toxic ion accumulation in the cytosol. The ability of plant cells to maintain low cytosolic toxic ion concentrations is associated with the ability of selected plants, viz. halophytes, to grow in high salt concentrations. Due to the negative electrical potential inside cells, mainly Na+ influx into roots occurs through ion channels
or various membrane transport proteins also facilitate passive diffusion of Na+ across the plasma membrane. The potentially relevant membrane transporters involved in the uptake and distribution of various ions also play an important role in mitigating salinity stress, and were identified by forward and reverse genetics, yeast complementation, Xenopus oocyte assays, transcriptomics, and proteomics approaches. This chapter provides an overview of ion transporters that have been assigned functions like uptake, efflux, compartmentation, and translocation of various toxic ions, that finally confers salt stress tolerance in plants. We highlight the significant contribution of different forms of ion transporter systems: present at the level of
20.1 Introduction / 374 20.2 Ion Transporters at the Plasma Membrane Mediating Salinity Stress Tolerance / 375
20.2.1 High-Affinity Potassium Transporters (HKTs) / 375 20.2.2 Salt Overlay Sensitive (SOS1) Transporters / 376 20.2.3 Nonselective Cation Channels (NSCCs) Transporters / 376
20.3 Ion Transporters Present on the Tonoplast, Mediating Salinity Stress Tolerance / 376 20.3.1 Na+/H+ Antiporters Present in Tonoplast (NHX) / 377 20.3.2 Cation Antiporters (CAX) / 378 20.3.3 Proton Pumps / 379
20.4 Major Intrinsic Proteins (MIPs) and Salt Stress Tolerance / 380 20.5 Transportation of Na+ in Whole Plant / 381 20.6 Conclusions and Future Perspectives / 384 Acknowledgments / 384 References / 384
plasma membrane, transporter systems related to vacuolar compartmentation, and membrane intrinsic proteins pertaining to salinity stress tolerance. Genetic engineering applications and strategies used to improve salinity stress
tolerance by modulating the transporter system are also discussed.
