Potassium and Potassium-Permeable Channels in Plant Salt Tolerance

Abstract

Salinity causes billion dollar losses in crop production around the globe and has also a significant social impact on rural communities. To breed salt tolerant crops, a better understanding of mechanisms mediating plant adaptive responses to salinity is needed. Over the last years, evidence has been accumulated suggesting that plants’ ability to maintain a high cytosolic K+/Na+ ratio appears to be critical to plant salt tolerance. This paper reviews molecular and ionic mechanisms contributing to potassium homeostasis in salinized plant tissues and discuss prospects for breeding for salt tolerance by targeting this trait. We show that K+ channels are instrumental to nearly all aspects of salinity stress signaling and tolerance, and the plant’s ability to control intracellular K+ homeostasis is arguably the most important feature of salt-tolerant species. The molecular identity of key genes, mediating plant adaptive responses to salinity, is analyzed, and the modes of their control are discussed. It is suggested that the major focus of plant physiologists and breeders should be on revealing the specificity of K+ channel regulation under saline conditions and a “fine tuning” of all mechanisms involved in the regulation of K+ homeostasis in plants, including both plasma- and endomembrane channels and transporters.