The salt-stress signaling network involved in the regulation of ionic and ROS homeostasis in poplar

Abstract

The fast-growing Populus spp. distributes in different climatic zones, and is widely used for tree plantations and afforestation. Besides its economic and ecological relevance, Populus also serves as a model species for elucidating physiological and molecular mechanisms underlying plant growth, development, and environmental adaptability. Salt-affected soil and secondly salinization is causing increasing agricultural and environmental problems in China. Populus euphratica exhibits a higher capacity than other poplars to tolerate salt stress. P. euphratica compartmentalize salt ions, Na+ and Cl−, in root vacuoles, thus diminishing NaCl loading into the xylem. P. euphratica roots promote Na+ extrusion into apoplastic space, and simultaneously reduce K+ loss under saline conditions. This enables salinized plants to maintain K+/Na+ homeostasis under salinity. Salt signals, such as Ca2+, H2O2, NO, H2S, and eATP are involved in the regulation of ionic and reactive oxygen species (ROS) homeostasis. This review introduces the important advances in physiological and molecular mechanisms in poplar adaptation to salt stress.