SALT STRESS RESPONSES OF HIGHER-PLANTS - THE ROLE OF PROTON PUMPS ANDNA+ H+-ANTIPORTERS/

In salt-stressed higher plants NaCl may either be excluded from the ce lls or sequestered into the vacuole. Different pathways may dominate i n different plants and different organs of the same plant. The protein s involved in salt transport across the plasma membrane and the tonopl ast i.e. proton pumps and Na+/H+-antiporters have been identified. Pro gress in cloning of the P-type H+-ATPase, the V-type H+-ATPase, and th e vacuolar H+-PP(i)ase has provided important tools for the study of t he molecular mechanisms involved in ion sequestration. However, not: a single plant has as yet been studied in sufficient detail to allow a comprehensive evaluation of the relative importance of individual tran sport processes for the salt tolerance of an intact plant. This review summarizes our present as yet limited knowledge and identifies promis sing areas for future research.