Abstract
Mangroves are woody plants tolerant to high salt conditions, found growing along the seashore in subtropical and tropical regions. The mechanisms of salt tolerance in the plants have been extensively described, but there are few reports on the cellular mechanisms. We analyzed the mechanism of salt tolerance using the suspension-cultured cells of B. sexangula. The salt stress with 50 mM NaCl induced an accumulation of Na+ in the cell, whereas that with 150 mM NaCl resulted in a transient increase of the Na+ content then decreased to the original level within 2 weeks. We screened the clones coding the cytoplasmic and vacuolar Na+/H+ antiporter genes from the cDNA library prepared from the cells to analyze the regulatory mechanism of the sodium ion level in the cells. We obtained a clone (BsNHE1) for a cytoplasmic Na+/H+ antiporter gene, and two clones (BsNHX1,2) for a vacuolar Na+/H+ antiporter genes.
