Isolation and characterization of a vacuolar sodium(+)/proton exchanger in Salicornia bigelovii Torr

The work in this thesis provided critical information about the vacuolar Na+/H+ exchanger in Salicornia bigelovii with a goal to understand its role in plant salt tolerance. A cDNA (SbNHX1) was isolated and showed 87% identity to the Na +/H+ exchanger from the glycophyte, Arabidopsis thaliana. DNA blot analysis suggests the presence of a family of Na+/H+ exchangers in Salicornia bigelovii . An increase in SbNHX1 transcript was seen in shoots of 200 mM NaCl-grown plants compared to transcript levels in 5 mM NaCI-grown plants. To understand whether the SbNHX1 cDNA conferred increased salt tolerance by virtue of its unique sequence, the coding region of SbNHX1 was cloned for expression in Arabidopsis thaliana . Potential Ca+2 regulation of vacuolar Na +/H+ exchange is shown using transport experiments.; The isolation of a vacuolar Na+/H+ exchanger from Salicornia bigelovii and its functional expression in Arabidopsis thaliana will provide information on the salt tolerance mechanisms used by halophytes. (Abstract shortened by UMI.)...