Abstract
Previously, cell type-specific expression of
AtHKT1;1
, a sodium transporter, improved sodium (Na
+
) exclusion and salinity tolerance in Arabidopsis. In the current work,
AtHKT1;1
, was expressed specifically in the root cortical and epidermal cells of an Arabidopsis GAL4-GFP enhancer trap line. These transgenic plants were found to have significantly improved Na
+
exclusion under conditions of salinity stress. The feasibility of a similar biotechnological approach in crop plants was explored using a GAL4-GFP enhancer trap rice line to drive expression of
AtHKT1;1
specifically in the root cortex. Compared with the background GAL4-GFP line, the rice plants expressing
AtHKT1;1
had a higher fresh weight under salinity stress, which was related to a lower concentration of Na
+
in the shoots. The root-to-shoot transport of
22
Na
+
was also decreased and was correlated with an upregulation of
OsHKT1;5
, the native transporter responsible for Na
+
retrieval from the transpiration stream. Interestingly, in the transgenic Arabidopsis plants overexpressing
AtHKT1;1
in the cortex and epidermis, the native
AtHKT1;1
gene responsible for Na
+
retrieval from the transpiration stream, was also upregulated. Extra Na
+
retrieved from the xylem was stored in the outer root cells and was correlated with a significant increase in expression of the vacuolar pyrophosphatases (in Arabidopsis and rice) the activity of which would be necessary to move the additional stored Na
+
into the vacuoles of these cells. This work presents an important step in the development of abiotic stress tolerance in crop plants via targeted changes in mineral transport.