Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2008
Publication Date: 5/1/2008
Citation: Zhang, H., Kim, M., Sun, Y., Dowd, S.E., Shi, H., Pare, P.W. 2008. Soil bacteria confer plant salt tolerance by tissue-specific regulation of the sodium transporter HKT1. Molecular Plant-Microbe Interactions. 21(6):737-744. Interpretive Summary: Soil salinity causes world problems with agricultural productivity. ARS scientists in Lubbock, TX, assisted Texas Tech University researchers in evaluating the role of the bacterium Bacillus subtilis in promoting salt tolerance in plants. The findings of this study show that this bacterium regulates one of its own genes to assist the plant in regulating salt concentrations. This study suggests that probiotics may be useful to increase agricultural productivity in high salinity soils around the world.
Technical Abstract: Elevated sodium (Na+) decreases plant growth and thereby agricultural productivity. The ion transporter HKT1 controls Na+ import in roots, yet dysfunction or over-expression of HKT1 fails to increase salt tolerance, raising questions as to HKT1’s role in regulating Na+ homeostasis. Here, we report that tissue-specific regulation of HKT1 by the soil bacterium Bacillus subtilis GB03 confers salt tolerance in Arabidopsis thaliana. Under salt stress (100 mM NaCl), GB03 concurrently down- and up-regulates HKT1 expression in roots and shoots, respectively, resulting in lower Na+ accumulation throughout the plant compared with controls. Consistent with HKT1 participation in GB03-induced salt tolerance, GB03 fails to rescue salt-stressed athkt1 mutants from stunted foliar growth and elevated total Na+, while salt-stressed Na+ export mutants sos3 show GB03-induced salt tolerance with enhanced shoot and root growth as well as reduced total Na+. These results demonstrate that tissue-specific regulation of HKT1 is critical for managing Na+ homeostasis in salt-stressed plants as well as underscores the breadth and sophistication of plant-microbe interactions.