DNA array analyses of Arabidopsis thaliana lacking a vacuolar Na+/H+ antiporter: impact of AtNHX1 on gene expression.

AtNHX1, a vacuolar cation/proton antiporter of Arabidopsis, plays an important role in salt tolerance, ion homeostasis and development. We used the T-DNA insertional mutant of AtNHX1 (nhx1 plants) and Affymetrix ATH1 DNA arrays to assess differences in transcriptional profiles and further characterize the roles of a vacuolar cation/proton antiporter. Mature, soil-grown plants were used in this study to approximate typical physiological growing conditions. A comparison of plants grown in the absence of salt stress yielded many transcripts that were affected by the absence of the AtNHX1 vacuolar antiporter. Furthermore, changes in gene expression due to a non-lethal salt stress (100 mm NaCl) in the nhx1 plants were significantly different from the changes seen in wild-type plants. The nhx1 transcriptome was differentially affected when the plants were grown in the absence or presence of salt. In conclusion, in addition to the known role(s) of AtNHX1 on ion homeostasis, the vacuolar cation/proton antiporter plays a significant role in intracellular vesicular trafficking, protein targeting, and other cellular processes.