Isolation of molecular markers for salt stress responses in Arabidopsis thaliana.

Characterization of many osmotic stress-induced genes has greatly contributed to the understanding of the physiological responses of plant cells to osmotic stress at the molecular level. In this study we constructed a subtraction library and generated 15 salt stress-inducible ESTs from this library to use as molecular markers that reflect the cellular responses to salt stress responses in Arabidopsis. The sequence analysis showed that 5 salt stress-inducible ESTs were identical to previously identified genes in Arabidopsis, 6 cDNAs were homologous to known genes found in plants as well as yeast, and 4 cDNAs were new genes. To confirm that expression of these clones are induced by salt stress, we carried out Northern blot analysis. When we examined for 15 cDNA clones, they were indeed induced by NaCl treatment. The induction level was variable among these genes ranging from approximately 2-fold to more than 50-fold. Also, Northern blot analysis revealed that these genes can be divided into three different induction patterns: early induction, late induction, and continuous induction.