ISOLATION OF MOLECULAR MARKERS FOR SALT STRESS RESPONSES IN ARABIDOPSIS-THALIANA

Characterization of many osmotic stress-induced genes has greatly cont ributed to the understanding of the physiological responses of plant c ells to osmotic stress at the molecular level. In this study we constr ucted a subtraction library and generated 15 salt stress-inducible EST s from this library to use as molecular markers that reflect the cellu lar responses to salt stress responses in Arabidopsis. The sequence an alysis showed that 5 salt stress-inducible ESTs were identical to prev iously identified genes in Arabidopsis, 6 cDNAs were homologous to kno wn 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 leve l was variable among these genes ranging from approximately 2-fold to more than 50-fold. Also, Northern blot analysis revealed that these ge nes can be divided into three different induction patterns: early indu ction, late induction, and continuous induction.