Auxin influences a variety of developmental and physiological processes. Early reports, suggested that auxin might affect plant stress response. We have identified a number of auxin responsive genes in Arabidopsis thaliana (L.) Heynh. by using cDNA an-ay and found that stress responsive genes, such as,Arabidopsis homolog of MEK kinase 1 (ATMEKK1), ReL/SpoT homolog 3 ( At-RSH3), Catalase 1 ( Cat1) and Ferritin 1 (Fer1), were down-regulated by auxin, indicating that auxin regulates ale expression of stress responsive genes. We also demonstrated that nitrilase genes, nitrilase I ( NIT]) and nitrilase 2 (NIT2) involving in indole-3-acetic acid (IAA) biosynthesis, were induced by salinity stress, suggesting that the level of IAA might increase in response to salinity stress. To dissect the signal pathway involved in the interaction, two auxin insensitive mutants, auxin resistant 2 (axr2) and auxin resistant 1-3 (axrl-3) were used. Stress responsive genes were induced by salt stress in wild type and axr2, but not in axr1-3. The result suggests that die interaction between auxin and stress responses may be linked in the ubiquitin pathway.
