MIR398 and expression regulation of the cytoplasmic Cu/Zn-superoxide dismutase gene in Thellungiella halophila plants under stress conditions

In the salt-tolerant plant Thellungiella halophila, expression of microRNA from MIR398 family, which regulated expression of superoxide dismutase (Cu/Zn-SOD) in Arabidopsis thaliana at posttranscriptional level, was revealed. The effects of various salinity levels, illumination intensity, and UV-B radiation on MIR398 expression was demonstrated by Northern-blot hybridization. These stressors changed the level of MIR398 expression in roots and leaves in opposite directions, which indicates a possible stress-dependent transport of MIR398 over the plant. Under salinity stress and UV-B irradiation, a negative correlation was observed between expression of MIR398 and its target, mRNA of Cu/Zn-SOD, one of the key enzymes of plant antioxidant defense. Thus, MIR398-dependent expression of CSD1 gene is characteristic of not only glycophytes but also halophytes, being organ-unspecific and independent of abiotic stressors affecting the plant.