Analysis of some physiological and biochemical parameters in AtrecQl4A mutant plants under salinity stress

RecQ family members play crucial roles in DNA repair, replication and recombination. The model plant Arabidopsis thaliana contains seven RecQ homologues. We already showed that inactivation of AtRecQl4A alters plant responses to genotoxic stress. In this report, some physiological and biochemical parameters in recQl4A mutant plants were investigated under salinity treatment. Wild type and recQl4A mutant plants were grown on Murashige and Skoog agar plates containing various concentrations of NaCl arranged in a completely randomized design. When plants were treated with 100-150 mM NaCl, damage to the plants was so high that we were not able to measure physiological or biochemical parameters accurately. In 75 mM NaCl, total soluble protein in all examined plant lines declined. In response to salinity treatment, mutant seedlings exhibited less dry weight and chlorophyll content, as compared to the wild type plants. However, total soluble sugar in the mutant seedlings was higher than that in wild type plants. Similarly, the catalase activity in the mutant plants was significantly higher than that of wild type, when plants were treated with 75 mM NaCl. Interestingly, increasing of NaCl concentration form 0 to 75 mM caused a significant reduction in the polyphenol oxidase activity in the mutant plants but not in the wild type plants. These results propose that the RecQl4A gene plays crucial roles in response of Arabidopsis plants to NaCl treatment and provide new insights in understanding mechanisms underlying plant salinity tolerance.