Investigation of the effects of abcisic acid on Arabidopsis thaliana sos5 mutant exposed to cadmium toxicity

The SOS5 locus (FLA4) is required for normal cell expansion, wall integrity, and maintenance of structure. The sos5 (fla4) mutant exhibits a short and fat root phenotype with abnormal root expansion under salt stress. Abscisic acid (ABA) is known to suppress this phenotype. The physiological, biochemical and molecular effects of this situation in relation to the ABA are not fully known. In this study, growth and development of mutant sos5 Arabidopsis thaliana with abnormal root phenotype were treated with 50 µM Cd and 5 µM ABA. Cd stress, internal Cd amounts, lipid peroxidation, proline, antioxidant enzyme activities were determined. After the stress application, RNA was isolated and cDNAs were synthesized. ABA1, CYP707A3, RD29A and RD29B genes were analyzed by reverse transcriptase enzyme. According to the findings, the existing cellular damage was eliminated, the intrinsic hydrogen peroxide (H 2 O 2 ) value decreased, the amount of proline increased, and antioxidant enzyme activities were induced by external ABA application to sos5 mutant plants under Cd stress compared to those under Cd stress alone. Due to these changes, the mutant plant was phenotypically very similar to the wild type. It was determined that ABA-related gene expressions in mutant plants under Cd stress were lower than wild type. The external application of ABA under Cd stress significantly reduced the amount of internal Cd in plants compared to the stress-only groups. Our study shows that the SOS5 gene locus is not only associated with salt stress, but also provides cell wall integrity under Cd stress.