The stress-responsive, SK5 subclass, dehydrin gene, CaDHN, has been identified from the Arctic mouse-ear chickweed Cerastium arcticum. CaDHN contains an unusual single cysteine residue (Cys143), which can form intermolecular disulfide bonds. Mutational analysis and a redox experiment confirmed that the dimerization of CaDHN was the result of an intermolecular disulfide bond between the cysteine residues. The biochemical and physiological functions of the mutant C143A were also investigated by in vitro and in vivo assays using yeast cells, where it enhanced the scavenging of reactive oxygen species (ROS) by neutralizing hydrogen peroxide. Our results show that the cysteine residue in CaDHN helps to enhance C. arcticum tolerance to abiotic stress by regulating the dimerization of the intrinsically disordered CaDHN protein, which acts as a defense mechanism against extreme polar environments.
Keywords: Arctic mouse-ear chickweed; cysteine; dehydrin; dimerization; intermolecular disulfide bond; reactive oxygen species.