Differential <i>cis</i>-regulatory regions of KS dehydrins of Arctic and temperate <i>Oxytropis</i> spp.

Dehydrins are intrinsically disordered proteins that play central roles in cryoprotection and osmotic stress tolerance in plants. In this study, we investigated orthologous KS dehydrin promoters from the Arctic <i>Oxytropis arctobia</i> (Fabaceae) and the temperate <i>O. splendens</i> using reporter gene constructs to evaluate transcriptional responses under abiotic stress conditions in transgenic <i>Lotus japonicus</i>. Reporter gene assays in freezeand heat-exposed <i>L. japonicus</i> plantlets showed that a specific region of the <i>O. splendens</i> promoter functions as a repressor, while both promoters contain temperature-responsive <i>cis</i>-elements. In parallel, we sequenced and analyzed the nuclear genomes of <i>O. arctobia</i> and <i>O. splendens</i>, focusing on identifying KS dehydrin orthologs and their regulatory regions. This revealed that the intron in the 3' UTR is highly conserved between three <i>Oxytropis</i> species and in close relatives, which may contribute to post-transcriptional regulation and adaptation to harsh environments.Together, these results demonstrate <i>cis</i>-regulatory divergence in dehydrin promoters and provide new insights into the molecular mechanisms and evolutionary trajectories of cold adaptation in <i>Oxytropis</i>.