Overexpression of Hevea brasiliensis HbCDS2 Gene Enhances Cold Tolerance in Transgenic Arabidopsis

Rubber tree (Hevea brasiliensis) is a crucial economic crop in tropical regions worldwide; however, low temperature in some areas have become a major source of abiotic stress that constrains the sustainable development of the natural rubber industry. Superoxide dismutase (SOD) is an enzyme that catalyzes the dismutation of the superoxide anion radical (O₂•^-) into oxygen (O₂) and hydrogen peroxide (H₂O₂). Thus, SOD is an important antioxidant defense under plant stress defense, and also may help to improve rubber tree protection from the cold. In this study, a Cu/Zn superoxide dismutase gene, HbCSD2, was successfully cloned from the rubber tree via PCR amplification. Subcellular localization analysis revealed that HbCSD2 is localized in the cytoplasm and nucleus. Under low-temperature stress, the seed germination rate, fresh weight, and survival rate of HbCSD2-overexpressing transgenic Arabidopsis were significantly higher than those of the wild-type (WT) plants. Conversely, the malformed seedling rate was considerably lower. Compared to WT plants, the transgenic Arabidopsis showed marked increases in SOD, catalase (CAT), and peroxidase (POD) activity, as well as the soluble sugar content. Meanwhile, the levels of malondialdehyde (MDA), H₂O₂, and O₂•^- were significantly lower. This study confirms that HbCSD2 enhances cold tolerance by boosting antioxidant enzyme activity and ROS scavenging capabilities, while reducing membrane lipid peroxidation. These findings offer valuable insights into the regulatory role of HbCSD2 and the mechanisms behind stress responses in the rubber tree.