Identification of Superoxide Dismutase (SOD) Gene Family in Ginkgo (Ginkgo biloba L.) and Role of GbSOD8 in Response to Salt Stress

Superoxide dismutase (SOD), a critical enzyme within the plant antioxidant defense system, serves as the primary shield against reactive oxygen species (ROS) under adverse environmental conditions. However, the characterization of GbSODs in ginkgo remains incomplete. In our study, a total of eight GbSODs were identified, which were unevenly distributed across 10 chromosomes and predominantly localized on the plasma membrane. Our phylogenetic analysis revealed that GbSODs from ginkgo and other species form three distinct groups, each characterized by specific binding domains and supported by relatively high bootstrap values. Our promoter analysis indicated that all GbSODs contained multiple cis-elements related to various abiotic stress responses. Our systemic analysis revealed that only one pair of GbSODs underwent segmental duplications. The transcriptome analysis showed the variable expression of GbSODs across different tissues, which were significantly influenced by drought, ultraviolet (UV), and salt stress, with GbSOD8 showing a particularly notable induction. Transgenic plants that overexpressed GbSOD8 exhibited enhanced antioxidant enzyme activities, elevated proline levels, and reduced malondialdehyde (MDA) content, collectively contributing to their improved salt tolerance compared to wild-type plants. Our findings expand the comprehensive understanding of the GbSOD gene family and provide a solid foundation for further elucidating the molecular mechanisms of GbSODs under salt stress.