Genome-Wide Identification of Superoxide Dismutase (SOD) Gene Family in Cymbidium Species and Functional Analysis of CsSODs Under Salt Stress in Cymbidium sinense

Abstract

Superoxide dismutase (SOD) enzymes are essential for reducing oxidative damage resulting from overabundant reactive oxygen species under abiotic stress. While the SOD gene family has been extensively studied in many species, research focusing on Cymbidium species remains limited. In this study, a comprehensive analysis of the SOD gene family in three Cymbidium genomes was conducted. A total of 23 SOD genes were identified, with nine SODs in C. sinense, eight in C. ensifolium, and six in C. goeringii. These SOD genes were categorized into three clades: Cu/Zn-SOD, Fe-SOD, and Mn-SOD, with the Cu/Zn-SOD being the most abundant in these three types. This classification was supported by analyses of conserved domains, motifs, and phylogenetic relationships. Cis-element prediction showed that stress-responsive elements were identified in most SODs. Transcriptomic data revealed that seven CsSODs exhibited a border expression in all sequenced tissues, while two exhibited undetectable expression levels. Further qRT-PCR analysis showed that all CsSODs were upregulated under salt stress, with some exhibiting significant changes in expression. These findings all highlight the crucial role of CsSODs in the salt stress response and provide valuable insights for further breeding salt-tolerance varieties of C. sinense.