Dendrobium catenatum is a member of epiphytic orchids with extensive range of pharmacological properties and ornamental values. Superoxide dismutase (SOD), a key member of antioxidant system, plays a vital role in protecting plants against oxidative damage caused by various biotic and abiotic stresses. So far, little is known about the SOD gene family in D. catenatum. In this study, eight SOD genes, including four Cu/ZnSODs, three FeSODs and one MnSOD, were identified in D. catenatum genome. Phylogenetic analyses of SOD proteins in D. catenatum and several other species revealed that these SOD proteins can be assigned to three subfamilies based on their metal co-factors. Moreover, the similarities in conserved motifs and gene structures in the same subfamily corroborated their classification and inferred evolutionary relationships. There were many hormone and stress response elements in DcaSODs, of which light responsiveness elements was the largest group. All DcaSODs displayed tissue-specific expression patterns and exhibited abundant expression levels in flower and leaf. According to public RNA-seq data and qRT-PCR analysis showed that the almost DcaSODs, except for DcaFSD2, were highly expressed under cold and drought treatments. Under heat, light, and salt stresses, DcaCSD1, DcaCSD2, DcaCSD3 were always significantly up-regulated, which may play a vital role in coping with various stresses. The expression levels of DcaFSD1 and DcaFSD2 were promoted by high light, suggesting their important roles in light response. These findings provided valuable information for further research on DcaSODs in D. catenatum.
Keywords: Dendrobium catenatum; gene expression; gene family; stresses; superoxide dismutase (SOD).