Identification of Superoxide Dismutase Gene Family in Gymnocarpos przewalskii and its Response to Salt Stress

Purpose To identify the members of the superoxide dismutase (SOD) gene family of Gymnocarpos przewalskii, analyze the expression regulation mode of the SOD gene in leaf tissues under NaCl stress, and explore the adaptive evolution mechanism of the SOD gene family of G. przewalskii to the environment.

Methods Leaves of G. przewalskii were used as experimental materials, the SOD gene family of G. przewalskii was identified and expression pattern was analyzed by plant physiological method and bioinformatics.

Results Seven SOD genes were identified, and the composition pattern of its subfamily FSD, CSD and MSD was 2∶3∶2, which were all under purifying selection. The SOD gene family of G. przewalskii contained seven protein conserved motifs, and the proteins were hydrophilic with weak stability. SOD activity in G. przewalskii leaves increased firstly then decreased, reaching the highest at 0.5% NaCl treatment, and SOD activity at 1.5% NaCl treatment was also significantly higher than that under the control. Under salt stress, FSD, CSD1, CSD3 and MSD2 genes were all significantly up-regulated, among which FSD1 and CSD1 genes had the highest expression level. The variation site of CSD1 gene in G. przewalskii leaves may lead to the increase of protein active center.

Conclusion The SOD gene family of G. przewalskii contains seven members, and the high expression of FSD1 and CSD1 genes under salt stress may be one of the reasons why G. przewalskii has strong salt tolerance. In addition, the increases of protein hydrophilicity and active center caused by amino acid site mutation of FSD1 and CSD1 have a certain effects on the catalytic activity of SOD.