Gene Expression and Activities of SOD in Cucumber Seedlings Were Related with Concentrations of Mn2+, Cu2+, or Zn2+ Under Low Temperature Stress

Effects of increasing Mn2+, Cu2+, or Zn2+ on SOD expressions were studied in cucumber seedlings under low temperature stress. Both gene expressions and activities of Cu/Zn-SOD and Mn-SOD in cucumber seedling leaves were induced by increasing Mn2+, Cu2+, or Zn2+ under low temperature stress, especially 48 h afterwards. The activities of Cu/Zn-SOD and Mn-SOD at 0 and 48 h after treatment were in accordance with their gene expression levels, which implied that the transcriptional regulation plays key roles in regulating their activities at the early stage of low temperature stress. Gene expressions of Cu/Zn-SOD and Mn-SOD declined at 96 h, but Cu/Zn-SOD and Mn-SOD activities still remain high, which suggested that Cu/Zn-SOD and Mn-SOD activities might be regulated by other factors after transcription at the later stage of low temperature stress. Therefore, we concluded that the increasing Mn2+, Cu2+, or Zn2+ could increase the capacity of scavenging ROS in cucumber seedlings under low temperature stress by inducing gene expressions of Cu/Zn-SOD and Mn-SOD, elevating activities of Cu/Zn-SOD, Mn-SOD, or regulating other factors after transcription.