Genome wide identification of superoxide dismutase (SOD) genes and their expression profiles under 1-methylcyclopropene (1-MCP) treatment during ripening of apple fruit

Abstract

The objective of this research was to determine the role that ethylene plays in superoxide dismutase (SOD) gene expression of apple fruit (Malus × domestica Borkh.) during ripening. Apple fruit at commercial maturity were treated with ethylene antagonists 1-methylcyclopropene (1-MCP) and stored at shelf temperature of 20 °C. Our data indicated that application of 1-MCP resulted in a reduced rate of softening and a delayed peak of ethylene and respiration. 1-MCP treatment reduced accumulation of superoxide anion (O2−) and hydrogen peroxide (H2O2) in both peel and pulp, enhanced SOD activity in pulp and peel to varying degrees during ripening. Expression of Cu/ZnSOD2, Cu/ZnSOD3, Cu/ZnSOD5, Cu/ZnSOD6, Cu/ZnSOD8, MnSOD2, MnSOD7 and MnSOD9 in pulp was enhanced by treatment with 1-MCP during the early ripening period, and conversely, their expression in pulp was reduced by it during the late ripening period compared to control group. Most SOD genes presented a fluctuating pattern of expression in peel after 1-MCP treatment during ripening. Expression of Cu/ZnSOD10 and MnSOD7 in peel was promoted by 1-MCP treatment during the late ripening period, while expression of MnSOD4 and FeSOD1 in peel was generally enhanced by it during the entire shelf life period compared with controls. Our results suggested that ethylene played a role in regulating SOD genes expression in both pulp and peel of ripening apple fruit.