Effects Of 1-MCP Treatment On The Expression Of SOD Gene Families During Ripening And Senescence Of Apple Fruit

In this paper,the early maturity variety‘Golden delicious'apple?Malus domestica Borkh.?was used as the test material to investigate the effect of 1-MCP treatment on storage quality and related metabolism of reactive oxygen species?ROS?after 1.0?L L^-1 1-MCP treatment for 24 hours under the condition of normal temperature storage?temperature 22±2?,relative humidity 50-55%?.Meanwhile,the SOD gene family members expressed in apple fruit were screened out from the apple genome,and their expression profiles under 1-MCP treatment was detected by qPCR.The main results are as follows:1.1-MCP treatment could maintain better quality of fruit and reduce the metabolism level of ROS during storage.The results showed that:1-MCP treatment reduced the ethylene release rate and respiratory intensity,and delayed the emergence of ethylene release and respiratory peaks of apple fruit during postharvest storage.However,compared with the control group,1-MCP treatment had no significant effect on the peak values of ethylene release and respiration intensity.In addition,flesh firmness was effectively maintained and the soluble solid content?SSC?was enhanced by 1-MCP treatment compared with the control.1-MCP treatment significantly increased the activity of superoxide dismutase?SOD?and inhibited the increase of hydrogen peroxide?H₂O₂?and malondialdehyde?MDA?content,and also delayed the superoxide anion(O₂^·-)production rate in both pulp and peel tissues.The results showed that 1-MCP had positive effects on reducing the rate of ROS production,and prevented the cell membrane from being damaged and delayed fruit senescence.2.Fourteen SOD genes were found to be expressed in different parts of fruit through identification of 31 SOD genes family members in apple genome.Cu/ZnSOD2,Cu/ZnSOD3,Cu/ZnSOD6,Cu/ZnSOD8,MnSOD2,MnSOD4,MnSOD7 and MnSOD9were expressed in both pulp and peel.Cu/ZnSOD5 and Mn/FeSOD were expressed only in the pulp,while Cu/ZnSOD9,Cu/ZnSOD10,FeSOD1 and FeSOD5 were expressed only in the peel.3.The expression profiles of the above fourteen expressed genes under 1-MCP treatment were detected by q-PCR.The results showed that the SOD gene family members had different response patterns to 1-MCP treatment in pulp and peel.Compared with the control,1-MCP treatment enhanced the expression of Cu/ZnSOD2,Cu/ZnSOD3,Cu/ZnSOD5,Cu/ZnSOD6,Cu/ZnSOD8,MnSOD2 and MnSOD7 in the pulp during the early storage period?from 0 d to 21 d?,while decreased their expression during the late storage period.At the early storage period,1-MCP treatment inhibited the expression of Cu/ZnSOD2,Cu/ZnSOD3,Cu/ZnSOD6,Cu/ZnSOD8,Cu/ZnSOD9,MnSOD2 and MnSOD9 in the peel.At the late storage period?from 28 d to 35 d?,1-MCP increased the expression of CuZnSOD10,MnSOD4,MnSOD7 and FeSOD5 in the peel.During the entire storage period,1-MCP treatment increased the expression of FeSOD1 and FeSOD5 in the peel.In conclusion,1-MCP could effectively maintain the postharvest storage quality,reduce the accumulation of ROS,delay the process of ripening and senescence of postharvest apple fruit,and thus prolong its storage life.1-MCP treatment could regulate the SOD activity and the expression of SOD gene during ripening and senescence of apple fruit after harvest.Therefore,ethylene plays a regulatory role in the process of ripening and senescence of apple fruit.