Effects Of Plant Growth Regulators On Postharvest Softening And Expression Of DkPG1 In Persimmon

In order to further explore the molecular regulation mechanism of PG during'Fuping Jianshi'(Diospyros kaki L.) postharvest softening with different treatments, and to improve the persimmon ripening and softening process, the responses of DkPG1 gene (DDBJ accession number EU816197) in persimmon fruit (Diospyros kaki L.) to propylene, 1-MCP, NAA, GA₃ at the room temperature were investigated by Real-time quantitative PCR(RT-qPCR) approach. Besides, Changes of fruit firmness, respiration rate, ethylene release rate, polygalacturonase(PG) activities were studied, in order to investigate the relation between the expression of PG gene DkPG1 and ethylene release rate, PG activities during the postharvest process of persimmon treated with propylene and 1-MCP, and to further provide the theorical evidence about effects of PG activity during persimmon softening, and new thoughts of controlling other fruits ripening and senescence process through biological technology.The results showed as follows:(1) During the persimmon softening process, expressions of DkPG1 had a discipline on the transcript level that it firstly increased to the maximum and then went down.(2) The expression of DkPG1 in persimmon was regulated by ethylene. The expression of DkPG1 in persimmon treated with propylene significantly increased, and the expression peak which was significantly higher than the control was advanced 12 d, while 1-MCP treatment made the expression of DkPG1 decrease, and the expression peak which was significantly lower than the control was delayed 12 d.(3) Compared with the control, the expression of DkPG1 in persimmon treated with NAA decreased, and the expression peak which was not significantly different with the control was delayed 4 d. The expression of DkPG1 in persimmon treated with GA₃ also decreased compared with the control, and its expression peak which was lower than the control was delayed 12 d.(4) Propylene accelerated the speed of persimmon softening process significantly, which made fruit firmness sharply decrease after the treatment and lose commercial value after 12 d storage, while treatment with 1-MCP significantly delayed the speed and made the fruits stay basically good after 20 d storage.(5) Propylene promoted the synthesis of endogenous ethylene, respiration rate and advanced both climacteric peaks, while 1-MCP treatment reduced ethylene's synthesis and respiration rate, and delayed the two climacteric peaks. The ethylene release peak in fruit treated with propylene appeared at the same day with its DkPG1 expression peak; 1-MCP treatment made its ethylene release peak appear 8 days earlier than the time of its DkPG1 expression peak.(6) The activity peaks of PG in persimmon treated with propylene significantly increased and were advanced, while 1-MCP treatment decreased and delayed the activity peak. PG activity peak in fruit treated with propylene appeared at the same day with its DkPG1 expression peak; 1-MCP treatment made its PG activity peak appear 4 days earlier than the time of its DkPG1 expression peak.