LAUSR

Studies were conducted to determine the efficacy and mechanism of 1-methylcyclopropene (1-MCP) and ethephon on softening of Ailsa Craig tomato fruit. Ethylene production, reduction of fruit firmness and protopectin content were suppressed in fruit exposed to 1.0 µL/L 1-MCP. Comparing with control fruit, the climacteric ethylene peak was delayed by approximately 12 d and polygalacturonase activity was strongly inhibited in 1.0 µL/L 1-MCP treated fruit. On the other hand, ethylene production, reduction of fruit firmness, protopectin content and polygalacturonase activity of 100 µL/L ethephon treated fruit were strongly promoted compared with these indexes of untreated fruit. Moreover, electrophoretic mobility shift assay (EMSA) and Chromatin Immunoprecipitation (ChIP) assay proved that the expression of PG and tomato fruit softening was regulated by the transcription activator RIN. Practical Applications The RIN transcription factor plays an indispensable role in fruit ripening and softening. According to the physiological index of tomato fruit under varied concentrations of 1-MCP and ethephon, optimal concentrations of 1-MCP and ethephon would be used for further studies and industrial applications. Furthermore our study clearly showed RIN transcription factor directly regulated the expression of PG. Since the importance of polygalacturonase (PG) activity and indispensable role of RIN during the process of fruit softening, it suggested that RIN affects tomato fruit softening via directly acting on PG. It provides new clues to understand the molecular mechanism of fruit softening. To sum, these results will help to further clarify the mechanism of tomato fruit softening, and to maintain the quality and prolong the shelf life of tomato fruit.