Although ABA signaling has been widely studied in Arabidopsis, the roles of core ABA signaling components in fruit remain poorly understood. Herein, we characterize SlPP2C1, a group A type 2C protein phosphatase that negatively regulates ABA signaling and fruit ripening in tomato. The SlPP2C1 protein was localized in the cytoplasm close to AtAHG3/AtPP2CA. The SlPP2C1 gene was expressed in all tomato tissues throughout development, particularly in flowers and fruits, and it was up-regulated by dehydration and ABA treatment. SlPP2C1 expression in fruits was increased at 30 d after full bloom and peaked at the B + 1 stage. Suppression of SlPP2C1 expression significantly accelerated fruit ripening which was associated with higher levels of ABA signaling genes that are reported to alter the expression of fruit ripening genes involved in ethylene release and cell wall catabolism. SlPP2C1-RNAi (RNA interference) led to increased endogenous ABA accumulation and advanced release of ethylene in transgenic fruits compared with wild-type (WT) fruits. SlPP2C1-RNAi also resulted in abnormal flowers and obstructed the normal abscission of pedicels. SlPP2C1-RNAi plants were hypersensitized to ABA, and displayed delayed seed germination and primary root growth, and increased resistance to drought stress compared with WT plants. These results demonstrated that SlPP2C1 is a functional component in the ABA signaling pathway which participates in fruit ripening, ABA responses and drought tolerance.

To investigate the effects of calyx on tomato fruit development and quality formation,we did two tests.In test1,calyxes were removed from fruits at 10,15,20,25,30,35 and 40d after flowering.Normal fruits with calyxes were used as control.Fruits were harvested at mature stage(6 days after turning)and analyzed.In test 2,we picked fruits at 25,30,35,40 and 45d after flowering,removed the calyxes and then stored at 25℃.The fruits with calyxes were used as a control.The results of test 1showed that removal of calyxes delayed fruits ripening,fruits weight and the content of ascorbic acid(Vc),flavonoids,and fruit cell wall materials.In terms of antioxidant enzymes,catalase(CAT)activity in treated fruits was lower than that of control,while peroxidase(POD)activity was higher the sugar-acid rate decreased.There is no significant difference in soluble solids between control and treated fruits.The results of test 2 showed that the ethylene production was reduced by half when calyxes were removed from fruits earlier than 30 dafter flowering.There was no significant difference in ethylene production between control and treated fruits from 35 dafter flowering.It can be therefore concluded that removing of calyx had some effects on the development growth and quality of tomato fruits.