PacCYP707A2 Negatively Regulates Cherry Fruit Ripening And The Functional Analysis Of SlPti4

Sweet cherry is a non-climacteric fruit and its ripening is regulated by abscisic acid (ABA) during fruit development. PacCYP707A2 encoding 8’-hydroxylase, a key enzyme in the oxidative catabolism of ABA was identified in sweet cherry fruits using tobacco rattle virus-induced gene silencing (VIGS).The experimental results indicated that PacCYP707A2 transcript levels were relatively low at 21 DAFB but increased dramatically to a maximum at 25 DAFB. After 25 DAFB, PacCYP707A2 expression dramatically decreased up to 36 DAF and matained that level after that. The expression of PacCYP707A2 was down-regulated to 15% of controls. In PacCYP707A2-RNAi-treated fruits, ripening and fruit colouring were promoted relative to control fruits, and both ABA accumulation and PacNCED1 transcript levels were up-regulated. Solid soluble, anthocyanin and fruit firmness changed accordingly. Silencing of PacCYP707A2 by VIGS significantly altered the transcripts of both ABA-responsive and ripening-related genes, including the ABA metabolism-associated genes NCED1 and CYP707As, the anthocyanin synthesis genes PacCHS, PacCHI, PacF3H, PacDFR, PacANS and PacUFGT, the ethylene biosynthesis gene PacACO1, and the transcription factor PacMYBA. These results suggest that PacCYP707A2 is a key regulator of ABA catabolism that functions as a negative regulator of fruit ripening.The tomato SlPti4 gene encodes a transcription factor which belongs to ethylene response factor ERF family. It was the downstream of ethylene signal transduction. In order to investigate the role of SIPti4 in tomato, We got SlPti4-RNAi tomato. The experimental results indicated that RNA interference-induced silencing of SIPti4 accelerated fruit ripening by 2-3 days, due to the advanced accumulation of ABA and the alteration of ABA signaling transcript which causes the modulation of ethylene and ripening associated genes; SlPti4-RNAi Plants were more sensitive to drought stress,18 days after water was cut off, more than 80% of SlPti4-RNAi leaves curled while in the control only 30% leaves curled. In the transgene plants, the content of ABA and the expression of SINCED1, SIPYLs, SlPP2Cs, were lower than the control; SlPti4-RNAi seeds were less sensitive to ABA. ABA content and SINCED2 expression in dry seeds of the two transgenic lines were markedly lower than the control. The expression of SIPYLs and SlPP2Cs was also lower than the control. Yeast two-hybrid analysis between SlPti4 and ABA signaling core components proved that SlPti4 interacted directly with PYL4/7/9 to regulate the activity of ABA receptor. In addition, SlPti4 could interact with SnRK2.5 in SnRK2s family. SlSnRK2.5 could transfer ABA signal through the interaction with downstream transcription factors, like S1ABF2, S1ABF4, and S1AB15 in tomato. These results suggest that SlPti4 invovles in fruit ripening, seed germination and drought stress response in tomato via modulating ABA signaling core components.