Study Of The Molecular Mechanism Of Abscisic Acid Metabolism And Signal Transduction Key Genes In Regulating Cherry And Tomato Fruit Ripening

Fruits are important economic organs of fruit crop and an important source of nutrients worldwide.Due to the ripening and senescence of fruit could not be controlled effectively,a large number of fruits lose during production,storage,transport and market,lead to huge economic losses and wasting of resources.Therefore,in order to explore the effective method to control fruit ripening and to extend the shelf life,and to meet the needs of people of high quality fruit supply,study toward the physiological,biochemical and molecular mechanism of fruit ripening should be performed actively.Abscisic acid is an important phytohormone,which plays an important role in regulating fruit ripening.But there are still lack of evidence at the molecular level related to the regulation of ABA on fruit ripening.In this study,we investigate the role of ABA during fruit ripening at both ABA homeostasis and signal transduction level by using non climacteric fruit cherry and model plant tomato as materials.This study provide evidence for clarify the molecular mechanism of ABA regulation fruit ripening.The important results of this study as follows:1.In this study,PacCYP707A1,which encodes 8-hydroxylase,a key enzyme in the oxidative catabolism of ABA,were identified in sweet cherry fruits using virus-induced gene silencing(VIGS)approach.Fruit ripening did not alter in PacCYP707A1-VIGS fruit compared with control.The expression of ABA metabolism and anthocyanin synthesis genes have no significantly difference between PacCYP707A1-VIGS and control fruit.Under drought stress condition,PacCYP707A1-VIGS fruit accumulate higher ABA level which lead to significantly low water loss rate compared to control.These results indicate that PacCYP707A1 regulates ABA content in response to dehydration in cherry fruit.2.In this study,SINCED1 genes encoding 9-cis-epoxycarotenoid dioxygenase(NCED,a key enzyme in the ABA biosynthetic pathway)and SICYP707A2 genes encoding ABA 8-hydroxylase(a key enzyme in the oxidative catabolism of ABA)were identified in tomato fruit by VIGS.We found that SlNCED1 and SICYP707A2 are key genes in the regulation of ABA synthesis and catabolism,and have positive and negative roles in regulating tomato fruit ripening,respectively.These results indicate the possibility to control fruit ripening by regulating fruit ABA level through ABA biosynthesis and catabolism.3.The function of tomato ABA glucosyltransferases gene SlUGT75C1,which is highly expressed in tomato fruit,was investigated in vivo using RNA interference approach.In SIUGT75C1-RNAi fruit,ABA content was elevated and ABA-GE content was decreased,which indicate that SIUGT75C1 regulated ABA homeostasis through ABA glucose conjugated pathway.Due to high ABA level,SIUGT75C1-RNAi fruits ripe early,however,the carotenoid content and the expression of carotenoid biosynthesis genes are down-regulated.These results suggest that ABA glucose conjugated pathway which mediated by SIUGT75C1 plays a crucial role in ABA-mediated fruit ripening in tomato.4.In order to investigate the mechanism of ABA regulated fruit ripening at signal transduction level,SIPP2C3,a key member of group A type 2C protein phosphatase,which involving in tomato ABA signal transduction,was selected.Supperession of SIPP2C3 results in typical ABA hypersensitive phenotype in seed dormancy and germination,primary root growth and response to drought,which suggest that SlPP2C3 act as a negative regulator in tomato ABA signaling.SlPP2C3-RNAi fruit ripening accelerated and ethylene release increased.Gene expression analysis finds that SIPP2C3 regulates fruit ripening maybe by mediating the expression of ethylene synthesis genes ACOs and ethylene receptor genes ETRs.Moreover,transcriptome data indicates that ABA signaling mediated by SIPP2C3 may regulates fruit cuticle formation.Taken together,this study prove that several ABA metabolism and signal transduction key genes play an important role in regulating cherry and tomato fruit ripening.The results indicate that it is possible to regulate fruit ripening and quality by manipulate ABA related genes through biotechnology.The results in this study laid a solid foundation for uncovering the regulation network of fruit development and ripening.Furthermore,these results provide theoretical basis for manipulation fiuit ripening,and provide a new ideal to fruit improvement through target molecular breeding.