Study Of ABA-ethylene Interaction On The Regulation Of Cherry Tomato Fruit Ripening

Tomato ripening is a complex process that is precisely regulated.Phytohormone ethylene and abscisic acid(ABA)have been proved to have important regulatory effects on tomato ripening.In the present study,cherry tomato 'Xin Taiyang' were used to study the effect and mechanism of ABA-ethylene interaction on fruit color development based on the confirmation of regulatory effect of ABA on tomato fruit ripening,and iTRAQ was used to study the regulatory role of ABA in tomato ripening at the protein level.Moreover,the possible interaction sites between ABA and ethylene signaling pathways were screened based on the RNA-Seq results in our previous research and then verified by a series of experiments.The results were summarized as follows:1.Exogenous ABA treatment accelerated the postharvest ripening process of cherry tomatoes via accelerating color development and ethylene production as well as carotenoids accumulation during the ripening process.Meanwhile,exogenous ABA might increase the accumulation of volatile compounds such as 1-peten-3-one(2.06-fold),?-damascenone(1.64-fold),benzaldehyde(3.29-fold)and benzyl cyanide(4.15-fold)via regulating the expression of some key genes implicated in the biosynthesis pathways of aromatic volatiles,including TomloxC,HPL,ADH2,LeCCD1B and SIBCAT1(the values of the log2 fold changes ranged from-3.02 to 2.97).2.ABA and ethylene played a synergistic role in the development of fruit color during tomato ripening.Exogenous ABA treatment accelerated the development of tomato fruit color by significantly up-regulating the expression levels of major genes related to carotenoids and flavonoids biosynthesis(ranging from 2.08 to 35 folds)and initiated the accumulation of carotenoids,phenolics and flavonoids.However,results in ABA+1-MCP treated fruit demonstrated that exogenous ABA could not significantly affect tomato color development without ethylene.The outcomes of gene promoter analysis revealed that,besides single existence of ABRE or ERE motifs,10 of these genes.3.ABA significantly affected the protein expression in tomato of 23 genes involvedin carotenoids biosynthesis pathway and 10 of 40 genes involved in flavonoid biosynthesis pathway possess both ABRE and ERE motifs in their 2000 bp upstream sequences respectively,suggesting that ABA and ethylene may affect fruit color development via the collaborative regulationfruit during ripening.Exogenous ABA treatment up-regulated the protein expression of ACO1 and proteins involved in carotenoids biosynthesis and cell wall degradation,then promoted the synthesis of ethylene and accelerated the color change and softening process,and finally accelerated the ripening process of tomato fruit.The protein-protein interaction network of the ABA-responsive proteins during tomato ripening showed that the interaction proteins mainly concentrated on the photosynthetic system and sugar metabolic pathways.Meanwhile,exogenous ABA treatment down-regulated the proteins involved in the photosynthesis pathway,indicating that the differentially protein expressionin photosynthesis pathway may be an important part of the ABA regulation in tomato ripening.4.Transcription factor S1COL4 is probably one of the interaction sites of ABA-ethylene crosstalk and plays a negative regulatory role in tomato ripening.In the present study,the full-length sequence of S1COL4 was successfully cloned from tomato fruit,and S1COL4 was proved to be a typical COL transcription factor through amino acid sequence analysis and subcellular localization.Y1-H gold analysis and double luciferase analysis showed that ABA inhibited or induced S1COL4 through S1AREB1,S1ABAI5-7 and S1ABF.The result of Chip-seq analysis showed that S1COL4 may participate in ethylene biosynthesis by interacting with ACS gene,and regulate the ripening process of tomato fruit by interacting with ethylene receptor ETRs and response factor AP2/ERFs.Combined the results of YlH-gold,double luciferase,Chip-seq and the transient silencing of S1COL4 in tomato fruit,we can primarily confirm that S1COL4 interacts ABA and ethylene signal pathways and plays a negative regulatory role during tomato ripening.5.A possible regulation model of ABA and ABA-ethylene interaction in tomato fruit during ripening was constructed based on the results of physiological and biochemical effects,transcriptome analysis,proteomics analysis and interaction sites of ABA-ethylene interaction during tomato fruit ripening.