The Molecular Mechanism Of Transcription Factors SlBEL11 In The Regulation Of Tomato Fruit Chlorophyll Metabolism And Ripening

Photosynthesis takes place in a specialized compartment,the chloroplast,which provide energy and necessary substances for the development of tomato fruit.Chlorophyll(Chl)is the main photosynthetically active pigments.Therefore,the development of chloroplasts and the metabolism of Chl play important roles in the tomato fruit ripening and quality traits.However,the research on the transcription factors which regulate chloroplast development and Chl metabolism is less,the mechanism is poorly understood.Here,we utilized virus-induced gene silencing combined with transgenic technique,and RNA-Seq to identify the function of SIBEL11,which involved in Chl synthesis and chloroplast development.The main results were as follows:1?In this work,we initially studied seven homeobox-containing transcription factors(TFs)with specific ripening-associated expression patterns by virus-induced gene silencing(VIGS)technology and found that inhibiting the expression of one of these TFs,BEL1-LIKE HOMEODOMAIN11(SlBEL11),significantly increased Chl levels in unripe Micro-Tom tomato fruit.2?This enhanced chloroplast development and Chl accumulation was further validated by generating stable RNA interference(RNAi)transgenic lines.RNA-sequencing(RNA-seq)of RNAi-SIBEL11 fruit at the mature green(MG)stage showed the functions of differentially expressed genes involved in thylakoid and generation of precursor metabolites and energy.3?RNA-sequencing(RNA-seq)of RNAi-SIBEL11 fruit at the mature green(MG)stage showed that 48 genes involved in Chl biosynthesis,photosynthesis and chloroplast development were significantly up-regulated compared to wild type(WT).Genomic global scanning for BELL binding sites combined with RNA-seq differential gene expression analysis showed that 22 of these 48 genes were potential target genes of SlBEL11 protein.These included Chl biosynthesis-related genes encoding for protochlorophyllide reductase(POR),magnesium chelatase H subunit(CHLH),and chlorophyllide a oxygenase(CAO),and chloroplast development-related genes encoding for chlorophyll a/b binding protein(CAB),homeobox protein knotted 2(TKN2)and ARABIDOPSIS PSEUDO RESPONSE REGULATOR 2-LIKE(APRR2-like).4?Electrophoretic mobility shift assay(EMSA)and chromatin immunoprecipitation quantitative PCR(ChIP-qPCR)assays were employed to verify that SlBEL11 protein could bind to the promoters of TKN2,CAB and POR.Dual luciferase reporter assay(DLR)were employed to verify that SlBEL11 protein down-regulate the expression of TKN2,CAB and POR.5?The SlBEL11 has multiple functions to regulate fruit development,ripening and abscission during the fruit development and ripening.Taken together,our findings demonstrate that SlBEL11 plays an important role in chloroplast development and Chl synthesis in tomato fruit.Meanwhile,SlBEL11 has multiple functions to regulate fruit development.