| Chinese plum?Prunus salicina L.?is an important stone fruit tree which native to China and cultivated worldwide.It is conveniently accepted by the majors of fruit farmers and consumers because of its advantages such as adaptability,diverse varieties,advantage nutrition and abundant substance of antioxidant.It's considered to be one of the most promising economic fruit trees.However,flavor characteristics have severely affected plum industry,for example,high acidity.The new cultivar of plum‘Huangguan'is an excellent variety certified from Fujian Province[Min?Fujian?S-SV-PS-009-2018].We would like to explore the key genes of the formation deeply in the acid and sugar quality,and to analyze its mechanism of transcriptional regulation in the quality of sugar and acid on plum fruit.In this study,the material is plum'Huangguan'fruit.HPLC and UPLC were used to detect and analyze the changes in components and content of soluble sugar and organic acid of fruit during the four key metabolic stages:Fruitlet?DAF 6 d?,Green?18 d?,Veraison?47 d?and Mature?63 d?.RNA-sequencing was performed on the fruits by Illumina Hi-seq 2500 platform during the four stages,and the sequencing results were analyzed.Combined with the results of transcriptome data and the change of content duiring fruit development,the key differentially expressed genes on fruit sugar and acid metabolism were selected out.Make sure the expression patterns of key structural genes,transporter genes and transcription factors and regulation of the quality of sugar and acid in plums were identified during fruit development.The main results are as follows:1.The quality of sugar and acid is significantly improved at the middle and late stage of fruit development?Green to Mature?.A total of8 kinds of organic acid were detected in the fruit:malic acid,tartaric acid,acetic acid,citric acid,ascorbic acid,succinic acid,oxalic acid and fumaric acid.The content of total acid fluctuated like a'Z'shape but it was not significant difference during fruit development.Among them,malic acid is the main component of organic acid in the fruits and it has shown a trend with significant increase during fruit development.The content of malate reached a peak at mature,which was 1.89 mg·g-1?FW?,accounting for 88.28%of the total acid.A total of four kinds of soluble sugar were detected in the fruit:glucose,fructose,sorbitol,and sucrose.The content of total sugar showed a trend with significant increase overall.Glucose and fructose are the main component of soluble sugar at mature,with content of 16.22 mg·g-1and 7.24 mg·g-1?FW?,accounting for 55.88%and 24.83%respectively.There are almost no sucrose in fruits at mature.2.Establish transcriptome c DNA libraries for 4 metabolic stages during fruit development.The clean reads obtained by sequencing were assembled using Cufflinks software.After further splicing and de-redundancy processing,26547 unigenes were obtained with an average sequence length with 1683 bp.The unigene matched more than70%of the genome of the plum?Prunus mume L.?.Using GO,KEGG and Swiss-Prot databases to annotate all unigenes,53.9%of that get annotation information.A pairwise comparison of the adjacent databases in the 4 stages was conducted,that is Green vs.Fruitlet,Veraison vs.Green and Mature vs.Veraison.A total of 7584 DEGs?differentially expressed genes?were detected.Among them,the most DEGs were expressed in the early development stage?Green vs.Fruitlet?with 5424genes,of which 2748 genes were up-regulated and 2676 genes were down-regulated.As time goes by,the number of DEGs between adjacent groups decreased gradually,3689 and 1690 respectively.The DEGs are mainly enriched in quality related pathways such as Biosynthesis of secondary metabolites?pmum01100?,Starch and sucrose metabolism?pmum00500?,Biosynthesis of amino acids?pmum01230?,Phenylalanine metabolism?pmum00360?and Flavonoid biosynthesis?pmum00941?.A total of 74 transcription factor?TF?gene families were identified in this study,with a total of 1119 TFs.Among them,the MYB transcription factor was the most,accounting for 8%?95?of the total.3.The malate metabolism shows the most intense at the early stage of fruit development.There obtain a total of 12 key genes from 7families were involved in the regulation of malate metabolism.And get the following deductions:NADP-ME?103340826?and PEPCK?103319416?were promotes the synthesis of malate.ALMT?103329500and 103341458?lead the accumulation of malic acid at the early stage of fruit development mainly.t DT?103326982?and VHP?103341138?promote accumulation of malic acid at the later stage.MYB?103341502?is presumed to be a key gene which regulate the accumulation of malate at the early stages.Morever,there are 7 MYB?103320403,103320378,103337666,103335149,103338374,103321763 and 103320278?may play an important play in regulating malic acid accumulation.4.The soluble sugar metabolism shows the most active in the early stage of fruit development.There obtain a total of 17 key genes which from 11 families were involved in regulating the metabolism of soluble sugar during fruit development.And get the following deduction:ERD6L?103322904?is involved in keep a balance of glucose between the inside and outside of vacuole;SS?103333990?and SDH?103335104?are mainly involved in accumulation of fructose at Green.SDH?103335104?is mainly involved in degradation of sorbitol at Green.SS?103333990?and PFK?103333391?are mainly involved in regulating the degradation of sucrose at the early stages of fruit development.Furthermore,NINV?103331108?is regulate the accumulation of total sugar in plum.The bzip?103320133,103320491,103336224,103321334 and 103335689?may participate in regulating the accumulation of glucose.Meanwhile,gene 103321334 and 103335689may also important b ZIP transcription factors that regulate the accumulation of glucose and fructose in fruits. |
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