title: Transcriptome and metabolome analyses of sugar and organic acid metabolism in Ponkan (Citrus reticulata) fruit during fruit maturation.
abstract: Ponkan (Citrus reticulata Blanco cv. Ponkan) is an important mandarin citrus in China. However, the low ratio of sugars to organic acids makes it less acceptable for consumers. In this work, three stages (S120, early development stage; S195, commercial harvest stage; S205, delayed harvest stage) of Ponkan fruit were selected for study. Among 28 primary metabolites analyzed in fruit, sugars increased while organic acids in general decreased. RNA-Seq analysis was carried out and 19,504 genes were matched to the Citrus clementina genome, with 85 up-regulated and 59 down-regulated genes identified during fruit maturation. A sucrose phosphate synthase (SPS) gene was included in the up-regulated group, and this was supported by the transcript ratio distribution. Expression of two asparagine transferases (AST), and a specific ATP-citrate lyase (ACL) and glutamate decarboxylase (GAD) members increased during fruit maturation. It is suggested that SPS, AST, ACL and GAD coordinately contribute to sugar accumulation and organic acid degradation during Ponkan fruit maturation. Both the glycolysis pathway and TCA cycle were accelerated during later maturation, indicating the flux change from sucrose metabolism to organic acid metabolism was enhanced, with citrate degradation occurring mainly through the gamma-aminobutyric acid (GABA) and acetyl-CoA pathways.
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: linqiong@zju.edu.cn.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: 804489925@qq.com.
authors.forename: Chengyang
authors.initials: C
authors.lastname: Wang
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: 664965671@qq.com.
authors.forename: Wencheng
authors.initials: W
authors.lastname: Dong
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: chongqingjiangqing@qq.com.
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiang
authors.affiliation: Quzhou Academy of Agricultural Science (Zhejiang Province), Quzhou 324000, PR China. Electronic address: 1335345870@qq.com.
authors.forename: Dengliang
authors.initials: D
authors.lastname: Wang
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: 544194544@qq.com.
authors.forename: Shaojia
authors.initials: S
authors.lastname: Li
authors.affiliation: College of Agronomy, Jiangxi Agricultural University, Nanchang 330045, PR China. Electronic address: chenming50@126.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.affiliation: Quzhou Academy of Agricultural Science (Zhejiang Province), Quzhou 324000, PR China. Electronic address: qzlcr@aliyun.com.
authors.forename: Chunrong
authors.initials: C
authors.lastname: Liu
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: adesun2006@zju.edu.cn.
authors.forename: Chongde
authors.initials: C
authors.lastname: Sun
authors.affiliation: Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China. Electronic address: akun@zju.edu.cn.
authors.forename: Kunsong
authors.initials: K
authors.lastname: Chen
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000143:Acids / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002951:Citrates / Q000378:metabolism; D002952:Citric Acid Cycle; D002957:Citrus / Q000235:genetics / Q000378:metabolism*; D005638:Fruit / Q000254:growth & development / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D006019:Glycolysis; D055442:Metabolome; D017423:Sequence Analysis, RNA; D013395:Sucrose / Q000378:metabolism; D059467:Transcriptome; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000143:Acids; D002951:Citrates; D005680:gamma-Aminobutyric Acid; D013395:Sucrose; D000105:Acetyl Coenzyme A
keywords: Metabolism; Metabolome; Organic acid; Ponkan; Sugar; Transcriptome