title: Effects of granulation on organic acid metabolism and its relation to mineral elements in Citrus grandis juice sacs.
abstract: We investigated the effects of granulation on organic acid metabolism and its relation to mineral elements in 'Guanximiyou' pummelo (Citrus grandis) juice sacs. Granulated juice sacs had decreased concentrations of citrate and isocitrate, thus lowering juice sac acidity. By contrast, malate concentration was higher in granulated juice sacs than in normal ones. The reduction in citrate concentration might be caused by increased degradation, as indicated by enhanced aconitase activity, whilst the increase in malate concentration might be caused by increased biosynthesis, as indicated by enhanced phosphoenolpyruvate carboxylase (PEPC). Real time quantitative reverse transcription PCR (qRT-PCR) analysis showed that the activities of most acid-metabolizing enzymes were regulated at the transcriptional level, whilst post-translational modifications might influence the PEPC activity. Granulation led to increased accumulation of mineral elements (especially phosphorus, magnesium, sulphur, zinc and copper) in juice sacs, which might be involved in the incidence of granulation in pummelo fruits.
authors.affiliation: Institute of Horticultural Plant Physiology, Biochemistry and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Horticulture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
authors.forename: Xian-You
authors.initials: XY
authors.lastname: Wang
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Qi
authors.forename: Chen-Ping
authors.initials: CP
authors.lastname: Zhou
authors.forename: Lin-Tong
authors.initials: LT
authors.lastname: Yang
authors.forename: Xin-Yan
authors.initials: XY
authors.lastname: Liao
authors.forename: Liu-Qing
authors.initials: LQ
authors.lastname: Wang
authors.forename: Dong-Huang
authors.initials: DH
authors.lastname: Zhu
authors.forename: Li-Song
authors.initials: LS
authors.lastname: Chen
mesh_terms: D000144:Acids, Acyclic / Q000032:analysis / Q000378:metabolism*; D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism; D001628:Beverages / Q000032:analysis*; D002681:China; D019343:Citric Acid / Q000032:analysis / Q000378:metabolism; D002957:Citrus / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D003300:Copper / Q000032:analysis; D004795:Enzyme Stability; D005511:Food Handling; D005638:Fruit / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D007523:Isocitrates / Q000032:analysis / Q000378:metabolism; D008274:Magnesium / Q000032:analysis; D008293:Malates / Q000032:analysis / Q000378:metabolism; D010316:Particle Size; D010730:Phosphoenolpyruvate Carboxylase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D010758:Phosphorus / Q000032:analysis; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000032:analysis; D014131:Trace Elements / Q000032:analysis*; D015032:Zinc / Q000032:analysis
chemical_list: D000144:Acids, Acyclic; D007523:Isocitrates; D008293:Malates; D010940:Plant Proteins; D014131:Trace Elements; D010758:Phosphorus; D019343:Citric Acid; D013455:Sulfur; D003300:Copper; C030298:malic acid; C034219:isocitric acid; D010730:Phosphoenolpyruvate Carboxylase; D000154:Aconitate Hydratase; D008274:Magnesium; D015032:Zinc
keywords: Aconitase; Citrate; Citrus grandis; Granulation; Malate; Organic acid metabolism; Phosphoenolpyruvate carboxylase (PEPC); Pummelo