果实柠檬酸代谢研究进展

doi:10.16420/j.issn.0513-353x.2021-0709

摘要/Abstract

摘要：

柠檬酸作为园艺作物果实中的重要有机酸之一，显著影响果实风味和口感。文中综述了园艺作物果实中柠檬酸盐合成、转运、储藏及利用等诸多环节在柠檬酸积累中的地位和作用，着重介绍质子泵在液泡膜质子传递以及调节柠檬酸积累中的作用，概述转录因子、环境气候因素、栽培管理措施和采后处理等在柠檬酸积累代谢中的作用。全面解析了柠檬酸合成代谢机制，以期为通过基因编辑精细调控果实柠檬酸含量，获得糖酸比更加适宜、口感最佳果实的研究提供参考。

关键词: 柠檬酸, 转运蛋白, 代谢, 果实酸度

Abstract:

Citric acid is one of the important organic acids in the Horticultural crop fruit. Citric acid significantly affects the taste and flavor of the fruit. This paper reviews the status and function of citric acid synthesis，transport，storage and utilization in the accumulation of fruit. This paper emphasized the influences of the proton transfer of proton pump in the tonoplast and the regulation of citric acid accumulation. In addition，it gives an overview to the status of transcription factors，environmental and climatic factors，cultivation management measures and postharvest treatments in the metabolism and accumulation of citric acid. Based on the comprehensive understanding of the metabolic mechanism of citric acid synthesis and accumulation，the accumulation of citric acid in the fruit can be finely regulated by gene editing，to obtain the fruit with more suitable sugar-to-acid ratio and better taste.

Key words: citric acid, transport protein, metabolism, fruit acidity

中图分类号:

赵永, 朱红菊, 杨东东, 龚成胜, 刘文革. 果实柠檬酸代谢研究进展[J]. 园艺学报, 2022, 49(12): 2579-2596.

ZHAO Yong, ZHU Hongju, YANG Dongdong, GONG Chengsheng, LIU Wenge. Research Progress of Citric Acid Metabolism in the Fruit[J]. Acta Horticulturae Sinica, 2022, 49(12): 2579-2596.

图/表 4

图1 果肉细胞中柠檬酸合成、贮藏及代谢示意图紫色字体表示反应过程的酶;红色字体表示TCA循环过程的中间产物;棕色字体表示跨膜运输的载体;双箭头的大箭头表示可逆反应的主要方向，双箭头的小箭头表示可逆的次要方向;蓝色虚线箭头表示多次反应后产物生成的方向;双箭头虚线表示跨膜运输的物质;粉红色双椭圆表示跨膜通道或载体;蓝色圆形表示质子泵。CS：柠檬酸合酶;ACO：顺乌头酸酶;NAD-IDH：NAD+-异柠檬酸脱氢酶;NADP-IDH：NADP+-异柠檬酸脱氢酶;NAD-a-KGDH：NAD+-a-酮戊二酸脱氢酶;STK：琥珀酸硫激酶;SDH：琥珀酸脱氢酶;FH：延胡索酸酶;NAD-MDH：NAD+-苹果酸脱氢酶;NAD-ME：NAD+-苹果酸酶;NADP-ME：NADP+-苹果酸酶;PDH：丙酮酸脱氢酶;PPDK：丙酮酸磷酸二激酶;PEPC：磷酸烯醇丙酮酸羧化酶;PEPCK：磷酸烯醇式丙酮酸羧激酶;ACL：ATP-柠檬酸裂解酶;GAD：谷氨酸脱羧酶;GS：谷氨酰胺合成酶。

Fig. 1 Schematic diagram of synthesis，storage and metabolism of citric acid in pulp cells The purple font represents the enzymes in the reaction process. The red font represents the intermediate product of the TCA cycle process. The brown font represents the carrier of transmembrane transport. The large arrows of the double arrows represent the main direction of the reversible reaction，and the small arrows of the double arrows represent the secondary direction of the reversible reaction. The blue dotted arrows represent the direction of product formation after multiple reactions. The dotted lines of double arrows represent materials transported for carriage of the transmembrane transport. The pink double ellipses represent transmembrane channels or carriers. The blue circles represent the proton pump. CS：citrate synthase;ACO：aconitase;NAD-IDH：NAD+-isocitrate dehydrogenase;NADP-IDH：NADP+-isocitrate dehydrogenase;NAD-a-KGDH：NAD+-a-oxoglutarate dehydrogenase;STK：succinic thiokinase;SDH：succinic dehydrogenase;FH：fumarase;NAD-MDH：NAD+-Malate Dehydrogenase;NAD-ME：NAD+-malic enzyme;NADP-ME：NADP+-malic enzyme;PDH：pyruvate dehydrogenase;PPDK：pyruvate orthophosphate dikinase;PEPC：phosphoenolpyruvate carboxylase;PEPCK：phosphoenolpyruvate carboxykinase;ACL：ATP-citrate lyase;GAD：glutamate decarboxylase;GS：glutamine synthetase. （Shimada et al.，2006;Sweetlove et al.，2010;Etienne et al.，2013;Guo et al.，2016;Sadka et al.，2019）.

图2 TCA循环过程及其中间代谢物嵌入其他代谢网络的示意图蓝色字体表示TCA循环反应过程的酶;TCA循环网络以外的箭头指向了TCA循环中间代谢物的消耗或生产的类型。TCA循环通路的中间代谢物能够作为碳骨架参与其他代谢通路，如柠檬酸先经由途径1最后进入mevalonate pathway的次生代谢物合成或脂肪酸延伸代谢;苹果酸能够通过途径3的乙醛酸循环途径生成;延胡索酸能够通过途径4的氨基酸合成途径以及途径5的嘌呤代谢途径生成;OAA参与途径2的氨基酸合成分解途径;2-OG能够通过途径6和途径7参与氮同化，也能够通过途径8 ~ 18参与氨基酸的合成分解。

Fig. 2 Schematic diagram of the TCA cycle process and its intermediate metabolites embedded in other metabolic networks The blue font represents the enzymes in the TCA cycle reaction process. The arrows outside the TCA cycle network point to the type of the consumption or the production of intermediate metabolites in the TCA cycle. The intermediate metabolites of the TCA cycle pathway can be used as a carbon skeleton to participate in other metabolic pathways，such as the citric acid firstly via pathway 1，and finally enter into the secondary metabolite synthesis or the fatty acid extension metabolism of the mevalonate pathway. The malic acid can be generated by the glyoxylic acid cycle of the third pathway. The fumaric acid can be generated by the pathway of the amino acid synthesis of the fourth pathway and the pathway of the purine metabolism of the fifth pathway. The OAA participates in the pathway of the amino acid synthesis and decomposition of the second pathway. The 2-OG can participate in the pathway of the nitrogen assimilation of the sixth and seventh pathways，and can also participate in the synthesis and decomposition of amino acids by the pathway from the eighth to eighteenth. （Sweetlove et al.，2010）

图3 线粒体中主要的羧酸转运蛋白绿色三角表示质子的电化学梯度，驱动有机酸在细胞质和线粒体间运输;箭头表示物质运输的方向;粉红色箭头表示柠檬酸盐运输的方向;双椭圆表示跨膜通道或载体;PiC：磷酸盐载体;PTP：丙酮酸转运蛋白;DTP：二羧酸盐转运蛋白;CTP：柠檬酸转运蛋白;DTC：二羧酸盐—三羧酸盐载体;OMT：酮戊二酸—苹果酸转运蛋白;OAT：草酰乙酸—苹果酸转运蛋白。

Fig. 3 Major carboxylic acid transport proteins in the mitochondria The green triangle represents the electrochemical gradients of protons that drives the transport of the organic acids between the cytoplasm and mitochondria. The arrows represent the direction of material transport. The pink arrow represent the direction of citrate transport. The double ellipses represent transmembrane channels or carriers. PiC：phosphate carrier;PTP：pyruvate transport protein;DTP：dicarboxylate transport protein;CTP：citrate transport protein;DTC：dicarboxylate-tricarboxylate carrier;OMT：oxoglutarate-malate transporter;OAT：oxaloacetate-malate transporter. （Laloi，1999;Etienne et al.，2002，2013;Picault et al.，2002）.

图4 柑橘汁囊细胞液泡内的柠檬酸盐稳态粉红色双椭圆表示跨膜通道或载体;蓝色圆形表示质子泵。 VHA：液泡H+-ATPase;VHP：液泡H+-焦磷酸酶;PH：质膜H+-ATPase。

Fig. 4 Citrate homeostasis in the vacuole of citrus juice sac cells The pink double ellipses represent transmembrane channels or carriers. The blue circles represent the proton pump. VHA：vacuolar H+-ATPase;VHP：Vacuolar H+-pyrophosphatase;PH：Plasma membrane H+-ATPase. （Guo et al.，2016;Shimada et al.，2006）.

参考文献 152

[1]	Angela R L P, Luca L C, Ivana P. 2014. The metabolic fate of citric acid as affected by cold storage in blood oranges. Journal of Plant Biochemistry & Biotechnology, 23:161-166.
[2]	Antoine S, Pailly O, Gibon Y, Luro F, Santini J, Giannettini J, Berti L. 2016. Short- and long-term effects of carbohydrate limitation on sugar and organic acid accumulation during mandarin fruit growth. Journal of the Science of Food and Agriculture, 96:3906-3914. doi: 10.1002/jsfa.7594 pmid: 26694637
[3]	Aprile A, Federici C, Close T J, De B L, Cattivelli L, Roose M L. 2011. Expression of the H⁺-ATPase AHA10 proton pump is associated with citric acid accumulation in lemon juice sac cells. Functional & Integrative Genomics, 11:551-563.
[4]	Araujo W L, Nunes-Nesi A, Nikoloski Z, Sweetlove L J, Fernie A R. 2012. Metabolic control and regulation of the tricarboxylic acid cycle in photosynthetic and heterotrophic plant tissues. Plant Cell Environment, 35 (1):1-21. doi: 10.1111/j.1365-3040.2011.02332.x URL
[5]	Ashok K, Alva D M J, Siva P, Bhimu P, Huating D, Kenneth S S. 2006. Potassium management for optimizing citrus production and quality. International Journal of Fruit Science, 6:3-43.
[6]	Bahrami A R, Chen Z H, Walker R P, Leegood R C, Gray J E. 2001. Ripening-related occurrence of phosphoenolpyruvate carboxykinase in tomato fruit. Plant Molecular Biology, 47:499-506. doi: 10.1023/a:1011842828723 pmid: 11669575
[7]	Bastias A, Lopez C M, Valcarcel M, Rosello S, Gomez C A, Casaretto J A. 2011. Modulation of organic acids and sugar content in tomato fruits by an abscisic acid-regulated transcription factor. Physiologia Plantarum, 141:215-226. doi: 10.1111/j.1399-3054.2010.01435.x URL
[8]	Brune A, Muller M, Taiz L, Gonzalez P, Etxeberria E. 2002. Vacuolar acidification in citrus fruit:comparison between acid lime(Citrus aurantifolia)and sweet lime(Citrus limmetioides)juice cells. Journal of the American Society for Horticultural Science, 127:171-177. doi: 10.21273/JASHS.127.2.171 URL
[9]	Bugaud C, Daribo M O, Beaut M P T N, Dubois C. 2009. Relative importance of location and period of banana bunch growth in carbohydrate content and mineral composition of fruit. Fruits, 64:63-74. doi: 10.1051/fruits/2009001 URL
[10]	Butelli E, Garcia-Lor A, Licciardello C, Las Casas G, Hill L, Recupero G R, Keremane M L, Ramadugu C, Krueger R, Xu Q, Deng X, Fanciullino A L, Froelicher Y, Navarro L, Martin C. 2017. Changes in anthocyanin production during domestication of Citrus. Plant Physiology, 173 (4):2225-2242. doi: 10.1104/pp.16.01701 URL
[11]	Butelli E, Licciardello C, Ramadugu C, Durand H M, Celant A, Reforgiato R G, Froelicher Y, Martin C. 2019. Noemi controls production of flavonoid pigments and fruit acidity and illustrates the domestication routes of modern citrus varieties. Current Biology, 29 (1):158-164. doi: S0960-9822(18)31539-2 pmid: 30581020
[12]	Byeon S E, Lee J. 2020. Differential responses of fruit quality and major targeted metabolites in three different cultivars of cold-stored figs(Ficus carica L.). Scientia Horticulturae, 260:108877. doi: 10.1016/j.scienta.2019.108877 URL
[13]	Canel C, Baileyserres J N, Roose M L. 1995. In-vitro C¹⁴ citrate uptake by tonoplast vesicles of acidless citrusi juice cells. Journal of the American Society for Horticultural Science, 120:510-514. doi: 10.21273/JASHS.120.3.510 URL
[14]	Cercos M, Soler G, Iglesias D J, Gadea J, Forment J, Talon M. 2006. Global analysis of gene expression during development and ripening of citrus fruit flesh. A proposed mechanism for citric acid utilization. Plant Molecular Biology, 62:513-527. pmid: 16897468
[15]	Chen F X, Liu X H, Chen L S. 2009. Developmental changes in pulp organic acid concentration and activities of acid-metabolising enzymes during the fruit development of two loquat(Eriobotrya japonica Lindl.)cultivars differing in fruit acidity. Food Chemistry, 114:657-664. doi: 10.1016/j.foodchem.2008.10.003 URL
[16]	Chen M, Xie X L, Lin Q, Chen J Y, Grierson D, Yin X R, Sun C D, Chen K S. 2013. Differential expression of organic acid degradation-related genes during fruit development of Navel Oranges(Citrus sinensis)in two habitats. Plant Molecular Biology Reporter, 31:1131-1140. doi: 10.1007/s11105-013-0583-2 URL
[17]	Chowdhury J O, Xie Y J, Duan Y Q, Hu X J, Wang Z D, Lin Q. 2019. UV-C treatment promotes quality of early ripening apple fruit by regulating malate metabolizing genes during postharvest storage. PLoS ONE, 14 (4):e0215472. doi: 10.1371/journal.pone.0215472 URL
[18]	Cohen S, Itkin M, Yeselson Y, Tzuri G, Portnoy V, Harel B R, Lev S, Sa'ar U, Davidovitz R R, Baranes N, Bar E, Wolf D, Petreikov M, Shen S, Ben D S, Rogachev I, Aharoni A, Ast T, Schuldiner M, Belausov E, Eshed R, Ophir R, Sherman A, Frei B, Neuhaus H E, Xu Y M, Fei Z J, Giovannoni J, Lewinsohn E, Tadmor Y, Paris H S, Katzir N, Burger Y, Schaffer A A. 2014. The PH gene determines fruit acidity and contributes to the evolution of sweet melons. Nature Communications, 5:4026. doi: 10.1038/ncomms5026 URL
[19]	Degu A, Hatew B, Nunes N A, Shlizerman L, Zur N, Katz E, Fernie A R, Blumwald E, Sadka A. 2011. Inhibition of aconitase in citrus fruit callus results in a metabolic shift towards amino acid biosynthesis. Planta, 234:501-513. doi: 10.1007/s00425-011-1411-2 pmid: 21528417
[20]	Ding Z J, Yan J Y, Xu X Y, Li G X, Zheng S J. 2013. WRKY 46 functions as a transcriptional repressor of ALMT1,regulating aluminum-induced malate secretion in Arabidopsis. Plant Journal, 76:825-835. doi: 10.1111/tpj.12337 URL
[21]	Divert C, Chabanet C, Schoumacker R, Martin C, Lange C, Issanchou S, Nicklaus S. 2017. Relation between sweet food consumption and liking for sweet taste in French children. Food Quality and Preference, 56:18-27. doi: 10.1016/j.foodqual.2016.09.009 URL
[22]	Eisenach C, Baetz U, Martinoia E. 2014. Vacuolar proton pumping:more than the sum of its parts? Trends in Plant Science, 19:344-346. doi: 10.1016/j.tplants.2014.03.008 URL
[23]	Emmerlich V, Linka N, Reinhold T, Hurth M A, Traub M, Martinoia E, Neuhaus H E. 2003. The plant homolog to the human sodium/dicarboxylic cotransporter is the vacuolar malate carrier. Proceedings of the National Academy of Sciences of the United States of America, 100:11122-11126.
[24]	Etienne A, Génard M, Lobit P, Mbeguié A M D, Bugaud C. 2013. What controls fleshy fruit acidity? A review of malate and citrate accumulation in fruit cells. Journal of Experimental Botany: 64 (6):1451-1469. doi: 10.1093/jxb/ert035 pmid: 23408829
[25]	Etienne C, Moing A, Dirlewanger E, Raymond P, Monet R, Rothan C. 2002. Isolation and characterization of six peach cDNAs encoding key proteins in organic acid metabolism and solute accumulation:involvement in regulating peach fruit acidity. Physiol Plant, 114:259-270. doi: 10.1034/j.1399-3054.2002.1140212.x URL
[26]	Fan Lin-lin, Zhao Wen-jing, Zhao Dan, Zhao Hong-xia, Li Meng-meng, Cai Qian-tong, Feng Xu-qiao. 2014. Effect of citric acid treatment on the quality of fresh-cut apple slices during storage. Food Science, 35:230-235. (in Chinese)
	范林林, 赵文静, 赵丹, 赵宏霞, 李萌萌, 蔡茜彤, 冯叙桥. 2014. 柠檬酸处理对鲜切苹果的保鲜效果. 食品科学, 35:230-235.
[27]	Faraco M, Spelt C, Bliek M, Verweij W, Hoshino A, Espen L, Prinsi B, Jaarsma R, Tarhan E, De B A H, Di S G P, Koes R, Quattrocchio F M. 2014. Hyperacidification of vacuoles by the combined action of two different P-ATPases in the tonoplast determines flower color. Cell Reports, 6:32-43. doi: 10.1016/j.celrep.2013.12.009 pmid: 24388746
[28]	Fukuda A, Chiba K, Maeda M, Nakamura A, Maeshima M, Tanaka Y. 2004. Effect of salt and osmotic stresses on the expression of genes for the vacuolar H⁺-pyrophosphatase,H⁺-ATPase subunit A,and Na⁺/H⁺ antiporter from barley. Journal of Experimental Botany, 55:585-594. doi: 10.1093/jxb/erh070 URL
[29]	Galvez S, Gadal P. 1995. On the function of the nadp-dependent isocitrate dehydrogenase isoenzymes in living organisms. Plant Science, 105:1-14. doi: 10.1016/0168-9452(94)04041-E URL
[30]	Gao Lei. 2018. Transcriptome analysis and fine mapping of major genes controlling flesh firmness and sour flesh in watermelon[Ph. D. Dissertation]. Zhengzhou:Chinese Academy of Agricultural Sciences. (in Chinese)
	高磊. 2018. 西瓜果肉硬度和酸味性状的转录组分析及主效基因的精细定位[博士论文]. 郑州:中国农业科学院.
[31]	Gaxiola R A, Palmgren M G, Schumacher K. 2007. Plant proton pumps. FEBS Lett, 581:2204-2214. doi: 10.1016/j.febslet.2007.03.050 pmid: 17412324
[32]	Gaxiola R A, Sanchez C A, Paez V J, Ayre B G, Elser J J. 2012. Genetic manipulation of a“Vacuolar”H⁺-PPase:from salt tolerance to yield enhancement under phosphorus-deficient soils. Plant Physiology, 159:3-11. doi: 10.1104/pp.112.195701 URL
[33]	Genchi G, Spagnoletta A, De S A, Stefanizzi L, Palmieri F. 1999. Purification and characterization of the reconstitutively active citrate carrier from maize mitochondria. Plant Physiology, 120:841-848. pmid: 10398720
[34]	Gil M, Esteruelas M, González K N E, Jiménez F F J, Canals J, Hermosín G Z F. 2013. Effect of two different treatments for reducing grape yield in Vitis vinifera cv Syrah on wine composition and quality:berry thinning versus cluster thinning. Journal of Agricultural & Food Chemistry, 61:4968-4978.
[35]	Giovannoni J J. 2004. Genetic regulation of fruit development and ripening. Plant Cell, 16:S170-S180. doi: 10.1105/tpc.019158 URL
[36]	Gong Rong-gao, Lü Xiu-lan, Zhang Guang-lun, Zeng Xiu-li, Luo Nan, Hu Qiang. 2006. Study on the organic acid-metabolizing enzymes in Robertson Navel orange fruit collected from different habitats. Journal of Fruit Science,(6):805-808. (in Chinese)
	龚荣高, 吕秀兰, 张光伦, 曾秀丽, 罗楠, 胡强. 2006. 罗伯逊脐橙在不同生境下果实有机酸代谢相关酶的研究. 果树学报,(6):805-808.
[37]	Guo L, Liu Y, Luo L, Hussain S B, Bai Y, Alam S M. 2020. Comparative metabolites and citrate-degrading enzymes activities in citrus fruits reveal the role of balance between ACL and _Cyt-ACO in metabolite conversions. Plants(Basel), 9 (3):350.
[38]	Guo L X, Shi C Y, Liu X, Ning D Y, Jing L F, Yang H, Liu Y Z. 2016. Citrate accumulation-related gene expression and/or enzyme activity analysis combined with metabolomics provide a novel insight for an orange mutant. Scientific Reports, 6:29343. doi: 10.1038/srep29343 URL
[39]	Han Y C, Kuang J F, Chen J Y, Liu X C, Xiao Y Y, Fu C C, Wang J N, Wu K Q, Lu W J. 2016. Banana transcription factor MaERF11 recruits histone deacetylase MaHDA1 and represses the expression of MaACO1 and expansins during fruit ripening. Plant Physiology, 171:1070-1084.
[40]	Hayashi M, Debellis L, Alpi A, Nishimura M. 1995. Cytosolic aconitase participates in the glyoxylate cycle in etiolated pumpkin cotyledons. Plant and Cell Physiology, 36:669-680. pmid: 7640891
[41]	Hélène G, Aline R, Michel B, Dominique G, Mathilde C. 2005. Fruit load or fruit position alters response to temperature and subsequently cherry tomato quality. Journal of the Science of Food & Agriculture, 85:1009-1016.
[42]	Hu D G, Sun C H, Zhang Q Y, An J P, You C X, Hao Y J. 2016. Glucose sensor MdHXK 1 phosphorylates and stabilizes MdbHLH3 to promote anthocyanin biosynthesis in apple. PLoS Genet, 12:e1006273. doi: 10.1371/journal.pgen.1006273 URL
[43]	Hu D G, Sun C H, Zhang Q Y, An J P, You C X, Hao Y J. 2019. The regulatory module MdPUB29-MdbHLH3 connects ethylene biosynthesis with fruit quality in apple. New Phytologist, 221:1966-1982. doi: 10.1111/nph.15511 URL
[44]	Hu X M, Shi C Y, Liu X, Jin L F, Liu Y Z, Peng S A. 2015. Genome-wide identification of citrus ATP-citrate lyase genes and their transcript analysis in fruits reveals their possible role in citrate utilization. Molecular Genetics and Genomics, 290:29-38. doi: 10.1007/s00438-014-0897-2 URL
[45]	Huang D, Wang X, Tang Z, Yuan Y, Xu Y, He J, Jiang X, Peng S A, Li L, Butelli E, Deng X, Xu Q. 2018. Subfunctionalization of the Ruby2-Ruby 1 gene cluster during the domestication of citrus. Nature Plants, 4 (11):930-941. doi: 10.1038/s41477-018-0287-6 pmid: 30374094
[46]	Hurth M A, Suh S J, Kretzschmar T, Geis T, Bregante M, Gambale F, Martinoia E, Neuhaus H E. 2005. Impaired pH homeostasis in Arabidopsis lacking the vacuolar dicarboxylate transporter and analysis of carboxylic acid transport across the tonoplast. Plant Physiology, 137:901-910. doi: 10.1104/pp.104.058453 URL
[47]	Hummel I, Pantin F, Sulpice R, Piques M, Rolland G, Dauzat M, Christophe A, Pervent M, Bouteille M, Stitt M, Gibon Y, Muller B. 2010. Arabidopsis plants acclimate to water deficit at low cost through changes of carbon usage:an integrated perspective using growth,metabolite,enzyme,and gene expression analysis. Plant Physiology, 154:357-372. doi: 10.1104/pp.110.157008 pmid: 20631317
[48]	Hussain S B, Shi C Y, Guo L X, Kamran H M, Sadka A, Liu Y Z. 2017. Recent advances in the regulation of citric acid metabolism in citrus fruit. Critical Reviews in Plant Sciences, 36:241-256. doi: 10.1080/07352689.2017.1402850 URL
[49]	Hussain S B, Shi C Y, Guo L X, Du W, Bai Y X, Kamran H M, Fernie A R, Liu Y Z. 2020. Type I H⁺-pyrophosphatase regulates the vacuolar storage of sucrose in citrus fruit. Journal of Experimental Botany, 71:5935-5947. doi: 10.1093/jxb/eraa298 pmid: 32589717
[50]	Iacobazzi V, Palma A D, Palmieri F. 1996. Cloning and sequencing of the bovine cDNA encoding the mitochondrial tricarboxylate carrier protein. Biochimica et Biophysica Acta(BBA)- Biomembranes, 1284:9.
[51]	Iannetta P P M, Escobar N M, Ross H A, Souleyre E J F, Hancock R D, Witte C P, Davies H V. 2004. Identification,cloning and expression analysis of strawberry(Fragaria × ananassa)mitochondrial citrate synthase and mitochondrial malate dehydrogenase. Physiologia Plantarum, 121:15-26. doi: 10.1111/j.0031-9317.2004.00302.x URL
[52]	Jawad U M, Gao L, Gebremeskel H, Safdar L B, Yuan P L, Zhao S J, Lu X Q, He N, Zhu H J, Liu W G. 2020. Expression pattern of sugars and organic acids regulatory genes during watermelon fruit development. Scientia Horticulturae,Scientia Horticulturae, 265:109102.
[53]	Jiang N, Jin L F, Teixeira D M Z, Gao H W, Liu Y Z, Peng S A. 2014. Activities of enzymes directly related with sucrose and citric acid metabolism in citrus fruit in response to soil plastic film mulch. Scientia Horticulturae, 168:73-80. doi: 10.1016/j.scienta.2014.01.021 URL
[54]	Kallsen C E, Sanden B, Arpaia M L. 2011. Early navel orange fruit yield,quality,and maturity in response to late-season water stress. HortScience, 46:1163-1169. doi: 10.21273/HORTSCI.46.8.1163 URL
[55]	Katz E, Boo K H, Kim H Y, Eigenheer R A, Phinney B S, Shulaev V, Negre Z F, Sadka A, Blumwald E. 2011. Label-free shotgun proteomics and metabolite analysis reveal a significant metabolic shift during citrus fruit development. Journal of Experimental Botany, 62:5367-5384. doi: 10.1093/jxb/err197 pmid: 21841177
[56]	Katz E, Fon M, Lee Y J, Phinney B S, Sadka A, Blumwald E. 2007. The citrus fruit proteome:insights into citrus fruit metabolism. Planta, 226:989-1005. pmid: 17541628
[57]	Krebs M, Beyhl D, Görlich E, Khaled A S A R, Marten I, Stierhof Y D, Hedrich R, Schumacher K. 2010. Arabidopsis V-ATPase activity at the tonoplast is required for efficient nutrient storage but not for sodium accumulation. Proceedings of the National Academy of Sciences of the United States of America, 107:3251-3256.
[58]	Kriegel A, Andres Z, Medzihradszky A, Kruger F, Scholl S, Delang S, Patir N M G, Gute G, Yang H, Murphy A S, Peer W A, Pfeiffer A, Krebs M, Lohmann J U, Schumacher K. 2015. Job Sharing in the endomembrane system:vacuolar acidification requires the combined activity of V-ATPase and V-PPase. Plant Cell, 27:3383-3396. doi: 10.1105/tpc.15.00733 URL
[59]	Laloi M. 1999. Plant mitochondrial carriers:an overview. Cellular and Molecular Life Sciences, 56:918-944. pmid: 11212326
[60]	Li Mingqi. 1989. Physiology of fruit. Beijing: Science Press:83-88. (in Chinese)
	李明启. 1989. 果实生理. 北京: 科学出版社:83-88.
[61]	Li S J, Liu X J, Xie X L, Allan A C, Ge H, Shen S L, Chen K S. 2016. The Citrus transcription factor,CitERF13,regulates citric acid accumulation via a protein-protein interaction with the vacuolar proton pump,CitVHA-c4. Scientific Reports, 6:20151. doi: 10.1038/srep20151 URL
[62]	Li S J, Liu X J, Xie X L, Sun C D, Grierson D, Yin X R, Chen K S. 2015. CrMYB73,a PH-like gene,contributes to citric acid accumulation in citrus fruit. Scientia Horticulturae, 197:212-217. doi: 10.1016/j.scienta.2015.09.037 URL
[63]	Li S J, Wang W L, Ma Y C, Liu S C, Grierson D, Yin X R, Chen K S. 2020. Citrus CitERF6 contributes to citric acid degradation via upregulation of CitAclalpha1,Encoding ATP-Citrate Lyase Subunit alpha. Journal of Agricultural and Food Chemistry, 68:10081-10087. doi: 10.1021/acs.jafc.0c03669 URL
[64]	Li S J, Yin X J, Wang W L, Liu X F, Zhang B, Chen K S. 2017. Citrus CitNAC62 cooperates with CitWRKY1 to participate in citric acid degradation via up-regulation of CitAco3. Journal of Experimental Botany, 68:3419-3426. doi: 10.1093/jxb/erx187 URL
[65]	Li Y, Liu B, Peng Y, Liu C, Li C. 2019. Exogenous GABA alleviates alkaline stress in Malus hupehensis by regulating the accumulation of organic acids. Scientia Horticulturae, 261:108982. doi: 10.1016/j.scienta.2019.108982 URL
[66]	Liao L, Dong T, Qiu X, Rong Y, Wang Z, Zhu J. 2019. Nitrogen nutrition is a key modulator of the sugar and organic acid content in citrus fruit. PLoS ONE, 14:e0223356. doi: 10.1371/journal.pone.0223356 URL
[67]	Liao L, Zhang W, Zhang B, Fang T, Wang X F, Cai Y, Ogutu C, Gao L, Chen G, Nie X, Xu J, Zhang Q, Ren Y, Yu J, Wang C, Deng C H, Ma B, Zheng B, You C X, Hu D G, Espley R, Lin-Wang K, Yao J L, Allan A C, Khan A, Korban S S, Fei Z, Ming R, Hao Y J, Li L, Han Y. 2021. Unraveling a genetic roadmap for improved taste in the domesticated apple. Molecular Plant, 14 (9):1454-1471. doi: 10.1016/j.molp.2021.05.018 pmid: 34022440
[68]	Licciardello C, Casas G, Las C M, Caruso P, Russo M P, Paolo D, Pietro R G, Recupero G, Reforgiato. 2016. The evolution of citrate metabolism in acidic and acidless citrus genotypes during fruit development and ripening. Acta Horticulturae, 1135:53-60.
[69]	Lin Q, Qian J, Zhao C, Wang D, Liu C, Wang Z, Sun C, Chen K. 2016. Low temperature induced changes in citrate metabolism in Ponkan(Citrus reticulata Blanco cv. Ponkan)Fruit during Maturation. PLoS ONE, 11:e0156703. doi: 10.1371/journal.pone.0156703 URL
[70]	Lin Q, Wang C Y, Dong W C, Jiang Q, Wang D L, Li S J, Chen M, Liu C R, Sun C D, Chen K S. 2015. Transcriptome and metabolome analyses of sugar and organic acid metabolism in Ponkan(Citrus reticulata)fruit during fruit maturation. Gene, 554:64-74. doi: 10.1016/j.gene.2014.10.025 URL
[71]	Liu R, Li B, Qin G, Zhang Z, Tian S. 2017. Identification and functional characterization of a tonoplast dicarboxylate transporter in tomato (Solanum lycopersicum). Frontiers in Plant Science, 8:186.
[72]	Liu S G, Yang Y L, Murayama H, Taira S, Fukushima T. 2004. Effects of CO₂ on respiratory metabolism in ripening banana fruit. Postharvest Biology and Technology, 33:27-34. doi: 10.1016/j.postharvbio.2004.01.006 URL
[73]	Liu X C, Lin X H, Liu S C, Zhu C Q, Grierson D, Li S J, Chen K S. 2021. The effect of NH₄ (+) on phosphoenolpyruvate carboxykinase gene expression,metabolic flux and citrate content of citrus juice sacs. Plant Physiology and Biochemistry, 167:123-131. doi: 10.1016/j.plaphy.2021.07.041 URL
[74]	Lu X P, Cao X J, Li F F, Li J, Xiong J, Long G Y, Cao S Y, Xie S X. 2016. Comparative transcriptome analysis reveals a global insight into molecular processes regulating citrate accumulation in sweet orange(Citrus sinensis). Physiologia Plantarum, 158:463-482. doi: 10.1111/ppl.12484 URL
[75]	Ma X, Li N, Guo J, Yang L, Sheng L. 2020. Involvement of CsPH 8 in citrate accumulation directly related to fruit storage performance of‘Bingtang’ sweet orange mutants. Postharvest Biology and Technology, 170:111316. doi: 10.1016/j.postharvbio.2020.111316 URL
[76]	Macrae A R, Moorhouse R. 1970. The oxidation of malate by mitochondria isolated from cauliflower buds. Eur J Biochem, 16:96-102. pmid: 4318476
[77]	Maeshima M. 2000. Vacuolar H⁺-pyrophosphatase. Biochimica Et Biophysica Acta-Biomembranes, 1465:37-51. doi: 10.1016/S0005-2736(00)00130-9 URL
[78]	Mao Yue-zhong. 2019. Quantitative study of sweet-sour taste interaction and taste sensors integration development[Ph. D. Dissertation]. Hangzhou:Zhejiang Gongshang Uuniversity. (in Chinese)
	毛岳忠. 2019. 甜酸味觉交互响应的量化研究和传感器组合研制[博士论文]. 杭州:浙江工商大学.
[79]	Mariko N, Hassimotto A, Lajolo F M. 2017. Brazilian native fruits as a source of phenolic compounds. Global Food Security and Wellness,105-124.
[80]	Martinez-Esteso M J, Selles M S, Lijavetzky D, Pedreno M A, Bru M R. 2011. A DIGE-based quantitative proteomic analysis of grape berry flesh development and ripening reveals key events in sugar and organic acid metabolism. Journal of Experimental Botany, 62:2521-2569. doi: 10.1093/jxb/erq434 URL
[81]	Martinoia E. 2018. Vacuolar transporters-companions on a longtime journey. Plant Physiology, 176:1384-1407. doi: 10.1104/pp.17.01481 pmid: 29295940
[82]	Martinoia E, Maeshima M, Neuhaus H E. 2007. Vacuolar transporters and their essential role in plant metabolism. Journal of Experimental Botany, 58:83-102. doi: 10.1093/jxb/erl183 pmid: 17110589
[83]	Massenti R, Lo Bianco R, Sandhu A K, Gu L, Sims C. 2016. Huanglongbing modifies quality components and flavonoid content of‘Valencia' oranges. Journal of Agricultural and Food Chemistry Agriculture, 96:73-78.
[84]	Mauricio G A, Luis T P, María C C Z, Pedro U, Bruno D. 2016. The unusual acid-accumulating behavior during ripening of Cherimoya(Annona cherimola Mill.)is linked to changes in transcription and enzyme activity related to citric and malic acid metabolism. Molecules, 21 (5):398. doi: 10.3390/molecules21050398 URL
[85]	McIntosh C A, Oliver D J. 1992. Isolation and characterization of the tricarboxylate transporter from pea mitochondria. Plant Physiol, 100:2030-2034. doi: 10.1104/pp.100.4.2030 pmid: 16653235
[86]	Mitsuda N, Enami K, Nakata M, Takeyasu K, Sato M H. 2001. Novel type Arabidopsis thaliana H⁺-PPase is localized to the Golgi apparatus. Febs Letters, 488:29-33. pmid: 11163790
[87]	Mohammed S A, Nishio S, Takahashi H, Shiratake K, Ikeda H, Kanahama K, Kanayama Y. 2012. Role of Vacuolar H⁺-inorganic pyrophosphatase in tomato fruit development. J Exp Bot, 63:5613-5621. doi: 10.1093/jxb/ers213 pmid: 22915738
[88]	Moraes B J, Belinato J R, Costa J H, Akiyama D Y, Pontes J G M, Kupper K C, Augusto F, Carvalho J E, Fill T P. 2019. Biological control of citrus postharvest phytopathogens. Toxins(Basel), 11 (8):460.
[89]	Morgan M J, Osorio S, Gehl B, Baxter C J, Kruger N J, Ratcliffe R G, Fernie A R, Sweetlove L J. 2013. Metabolic engineering of tomato fruit organic acid content guided by biochemical analysis of an introgression line. Plant Physiology, 161:397-407. doi: 10.1104/pp.112.209619 pmid: 23166354
[90]	Muller M L, Irkens K U, Rubinstein B, Taiz L. 1996. On the mechanism of hyperacidification in lemon-comparison of the vacuolar H⁺-ATPase activities of fruits and epicotyls. Journal of Biological Chemistry, 271:1916-1924. doi: 10.1074/jbc.271.4.1916 URL
[91]	Nishawy E, Sun X H, Ewas M, Ziaf K, Xu R W, Wang D, Amar M, Zeng Y L, Cheng Y J. 2015. Overexpression of Citrus grandis DREB gene in tomato affects fruit size and accumulation of primary metabolites. Scientia Horticulturae, 192:460-467. doi: 10.1016/j.scienta.2015.06.035 URL
[92]	Park S, Li J S, Pittman J K, Berkowitz G A, Yang H B, Undurraga S, Morris J, Hirschi K D, Gaxiola R A. 2005. Up-regulation of a H⁺-pyrophosphatase(H⁺-PPase)as a strategy to engineer drought-resistant crop plants. Proceedings of the National Academy of Sciences of the United States of America, 102:18830-18835.
[93]	Peng A, Chen S, Lei T, Xu L, He Y, Wu L, Yao L, Zou X. 2017. Engineering canker-resistant plants through CRISPR/Cas9-targeted editing of the susceptibility gene CsLOB1 promoter in citrus. Plant Biotechnology Journal, 15:1509-1519. doi: 10.1111/pbi.12733 URL
[94]	Picault N, Palmieri L, Pisano I, Hodges M, Palmieri F. 2002. Identification of a novel transporter for dicarboxylates and tricarboxylates in plant mitochondria. Bacterial expression,reconstitution,functional characterization,and tissue distribution. J Biol Chem, 277:24204-24211. doi: 10.1074/jbc.M202702200 URL
[95]	Primo C, Pizzio G A, Yang J, Gaxiola R A, Scholz S J, Hirschi K D. 2019. Plant proton pumping pyrophosphatase:the potential for its pyrophosphate synthesis activity to modulate plant growth. Plant Biol(Stuttg), 21:989-996.
[96]	Rao M J, Zuo H, Xu Q. 2021. Genomic insights into citrus domestication and its important agronomic traits. Plant Commun, 2:100138. doi: 10.1016/j.xplc.2020.100138 URL
[97]	Ratajczak R, Lüttge U, Gonzalez P, Etxeberria E. 2003. Malate and malate-channel antibodies inhibit electrogenic and ATP-dependent citrate transport across the tonoplast of citrus juice cells. Journal of Plant Physiology, 160 (11):1313-1317. pmid: 14658383
[98]	Regalado A, Pierri C L, Bitetto M, Laera V L, Pimentel C, Francisco R, Passarinho J, Chaves M M, Agrimi G. 2013. Characterization of mitochondrial dicarboxylate/tricarboxylate transporters from grape berries. Planta, 237:693-703. doi: 10.1007/s00425-012-1786-8 pmid: 23096487
[99]	Rocha A M C N, Brochado C M, Morais A M M B. 1998. Influence of chemical treatment on quality of cut apple(cv. Jonagored). Journal of Food Quality, 21:13-28. doi: 10.1111/j.1745-4557.1998.tb00500.x URL
[100]	Rodriguez L D, Lemmon Z H, Man J, Bartlett M E, Lippman Z B. 2017. Engineering quantitative trait variation for crop improvement by genome editing. Cell, 171:470-480. doi: 10.1016/j.cell.2017.08.030 URL
[101]	Rong W, Qi L, Wang A, Ye X, Du L, Liang H, Xin Z, Zhang Z. 2014. The ERF transcription factor TaERF3 promotes tolerance to salt and drought stresses in wheat. Plant Biotechnology Journal, 12:468-479. doi: 10.1111/pbi.12153 pmid: 24393105
[102]	Sadka A, Dahan E, Cohen L, Marsh K B. 2000. Aconitase activity and expression during the development of lemon fruit. Physiologia Plantarum, 108:255-262. doi: 10.1034/j.1399-3054.2000.108003255.x URL
[103]	Sadka A, Dahan E, Or E, Roose M L, Marsh K B, Cohen L. 2001. Comparative analysis of mitochondrial citrate synthase gene structure,transcript level and enzymatic activity in acidless and acid-containing Citrus varieties. Australian Journal of Plant Physiology, 28:383-390.
[104]	Sadka A, Shlizerman L, Kamara I, Blumwald E. 2019. Primary metabolism in citrus fruit as affected by its unique structure. Frontiers in Plant Science, 10:1167. doi: 10.3389/fpls.2019.01167 pmid: 31611894
[105]	Saidani F, Gimeneze R, Aubert C, Chalot G, Betran J A, Gogorcena Y. 2017. Phenolic,sugar and acid profiles and the antioxidant composition in the peel and pulp of peach fruits. Journal of Food Composition and Analysis, 62:126-133. doi: 10.1016/j.jfca.2017.04.015 URL
[106]	Saradhuldhat P, Paull R E. 2007. Pineapple organic acid metabolism and accumulation during fruit development. Scientia Horticulturae, 112:297-303. doi: 10.1016/j.scienta.2006.12.031 URL
[107]	Scherer R, Rybka A C P, Ballus C A, Meinhart A D, Teixeira J, Godoy H T. 2012. Validation of a HPLC method for simultaneous determination of main organic acids in fruits and juices. Food Chemistry, 135:150-154. doi: 10.1016/j.foodchem.2012.03.111 URL
[108]	Schilling R K, Tester M, Marschner P, Plett D C, Roy S J. 2017. AVP1:one Protein,many roles. Trends in Plant Science, 22:154-162. doi: S1360-1385(16)30197-2 pmid: 27989652
[109]	Schumacher K. 2014. pH in the plant endomembrane system-an import and export business. Current Opition in Plant Biology, 22:71-76.
[110]	Segami S, Asaoka M, Kinoshita S, Fukuda M, Maeshima M. 2018. Biochemical,structural and physiological characteristics of vacuolar H⁺-Pyrophosphatase. Plant and Cell Physiology, 59 (7):1300-1308. doi: 10.1093/pcp/pcy054 pmid: 29534212
[111]	Sheng L, Shen D, Yang W, Zhang M, Zeng Y, Xu J, Deng X, Cheng Y. 2017. GABA pathway rate-limit citrate degradation in postharvest citrus fruit evidence from HB Pumelo(Citrus grandis)× Fairchild(Citrus reticulata)hybrid Population. Journal of Agricultural and Food Chemistry, 65:1669-1676. doi: 10.1021/acs.jafc.6b05237 pmid: 28150945
[112]	Shi C Y, Bilal H S, Guo L X, Yang H, Ning D Y, Liu Y Z. 2018. Genome-wide identification and transcript analysis of vacuolar-ATPase genes in citrus reveal their possible involvement in citrate accumulation. Phytochemistry, 155:147-154. doi: 10.1016/j.phytochem.2018.08.007 URL
[113]	Shi C Y, Hussain S B, Yang H, Bai Y X, Khan M A, Liu Y Z. 2019. CsPH8,a P-type proton pump gene,plays a key role in the diversity of citric acid accumulation in citrus fruits. Plant Science, 289:110288. doi: 10.1016/j.plantsci.2019.110288 URL
[114]	Shi C Y, Song R Q, Hu X M, Liu X, Jin L F, Liu Y Z. 2015. Citrus PH5-like H⁺-ATPase genes:identification and transcript analysis to investigate their possible relationship with citrate accumulation in fruits. Frontiers in Plant Science, 6:135.
[115]	Shimada T, Nakano R, Shulaev V, Sadka A, Blumwald E. 2006. Vacuolar citrate/H⁺ symporter of citrus juice cells. Planta, 224:472-480. doi: 10.1007/s00425-006-0223-2 URL
[116]	Song C Z, Wang C, Xie S, Zhang Z W. 2018. Effects of leaf removal and cluster thinning on berry quality of Vitis vinifera cultivars in the region of Weibei Dryland in China. Journal of Integrative Agriculture, 17:1620-1630. doi: 10.1016/S2095-3119(18)61990-2 URL
[117]	Steuer R, Nesi A N, Fernie A R, Gross T, Blasius B, Selbig J. 2007. From structure to dynamics of metabolic pathways:application to the plant mitochondrial TCA cycle. Bioinformatics, 23:1378-1385. doi: 10.1093/bioinformatics/btm065 pmid: 17344242
[118]	Strazzer P, Spelt C E, Li S J, Bliek M, Federici C T, Roose M L, Koes R, Quattrocchio F M. 2019. Hyperacidification of Citrus fruits by a vacuolar proton-pumping P-ATPase complex. Nature Communications, 10 (1):744. doi: 10.1038/s41467-019-08516-3 pmid: 30808865
[119]	Suzuki Y, Shiratake K, Yamaki S. 2000. Seasonal changes in the activities of vacuolar H⁺-pumps and their gene expression in the developing Japanese pear fruit. Journal of the Japanese Society for Horticultural Science, 69:15-21.
[120]	Sweetlove L J, Beard K F M, Nunes N A, Fernie A R, Ratcliffe R G. 2010. Not just a circle:flux modes in the plant TCA cycle. Trends in Plant Science, 15:462-470. doi: 10.1016/j.tplants.2010.05.006 pmid: 20554469
[121]	Sweetman C, Deluc L G, Cramer G R, Ford C M, Soole K L. 2009. Regulation of malate metabolism in grape berry and other developing fruits. Phytochemistry, 70:1329-1344. doi: 10.1016/j.phytochem.2009.08.006 pmid: 19762054
[122]	Tan F Q, Zhang M, Xie K D, Fan Y J, Song X, Wang R, Wu X M, Zhang H Y, Guo W W. 2019. Polyploidy remodels fruit metabolism by modifying carbon source utilization and metabolic flux in Ponkan mandarin(Citrus reticulata Blanco). Plant Science, 289:110276. doi: 10.1016/j.plantsci.2019.110276 URL
[123]	Tang N, An J, Deng W, Gao Y, Li Z. 2020. Metabolic and transcriptional regulatory mechanism associated with postharvest fruit ripening and senescence in cherry tomatoes. Postharvest Biology and Technology, 168:111274. doi: 10.1016/j.postharvbio.2020.111274 URL
[124]	Terol J, Soler G, Talon M, Cercos M. 2010. The aconitate hydratase family from Citrus. BMC Plant Biology, 10:222. doi: 10.1186/1471-2229-10-222 pmid: 20958971
[125]	Terrier N, Sauvage F X, Ageorges A, Romieu C. 2001. Changes in acidity and in proton transport at the tonoplast of grape berries during development. Planta, 213:20-28. pmid: 11523652
[126]	Tian S, Jiang L, Gao Q, Zhang J, Zong M, Zhang H, Ren Y, Guo S, Gong G, Liu F, Xu Y. 2017. Efficient CRISPR/Cas9-based gene knockout in watermelon. Plant Cell Reports, 36:399-406. doi: 10.1007/s00299-016-2089-5 pmid: 27995308
[127]	Tian S, Jiang L, Cui X, Zhang J, Guo S, Li M, Zhang H, Ren Y, Gong G, Zong M, Liu F, Chen Q, Xu Y. 2018. Engineering herbicide-resistant watermelon variety through CRISPR/Cas9-mediated base-editing. Plant Cell Reports, 37:1353-1356. doi: 10.1007/s00299-018-2299-0 pmid: 29797048
[128]	Umer M J, Bin S L, Gebremeskel H, Zhao S J, Yuan P L, Zhu H J, Kaseb M O, Anees M, Lu X Q, He N, Gong C S, Liu W G. 2020. Identification of key gene networks controlling organic acid and sugar metabolism during watermelon fruit development by integrating metabolic phenotypes and gene expression profiles. Horticulture Research, 7 (1):193. doi: 10.1038/s41438-020-00416-8 pmid: 33328462
[129]	Verweij W, Spelt C, Di S G P, Vermeer J, Reale L, Ferranti F, Koes R, Quattrocchio F. 2008. An H⁺ P-ATPase on the tonoplast determines vacuolar pH and flower colour. Nature Cell Biolology, 10:1456-1462.
[130]	Wang L, He F, Huang Y, He J X, Yang S Z, Zeng J W, Deng C L, Jiang X L, Fang Y W, Wen S H, Xu R W, Yu H W, Yang X M, Zhong G Y, Chen C W, Yan X, Zhou C F, Zhang H Y, Xie Z Z, Larkin R M, Deng X X, Xu Q. 2018. Genome of wild mandarin and domestication History of Mandarin. Molecular Plant, 11:1024-1037. doi: S1674-2052(18)30187-4 pmid: 29885473
[131]	Wang L, Huang Y, Liu Z, He J, Jiang X, He F, Lu Z, Yang S, Chen P, Yu H, Zeng B, Ke L, Xie Z, Larkin R M, Jiang D, Ming R, Buckler E S, Deng X, Xu Q. 2021. Somatic variations led to the selection of acidic and acidless orange cultivars. Nature Plants, 7:954-965. doi: 10.1038/s41477-021-00941-x pmid: 34140668
[132]	Wang S, Zhou Y, Luo W, Deng L, Zeng K. 2020. Primary metabolites analysis of induced citrus fruit disease resistance upon treatment with oligochitosan,salicylic acid and Pichia membranaefaciens. Biological Control, 148:104289. doi: 10.1016/j.biocontrol.2020.104289 URL
[133]	Wang Y Z, Xu H B, Zhang G X, Zhu H L, Zhang L X, Zhang Z Z, Zhang C Q, Ma Z Q. 2009. Expression and responses to dehydration and salinity stresses of V-PPase gene members in wheat. Journal of Genetics and Genomics, 36:711-720. doi: 10.1016/S1673-8527(08)60164-2 pmid: 20129398
[134]	Wehner G G, Balko C C, Enders M M, Humbeck K K, Ordon F F. 2015. Identification of genomic regions involved in tolerance to drought stress and drought stress induced leaf senescence in juvenile barley. BMC Plant Biology, 15:125. doi: 10.1186/s12870-015-0524-3 pmid: 25998066
[135]	Wei Q, Ma Q, Zhou G, Liu X, Ma Z, Gu Q. 2021. Identification of genes associated with soluble sugar and organic acid accumulation in‘Huapi’kumquat(Fortunella crassifolia Swingle) via transcriptome analysis. Journal of the Science of Food and Agriculture, 101 (10):4321-4331. doi: 10.1002/jsfa.11072 URL
[136]	Wu S, Li M, Zhang C, Tan Q, Yang X, Sun X, Pan Z, Deng X, Hu C. 2021a. Effects of phosphorus on fruit soluble sugar and citric acid accumulations in citrus. Plant Physiology Biochemistry, 160:73-81. doi: 10.1016/j.plaphy.2021.01.015 URL
[137]	Wu S W, Zhang C M, Li M, Tan Q L, Sun X C, Pan Z Y, Deng X Y, Hu C X. 2021b. Effects of potassium on fruit soluble sugar and citrate accumulations in Cara Cara navel orange(Citrus sinensis L. Osbeck). Scientia Horticulturae, 283 (6):110057. doi: 10.1016/j.scienta.2021.110057 URL
[138]	Xie X B, Li S, Zhang R F, Zhao J, Chen Y C, Zhao Q, Yao Y X, You C X, Zhang X S, Hao Y J. 2012. The bHLH transcription factor MdbHLH3 promotes anthocyanin accumulation and fruit colouration in response to low temperature in apples. Plant,Cell & Environment, 35:1884-1897.
[139]	Yang C, Chen T, Shen B, Sun S, Song H, Chen D, Xi W. 2019. Citric acid treatment reduces decay and maintains the postharvest quality of peach (Prunus persica L.)fruit. Food Science & Nutrition, 7 (11):3635-3643.
[140]	Yang J, Zhang J, Niu X Q, Zheng X L, Chen X, Zheng G H, Wu J C. 2021. Comparative transcriptome analysis reveals key genes potentially related to organic acid and sugar accumulation in loquat. PLoS ONE, 16:e0238873. doi: 10.1371/journal.pone.0238873 URL
[141]	Yang Ying-ying, Gao Yang, Zheng Jia-peng, Gan Wu, Xiang Miao-lian, Chen Ming, Chen Jing-yin. 2016. Advances in research on the approach of degradation metabolism of citric acid in citrus fruit and its regulation. Acta Agriculturae Universitatis Jiangxiensis, 38 (3):476-482. (in Chinese)
	杨滢滢, 高阳, 郑嘉鹏, 甘武, 向妙莲, 陈明, 陈金印. 2016. 柑橘果实柠檬酸降解代谢途径与调控研究进展. 江西农业大学学报, 38 (3):476-482.
[142]	Ye J, Wang X, Hu T, Zhang F, Wang B, Li C, Yang T, Li H, Lu Y, Giovannoni J J, Zhang Y, Ye Z B. 2017. An InDel in the promoter of Al-ACTIVATED MALATE TRANSPORTER9 selected during tomato domestication determines fruit malate contents and aluminum tolerance. Plant Cell, 29:2249-2268. doi: 10.1105/tpc.17.00211 URL
[143]	Yen C R, Koch K E. 1990. Developmental changes in translocation and localization of ¹⁴C-labeled assimilates in grapefruit:light and dark CO₂fixation by leaves and fruit. Journal of the American Society for Horticultural Science American Society for Horticultural Science, 115:815-819.
[144]	Yin D, Sun D, Han Z, Ni D, Norris A, Jiang C Z. 2019. PhERF2,an ethylene-responsive element binding factor,plays an essential role in waterlogging tolerance of petunia. Horticulture Research, 6:83. doi: 10.1038/s41438-019-0165-z URL
[145]	Yin X R, Allan A C, Chen K S, Ferguson I B. 2010. Kiwifruit EIL and ERF genes involved in regulating fruit ripening. Plant Physiology, 153:1280-1292. doi: 10.1104/pp.110.157081 URL
[146]	Yu J Q, Gu K D, Sun C H, Zhang Q Y, Wang J H, Ma F F, You C X, Hu D G, Hao Y J. 2021. The apple bHLH transcription factor MdbHLH3 functions in determining the fruit carbohydrates and malate. Plant Biotechnology of Journal, 19:285-299. doi: 10.1111/pbi.13461 URL
[147]	Zhang Li-na. 2018. Effect of different preservation treatments on the quality of fresh-cut apple[M. D. Dissertation]. Yantai: Yantai University. (in Chinese)
	张丽娜. 2018. 保鲜方式对鲜切苹果品质影响的研究[硕士论文]. 烟台: 烟台大学.
[148]	Zhang G, Xie S. 2014. Influence of water stress on the citric acid metabolism related gene expression in the Ponkan fruits. Agricultural Science, 5:9.
[149]	Zhao H, Chen G, Sang L, Deng Y, Gao L, Yu Y, Liu J. 2021. Mitochondrial citrate synthase plays important roles in anthocyanin synthesis in petunia. Plant Science, 305:110835. doi: 10.1016/j.plantsci.2021.110835 URL
[150]	Zhou D, Zhang Q, Li P, Pan L, Tu K. 2020. Combined transcriptomics and proteomics analysis provides insight into metabolisms of sugars,organic acids and phenols in UV-C treated peaches during storage. Plant Physiology and Biochemistry, 157:148-159. doi: 10.1016/j.plaphy.2020.10.022 URL
[151]	Zhao X, Yuan X, Chen S, Fu D Q, Jiang C Z. 2019. Metabolomic and transcriptomic analyses reveal that a MADS-Box transcription factor TDR4 regulates tomato fruit quality. Frontiers in Plant Science, 10:792. doi: 10.3389/fpls.2019.00792 URL
[152]	Zhou Y, He W, Zheng W, Tan Q, Xie Z, Zheng C, Hu C. 2018. Fruit sugar and organic acid were significantly related to fruit Mg of six citrus cultivars. Food Chemistry, 259:278-285. doi: S0308-8146(18)30535-1 pmid: 29680055