植物激素调控采后柑橘果皮色泽形成的机理研究进展

艾椰茹1,汪华丽1,韩晋1,韩赛影1,邓丽莉1,2*

1(西南大学 食品科学学院,重庆,400715)2(西南大学,果蔬物流保鲜与营养品质调控研究中心,重庆,400715)

摘 要 柑橘是种植最为广泛且价值颇高的水果作物之一。果皮色泽不仅与柑橘成熟度密切相关,还直接影响消费者购买意愿,影响其商品价值。柑橘果皮着色过程受到柑橘本身的遗传背景、发育阶段和组织结构等内在因素,及贮藏温度和光照等环境因素的影响。此外,内源植物激素的变化和外源植物激素处理均对柑橘果实着色有重要影响。植物激素中乙烯、脱落酸、茉莉酸和生长素在促进柑橘果皮转色过程中发挥重要作用,而赤霉素通常被视为果皮转色的负调节因子。植物激素通过影响激素代谢和信号转导,改变内源激素比例,重建内源激素平衡,进而通过调控叶绿素和类胡萝卜素代谢途径相关基因的表达,影响柑橘果皮的色泽。此外,多种转录因子被证明参与柑橘色素调节、激素代谢和信号转导,而植物激素能通过影响转录因子调节作用影响柑橘果皮着色。该综述查阅国内外相关研究,总结了近年来植物激素调控柑橘果皮色泽的研究概况,以期为后续研究提供参考。

关键词 植物激素;柑橘;色泽;色素;激素平衡;转录因子

柑橘是目前种植最为广泛且价值颇高的水果作物之一。截至2023年,我国柑橘年产量达6 433.76万t[1],位居世界首列。通过调整早、中、晚熟柑橘品种结构,我国基本实现柑橘鲜果周年供应。果皮色泽是柑橘重要的外观品质特征之一,常被作为判断果实是否成熟的指标,往往也是消费者挑选柑橘的直接依据[2]。因此,在实际生产中,有效地调控柑橘果皮色泽能在一定程度上提高柑橘的经济价值,对柑橘产业发展具有极其重要的意义。

柑橘果皮色泽受多种因素影响,除柑橘自身的遗传背景、发育阶段与组织结构等内在因素外,还包括贮藏温度、光照等环境因素[3-5]。采后低温(5 ℃)和高温(32 ℃)贮藏均抑制蜜橘果皮转色,但低温(15 ℃)贮藏能促进蜂蜜脐橙转为鲜艳的橙红色[4,6]。红光、蓝光处理促进蜜橘、甜橙、葡萄柚等柑橘果皮转色[7-9],但蓝光导致体外培养的夏橙果皮叶绿素积累,促进其返青[5]。采后紫外线处理影响特早熟柑橘果皮叶绿素降解和类胡萝卜素积累,从而有效改善果皮色泽[10]。此外,植物激素在柑橘类果实色泽发育中发挥着重要的调节作用。但不同类型的植物激素对果皮着色过程具有不同影响,乙烯、脱落酸(abscisic acid,ABA)、茉莉酸(jasmonic acid,JA)和生长素等植物激素能够降低果皮中叶绿素含量,促使类胡萝卜素积累,进而加速果皮着色;而赤霉素(gibberellin,GA)通常对果皮转色起抑制作用[11]。此外,在柑橘果实着色的不同阶段,不同种类植物激素之间,通过协同或拮抗等方式在柑橘果实采后着色过程中发挥重要作用。本综述通过查阅国内外相关研究,总结了近年来植物激素调控采后柑橘果皮色泽的研究概况,以期为有效解决柑橘果皮着色不均等产业问题,推动柑橘产业高质量健康发展提供参考。

1 柑橘果实着色与调控

1.1 柑橘果实着色特征

不同品种的柑橘类水果在外观上展现出多样化的色彩。其中,青柠呈绿色,柠檬为明亮的黄色,甜橙类多为鲜艳的橙色,橘类呈现橙色或红色,柚类颜色差异较大,涵盖从淡黄色到粉红色等范围[12]。柑橘类水果丰富的颜色主要取决于叶绿素、类胡萝卜素和花青素等色素的组成、含量和比例。叶绿素通常使未成熟的柑橘类果实以及青柠、绿橙等特殊品种呈现绿色;类胡萝卜素则赋予完全成熟的柑橘类水果各种独特的红色、橙色和黄色;花青素则主要参与血橙等品种果肉的着色[13]。叶绿素和类胡萝卜素是大部分柑橘果皮中的主要色素,两者含量随着果实的成熟而变化。在柑橘果实成熟过程中,叶绿素迅速降解,同时类胡萝卜素大量积累,致使果皮颜色从绿色逐渐转变为黄色、橙色或红色。

柑橘果实着色常呈现区域性差异。留树蜜橘果皮的着色通常由果顶向果蒂延伸,而采后贮藏的蜜橘则相反,着色从果蒂向果顶延伸,且采后贮藏的蜜橘果实着色速度快于留树蜜橘[14]。在乙烯褪绿过程中,蜜橘果蒂部位的果皮先着色,比赤道部位快,这可能是因为2个部位的果皮在叶绿素降解和类胡萝卜素积累方面存在差异所致[15]。塔罗科血橙果肉也存在梯度着色现象,即果顶部位先于果蒂部位着色,外侧果肉先于内侧果肉着色[16],这种梯度着色现象可能与色素物质的梯度分布有关。柠檬采后褪绿过程中,出现黄绿相间的斑驳情况,这与果皮中的色素物质(叶绿素、类胡萝卜素)和激素(如生长素、ABA、GA等)分布不均匀密切相关[17]。此外,柑橘果实不同部位的着色差异可能与成熟度相关,夏橙果实返青部位的糖含量低于未返青部位,呈梯度分布形式[18]

1.2 柑橘果实采后色泽调控的目的和意义

早、中、晚熟柑橘品种搭配种植是实现柑橘果实周年供应的重要手段。然而,早熟和晚熟柑橘往往存在着色方面的问题。早熟柑橘因生长周期短,成熟期低温积累不足,导致果皮和果肉成熟不同步,即果皮达到上市颜色标准的时间明显晚于果肉成熟的时间[19]。而晚熟柑橘由于生长周期较长,且受高温和光照等因素影响,夏橙可能会出现返青现象,W.默科特则可能出现着色不均匀的情况[20-21]。因此,对早熟和晚熟柑橘的果皮色泽进行采后调控,能促使其符合上市标准,满足市场对柑橘果实外观色泽的要求,这对提高鲜食柑橘果实的经济价值具有重要意义。

2 植物激素对采后柑橘果皮色泽的调控

2.1 乙烯对采后柑橘果皮色泽的调控

乙烯是调控果实成熟的重要植物激素。虽然柑橘属于非呼吸跃变型果实,但外源乙烯处理可以改善柑橘果皮颜色。将柑橘与呼吸跃变型果实(香梨、猕猴桃、番茄、香蕉)共同贮藏,能够促进其果皮着色[22]。生产上,常采用乙烯对着色不佳的柑橘果实进行褪绿处理[23]。目前,已在脐橙[24]、萨摩蜜柑[2]和‘尤里卡’柠檬[25]等柑橘品种中得以应用。

乙烯对柑橘果实的褪绿效果受多种因素影响,包括乙烯处理浓度、处理时间、温度、相对湿度,以及柑橘的品种、成熟度等[2]。研究表明,过高浓度乙烯处理会加速果蒂褐变和病害发生[26],而适宜浓度乙烯处理(1~10 mg/L)不仅能够改善柑橘外观色泽,而且对果肉品质无明显不良影响[24]。进一步的研究发现,果皮颜色变化很大程度上取决于褪绿过程的持续时间而非乙烯浓度,并且高浓度乙烯可能不会缩短褪绿所需时间[27]。此外,乙烯与高温[28]、蓝光[29]共同处理,或在乙烯处理前进行预冷,均可以提高其褪绿效果[30]。乙烯处理对不同品种柑橘果实的褪绿效果存在差异,其中对蜜橘的效果最为显著,对脐橙的褪绿效果优于柠檬[31]。此外,乙烯对成熟度较高的柑橘果实的褪绿效果更佳。采收时果皮全绿的脐橙经乙烯处理后,果皮颜色转变为淡黄色;而采收时开始转色的脐橙经相同处理后,果皮颜色呈黄橙色[32]。然而,对于晚熟柑橘夏橙,在自然转色前进行乙烯利处理褪绿效果良好,但在果实成熟度较高且发生返青现象时,乙烯利处理未能实现有效的褪绿[33]。因此,在实际生产中,通过精确控制乙烯处理条件(乙烯处理浓度、处理时间、环境温度、CO2含量、相对湿度等条件[34]),大部分柑橘可达到理想褪绿效果,并避免可能的负面影响。

乙烯通过调控柑橘叶绿素降解和类胡萝卜素积累,改善柑橘果皮的颜色[32]。乙烯处理可以降低叶绿素含量,同时促进八氢番茄红素、六氢番茄红素、9-顺式紫黄质和β-柠乌素等呈色类胡萝卜素积累,进而促进果皮转色[32, 35]。经乙烯处理后,叶绿素降解相关基因CLH1PPH,以及类胡萝卜素生物合成相关基因PSY1LCYb2aNCED5CCD4等基因的表达均在不同程度上有所响应[36-37]。乙烯处理可诱导采后柑橘中bHLH和ERF等家族转录因子的表达,这些转录因子参与调控柑橘叶绿素和类胡萝卜素代谢途径,促进柑橘果皮的转色[38-39]。其中,CcbHLH35通过结合叶绿素降解基因(ChlaseNYC1PAORCCR)和类胡萝卜素合成基因(PSY1BCH2NCED)的启动子,激活其表达,促进果皮着色[40]。CitERF6和CitERF13启动子的激活以及随后CitERF6和CitERF13之间的自动、相互调节导致叶绿素降解相关基因PPH表达量的增加[38, 41]。ERF114激活叶绿素降解基因(CLH1PPH)的表达,导致果皮中叶绿素含量减少[37]。而CsERF061通过直接调节一系列关键类胡萝卜素代谢基因(PSY1PDSCRTISOLCYb1BCHZEPNCED3CCD1CCD4)来促进类胡萝卜素积累[42]。此外,CitERF061直接结合CitZAT4启动子并诱导其表达,而CitZAT4通过抑制CitLCYE的表达和诱导CitLCYBCitHYDCitNCED2的表达来调节类胡萝卜素代谢流从α分支转移到β分支,促进β分支橙色类胡萝卜素积累,最终促进柑橘转色[43]

2.2 ABA对采后柑橘果皮色泽的调控

ABA在调节非呼吸跃变型果实成熟和衰老过程中起着重要作用[44],且ABA是类胡萝卜素代谢途径的最终产物。因此,ABA被视为调节柑橘类果实色泽发育的重要激素之一。外源ABA处理促进柑橘果皮转色,同时影响内源ABA的含量及相关基因的表达[45],而人工合成ABA抑制剂去甲二氢愈创木酸会显著抑制果皮着色[46]。研究发现,脐橙突变体褪绿速度较慢且ABA含量低于野生型,表明ABA可能参与柑橘果实转色过程[47]。在瓯柑发育过程中,由于ABA生物合成水平减少,导致滞绿突变体青瓯柑产生[48]。青瓯柑ABA含量低于瓯柑,外源ABA处理可以促进青瓯柑转色,但不能促进瓯柑转色,进一步阐明内源ABA含量可能是造成青瓯柑和瓯柑转色差异的原因[49]。在类胡萝卜素代谢中,紫黄质和新黄质作为中间产物,在9-顺-环氧类胡萝卜素双加氧酶(9-cis-epoxycarotenoid dioxygenase,NCED)的作用下分解生成ABA[50]。NCEDs是ABA合成的关键限速酶,在青瓯柑中,CrNCED5的表达降低导致α-胡萝卜素和β-胡萝卜素的转化延迟,从而影响ABA的生物合成[51]

外源ABA通过调控叶绿素、类胡萝卜素和内源ABA的合成与降解,影响柑橘果皮着色过程。在这一过程中,转录因子发挥着重要的调控作用。CrMYB68CrNAC036等转录因子不但能特异性地下调CrNCED5的表达,还能协同调控CrNCED5,影响ABA的生物合成,进而影响柑橘着色[52]。CsMADS5[53]、CsMADS6[54]对柑橘类胡萝卜素的生物合成起正调控作用。CsMADS3直接对叶绿素降解及类胡萝卜素生物合成途径中的关键基因(CsSGRCsPSY1CsLCYb2)进行调控,并间接改变ABA与GA的含量,以此调控柑橘果皮中叶绿素与类胡萝卜素的含量[55]。CsHB5通过直接与ABA生物合成基因(BCH1NCED2)的启动子结合,激活其转录,促进ABA积累[56]。CsHB5也能与CsbZIP44相互作用,通过结合其启动子增强CsbZIP44表达,形成转录调控模块CsHB5-CsbZIP44,从而进一步增强其功能。此外,ABA的积累对CsHB5-CsbZIP44调节模块产生正反馈效应,调节类胡萝卜素生物合成。同时,外源ABA处理可通过激活CsHB5-CsbZIP44调控模块来改善采后贮藏期间柑橘类果皮的颜色[57]

2.3 JA对采后柑橘果皮色泽的调控

JA是一种与果实成熟紧密相关的植物激素,它能够影响果实质地和色泽的变化,同时能够促进糖、氨基酸及挥发性化合物等营养和风味物质的积累[58-59]。从现有的研究来看,JA对柑橘着色的影响并非单一的促进或抑制。晚熟芽变锦橙出现延迟转色现象,其内源JA含量远高于野生型锦橙,这表明高含量的JA可能会阻碍柑橘果皮的着色过程[60]。然而,JA及其主要活性形式茉莉酸异亮氨酸与温州蜜柑的总类胡萝卜素及叶黄素的含量呈正相关,在W.默科特中,JA与最终呈色的β-柠乌素、玉米黄质和β-隐黄质的含量呈负相关[61],这又暗示了JA在柑橘着色过程中存在促进作用的可能性。因此,JA在调控采后柑橘果皮色泽方面具有重要作用,但具体的调控机制较为复杂,需要综合多方面因素考量。

茉莉酸甲酯(methyl jasmonate,MeJA)是茉莉酸类化合物的一种重要衍生物,由茉莉酸羧基甲基转移酶催化JA生成[62]。在柑橘叶片中发现,外源MeJA处理可以通过提高叶绿素合成关键酶的活性来促进叶绿素的积累,同时,还会降低单半乳糖甘油二酯与双半乳糖甘油二酯的比例并抑制JA生物合成中关键酶的活性,从而影响内源JA的合成[63]。REHMAN等[64]的研究表明,采前喷施(5.0、7.5 mmol/L)MeJA可诱导脐橙果皮中类胡萝卜素的积累并加速果实着色。采后MeJA熏蒸(0.2 mmol/L)特早熟温州蜜柑能够诱导脱镁叶绿酸a加氧酶(pheophorbide A oxygenase,PAO)和八氢番茄红素合成酶(phytoene synthase,PSY)基因表达,促进叶绿素a降解和类胡萝卜素积累,从而使特早熟柑橘采后贮藏期褪绿过程提前[10]。然而在体外培养的柑橘汁胞中,MeJA通过抑制类胡萝卜素合成基因CitHYb的表达,影响类胡萝卜素的积累[65]

此外,一些转录因子参与调控JA的合成及信号转导途径。CsESE3通过直接结合磷脂酶CsPLIP1启动子,促进JA的生物合成[66]。奉节晚橙相较于其野生型,自绿熟期转色速度减慢,而MYB21在野生型中的表达明显高于奉节晚橙,表明MYB21可能参与调控JA生物合成途径影响柑橘果皮着色过程[67]。MYC2是JA信号途径中的核心调控因子,参与植物逆境防御、生长发育及次生代谢等进程[68]。外源MeJA促进纽荷尔脐橙果皮关键呈色色素β-柠乌素积累,促进果皮着色。在该过程中,CsMYC2结合β-柠乌素合成途径的关键基因CsCCD4b启动子,正调控其表达。同时,CsMYC2激活CsMPK6的表达,二者存在互作,一方面抑制CsMYC2结合其下游启动子,另一方面促进CsMYC2蛋白降解,从而精准调控柑橘对JA的响应,防止柑橘果实对JA响应过度[69]

2.4 生长素对采后柑橘果皮色泽的调控

生长素是最早被发现的一类植物激素,在植物的生长发育、衰老以及各种胁迫反应中发挥重要作用[70]。天然植物生长素种类繁多,包括吲哚乙酸(indoleacetic acid,IAA)、吲哚丁酸(indolebutyric acid,IBA)、萘乙酸(naphthylacetic acid,NAA)等,其中IAA是最主要的天然活性生长素,而人工合成生长素类似物2,4-二氯苯氧乙酸(2, 4-dichlorophenoxyacetic acid,2,4-D)常应用于柑橘采后保鲜。

内源生长素的差异可能是影响不同品种柑橘着色差异的因素之一。在4个色泽差异明显的柑橘品种中未观察到生长素在不同时期的差异变化,但不同品种间IAA含量差异较大,纽荷尔脐橙中IAA含量相比于其他品种始终保持较高水平,而温州蜜柑和W.默科特的生长素含量较低,转色不明显的高班柚中没有检测到生长素[61]。内源生长素随着柑橘的成熟过程不断变化,在锦橙果实中,IAA含量随着锦橙果实成熟逐渐下降,果实基本完熟后稍有上升,表明IAA主要调控锦橙果实成熟早期和果实完熟后的过程[60]

不同品种的柑橘对不同生长素的响应存在差异。在柑橘采后使用不同生长素(2,4-D、3,5,6-TPA、Fluroxypyr和MCPA)对其进行处理发现,4种生长素均使柠檬果皮着色过程迟滞,2,4-D对蜜橘果皮的着色没有显著影响,除2,4-D外其余3种生长素均使蜜橘果皮着色迟滞,然而生长素对脐橙果皮着色过程影响较小[71]。2,4-D、3,5,6-TPA、Fluroxypyr和MCPA可能干扰了柑橘果皮中色素合成相关基因的表达,从而影响柑橘果皮着色过程。而NAA和IAA则表现出促进柑橘着色的作用,NAA处理可以使蜜橘果皮中β-胡萝卜素、β-隐黄质、叶黄素、全反式紫罗兰黄质和9-顺式紫罗兰黄质的含量显著增加,同时类胡萝卜素生物合成基因(PSYZDSLCYb1LCYb2LCYeHYbHYeZEP)表达显著上调[72]。在柑橘果皮和愈伤组织中发现,IAA处理后促进其类胡萝卜素积累,响应IAA的转录因子CsAGL6表达上调,而转录因子CsAGL6也能调控愈伤组织中IAA的合成,二者之间存在反馈调节机制[73],这表明NAA和IAA通过影响类胡萝卜素合成基因或相关转录因子来促进类胡萝卜素的积累。

2.5 GA对采后柑橘果皮色泽的调控

GA是一类广泛存在于植物生长和发育过程中的植物激素,特别是在果实的成熟、开花、发芽和伸长等方面[74]。研究表明,GA通过调节多种植物生理过程,直接影响果实的外观和内在质量。而外源GA处理对果实色泽的增强或抑制作用取决于物种、组织类型等因素[75]。在柑橘果实中,外源GA处理通过影响柑橘果实叶绿素降解和类胡萝卜素积累,阻碍色泽发育[76]。GA、叶绿素和类胡萝卜素有共同的前体物质牻牛儿基牻牛儿基焦磷酸(geranylgeranyl diphosphate,GGPP)[77],三者的生物合成之间存在一定竞争关系。外源GA3处理抑制柑橘果皮内源GA3的迅速下降[78],进入类胡萝卜素合成途径的GGPP含量并未增加,延缓了柑橘果皮类胡萝卜素积累,使果皮颜色发育受阻。而转录因子CsTT8可正向调节柑橘甲基赤藓糖醇磷酸(methylerythritol phosphate,MEP),减少GGPP向GA的转化,使其更多地转化为类胡萝卜素,促进柑橘果皮类胡萝卜素的积累[79]。此外,高浓度GA3处理也抑制卡拉卡拉红肉脐橙中番茄红素及β-胡萝卜素的积累[80]。GA能够延缓克莱门氏小柑橘色泽的改变,使PAO和PSY基因的表达下调[81]。研究表明,GA处理通过减少乙烯诱导基因及类胡萝卜素代谢相关基因的表达来延迟柑橘果实的色泽变化[82]。GA处理不同品种的柑橘汁胞(蜜柑、甜橙、柠檬)均使其类胡萝卜素含量降低,但GA对3个品种的基因表达的影响不同。在蜜柑中,与叶黄素合成相关的基因CitLCYb1CitLCYb2下调表达,导致β-隐黄质、紫黄质和9-顺式-紫黄质含量降低;在甜橙中,CitPSYCitPDSCitZDSCitLCYb2CitHYbCitZEP等基因同时下调与类胡萝卜素含量的降低呈现一致的结果;而在柠檬中,CitPSYCitPDSCitZDSCitLCYb1CitHYbCitZEP的表达上调,与类胡萝卜素含量变化呈现相反趋势[83]。采前GA喷施返青期的夏橙,会诱导叶绿素合成基因(CitGGDRCitCHL27CitPORACitCAO)上调表达,同时叶绿素降解基因(CitCLH1CitSGRCitPPHCitPAOCitRCCR)下调表达,从而导致叶绿素含量增加,加速其返青过程,在该过程中同样观察到类胡萝卜素合成基因的下调和类胡萝卜素含量的降低[84]。转录因子BBX22直接结合并激活一系列关键基因的表达,包括参与GA代谢的GA2ox8、类胡萝卜素生物合成基因PSY1、以及花青素调控基因Ruby1,进而影响柑橘果实颜色[85]

3 植物激素互作对采后柑橘色泽发育的影响

果实着色过程受多种因素调控,包括植物激素、温度、光照、转录调控及遗传背景等因素[86]。其中,植物激素对果实着色的调控不仅取决于某一激素的消长或其绝对浓度的变化,还取决于各激素之间的相互作用。主要是促进生长类激素、抑制生长类激素和促进成熟类激素的消长,引起内源激素的动态平衡被重建[87]。常用IAA、GA与ABA之间的比值变化代表激素之间的平衡关系,比值的高低反映出促进生长类激素与抑制生长类激素所占的主导作用不同[88]。内源激素的失衡会导致果实出现生理障碍,代谢紊乱,例如出现裂果[89]、汁胞粒化[88]等情况。

植物激素互作调控呼吸跃变型果实色泽形成机理的研究较多。如在‘红早酥’梨中,MeJA协同乙烯处理使黄酮类物质积累,促进果皮变黄,而MeJA协同1-甲基环丙烯促进果皮中花青素积累而使果皮呈现红色[90]。在番茄、苹果等呼吸跃变型果实中发现,同一转录因子可以调控不同激素信号途径,进而影响果实着色过程。其中,MdbHLH162通过整合GA和JA信号调控苹果花青素的合成[91]。ERF4与JAZ及MYC2相互作用,调节乙烯生物合成基因ACS1ACO1的表达,影响内源乙烯的生成,促进苹果转色[92]。此外,外源生长素激活MdARF5PpARF6的表达,调控乙烯合成途径,促进果实着色过程[93-94]。而外源NAA则通过更为复杂的机制调控苹果果实着色过程,NAA抑制果实中MdNAC104的转录,进而抑制其对MdACS1MdERF3的负调控作用,诱导MdACS1表达,促进乙烯合成,最终影响果实着色[95]

近年的研究表明,柑橘果实的着色也与多种植物激素的互作密切相关。在柑橘果实中,外源ABA和乙烯共同处理虽能促进其转色,但并未有加和作用,这表明ABA和乙烯可能通过相对独立的途径来调控柑橘转色过程,且JA和IAA等内源激素也参与其中[49]。对夏橙进行乙烯利褪绿处理时,相较于转色期,返青期可能出现褪绿效果的迟滞现象,这可能是由内源激素动态变化所引起的[96]。此外,乙烯响应因子CsERF110和CsERF53形成转录调控模块,通过在ABA信号转导和类胡萝卜代谢之间建立正反馈回路,对ABA介导的柑橘果实着色进行正向调控[97],这表明乙烯和ABA的串扰可调控柑橘果皮着色过程。GA和二氢茉莉酸丙酯(propyl dihydrojasmonate,PDJ)联合处理可以抑制宽皮柑橘的浮皮发生,但这一处理延缓了柑橘果皮的着色[98],采前和采后生长素处理均诱导乙烯生物合成基因(ACS1ACS2ACO)的表达和内源乙烯的产生,从而改善GA和PDJ联合处理引起的着色不佳现象[99]。这些结果表明,植物激素通过整合多种植物激素信号途径,协同调控果实色泽,然而,采后柑橘果皮着色过程中植物激素相互作用的复杂机制仍有待深入探究。

4 总结与展望

柑橘果皮色泽是柑橘重要的外观品质之一,而柑橘果皮着色是一个较为复杂的代谢过程,涉及到叶绿素的降解及类胡萝卜素、花青素的积累。了解采后柑橘果皮色泽调控的机制,能够为实现果皮均匀着色、提高柑橘果实外观品质提供重要依据。本文中提到的5种植物激素在调控采后柑橘果皮着色中发挥着重要的作用。其中,乙烯、ABA、JA和生长素能够促进柑橘果皮转色,而GA多呈现抑制转色作用。首先,这些激素通过调控叶绿素和类胡萝卜素代谢途径基因表达,改变呈色物质的比例,而调控柑橘果皮色泽。其次,转录因子参与调节色素代谢、激素代谢和信号转导等途径,植物激素又能通过影响转录因子的调节作用,而影响柑橘果皮着色过程。此外,植物激素影响了相关激素代谢及信号转导途径,改变了内源激素的比例,重建了内源激素平衡,而影响柑橘果皮着色。

目前对果实激素的研究大多通过分析突变材料与野生型之间的差异或者外源施加激素类似物的手段来进行。外源激素的应用通常会引起内源激素的变化,同一植物激素同一施用浓度在不同品种的柑橘中可能会表现出不同的效果,而同一品种的柑橘对不同浓度的植物激素的响应可能也存在差异,此外,植物激素之间存在复杂的相互作用机制,内源激素如何相互作用共同调控柑橘果皮色泽的研究还未深入透彻。同时,植物激素之间存在协同和拮抗作用,外源植物激素之间的相互作用尚未完全揭示,如何筛选出具有相互作用的外源激素,并将其应用于柑橘生产中,仍然需要进一步深入研究。另外,柑橘的着色过程并非由植物激素单一调控,是与温度、光照等多种因素共同作用的结果,目前对这种调控网络的认识还未明晰。这些都需要我们进行更深入的研究和探讨。继续深入探究植物激素与柑橘果皮色泽之间的关系,有助于改善早熟和晚熟柑橘着色不佳等生产问题,提高柑橘外观品质,进一步提升柑橘的经济价值,对柑橘实际生产具有重要意义。

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Advances in the mechanism of phytohormone in regulating coloration of postharvest citrus peel

AI Yeru1, WANG Huali1, HAN Jin1, HAN Saiying1, DENG Lili1,2*

1(College of Food Science, Southwest University, Chongqing 400715, China)2(Research Center for Fruits and Vegetables Logistics Preservation and Nutritional Quality Control, Southwest University, Chongqing 400715, China)

ABSTRACT Citrus is one of the most extensively cultivated and economically significant fruit crops.The color of citrus peel serves as an indicator of ripeness, influencing both consumer preferences and commercial value.The coloration of citrus peel is determined by internal factors such as citrus genetic background, developmental stage, and tissue structure, along with environmental factors like storage temperature and light.In addition, changes in endogenous phytohormones and exogenous phytohormone treatment play a critical role in the coloration of citrus fruits.Notably, phytohormones like ethylene, abscisic acid, jasmonic acid, and auxin are crucial in enhancing citrus peel coloration, while gibberellin typically acts as a suppressor.The coloration of citrus peel is influenced by the regulation of genes related to phytohormone metabolism and signal transduction by theses phytohormones.This process restores the balance of endogenous phytohormones, thereby regulating genes involved in the pathways of chlorophyll and carotenoid metabolism.Transcription factors are essential for regulating not only chlorophyll and carotenoid metabolism but also phytohormone metabolism and signal transduction.Furthermore, phytohormones influence coloration by regulating the functions of these transcription factors.This review consulted relevant domestic and international research, summarized recent advancements in the understanding of the regulation of citrus peel color by phytohormones, and offers a reference for future studies.

Key words phytohormone;citrus;color;pigment;phytohormone balance;transcription factor

DOI:10.13995/j.cnki.11-1802/ts.041196

引用格式:艾椰茹,汪华丽,韩晋,等.植物激素调控采后柑橘果皮色泽形成的机理研究进展[J].食品与发酵工业,2025,51(15):392-400.AI Yeru, WANG Huali, HAN Jin, et al.Advances in the mechanism of phytohormone in regulating coloration of postharvest citrus peel[J].Food and Fermentation Industries,2025,51(15):392-400.

第一作者:硕士研究生(邓丽莉副教授为通信作者,E-mail:denglili_361@163.com)

基金项目:国家自然科学基金面上项目(32172263)

收稿日期:2024-09-30,改回日期:2024-11-26