柑橘果实柠檬酸代谢研究进展

柑橘果实中柠檬酸含量是决定果实品质好坏的重要因素之一.综述柑橘成熟果实中有机酸的种类、柑橘果实发育过程中柠檬酸的代谢、调控、相关酶及柠檬酸代谢的分子生物学研究等内容;详细介绍柠檬酸的代谢途径及相关酶活性的变化,并提出今后的研究方向、思路和需要解决的问题.     

柑橘果实糖份积累与代谢研究进展

从柑橘果实糖份的来源、种类、动态变化,与糖代谢有关的酶活性,糖代谢的分子生物学几个方面综述了研究进展.     

果实柠檬酸代谢研究进展

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。     

柑橘果实色素—类胡萝卜素的研究进展

柑橘果实丰富多彩,广受大众喜爱,外观色泽作为消费者选择看重的果实品质之一,其研究就显得格外重要。类胡萝卜素是柑橘果实呈色的主要贡献者,成为近年来柑橘果实色素研究的重点。类胡萝卜素包括胡萝卜素和叶黄素两大类,不同的色素单体呈现黄到橙红甚至紫红多种颜色,其丰富多样的组成给与柑橘果实丰富的颜色表现。笔者概述了柑橘果实呈色色素的主要来源、内外部及其他影响因素、3条合成途径(番茄红素、胡萝卜素和含氧类胡萝卜素生物合成),并介绍了类胡萝卜素对植物体和人体的生理活性功能,但目前对类胡萝卜素的分解过程以及分解产物存在形式和生理功能的研究较少,有待进一步深入开展。     

柑橘果实有机酸代谢研究进展

柑橘果实中有机酸含量是决定果实品质好坏的重要指标之一,降低果实中有机酸含量提高果实品质一直是人们研究的一个热点及难点。综述了柑橘果实中柠檬酸的合成与降解、柑橘果实中有机酸代谢相关酶、柑橘果实柠檬酸的跨膜运输及柑橘果实有机酸的调控等方面内容。尤其是柠檬酸新的降解途径、柠檬酸跨膜运输时液泡内外柠檬酸盐的动静态平衡和分子方面给出了国内外最新研究进展,推测柑橘果实发育后期柠檬酸的急剧下降可能是由于其参与了GABA途径并最终代谢成氨基酸而导致的;详细介绍了柠檬酸离子与氢离子在液泡内外转运的模型。最后总结讨论了柑橘果实有机酸调控的思路,提出了今后的研究方向、思路和需要解决的问题。     

柑橘果实生物活性物质与糖尿病防治研究进展

柑橘果实含丰富的营养和生物活性物质,具有重要的营养、医药和保健价值.现有报道表明,柑橘果实的类黄酮、香豆素类、单萜类、果胶等生物活性物质均有防治糖尿病的功效.系统地回顾了近年来柑橘果实生物活性物质与糖尿病防治的有关研究报道,总结了有关物质防治糖尿病的机理及取得的进展,旨在为进一步开发利用我国丰富的柑橘资源提供新信息.     

柑橘转录因子CsbHLH3调控柠檬酸代谢的功能解析

转录因子CsbHLH3调控柑橘果实柠檬酸代谢过程中的具体机制尚不清楚。以冰糖橙果实cDNA为材料,克隆了CsbHLH3。瞬时转化烟草亚细胞定位显示CsbHLH3蛋白定位在细胞核。异位表达CsbHLH3的阳性番茄果实中CsbHLH3的表达显著上升,同时柠檬酸含量显著降低。定量分析表明,CsbHLH3在番茄中异位表达引起了柠檬酸降解相关基因SlACO3b、SlGDH及液泡膜质子泵基因SlPH8的上调。相反,在冰糖橙叶片中瞬时抑制CsbHLH3会引起柠檬酸降解相关基因CsGABP、CsACO2、CsACLα1、Cs ACLα2及液泡膜质子泵基因CsPH8、CsVHP2、CsVHP3的下调表达,其柠檬酸含量显著高于空载对照。通过酵母单杂交和EMSA试验证实CsbHLH3均能够靶定PH8和GABP启动子调控其表达。上述结果表明转录因子CsbHLH3是通过调控柠檬酸代谢途径多个相关基因包括PH8和降解途径基因GABP的表达综合负调控柠檬酸的水平。     

柑橘果实糖积累与蔗糖代谢酶活性的研究

研究了脐橙、柠檬果实发育过程中汁胞和果皮内糖含量与糖代谢酶活性的变化。结果表明：不同柑橘品种、不同部位糖积累和相关酶活性变化不同。柑橘汁胞和果皮中还原糖含量均高于蔗糖含量。随着脐橙汁胞中糖分的积累,酸性转化酶(SAd)活性持续下降,至采收时几乎为零,说明SAd 的下降与脐橙汁胞糖分积累有很大关系。柠檬汁胞中的中性转化酶(NI)活性随着果实成熟而下降,在成熟时保持极低水平,而此时SAd 活性则较高,是其它酶活性的6倍以上,表明柠檬汁胞中糖分的利用在果实成熟前与NI活性有极大的关系,在成熟期则与高SAd 活性有关。脐橙和柠檬汁胞间糖组分的明显差异和相关酶的变化动态表明蔗糖合成酶(SS)和转化酶在柑橘汁胞糖代谢中可能起到重要作用。     

调控番茄果实柠檬酸含量的基因定位

为了挖掘调控番茄果实柠檬酸含量的关键基因，以栽培番茄(Solanum lycopersicum‘Moneymaker’)和野生醋栗番茄(Solanum pim pinellifolium ‘PI365967’)为亲本构建的重组自交系群体为材料，利用混池重测序技术挖掘到6个控制柠檬酸含量的QTL。其中位于6号染色体末端的主效QTL qCA6.1表型贡献率高达19.28%。为对该位点进行定位，从重组自交系群体中挑选出2份柠檬酸含量差异较大，且只在主效位点存在基因型差异的株系作为亲本，构建BC₂F₂定位群体，通过交换单株后代鉴定，将定位区间缩小到342kb区间内，并开发了连锁分子标记，为后续克隆基因奠定了基础，也为改良番茄果实柠檬酸含量提供了重要选择标记。     

柑橘果实中酚酸类化合物研究进展

柑橘是世界上种植最多的水果之一,广泛地分布于热带、亚热带和温带区域,主要包括甜橙类、宽皮柑橘类、葡萄柚和柚类、柠檬类、杂柑类和金柑类等[1]。我国是世界柑橘生产大国,2019年柑橘种植面积为2.61×10^(6)hm^(2),产量高达4.58×10^(7)t[2]。我国柑橘类水果消费以鲜食为主,部分以罐头、果汁形式进行加工。柑橘果实中富含对人体健康有益的活性成分和抗氧化物质如维生素、矿物质、酚类、萜类等[3]。     

Cellular wall metabolism in citrus fruit pericarp and its relation to creasing fruit rate

Citrus creasing results in serious economic loss in many citrus orchards. Based on the different incidence of creasing, two sweet orange cultivars ‘Hong Jiang’ (grafting chimaera of which flesh is mostly from Citrus reticulata Blanco and peel is from Citrus sinensis Osbeck in) and ‘An Liu’ (Citrus sinensis Osbeck) were used to investigate the creasing rate. The ultrastructure in cellular wall, cellular wall component, cellular wall degradation-related enzymes and expansin (Ct-Exp1) of sweet orange during fruit ripening in field were comparatively analyzed. ‘Hong Jiang’ sweet orange had a higher creasing rate than ‘An Liu’ during ripening. The activities of polygalacturonase, cellulase and pectinesterase in cellular wall of ‘Hong Jiang’ increased more markedly compared with ‘An Liu’. The increases in the content of soluble pectin, ionically associated pectin, covalently bound pectin, hemicellulose and cellulose of ‘Hong Jiang’ were higher than those of ‘An Liu’. Furthermore, the enhanced degradation of the ultrastructure in the albedo cellular walls was observed in ‘Hong Jiang’. Moreover, the northern blot analysis indicated that the Ct-Exp1 gene expressed more strongly in peel of ‘Hong Jiang’ than ‘An Liu’ during fruit ripening. These data suggest that enhanced loss of pectin and cellulose in the cellular walls of peel tissue of sweet orange could result in fruit creasing.     

Nitrogen accumulation induced by phosphorus deficiency in citrus plants

Growth responses and nitrogen constituents were tested in young citrus trees grown on gradually decreasing amounts of phosphorus in greenhouse solution cultures. The phosphorus concentration in dry matter of minus-P leaves dropped to a third of that in control leaves and then remained steady throughout the experiment, while the total nitrogen concentration was low at the beginning and, rising gradually, reached an enormous amount. Nitrogen estimations in minus-P leaves showed the specific dynamics of the soluble nitrogen fraction: its content was low at the onset of the deficiency, and rose rapidly due to intensive accumulation of arginine in the tissues. Under conditions of acute phosphorus deficiency, arginine constituted more than 60% of the free amino acids and arginine nitrogen above 40% of the total, while in normal leaves arginine did not exceed 8% of the free amino acids, and about 1–% of the total.Similar patterns of increased nitrogen level due to arginine accumulation were found in leaves of phosphorus-deficient grapefruit and orange trees under field conditions.     

快速液相色谱法测定柑橘中6种类黄酮化合物含量

为建立一种快速分析测定柑橘果实中6种类黄酮(橙皮苷、柚皮苷、新橙皮苷、川皮素、桔皮素、橙黄酮)化合物的技术方法,以蜜橘为材料,利用加速溶剂萃取技术对柑橘果实中的6种类黄酮化合物进行提取,并通过快速液相色谱对样品中的类黄酮化合物进行分离测定。结果显示,该方法可以同时测定6种类黄酮化合物,并且具有良好的回收率和精密度。整个提取测定技术快速、简单、准确,适合柑橘果实中6种类黄酮化合物含量的测定。     

杨梅果实发育与糖的积累及其关系研究

以东魁、荸荠种、水梅为试材,研究了杨梅果实发育与糖积累及其关系。根据杨梅果实大小的增加将果实发育大致分为3个阶段,呈双“S型”曲线动态变化:第1阶段(约盛花32d前)果实纵、横径增长最快;第2阶段(32-63d)果核发育硬化,果重增加明显;第3阶段(63d至成熟)果实进入快速增长高峰,果重迅速增加,光合产物在果实中迅速积累。杨梅果实中积累的糖主要是蔗糖,果糖和葡萄糖仅占总糖的1/4,蔗糖含量在发育初期和中期都较低,盛花52d后开始快速积累直至果实成熟,东魁高于水梅、荸荠种;葡萄糖和果糖变化大致保持同步,第1阶段较高,第2阶段降到最低,第3阶段迅速积累达到最高,与蔗糖积累基本保持一致,成熟时东魁与水梅较荸荠种高且相近。杨梅果实中酸性转化酶(Ivr)与中性转化酶(Nvr)活性变化趋势相同,幼果早期最高,中期降低后维持较低活性直至成熟。品种间pH值变幅相似,果实发育第1阶段最高,第2阶段降到最低,转色后上升。相关分析表明:果实发育动态与蔗糖、葡萄糖、果糖的积累存在着极显著的相关关系,其中果实横径的增加与果实糖积累组分中蔗糖的变化2者间相关性最大(r=0.93255**)。     

郁闭柑橘园改造对植株光化学反应参数及果实品质的影响

【目的】探明不同整形改造技术对郁闭树体有效光合辐射、叶绿素荧光及果实品质等的影响,为果树冠层微生态环境优化及高产稳产提供理论依据。【方法】以15 a(年)生枳橙砧‘奥林达’夏橙为试材,分别对郁闭植株(CK)进行开心形、篱壁形和变则主干形修剪处理,然后利用CI-110植物冠层分析仪测定植株冠层有效光合辐射分布、利用多功能植物效率分析仪M-PEA测定叶片快速叶绿素荧光的变化。【结果】不同处理植株的光合有效辐射、光合色素含量、快速叶绿素荧光参数在6月至9月差异明显:树体有效光合辐射(PAR)逐月明显下降;叶片光合色素呈先明显上升后略微下降的趋势;在试验测定阶段,植株叶片光系统活性、光能利用率、光合机构性能逐渐提高,叶片放氧复合体(OEC)受到伤害程度降低。几种整形改造方式对树体各项生理指标的影响明显,开心形、篱壁形和主干形等3种处理植株光合有效辐射、光合色素含量、光能利用率及光系统性能等均较对照明显提高。单株产量及果实品质以开心形最优,篱壁形、主干形次之,但均优于对照。【结论】通过树形改造改善了冠层微生态重要因子即光合有效辐射状况,树体的叶片光合色素含量、光合结构性能、光合机构自我保护能力、光合效率、PSI与PSII的协调性等都有极大的提升,明显改善了植株单株产量及果实品质。     

Cloning and characterization of 5 MADS-box cDNAs isolated from citrus fruit tissue

We isolated and characterized 5 MADS-box cDNA clones of CitMADS1, CitMADS3, CitMADS5, CitMADS6 and CitMADS8 from fruit tissues of Satsuma mandarin (Citrus unshiu Marc.). Sequence analysis revealed that they have high sequence identities with known MADS-box genes and that their predicted proteins possess the general structural features of the M domain and the K domain. In a phylogenetic tree with 24 known Arabidopsis MADS-box genes, 5 Citrus MADS-box genes were classified into 4 clades of the MADS-box gene with independent gene functions. Their broad expression profiles in the Citrus life cycle suggested that they play roles in flower and fruit development. Most of them, except CitMADS1 and CitMADS3, are expressed in seedlings before the phase transition from vegetative to reproductive growth. CitMADS1 and CitMADS3 are not expressed in vegetative organs and could serve as a molecular marker for reproductive development.     

Relation of peel damage in citrus fruit to wind climate in orchard and its control

Peel damage originated by wind is the main abiotic cause of citrus fruit discards for export in Uruguay. Natural windbreaks such as Eucalyptus and Casuarinas have not been effective in reducing it. This research was carried out during three years in a citrus orchard situated in the coastal plain of Uruguay (35° SL). The purpose of this work was to study wind climate inside the orchard, fruit seasonal sensitivity, basal leaf effect on the onset and evolution of peel damage, and the efficiency of artificial windbreaks to reduce fruit discard of ‘Ellendale’ tangor. Average wind velocity in the orchard did not exceed 5 m s⁻¹. First peel scars were evident two weeks after petal fall and damaged fruit percentage importantly increased during the first stage of fruit growth. Low energy vortexes caused almost permanent friction between basal leaves and the developing fruitlets growing in their axil. Removal of the basal leaf decreased significantly wind damaged fruit. Natural wind flow modification through the use of semi-porous artificial windbreak nets (5 cm by 10 cm mesh) modified low energy vortexes and increased significantly the percentage of export quality fruit. We conclude that this type of net is more efficient than natural windbreaks or classical nets to reduce wind damage in citrus fruit.     

Pineapple organic acid metabolism and accumulation during fruit development

Developmental changes in pineapple (Ananas Comosus (L.) Merrill) fruit acidity was determined for a ‘Smooth Cayenne’ high acid clone PRI#36-21 and a low acid clone PRI#63-555. The high acid clone gradually increased in fruit acidity from 1.4 meq/100 ml 6 weeks from flowering, and peaked a week before harvest at ca 10 meq/100 ml. In contrast, the low acid clone increased in acidity 6 to 8 weeks after flowering, peaked 15 weeks after flowering at ca. 9 meq per/100 ml and then sharply declined in 2 weeks to 6 meq/100 ml. The increased in total soluble solids (TSS) of the low acid clone began 6 weeks after flowering and for the high acid clone at 12 weeks after flowering. The increase in titratable fruit acidity (TA) paralleled the changes in the citric acid content of both clones. Citric acid content increased from less than 1 mg/g at 6 weeks after flowering to 6 to 7 mg/g, 9 weeks later. The malic acid concentration in both clones varied between 3 and 5 mg/g and showed no marked changes just before harvest. The developmental changes in fruit potassium were significantly correlated with fruit acidity and fruit total soluble solids in both the high and low acid clones. Developmental changes in acid-related enzymatic activities showed an increase in citrate synthase (EC 4.1.3.7) activity that occurred a week before harvest, coincided with the peak in citric acid in the high acid clone. An increase in aconitase (ACO, EC 4.2.1.3) activity was observed just before harvest as the decline in acidity occurred in the low acid clone. The activities of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), malate dehydrogenase (MDH, EC 1.1.1.37) and malic enzyme (ME, EC 1.1.1.40) did not parallel any changes in fruit acidity. The results indicated that the change in pineapple fruit acidity during development was due to changes in citric acid content. The major difference in acid accumulation occurred in the low acid clone just before harvest when acidity declined by one-third. The activities of citrate synthase and aconitase possibly played a major role in pineapple fruit acidity changes.