乙酰水杨酸和乙烯处理对猕猴桃果实后熟软化的影响

以猕猴桃（Actinidia deliciosa(A.Chev.)C.F.Liang et A.R.Ferguson cv.Bruno)果实为试材,研究乙酰水杨酸（ASA）与乙烯处理对果实内源水杨酸（SA）含量变化以及后熟软化相关因子的影响,探讨SA在果实成熟衰老进程的作用。研究结果表明：果实后熟软化进程中,内源SA水平呈下降变化,组织中SA水平与果实硬度变化呈极显著正相关关系（r=0.9694),ASA处理可显著地维持组织中较高的SA水平,抑制脂氧合酶（LOX）和丙二烯氧合酶（AOS）活性增加,减低O2^-生成速率,维持细胞膜稳定性,进而抑制了乙烯生物合成或推迟乙烯跃变的到来,延缓了果实后熟软化进程,这些效应主要表现在乙烯跃变之前或乙烯跃变前期;相反,外源乙烯处理则显著降低果实组织中内源SA水平,促进LOX和AOS活性的增加,促使O2^-积累,增加了细胞膜透性,促使乙烯跃变的提前到来,加速了果实的后熟软化。推测组织中的内源SA水平与细胞膜脂过氧化作用密切相关,外源ASA可能作为一种O2^-等自由基的清除剂或是细胞膜稳定剂在组织成熟衰老过程中起作用。     

采后黄花梨(Pyrus pyrifolia Nakai.)果实中丙二烯氧合酶的生理功能

以不同成熟时期黄花梨果实为材料 ,研究果实采后成熟衰老进程中丙二烯氧合酶 (AOS)与几个成熟衰老相关因子的关系 ,探讨AOS的生理功能。结果表明 :2 0℃下不同成熟时期果实成熟衰老进程中的AOS活性变化均为峰形曲线 ,活性峰值出现在采后 10～ 12d ,先于乙烯跃变峰 2～ 4d ;果实成熟衰老各种相关因子的变化峰值出现的先后顺序依次是 :脂氧合酶(LOX)、自由基 (O- ·2 )、AOS、ACC (1 氨基环丙烷 1 羧酸 )合成酶、ACC、ACC氧化酶 ,最后为乙烯跃变峰的出现。 1℃下贮藏果实的AOS活性、乙烯合成和其他成熟衰老相关酶活性均受到强烈抑制 ,ACC和O- ·2 含量也较低 ,果实衰老进程被显著延缓。推测AOS是乙烯合成的上游调控因子之一。     

乙酰水杨酸处理对猕猴桃果实成熟衰老的影响及其作用机理

以不同后熟软化阶段猕猴桃果肉组织圆片为材料 ,在 2 0℃下用 1.0mmol L(pH 3.5 )的乙酰水杨酸(ASP)分别处理 4、12和 2 4h后 ,分析其对果实成熟衰老相关因子的影响。结果表明 ,随着果实成熟衰老 ,内源游离SA下降 ,LOX活性增加 ,超氧自由基 (O- ·2 )生成速率增加 ,乙烯释放量加大 ;ASP处理促使组织内源SA水平的增加 ,降低了O- ·2 生成速率 ,抑制了LOX、ACC合成酶和ACC氧化酶的活性以及乙烯的生成。推测ASP可能作为O- ·2 等自由基清除剂 ,通过负反馈调控LOX途径 ,延缓果实的成熟衰老     

脂氧合酶、茉莉酸和水杨酸对猕猴桃果实后熟软化进程中乙烯生物合成的调控

20℃下后熟果实的LOX活性增加先于自由基产生和乙烯生成;JA处理对果实后熟软化启动期(采后1d)和果实快速软化期(采后5d)果实切片中的LOX活性、自由基产生和乙烯生物合成有促进作用,至果实软化后期(采后7d)这种效应消失;亚油酸只在采后1d果实切片中促使LOX活性和乙烯生成;SA处理抑制了果实后熟进程中组织切片的LOX活性、自由基产生和乙烯的生物合成;SA和JA对LOX活性和乙烯生物合成具有明显的拮抗作用。     

IAA、ABA和乙烯利对梨枣采后某些生理指标的影响

梨枣采后乙烯释放量、丙二醛(MDA)含量和脂氧合酶(LOX)活性呈上升而硬度、维生素C(VC)含量和好果率呈逐渐下降趋势.IAA、ABA、乙烯利促进枣果采后初期的乙烯生成,提高梨枣中MDA含量和LOX活性,加速梨枣软化,降低梨枣的VC含量和好果率;ABA的作用更加明显.LOX活性与果肉硬度及好果率呈显著负相关,暗示LOX与枣果的软化衰老有一定关系.     

脂氧合酶与猕猴桃果实后熟软化的关系

２０℃下贮藏果实的脂氧合酶（ＬＯＸ）活性随着后熟进程保持上升,其活性与果实硬度的变化呈极显著负相关,油酸,亚油酸和亚麻酶等不饱和脂肪酸的组分比例变化较大,而棕榈酸和硬脂酸等饱和脂肪酸的组分比例变化很小;０℃贮藏果实中的ＬＯＸ活性被强烈抑制,果实后熟软化进程被明显延缓,５种脂肪酸组分比例变化均较平稳;外源乙烯处理显著促进了ＬＯＸ活性的增加,加速了果实后熟软化进程。     

脂氧合酶与猕猴桃果实后熟软化的关系

２０ ℃下贮藏果实的脂氧合酶（ＬＯＸ） 活性随着后熟进程持续上升,其活性与果实硬度的变化呈极显著负相关,油酸、亚油酸和亚麻酸等不饱和脂肪酸的组分比例变化较大,而棕榈酸和硬脂酸等饱和脂肪酸的组分比例变化很小;０ ℃贮藏果实中的ＬＯＸ 活性被强烈抑制,果实后熟软化进程被明显延缓,５ 种脂肪酸组分比例变化均较平稳;外源乙烯处理显著促进了ＬＯＸ 活性的增加,加速了果实后熟软化进程。     

2,4-二硝基苯酚对采后龙眼果皮脂氧合酶活性和膜脂脂肪酸组分的影响

以'福眼'龙眼(Dimocarpus longan Lour.'Fuyan')果实为材料,研究呼吸解偶联剂2,4-二硝基苯酚(DNP)对采后果皮脂氧合酶(LOX)活性、膜脂脂肪酸组分和细胞膜透性的影响及其与果皮褐变的关系.结果表明:DNP处理导致龙眼果皮细胞膜透性、LOX活性和褐变指数增加,膜脂脂肪酸组分中的棕榈酸(C16:0)、硬脂酸(C18:0)等饱和 脂肪酸的组分增加,亚油酸(C18:2)、亚麻酸(C18:3)和花生一烯酸(C20:1)等不饱和脂肪酸的组分下降,脂肪酸不饱和指数和脂肪酸不饱和度下降.因此认为,DNP促进了龙眼果实果皮褐变可能是由于提高了LOX活性,促进了膜脂不饱和脂肪酸的降解而引起膜系统完整性受损,最终导致细胞膜结构的破坏,使酚酶与酚类物质接触而引起酚类物质氧化的结果.     

番茄果实成熟过程中钙调素含量变化及其与乙烯生成的关系

应用酶联免疫吸附法(ELISA)测定番茄(Lycopersicon esculentum Mill大红品种)果实成熟过程中钙调素(CaM)含量的变化。果实开始成熟(发白期),CaM含量随着呼吸跃变上升,成熟时(粉红期)达到最大,过熟衰老时则下降。果实内部乙烯浓度、ACC含量及其合成酶活性也随跃变而增加,随过熟衰老而降低。GaM含量在果实不同部位中的分布有明显差异,跃变上升期以子房腔组织含量最高,并由中心向外逐渐降低,外周果皮含量最低。此时用外源乙烯催熟处理促进各部位CaM增加。成熟衰老时子房腔组织首先衰老,CaM含量大为降低,但在中柱和果皮中却高于跃变上升期。外源乙烯促进衰老使CaM下降。Ca~(2+)促进番茄圆片CaM含量增高和乙烯产生,CaM抑制剂CPZ,TFP在降低CaM含量的同时也抑制乙烯的产生。     

1-MCP处理对黄花梨果实采后生理的影响

以黄花梨为试验材料,研究常温(26～33℃)条件下1-甲基环丙烯(1-MCP)延缓果实后熟衰老和膜脂过氧化的效应。结果表明:0.5、1.0、1.5μL.L-11-MCP处理可以不同程度地延缓果实采后品质下降,其中以1.0μL.L-1的处理作用效果最明显。1.0μL.L-11-MCP处理明显抑制过氧化物酶(POD)、超氧化物歧化酶(SOD)活性的下降和脂氧合酶(LOX)活性、MDA含量的增加,降低果实呼吸速率,推迟呼吸峰和乙烯峰的出现,从而延缓果实的成熟衰老。     

Role of Brassinosteroids, Ethylene, Abscisic Acid, and Indole-3-Acetic Acid in Mango Fruit Ripening

Rapid ripening of mango fruit limits its distribution to distant markets. To better understand and perhaps manipulate this process, we investigated the role of plant hormones in modulating climacteric ripening of ??Kensington Pride?? mango fruits. Changes in endogenous levels of brassinosteroids (BRs), abscisic acid (ABA), indole-3-acetic acid (IAA), and ethylene and the respiration rate, pulp firmness, and skin color were determined at 2-day intervals during an 8-day ripening period at ambient temperature (21?±?1°C). We also investigated the effects of exogenously applied epibrassinolide (Epi-BL), (+)-cis, trans-abscisic acid (ABA), and an inhibitor of ABA biosynthesis, nordihydroguaiaretic acid (NDGA), on fruit-ripening parameters such as respiration, ethylene production, fruit softening, and color. Climacteric ethylene production and the respiration peak occurred on the fourth day of ripening. Castasterone and brassinolide were present in only trace amounts in fruit pulp throughout the ripening period. However, the exogenous application of Epi-BL (45 and 60?ng?g^?1 FW) advanced the onset of the climacteric peaks of ethylene production and respiration rate by 2 and 1?day, respectively, and accelerated fruit color development and softening during the fruit-ripening period. The endogenous level of ABA rose during the climacteric rise stage on the second day of ripening and peaked on the fourth day of ripening. Exogenous ABA promoted fruit color development and softening during ripening compared with the control and the trend was reversed in NDGA-treated fruit. The endogenous IAA level in the fruit pulp was higher during the preclimacteric minimum stage and declined during the climacteric and postclimacteric stages. We speculate that higher levels of endogenous IAA in fruit pulp during the preclimacteric stage and the accumulation of ABA prior to the climacteric stage might switch on ethylene production that triggers fruit ripening. Whilst exogenous Epi-BL promoted fruit ripening, endogenous measurements suggest that changes in BRs levels are unlikely to modulate mango fruit ripening.     

A role for jasmonates in climacteric fruit ripening

Jasmonates are a class of oxylipins that induce a wide variety of higher-plant responses. To determine if jasmonates play a role in the regulation of climacteric fruit ripening, the effects of exogenous jasmonates on ethylene biosynthesis and color, as well as the endogenous concentrations of jasmonates were determined during the onset of ripening of apple (Malus domestica Borkh. cv. Golden Delicious) and tomato (Lycopersicon esculentum Mill. cv. Cobra) fruit. Transient (12 h) treatment of pre-climacteric fruit discs with exogenous jasmonates at low concentration (1 or 10 μM) promoted ethylene biosynthesis and color change in a concentration-dependent fashion. Activities of both 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase and ACC synthase were stimulated by jasmonate treatments in this concentration range. The endogenous concentration of jasmonates increased transiently prior to the climacteric increase in ethylene biosynthesis during the onset of ripening of both apple and tomato fruit. The onset of tomato fruit ripening was also preceded by an increase in the percentage of the cis-isomer of jasmonic acid. Inhibition of ethylene action by diazocyclopentadiene negated the jasmonate-induced stimulation of ethylene biosynthesis, indicating jasmonates act at least in part via ethylene action. These results suggest jasmonates may play a role together with ethylene in regulating the early steps of climacteric fruit ripening. Received: 14 August 1997 / Accepted: 4 October 1997     

猕猴桃果实乙烯受体基因Ad-ETR1的克隆及其表达

以"布鲁诺"美味猕猴桃(Actinidia deliciosa cv.Bruno)果实为材料,根据其它植物乙烯受体氨基酸保守区序列,设计简并引物,通过RT-PCR扩增出1个657bp大小的cDNA片段(Ad-ETR1)该片段编码219个氨基酸,与其它植物乙烯受体及其基因的氨基酸及核苷酸同源性在72%～90%之间.Northern杂交结果表明,猕猴桃果实成熟衰老进程中Ad-ETR1 mRNA的积累趋于增加.这种积累的最大值出现在乙烯进入跃变之后;乙烯处理可以促使Ad-ETR1 mRNA最大值提前出现,乙酰水杨酸(ASA)处理则显著抑制Ad-ETR1表达.     

苹果果实香气产生过程中氨基酸和脂肪酸含量及一些相关酶活性的变化

研究了苹果果实成熟期间香气和乙烯的产生动态,以及游离氨基酸、游离脂肪酸含量和脂氧合酶(LOX)、醇-酰基转移酶(AAT)活性的变化.结果表明,果实香气物质是随着乙烯释放的增加而产生和增加的.在此过程中,异亮氨酸大量积累.游离脂肪酸在果实香气很少时呈增加趋势;随着香气产生的增多而迅速下降;乙烯高峰过后又有增加.脂氧合酶活性随着果实成熟而提高,其活性在乙烯释放达到高峰时达到最大值,之后迅速下降.醇-酰基转移酶活性在果实开始产生香气时迅速增加,之后保持较高活性.     

香蕉果实XET cDNA的克隆及其在成熟软化的果实果皮和果肉中的表达分析

木葡聚糖内糖基转移酶(Xyloglucan endotransglycosylase,XET)通过分解细胞壁半纤维素多糖的主要成分--木葡聚糖而参与果实软化.为了阐明香蕉(Musa acuminata.Colla cv.GrandNain)果实成熟过程中的软化与细胞壁代谢酶XET基因表达模式的关系,采用RT-PCR和RACE-PCR方法,首次从成熟香蕉果实果肉中分离了编码XT基因的全长cDNA(MA-XET1,全长1 095 bp).序列分析表明,MA-XET1的5'端和3'端的非翻译区分别为66 bp和1 89bp,该片段含有一个完整的开放读码框,编码280个氨基酸,推导的MA-XET1蛋白质中存在XET蛋白的催化活性部位DEIDFEFL.Southern杂交表明,MA-XET1在香蕉基因组中由多拷贝基因编码.Northern分析显示,跃变前期的果肉中,不能检测MA-XET1基因的表达,跃变期的果实果肉中MA-XET1表达增加,跃变后期该基因表达略有减弱;在跃变前期的果实果皮中,MA-XET1的积累较低,跃变期的果实果皮中积累大幅增加,而后迅速下降.Propylene(丙烯,乙烯的类似物)处理降低香蕉果实果皮和果肉的硬度,而且propylene促进MA-XET1在果皮和果肉中的积累.这些结果表明,MA-XET1参与香蕉果实成熟过程中的果皮和果肉软化,并且,MA-XET1的表达在转录水平上受乙烯调控.     

Polygalacturonase gene expression in kiwifruit: relationship to fruit softening and ethylene production

In kiwifruit, much of the softening process occurs prior to the respiratory climacteric and production of ethylene. This fruit therefore represents an excellent model system for dissecting the process of softening in the absence of endogenous ethylene production. We have characterized the expression of three polygalacturonase (PG) cDNA clones (CkPGA, B and C) isolated from fruit of Actinidia chinensis. Expression of CkPGA and B was detected by northern analysis only in fruit producing endogenous ethylene, and by RT-PCR in other tissues including flower buds, petals at anthesis, and senescent petals. CkPGA promoter fragments of 1296, 860 and 467 bp fused to the -glucuronidase (uidA) reporter gene directed fruit-specific gene expression during the climacteric in transgenic tomato. CkPGC gene expression was observed in softening fruit, and reached maximum levels (50-fold higher than for CkPGA and B) as fruit passed through the climacteric. However, expression of this gene was also readily detected during fruit development and in fruit harvested prior to the onset of softening. Using RT-PCR, expression of CkPGC was also detected at low levels in root tips and in senescent petals. These results suggest that PG expression is required not only during periods of cell wall degeneration, but also during periods of cell wall turnover and expansion.     

番茄果实中乙烯与多聚半乳糖醛酸酶的关系

乙烯与多聚半乳糖醛酸酶(PG)都是果实成熟过程中关键的调节因子.一方面,在有乙烯合成缺陷的转反义ACS番茄和乙烯感受缺陷的Nr突变体番茄果实中PG基因表达量都明显下降,PG酶活性明显降低;用外源乙烯(100 μL/L)处理绿熟期番茄果实使PG基因的表达明显增强,而1-甲基环丙烯(1-MCP,1 μL/L)处理转色期番茄果实明显抑制PG基因表达.另一方面,转反义PG基因番茄果实乙烯释放量在授粉后低于其野生型,番茄乙烯受体基因LeETR4和乙烯反应因子LeERF2基因表达量比野生种低.PG降解果胶的产物D-GA(100 mg/L)促进未熟期番茄果实中的乙烯生成和LeETR4、LeERF2基因的表达.