低温对梨(Pyrus communis L.)果实后熟过程中乙烯合成和反应的影响(英文)

Passe Crassane梨果实采后需经过 6 0～ 80d的低温处理才能正常后熟。为了明确低温促进果实成熟的机理 ,对果实进行了低温和低温结合 1 MCP(1 甲基环丙烯 ,乙烯作用抑制剂 )和丙烯 (乙烯类似物 )处理。研究发现 :果实经低温处理后 ,乙烯合成前体———ACC含量大幅度升高 ,而未经低温处理的果实 ,无论贮藏在空气中或用丙烯 1 0 0 0μl/L处理 ,果实中ACC、M ACC含量均保持较低水平。但冷藏前用 1 MCP处理可抑制冷藏果实或冷藏后升温的果实ACC含量的增高。这说明果实的后熟过程与低温和依赖乙烯的ACC合成酶的活性和基因的表达密切相关。未经冷藏的果实于 2 0℃下用丙烯处理 ,果实不能自发合成乙烯 ,但当果实经过冷藏后再用丙烯处理 ,则果实对丙烯的反应能力随冷藏时间延长而增强。为了进一步了解低温诱导的乙烯反应过程。我们对乙烯受体基因进行了研究。定量PCR分析结果表明 ,与拟南芥ETR1同源的基因的表达不受低温的调节。但冷藏后升温 ,或在升温后用丙烯处理时 ,mRNA含量降低。这些结果说明 ,低温可能是通过影响乙烯信号转导途径下游的其它因子而调节依赖乙烯的ETR1基因和ACC合成酶基因的表达 ,从而影响果实的成熟过程     

果实成熟乙烯相关基因工程研究进展(综述)

果实成熟是一个复杂的生理生化过程,而乙烯是引发果实成熟的主要因素.本文简述乙烯合成过程中S-腺苷甲硫氨酸水解酶、ACC合成酶与ACC氧化酶、ACC脱氨酶基因和乙烯受体突变体的特性及克隆;同时,评述利用基因工程技术控制果实成熟的应用前景.     

果实成熟的基因工程研究

乙烯是催化果实成熟的内源植物激素。本文简要介绍用植物基因工程的手段分离和鉴定出乙烯合成和果实成熟有关的多聚半乳糖醛酸酶、ＡＣＣ氧化酶、ＡＣＣ合酶及ＡＣＣ脱氨酶的基因。并利用反意ＲＮＡ技术将它们的反意ＲＮＡ转入番茄中,得到了相应的反意转基因植株和果实,实现了在基因水平上对果实成熟的调控,开辟了植物育种的新途径。     

香蕉一个Ⅲ类酸性几丁质酶基因与果实成熟关系的研究

为了解Ⅲ类酸性几丁质酶基因(MaCHⅢ)与香蕉果实采后成熟过程的相互关系,对经乙烯和1-甲基环丙烯(1-MCP)处理的巴西香蕉果实采后乙烯释放量、Ⅲ类酸性几丁质酶基因(MaCHⅢ)表达以及几丁质酶活性进行了测定.结果显示:(1)乙烯催熟处理的香蕉果实,乙烯释放量比对照处理的果实提前15 d达到高峰;1-MCP处理的香蕉果实,乙烯生物合成和果实成熟明显受到了抑制.(2)外源乙烯加速了MaCHⅢ基因的下调表达和Ⅲ类酸性几丁质酶活性的下降,MaCHⅢ表达量和Ⅲ类酸性几丁质酶活性分别在采后第3天和第4天下降到最小值.(3)1-MCP处理使MaCHⅢ基因呈现上调表达,Ⅲ类酸性几丁质酶活性上升,MaCHⅢ基因表达量和Ⅲ类酸性几丁质酶活性分别在采后18 d和25 d达到高峰.研究表明,MaCHⅢ基因可能与香蕉果实采后成熟呈负相关.     

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.     

甜瓜乙烯受体基因Cm-ETR1 cDNA的克隆及表达特性分析

乙烯感知和信号转导的初始成分是乙烯受体,为探明甜瓜乙烯受体基因Cm-ETR1在甜瓜果实成熟过程中的作用,以甜瓜品种河套蜜瓜为材料,根据GenBank中登录的甜瓜乙烯受体基因Cm-ETR1的cDNA序列(登录号为AF054806),设计合成特异性引物,采用RT-PCR技术克隆得到Cm-ETR1基因全长cDNA序列,提交到GenBank中(登录号为EF495185)。序列分析表明,序列长度为2 256 bp,编码区为2 223 bp,编码740个氨基酸,与已报道的cantalupenis甜瓜ETR1基因的cDNA序列完全一致。Cm-ETR1蛋白的系统进化树分析结果表明,该乙烯受体蛋白在各物种间高度保守,与黄瓜乙烯受体蛋白相似性最高,一致性为99%,与龙眼乙烯受体蛋白相似性最低,一致性为86%。定量PCR分析结果显示,随着甜瓜果实内源乙烯合成量和成熟程度的增加,Cm-ETR1基因的表达量同步增加,在果实乙烯跃变期,Cm-ETR1的表达量也达到最高值,内源乙烯合成量与Cm-ETR1基因表达量间呈显著正相关,表明Cm-ETR1基因在甜瓜果实成熟过程中可能具有重要的作用。     

通过表达ACC脱氨酶基因控制番茄果实的成熟

乙烯在跃变型果实的成熟过程中起着触发呼吸跃变和促进果实成熟的作用。细菌来源的1-氨基环丙烷-1-羧酸(ACC)脱氨酶能降解乙烯的直接前体ACC,从而抑制植物体内乙烯的合成。我们用PCR方法从假单孢杆菌中克隆到ACC脱氨酶基因并通过农杆菌介导的方法将其转入番茄(Lycopersicun esculentum)中。再生植株经Southern blot检测证明,ACC脱氨酶基因已整合到番茄基因组中并稳定表达。转基因番茄果实成熟期的推迟时间与体内乙烯的抑制程度有相关性。转基因番茄植株乙烯的合成降低80%左右,果实在离体条件下可保鲜75d左右。研究ACC脱氢酶基因在植物体内的作用可阐明高等植物体内乙烯的作用机理并为培育耐贮藏果蔬品种打下基础。     

番茄rin位点上的一个MADS盒基因调控果实成熟

ｒｉｎ番茄突变体的乙烯生成和果实成熟均受到抑制 ,除此之外还表现萼片增大和花序决定性丧失。尽管该突变体维持良好的乙烯敏感性 ,但果实成熟却不能被外源乙烯诱导 ,这暗示ＲＩＮ基因编码的产物同时调控依赖于和不依赖于乙烯的成熟过程。作者先前的研究已表明ｒｉｎ位点定位于番茄第 5染色体。本文报道通过定位克隆发现ｒｉｎ位点上存在两个串联的ＭＡＤＳ盒基因 ,分别定名为ＬｅＭＡＤＳ＿ＲＩＮ和ＬｅＭＡＤＳ＿ＭＣ ,前者调控果实成熟过程而后者则影响萼片先育和花序决定性。这两个基因的功能通过正义转化ｒｉｎ番茄和反义转化野生型番…     

乙烯受体在果实成熟及花衰老中的研究进展

乙烯受体是乙烯信号转导网络的第一个转导元件,通过调控受体基因的表达,可以调节植物对乙烯的敏感性,以调控果实的成熟及花衰老进程的响应。随着人们对乙烯受体研究的深入,乙烯受体突变体及受体抑制剂在采后果实和切花保鲜上的应用已受到广泛关注。就近年来关于乙烯受体的相关研究进展进行综述,重点介绍了乙烯受体的分子调控机制及乙烯受体在果实成熟和花衰老中的应用,并对今后乙烯受体的研究方向作了展望,以期为进一步研究提供参考。     

苹果果实花青素形成与乙烯释放的关系

新红星苹果果实在盛花后１１０ｄ以前花青素含量较低,以后随果实进一步发育而迅速增加,盛花后１１０￣１２０ｄ内为花青素积累高峰,果实乙烯释放与花青素积累过程变化规律一致。果实伤害处理明显刺激果皮乙烯及花青素形成,花青素出现时期晚于乙烯已明显开始增加期。Ａｇ＾＋能部分抑制伤害果实花青素的形成,果实阴、阳面果皮的乙烯释放速率在果实成熟期间差别不大。     

Characterization of a strawberry late-expressed and fruit-specific peptide methionine sulphoxide reductase

We have cloned and characterized a cDNA clone, called Fapmsr , coding for a putative peptide methionine sulphoxide [Met(O)] reductase (PMSR, EC 1.8.4.6) from strawberry fruits ( Fragaria x ananassa ). This gene is involved in the repair of inactive peptides and proteins caused for the oxidation of methionine residues to Met(O). Expression of the Fapmsr was only detected in the receptacles of red mature fruits and not in young or immature fruits nor in other plant tissues such as flowers, leaves, runners, roots or achenes. Expression of the Fapmsr gene was activated in green immature fruits when achenes were removed from receptacles, and this was prevented by the application of exogenous auxins such as naphthaleneacetic acid. The enzyme produced and purified by cloning the strawberry cDNA in frame with the C-terminal sequence of the glutathione S-transferase gene can reduce free Met(O) to methionine as analysed by reverse phase high performance liquid chromatography. We have also set up a PMSR protection assay that demonstrates that this enzyme can protect in vivo against the damage produced by the addition of H₂O₂.     

Metabolism of cyclic carotenoids: a model for the alteration of this biosynthetic pathway in Capsicum annuum chromoplasts

The biosynthetic pathway of cyclic carotenoid is known to be quantitatively and qualitatively different in the non-green plastids of Capsicum annuum fruits compared with chloroplasts. Here, the cloning is described of a novel cDNA from this organism, which encodes an enzyme catalyzing the cyclization of lycopene to β-carotene when expressed in Escherichia coli . The corresponding gene is constitutively expressed during fruit development. Significant amino acid sequence identity was observed between this enzyme and capsanthin/capsorubin synthase which is involved in the synthesis of the species-specific red carotenoids of C. annuum fruits. The latter enzyme was found also to possess a lycopene β-cyclase activity when expressed in E. coli . A model is proposed for the origin of the capsanthin/capsorubin synthase gene and the role of this enzyme, together with the newly cloned lycopene cyclase, in the specific re-channeling of linear carotenoids into β-cyclic carotenoids in C. annuum ripening fruits.     

An Antisense Pectin Methylesterase Gene Alters Pectin Chemistry and Soluble Solids in Tomato Fruit

Pectin methylesterase (PME, EC 3.1.11) demethoxylates pectins and is believed to be involved in degradation of pectic cell wall components by polygalacturonase in ripening tomato fruit. We have introduced antisense and sense chimeric PME genes into tomato to elucidate the role of PME in fruit development and ripening. Fruits from transgenic plants expressing high levels of antisense PME RNA showed <10% of wild-type PME enzyme activity and undetectable levels of PME protein and mRNA. Lower PME enzyme activity in fruits from transgenic plants was associated with an increased molecular weight and methylesterification of pectins and decreased levels of total and chelator soluble polyuronides in cell walls. The fruits of transgenic plants also contained higher levels of soluble solids than wild-type fruits. This trait was maintained in subsequent generations and segregated in normal Mendelian fashion with the antisense PME gene. These results indicate that reduction in PME enzyme activity in ripening tomato fruits had a marked influence on fruit pectin metabolism and increased the soluble solids content of fruits, but did not interfere with the ripening process.     

Antioxidant and anti-inflammatory properties of tomato fruits synthesizing different amounts of stilbenes

Resveratrol, a plant phenolic compound, is found in grapes and red wine, but is not widely distributed in other common food sources. The pathway for resveratrol biosynthesis is well characterized. Metabolic engineering of this compound has been achieved in tomato plants ( Lycopersicon esculentum Mill.) in order to improve their nutritional value. Tomato plants synthesizing resveratrol were obtained via the heterologous expression of a grape ( Vitis vinifera L.) cDNA encoding for the enzyme stilbene synthase (StSy), under the control of the fruit-specific promoter TomLoxB. The resulting LoxS transgenic plants accumulated trans -resveratrol and trans -piceid, in particular in the skin of the mature fruits. Quantitative analyses carried out on LoxS fruits were compared with those of a tomato line constitutively expressing the stsy gene (35SS). The LoxS fruits contained levels of trans -resveratrol that were 20-fold lower than those previously reported for the 35SS line. The total antioxidant capability and ascorbate content in transformed fruits were also evaluated, and a significant increase in both was found in the LoxS and 35SS lines. These results could explain the higher capability of transgenic fruits to counteract the pro-inflammatory effects of phorbol ester in monocyte–macrophages via the inhibition of induced cyclo-oxygenase-2 enzyme.     

A piperic acid CoA ligase produces a putative precursor of piperine,the pungent principle from black pepper fruits

Black pepper (Piper nigrum L.) is known for its high content of piperine, a cinnamoyl amide derivative regarded as largely responsible for the pungent taste of this widely used spice. Despite its long history and worldwide use, the biosynthesis of piperine and related amides has been enigmatic up to now. In this report we describe a specific piperic acid CoA ligase from immature green fruits of P. nigrum. The corresponding enzyme was cloned and functionally expressed in E. coli. The recombinant enzyme displays a high specificity for piperic acid and does not accept the structurally related feruperic acid characterized by a similar C‐2 extension of the general C6–C3 phenylpropanoid structure. The enzyme is also inactive with the standard set of hydroxycinnamic acids tested including caffeic acid, 4‐coumaric acid, ferulic acid, and sinapic acid. Substrate specificity is corroborated by in silico modelling that suggests a perfect fit for the substrate piperic acid to the active site of the piperic acid CoA ligase. The CoA ligase gene shows its highest expression levels in immature green fruits, is also expressed in leaves and flowers, but not in roots. Virus‐induced gene silencing provided some preliminary indications that the production of piperoyl‐CoA is required for the biosynthesis of piperine in black pepper fruits.     

Effect of the Colorless non-ripening mutation on cell wall biochemistry and gene expression during tomato fruit development and ripening

The Colorless non-ripening (Cnr) mutation in tomato (Solanum lycopersicum) results in mature fruits with colorless pericarp tissue showing an excessive loss of cell adhesion (A.J. Thompson, M. Tor, C.S. Barry, J. Vrebalov, C. Orfila, M.C. Jarvis, J.J. Giovannoni, D. Grierson, G.B. Seymour [1999] Plant Physiol 120: 383-390). This pleiotropic mutation is an important tool for investigating the biochemical and molecular basis of cell separation during ripening. This study reports on the changes in enzyme activity associated with cell wall disassembly in Cnr and the effect of the mutation on the program of ripening-related gene expression. Real-time PCR and biochemical analysis demonstrated that the expression and activity of a range of cell wall-degrading enzymes was altered in Cnr during both development and ripening. These enzymes included polygalacturonase, pectinesterase (PE), galactanase, and xyloglucan endotransglycosylase. In the case of PE, the protein product of the ripening-related isoform PE2 was not detected in the mutant. In contrast with wild type, Cnr fruits were rich in basic chitinase and peroxidase activity. A microarray and differential screen were used to profile the pattern of gene expression in wild-type and Cnr fruits. They revealed a picture of the gene expression in the mutant that was largely consistent with the real-time PCR and biochemical experiments. Additionally, these experiments demonstrated that the Cnr mutation had a profound effect on many aspects of ripening-related gene expression. This included a severe reduction in the expression of ripening-related genes in mature fruits and indications of premature expression of some of these genes in immature fruits. The program of gene expression in Cnr resembles to some degree that found in dehiscence or abscission zones. We speculate that there is a link between events controlling cell separation in tomato, a fleshy fruit, and those involved in the formation of dehiscence zones in dry fruits.