1-MCP对植物乙烯反应的抑制和应用

综述了1-MCP在受体水平上抑制植物对乙烯反应的作用机制,并对其在调控果实,蔬菜和花卉成熟衰老中的潜在应用价值作了介绍。     

花衰老相关的乙烯信号转导基因研究进展

乙烯在许多切花衰老过程中起着重要的调节作用,不同的植物乙烯信号转导组分在花衰老过程中有不同的转录调节特性。根据乙烯信号转导标准模式,通过调节乙烯信号转导基因表达能够调控花对乙烯的敏感性,深入研究乙烯信号转导机制;可能有多条途径可延缓切花衰老。综述了香石竹和月季等几种观赏植物在花衰老过程中乙烯受体和乙烯信号转导基因表达及特性。     

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。     

果实成熟的基因调控

果实的成熟过程是由一系列生理生化学变化过程组成,这些变化过程受到外界环境条件、植激素和基因的调控。随着近年来有关果实成熟衰老的基因的分离,定性及反义基因技术在控制果实成熟上的成功应用,对揭示果实成熟衰老的分子机理起到了重要作用。本文就近来果实成熟基因调控研究进展作一简要评述。     

果实成熟的基因调控

果实的成熟过程是由一系列生理生化变化过程组成,这些变化过程受到外界环境条件、植物激素和基因的调控。随着近年来有关果实成熟衰老的基因的分离、定性及反义基因技术在控制果实成熟上的成功应用,对揭示果实成熟衰老的分子机理起到了重要作用。本文就近年来果实成熟基因调控研究进展作一简要评述 。     

乙烯对蜡梅切花开放衰老及乙烯受体基因表达的影响

为探索乙烯是否参与蜡梅花朵开放衰老进程的调控,利用气相色谱法测定分析不同发育阶段花朵的乙烯释放情况,同时分析乙烯、1-甲基环丙烯(1-MCP)处理对切花开放衰老进程和乙烯受体基因表达的影响。结果表明:蜡梅花朵开放衰老过程中有微量乙烯的产生,在盛开期出现峰值;外源乙烯显著加快了花朵开放衰老进程,缩短切花瓶插寿命1.9 d,而1-MCP处理则延长瓶插寿命2.4 d;存在受乙烯和1-MCP影响其在蜡梅花朵中表达的乙烯受体基因成员CpETR-1、CpETR-2、CpETR-3,且3个基因的转录水平变化与开放衰老进程关联较为紧密。说明蜡梅乙烯释放量虽然很低,但乙烯参与了蜡梅花朵开放和衰老的调控,影响其进程和相关乙烯受体基因的表达。     

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.     

番茄突变体Epinastics的乙烯反应表现型分析

对番茄(Lycopersicoin esculentum Mil1.)突变体Epinastics(Epi)及其野生亲本VFN幼苗、成长植株和果实生长发育与成熟特性进行了系统研究和比较分析.Epi突变体从幼苗到果实都有乙烯过量合成,在黄化幼苗部分三重反应、成长植株叶柄严重上位生长、器官脱落和果实加速成熟等多方面表现出明显增强的乙烯反应,与已知的乙烯反应模式相符.强烈的顶端优势、紧凑的植株形态提示乙烯在植物的顶端优势调节中可能起着重要的作用.Epi突变体黄化幼苗项勾缩小、叶片和花瓣衰老延迟,与传统的乙烯反应不符,提示植物不同的生长发育特性由不同的乙烯信号转导途径调控.     

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。     

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     

Role of ethylene receptors during senescence and ripening in horticultural crops

The past two decades have been rewarding in terms of deciphering the ethylene signal transduction and functional validation of the ethylene receptor and downstream genes involved in the cascade. Our knowledge of ethylene receptors and its signal transduction pathway provides us a robust platform where we can think of manipulating and regulating ethylene sensitivity by the use of genetic engineering and making transgenic. This review focuses on ethylene perception, receptor mediated regulation of ethylene biosynthesis, role of ethylene receptors in flower senescence, fruit ripening and other effects induced by ethylene. The expression behavior of the receptor and downstream molecules in climacteric and non climacteric crops is also elaborated upon. Possible strategies and recent advances in altering the ethylene sensitivity of plants using ethylene receptor genes in an attempt to modulate the regulation and sensitivity to ethylene have also been discussed. Not only will these transgenic plants be a boon to post-harvest physiology and crop improvement but, it will also help us in discovering the mechanism of regulation of ethylene sensitivity.     

Members of the tomato LeEIL (EIN3-like) gene family are functionally redundant and regulate ethylene responses throughout plant development

The plant hormone ethylene regulates many aspects of growth, development and responses to the environment. The Arabidopsis ETHYLENE INSENSITIVE3 (EIN3) protein is a nuclear-localized component of the ethylene signal-transduction pathway with DNA-binding activity. Loss-of-function mutations in this protein result in ethylene insensitivity in Arabidopsis. To gain a better understanding of the ethylene signal-transduction pathway in tomato, we have identified three homologs of the Arabidopsis EIN3 gene (LeEILs). Each of these genes complemented the ein3-1 mutation in transgenic Arabidopsis, indicating that all are involved in ethylene signal transduction. Transgenic tomato plants with reduced expression of a single LeEIL gene did not exhibit significant changes in ethylene response; reduced expression of multiple tomato LeEIL genes was necessary to reduce ethylene sensitivity significantly. Reduced LeEIL expression affected all ethylene responses examined, including leaf epinasty, flower abscission, flower senescence and fruit ripening. Our results indicate that the LeEILs are functionally redundant and positive regulators of multiple ethylene responses throughout plant development.     

Compounds Interacting with the Ethylene Receptor in Plants

Abstract: Some of the compounds binding to the ethylene receptor induce an ethylene response, but others prevent it. The compounds preventing an ethylene response have been developed into a means for protecting plants against ethylene and extending the life of some plant material. 1-Methylcyclopropene (1-MCP), a compound now commercially available under the names EthylBloc and SmartFresh™, is currently being used on flowers, fruit and vegetables with great success. In ethylene sensitive flowers, among other responses, it prevents senescence and abscission of plant organs; in fruit and vegetables it slows down the ripening process. Other similar compounds are now being developed for a range of methods of application.     

Manipulation of ethylene biosynthesis

The plant hormone ethylene is involved in many plant processes ranging from seed germination to leaf and flower senescence and fruit ripening. Ethylene is synthesized from methionine, via S-adenosyl-L-methionine (SAM) and 1-amino-cyclopropane-1-carboxylic acid (ACC). The key ethylene biosynthetic enzymes are ACC synthase (ACS) and ACC oxidase (ACO). Manipulation of ethylene biosynthesis by chemicals and gene technology is discussed. Biotechnological modification of ethylene synthesis is a promising method to prevent spoilage of agricultural and horticultural products.     

Ethylene hormone receptor action in Arabidopsis.

Small gaseous molecules play important roles in biological signaling in both animal and plant physiology. The hydrocarbon gas ethylene has long been known to regulate diverse aspects of plant growth and development, including fruit ripening, leaf senescence and flower abscission. Recent progress has been made toward identifying components involved in ethylene signal transduction in the plant Arabidopsis thaliana. Ethylene is perceived by five receptors that have similarity to two-component signaling proteins. The hydrophobic amino-terminus of the receptors binds ethylene, and mutations in this domain both prevent ethylene binding and confer ethylene insensitivity to the plant; the carboxyl-terminal portion of the receptors has similarity to bacterial his tidine protein kinases. Genetic data suggest a model in which ethylene binding inhibits receptor signaling, yet precisely how these receptors function is unclear. Two of the receptors have been found to associate with a negative regulator of ethylene responses called CTR1, which appears to be a mitogen-activated protein kinase (MAPK) kinase kinase.     

Ethylene receptor expression is regulated during fruit ripening, flower senescence and abscission

Using theArabidopsis ethylene receptorETR1 as a probe, we have isolated a tomato homologue (tETR) from a ripening cDNA library. The predicted amino acid sequence is 70% identical toETR1 and homologous to a variety of bacterial two component response regulators over the histidine kinase domain. Sequencing of four separate cDNAs indicates that tETR lacks the carboxyl terminal response domain and is identical to that encoded by the tomatoNever ripe gene. Ribonuclease protection showed tETR mRNA was undetectable in unripe fruit or pre-senescent flowers, increased in abundance during the early stages of ripening, flower senescence, and in abscission zones, and was greatly reduced in fruit of ripening mutants deficient in ethylene synthesis or response. These results suggest that changes in ethylene sensitivity are mediated by modulation of receptor levels during development.     

Ethylene and fruit ripening

The latest advances in our understanding of the relationship between ethylene and fruit ripening are reviewed. Considerable progress has been made in the characterisation of genes encoding the key ethylene biosynthetic enzymes, ACC synthase (ACS) and ACC oxidase (ACO) and in the isolation of genes involved in the ethylene signal transduction pathway, particularly those encoding ethylene receptors ( ETR ). These have allowed the generation of transgenic fruit with reduced ethylene production and the identification of the Nr tomato ripening mutant as an ethylene receptor mutant. Through these tools, a clearer picture of the role of ethylene in fruit ripening is now emerging. In climacteric fruit, the transition to autocatalytic ethylene production appears to result from a series of events where developmentally regulated ACO and ACS gene expression initiates a rise in ethylene production, setting in motion the activation of autocatalytic ethylene production. Differential expression of ACS and ACO gene family members is probably involved in such a transition. Finally, we discuss evidence suggesting that the NR ethylene perception and transduction pathway is specific to a defined set of genes expressed in ripening climacteric fruit and that a distinct ETR pathway regulates other ethylene-regulated genes in both immature and ripening climacteric fruit as well as in non-climacteric fruit. The emerging picture is one where both ethylene-dependent and -independent pathways coexist in both climacteric and non-climacteric fruits. Further work is needed in order to dissect the molecular events involved in individual ripening processes and to understand the regulation of the expression of both ethylene-dependent and -independent genes.     

New volatile and water-soluble ethylene antagonists

Twenty cyclopropenes were prepared and their anti-ethylene activity was evaluated in the fruit ripening and plant senescence bioassays. The treatment of banana fruits with developed antagonists led to delay of fruit ripening. Some antagonists were capable to extend exhibition life of cut mini carnation flowers as well as delay senescence of bean leaves. The potency of ethylene antagonists declined with increase in molecular weight and reduction in their solubility in water, irrespective of bioassay used. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 4, pp. 585–591. The text was submitted by the author in English.