高等植物赤霉素3-β-双氧化酶基因研究进展

赤霉素3-β-双氧化酶（GA3ox）是赤霉素（GA）生物合成过程中的关键酶之一;直接作用于活性GA的生成;在植物的生长发育过程中发挥着重要作用。GA3ox已在拟南芥、烟草、高粱和杨树等多种植物中得到克隆;在植物个体的不同生长阶段、不同组织中GA3ox的表达量均存在着差异;这主要是由物种内在的遗传因素所决定的;同时环境因子和外源激素处理对GA3ox表达也有着显著的影响。通过对基因突变体的研究;揭示出GA3ox突变导致GA的生物合成受阻而间接影响植物的生长;导致植物茎秆、花、种子、果、根等部位性状的改变;包括植株矮化、结籽困难等。过量表达GA3ox基因促进GA的生成;诱导细胞的分裂与分化;促进根尖的径向伸长、种子萌发等。主要从GA3ox的基因克隆与表达模式及其功能效应两方面综述了其在高等植物中研究进展;通过对GA3ox在不同植物中的相关功能研究;探讨其在植物生长发育过程中的具体作用;以期为了解GA3ox对植物生长发育的调控机制提供参考;也有助于在生产实践中更好地利用GA3ox开展基因工程研究;定向培育植物新品种。     

烟草赤霉素2-氧化酶基因NtGA2ox1的克隆、表达及亚细胞定位分析

赤霉素2-氧化酶(GA2ox)通过2-β-羟基化作用产生失活的赤霉素,进而调节植物体内的赤霉素的活性水平。前期,本研究在烟草侧枝发育突变体转录组数据中,发现一个赤霉素2-氧化酶基因,其表达水平与野生型相比存在显著差异,命名为NtGA2ox1。为了更好地研究该基因在烟草侧枝发育中的作用,本研究从普通烟草中分离克隆了NtGA2ox1基因。通过测序分析该基因的编码及全长序列,发现NtGA2ox1基因含有2个外显子和1个内含子,编码一条长度为379个氨基酸的序列。同源进化分析表明,该基因在多种植物中存在同源序列,特别是茄科植物。组织特异性表达分析发现,NtGA2ox1基因在烟草的各个生长阶段均有表达,其中,在花和根中表达量较高。同时,激光共聚焦显微镜结果表明,YFP-NtGA2ox1融合蛋白在细胞质和细胞核中有很强的荧光信号,表明NtGA2ox1蛋白很可能定位于细胞核和细胞质中。本研究为进一步研究赤霉素调控烟草侧枝发育提供了理论依据。     

尿酸氧化酶基因的克隆、表达及其产物的应用

克隆了产朊假丝酵母(Candida utilis)AS2-117尿酸氧化酶(Urate Oxidase,Uricase,EC1.7.3.3)的基因。将此基因插入原核表达质粒pET21a后转化大肠杆菌BL21(DE3),获得高表达的重组转化子菌株。经IPTG诱导,重组尿酸酶基因表达量可达菌体可溶性蛋白的40%。重组尿酸氧化酶为有酶活性的可溶蛋白。Western印迹分析证实表达产物有免疫学活性。经DEAE DE52纤维素离子交换柱层析纯化,目的蛋白纯度可达95%。重组蛋白和天然蛋白的理化特征比较证明重组蛋白的热稳定性有较大提高。酶盒配制和临床应用实验表明重组蛋白可代替天然蛋白进行临床血清尿酸的分析。     

高等植物赤霉素生物合成及其调节研究进展

主要介绍近年来高等植物中生物活性GAs的生物合成,拟南芥GA生物合成途径中关键酶基因（GA1-GA5）的克隆和GA3基因CYP701A3在酵母（Saccharomyces cerevisiae）中的成功表达。评述了活性GAs对赤霉素生物合成的反馈抑制作用和反馈调节中信号的传递和接收问题。高等植物中光周期对GA生物合成的调节主要是在20_氧化和/或3β_羟基化步骤。     

棉花GA 20-氧化酶基因转毛白杨的研究

以毛白杨为材料,研究了超量表达赤霉素合成酶基因(GA20-氧化酶基因)对毛白杨根、茎和叶的生长以及组织结构的影响,结果显示,表达GA20-氧化酶基因能显著提高毛白杨茎的生长,但是对根系的生长带来负面影响.同时,超量表达GA20-氧化酶基因促进了毛白杨茎木质部的生长,抑制了韧皮部和皮层的生长.研究结果表明GA20-氧化酶基因在毛白杨遗传改良中具有一定的应用价值.     

棉花赤霉素氧化酶同源基因GhGA20ox1在烟草中的功能表达

为研究棉花GA20-氧化酶同源基因GhGA20ox1的功能,将该基因转入本明烟（N．benthamiana）中进行超量表达。RT-PCR分析表明GhGA20ox1基因在转基因植株中得到了不同水平的表达。GhGA20ox1基因的超量表达促进了本明烟中的GA4＋7合成,并导致赤霉素过量的表型出现。转基因本明烟的表型变化程度与GhGA20ox1基因的表达水平和GA4＋7的含量一致。这些结果表明,GhGA20ox1基因编码一个有功能的GA20-氧化酶,能够在转基因烟草中促进活性GA（GA4＋7）的合成,可以用作目的基因来提高棉花纤维和其他植物的内源GA水平。     

高等植物赤霉素生物合成关键组分GA20-oxidase氧化酶基因的研究进展北大核心CSCD

GA-20氧化酶(GA-20 oxidase)是重要的GA生物合成和调控酶,直接催化生成有生物活性的GAs,是一种多功能酶,最显著的特点就是负反馈调节。GA20-氧化酶在植物发育和生理过程中起着重要的调控作用。综述了高等植物体内GA20氧化酶基因的克隆及表达调控研究及其对株高、纤维、开花、产量性状等影响,重点阐述了GA20氧化酶基因与激素、光周期、抗性等之间的相互作用,以便更好地揭示GA-20氧化酶信号网络系统及其作用机制。     

薇甘菊乙醇酸氧化酶基因的克隆、序列分析和原核表达

利用SSH和RACE相结合的方法获得了薇甘菊乙醇酸氧化酶基因cDNA全长,并对该序列进行了生物信息学分析。随后将该基因的cDNA编码区克隆到原核表达载体pET-32a(+)中,构建重组表达质粒,转化到大肠杆菌Rosetta-gami(DE3)中进行表达。序列分析表明,薇甘菊乙醇酸氧化酶基因cDNA全长1 363 bp,编码369个氨基酸,命名为MmGO（GenBank登录号EU716626）,推测的MmGO分子量为40.32 kDa,等电点为8.99。系统进化分析表明,MmGO与芸苔的GO序列亲缘关系比较近。将该基因重组到pET-32a(+)中进行原核表达,经0.1 mmol·L^-1 IPTG,25℃诱导4 h,获得了具有较高表达水平的融合蛋白6×His MmGO,Western-blot证实表达的6×His-MmGO能与抗6×His的单抗发生特异性反应,分子量约为60 kDa,与预测的融合蛋白6×His-MmGO分子量相符。为进一步研究融合蛋白6×His-MmGO的活性和功能奠定了基础。     

胆固醇氧化酶基因的克隆与表达

胆固醇是人体中主要的固醇类化合物,人体内胆固醇主要来源于自身的合成,也有一部分来自食物。胆固醇代谢和输送的异常往往与动脉粥样硬化相关联,能够引起心肌梗死、中风、动脉瘤和胆石症等疾病。胆固醇的一些代谢产物如类甾醇和类甾烷酮有致癌作用。所以检测血浆中和食物中胆固醇的含量在临床上具有重要的意义［１,２］。 胆固醇氧化酶可以和胆固醇脂酶和过氧化氢酶复合在一起,作为血浆总胆固醇含量的诊断试剂。也可将这３种酶固定在膜上,做成酶电极,这样使用起来更方便。胆固醇氧化酶能够降低食品中的胆固醇含量,也可以将胆固醇氧…     

高等植物GA 20-氧化酶研究进展

GA20-氧化酶（GA 20-oxidase）是高等植物体内GA生物合成途径中最重要的限速酶,它能够催化从GA12到GA9及GA53到GA20-系列的氧化反应。作者对近年来有关GA20一氧化酶的特征,GA20一氧化酶基因及编码蛋白、GA20一氧化酶基因表达调控进行了综合评述,并对GA20一氧化酶基因转化在农业、林业、;园艺业方面的应用前景进行了展望。     

Expression of novel rice gibberellin 2-oxidase gene is under homeostatic regulation by biologically active gibberellins

We have cloned two genes for gibberellin (GA) 2-oxidase from rice (Oryza sativa L.). Expression of OsGA2ox2 was not observed. The other gene, OsGA2ox3, was expressed in every tissue examined and was enhanced by the application of biologically active GA. Recombinant OsGA2ox3 protein catalyzed the metabolism of GA₁ to GA₈ and GA₂₀ to GA₂₉-catabolite. These results indicate that OsGA2ox3 is involved in the homeostatic regulation of the endogenous level of biologically active GA in rice. Electronic Publication     

Dissection of GA 20-oxidase members affecting tomato morphology by RNAi-mediated silencing

GA 20-oxidase is a key enzyme involved in gibberellin (GA) biosynthesis. In tomato, the GA 20-oxidase gene family consists of three members: GA20ox1, GA20ox2, and GA20ox3. To investigate the roles of these three genes in regulating plant growth and development, we used RNA interference technology to generate three kinds of transgenic tomato plants with suppressed expression of each three individual genes. Suppression of GA20ox1 or GA20ox2 resulted in shorter stems, a decreased length of internodes, and small dark green leaves while plants with decreased expression of GA20ox3 had no visible changes on stems and leaves. The plants of the three transgenic lines can flower and set fruits normally, but the seeds from these plants germinated slower than that from the normal plants. Decreased levels of endogenous GAs were detected in the apex of the three transgenic lines. These results demonstrate that the three GA 20-oxidase genes play different roles in the control of plan vegetative growth, but show no effects on flower and fruit development.Equal contribution authors: J. Xiao and H. Li.     

Protein analysis of dwarfed transgenic rice plants overexpressing GA2-oxidase gene

Using 2-D electrophoresis, we analyzed proteins from transgenic rice overexpressing gibberellin acid (GA) catabolic enzyme, GA2-oxidase. These results indicate eight specific proteins differentially expressed in the transformed rice stems of T₁ generation, but non in case of T₂ generation. Proteins isolated from different stages of leaves of T₁ generation showed no significant differences, except one-month-old leaf, where five differentially expressed proteins are visible.This work was supported in part by a research project of an Identification and Analysis of Proteins for Gene Discovery and Elucidation of Functions of Useful Genes in Rice Genome from Ministry of Agriculture, Forestry and Fisheries, and also supported by a part of grant from the Program of Basic Research Activities for Innovative Biosciences. Martin Hajduch was supported by European Commission’s specific research and technological development program “Confirming the International Role of Community Research” 1998-2002 (EU Fellowship to Japan). The authors are solely responsible for the content of this paper and it does not represent the opinion of the Community, and the Community is not responsible for any of use that might be made of date appearing herein.     

Activation of gibberellin 2-oxidase 6 decreases active gibberellin levels and creates a dominant semi-dwarf phenotype in rice (Oryza sativa L.)

Gibberellin (GA) 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant dwarf and GA-deficient phenotype,with a final stature that was less than half of its wild-type counterpart.The endogenous bioactive GAs are markedly decreased in the H032 mutant,and application of bioactive GAs (GA3 or GA4) can reverse the dwarf phenotype.The integrated T-DNA was detected 12.8 kb u...     

Identification of a Peptide Mimic of Bioactive Gibberellins with Affinity to GA 2-Oxidase

Previously we reported the first example of peptide mimics of a small hydrophobic molecule, a phytohormone gibberellin. The second peptide mimic of gibberellin has been identified from random peptide libraries by its affinity to a type of catalyzing enzyme of gibberellins, which specifically recognizes bioactive gibberellins. These results suggest that even hydrophobic compounds can be mimicked by peptides.