甜菜碱与植物耐盐基因工程

向非甜菜碱积累植物导入甜菜碱合成途径是提高植物耐盐性的策略之一。甜菜碱是一种无毒的有机小分子化合物。盐胁迫下,它能在植物细胞中迅速积累以维持细胞的渗透平衡,并对胞内的一些重要酶类起保护作用。编码甜菜碱合成酶的基因已被克隆,并应用于植物耐盐基因工程。本文介绍了甜菜碱的生理作用、合成酶及相关基因的特性,并结合本实验室的工作对甜菜碱基因工程及其进展作了简单的综述。     

甜菜碱与植物耐盐基因工程

向非甜菜碱积累植物导入甜菜碱合成途径是提高植物耐盐性的策略之一。甜菜碱是一种无毒的有机小分子化合物。盐胁迫下 ,它能在植物细胞中迅速积累以维持细胞的渗透平衡 ,并对胞内的一些重要酶类起保护作用。编码甜菜碱合成酶的基因已被克隆 ,并应用于植物耐盐基因工程。本文介绍了甜菜碱的生理作用、合成酶及相关基因的特性 ,并结合本实验室的工作对甜菜碱基因工程及其进展作了简单的综述     

类胡萝卜素合成的相关基因及其基因工程

类胡萝卜素具有多种生物功能,尤其在保护人类健康方面起着重要的作用,如它们是合成维生素A的前体,能够增强人体免疫力和具有防癌抗癌的功效。人体自身不能合成类胡萝卜素,必须通过外界摄入;但类胡萝卜素在许多植物中含量较低,并且很难用化学方法合成。随着类胡萝卜素生物合成途径的阐明及其相关基因的克隆,运用基因工程手段调控类胡萝卜素的生物合成已成为可能。本文综述了微生物和高等植物类胡萝卜素生物合成途径中相关基因的克隆,以及运用这些基因通过异源微生物生产类胡萝卜素和提高作物类胡萝卜素含量的基因工程研究进展。     

甜菜碱提高植物抗寒性的机理及其应用

甜菜碱是植物重要的渗透调节物质,在低温等逆境条件下,许多植物细胞中迅速积累甜菜碱以维持细胞的渗透平衡.对近几年来甜菜碱提高植物抗寒性的机理研究及其应用,包括甜菜碱的生物合成途径、低温胁迫下甜菜碱对植物的保护机理、甜菜碱合成酶基因的转化及外源甜菜碱在植物抗寒中的应用进行了综述.     

高等植物叶绿素生物合成的研究进展

叶绿素是植物叶绿体内参与光合作用的重要色素,其功能是捕获光能并驱动电子转移到反应中心.整个叶绿素生物合成过程(L-谷氨酰-tRNA→叶绿素a→叶绿素b)需要15步反应,涉及15种酶,迄今在模式植物拟南芥中已分离到27个编码这些酶的基因,完成了以拟南芥为代表的被子植物叶绿素生物合成全部基因的克隆.本文主要对近年来国内外有关植物叶绿素的生物合成过程及相关酶基因的克隆、生物合成途径中2个关键步骤(σ-氨基酮戊酸(ALA)合成和Mg离子插入原卟啉Ⅸ的调节)、影响叶绿素生物合成的主要因素(光、温度、营养元素等),以及叶绿素生物合成相关酶的其他生物学功能等的研究进展进行综述.     

植物抗旱耐盐基因的研究进展

近几年许多与植物抗旱耐盐相关基因被克隆和分析,同时通过转基因技术将这些基因转到植物中异源表达,能显著提高转基因植物的抗旱耐盐能力。这些基因主要包括渗透调节基因、蛋白类基因(如信号传导中的蛋白激酶基因)及转录因子等。在逆境条件下,渗透调节基因通过合成脯氨酸、甜菜碱、糖类和多胺类等渗透调节物质维持植物中的渗透平衡;蛋白激酶基因产物是细胞信号传导中的组分,这些基因能促进植物对干旱失水反应和逆境信号的传递,启动抗逆基因的表达;转录因子通过与相关基因的特异性结合来调控其表达,进而产生相关调控蛋白等物质增强植物在逆境中的生存能力。本文主要综述了这三类抗逆基因的研究现状及其生物学机理,讨论并分析这些基因在应用中尚待解决的问题,为发掘更多的抗逆性的基因资源和进一步开展分子育种工作提供参考。     

植物类胡萝卜素生物合成及其相关基因在基因工程中的应用

近年来类胡萝卜素生物合成基因的分离与功能鉴定,为应用基因工程技术改变植物体内类胡萝卜素成份和提高类胡萝卜素含量提供了新的基因资源.有关类胡萝卜素合成的生物化学及其在体内调控研究的新进展,使通过遗传操作调控植物体内类胡萝卜素生物合成途径成为可能.该文综述了类胡萝卜素生物合成途径及其相关基因的研究现状,并结合作者的工作介绍了应用转基因技术改变植物体内类胡萝卜素成份与含量的最新成功的事例.     

甜菜碱提高植物抗盐性的作用机理及其遗传工程研究进展

系统地讨论了甜菜碱在提高植物抗盐性中的作用机理及其国内外研究进展,并对甜菜碱生物合成过程中关键酶及其遗传工程的研究进展进行了综述。提出在进一步弄清甜菜碱提高植物抗盐性作用机理的基础上,应在重要作物中开展甜菜碱合成相关基因的导入,以期获得耐盐植物新品种。     

产番茄红素基因工程菌的研究进展

番茄红素是一种重要的类胡萝卜素,具有许多生物功能和生物活性,尤其在保护人类健康方面起着重要的作用。随着番茄红素生物合成途径的阐明及其相关基因的克隆,运用基因工程手段调控番茄红素的合成已经成为可能。本文首先综述了番茄红素生物合成途径及合成途径中相关基因的克隆,然后对近年来构建的番茄红素基因工程菌进行了全面的总结,包括：运用DNA重组技术使异源微生物大肠杆菌、酵母等生产番茄红素,以及通过过表达特定基因从而提高霉菌等产番茄红素的量,最后分析了改造过程中存在的主要问题,并展望了未来的研究方向。     

芪类化合物及其合成酶的研究进展

芪类化合物,是一种抗菌的植物抗毒素,因其具有抑菌、抗氧化、抗肿瘤等多种生物活性,越来越受到人们的重视。近年来与合成芪类化合物直接相关的芪合酶功能基因也相继在不同植物中被发现,以芪合酶为基础的转基因研究范围也不断扩大。对芪类化合物的生物合成途径、生物活性,芪合酶的结构、功能,以及芪合酶基因和转芪合酶基因的最新研究进展情况进行综述,以期为进一步的研究该类成分及获取相关功能基因而提供科学依据。     

植物耐盐基因工程研究进展

盐害是影响植物生长和作物产量的主要因素之一。用于提高植物耐盐性的基因工程方法很多,最常见的就是在植物中过量表达抗盐相关的功能基因,包括植物信号传导蛋白基因、植物离子通道蛋白基因和合成小分子渗透剂的酶基因等。归纳了近年来植物耐盐基因工程的研究进展,并展望了植物耐盐基因工程的研究前景。     

Chloroplast lysates support directed mutagenesis via modified DNA and chimeric RNA/DNA oligonucleotides

Chimeric RNA/DNA and modified DNA oligonucleotides have been shown to direct gene-conversion events in vitro through a process involving proteins from several DNA-repair pathways. Recent experiments have extended the utility of these molecules to plants, and we previously demonstrated that plant cell-free extracts are competent to support oligonucleotide-directed genetic repair. Using this system, we are studying Arabidopsis DNA-repair mutants and the role of plant proteins in the DNA-repair process. Here we describe a method for investigating mechanisms of plastid DNA-repair pathways. Using a genetic readout system in bacteria and chimeric or modified DNA oligonucleotides designed to direct the conversion of mutations in antibiotic resistance genes, we have developed an assay for genetic repair of mutations in a spinach chloroplast lysate system. We report genetic repair of point and frameshift mutations directed by both types of modified oligonucleotides. This system enables the mechanistic study of plastid gene repair and facilitates the direct comparison between plant nuclear and organelle DNA-repair pathways.     

Recognition and response in plant-pathogen interactions

Most plants are resistant to the majority of pathogens. Susceptibility is the exception to the more common state of resistance, i.e., being refractory to infection. However, plant pathogens cause serious economic losses by reducing crop yield and quality. Although such organisms are relatively simple genetic entities, in plants, the mechanisms underlying the generation of disease symptoms and resistance responses are complex and, often, unknown. The study of genes associated with plant-pathogen resistance addresses fundamental questions about the molecular, biochemical, cellular, and physiological means of these interactions. Over the past 10 years, the cloning and analysis of numerous plant resistance genes has led researchers to formulate unifying theories about resistance and susceptibility, and the co-evolution of plant pathogens and their hosts. In this review, we discuss the identification of response genes that have been characterized at the molecular level, as well as their putative links to various signaling pathways. We also summarize the knowledge regarding crosstalk among signaling pathways and plant resistance genes.     

A comparative genomic analysis of plant hormone related genes in different species

Plant hormones are small molecules that play important roles throughout the life span of a plant,known as auxin,gibberellin,cytokinin,abscisic acid,ethylene,jasmonic acid,salicylic acid,and brassinosteroid.Genetic and molecular studies in the model organism Arabidopsis thaliana have revealed the individual pathways of various plant hormone responses.In this study,we selected 479 genes that were convincingly associated with various hormone actions based on genetic evidence.By using these 479 genes as queries,a genome-wide search for their orthoiogues in several species(microorganisms,plants and animals) was performed.Meanwhile,a comparative analysis was conducted to evaluate their evolutionary relationship.Our analysis revealed that the metabolisms and functions of plant hormones are generally more sophisticated and diversified in higher plant species.In particular,we found that several phytohormone receptors and key signaling components were not present in lower plants or animals.Meanwhile,as the genome complexity increases,the orthologne genes tend to have more copies and probably gain more diverse functions.Our study attempts to introduce the classification and phylogenic analysis of phytohormone related genes,from metabolism enzymes to receptors and signaling components,in different species.     

Environmentally friendly approaches to genetic engineering

Summary Several environmental problems related to plant genetic engineering may prohibit advancement of this technology and prevent realization of its full potential. One such common concern is the demonstrated escape of foreign genes through pollen dispersal from transgenic crop plants to their weedy relatives, creating super weeds or causing gene pollution among other crops or toxicity of transgenic pollen to nontarget insects. The high rates of gene flow from crops to wild relatives (as high as 38% in sunflower and 50% in strawberries) are certainly a serious concern. Maternal inheritance of the herbicide resistance gene via chloroplast genetic engineering has been shown to be a practical solution to these problems. Another common concern is the suboptimal production of Bacillus thuringiensis (Bt) insecticidal protein or reliance on a single (or similar) B.t. protein in commercial transgenic crops, resulting in B.t. resistance among target pests. Clearly, different insecticidal proteins should be produced in lethal quantities to decrease the development of resistance. Such hyperexpression of a novel B.t. protein in chloroplasts has resulted in 100% mortality of insects that are up to 40 000-fold resistant to other B.t. proteins. Yet another concern is the presence of antibiotic resistance genes in transgenic plants that could inactivate oral doses of the antibiotic or be transferred to pathogenic microbes in the GI tract or in soil, rendering them resistant to treatment with such antibiotics. Cotransformation and elimination of antibiotic resistant genes from transgenic plants using transposable elements via breeding are promising new approaches. Genetic engineering efforts have also addressed yet another concern, i.e., the accumulation and persistence of plastics in our environment by production of biodegradable plastics. Recent approaches and accomplishments in addressing these environmental concerns via chloroplast genetic engineering are discussed in this review.     

Disease Resistance in Maize and the Role of Molecular Breeding in Defending Against Global Threat

Diseases are a potential threat to global food security but plants have evolved an extensive array of methodologies to cope with the invading pathogens. Non-host resistance and quantitative re- sistance are broad spectrum forms of resistance, and all kinds of resistances are controlled by extremely diverse genes called "R- genes". R-genes follow different mechanisms to defend plants and PAMP-induced defenses in susceptible host plants are referred to as basal resistance. Genetic and phenotypic diversity are vital in maize (Zea mays L.); as such, genome wide association study (GWAS) along with certain other methodologies can explore the maximum means of genetic diversity. Exploring the complete genetic archi- tecture to manipulate maize genetically reduces the losses from hazardous diseases. Genomic studies can reveal the interaction be- tween different genes and their pathways. By confirming the specific role of these genes and protein-protein interaction (proteomics) via advanced molecular and bioinformatics tools, we can shed a light on the most complicated and abstruse phenomena of resistance.     

Transient expression assays in grapevine: a step towards genetic improvement

In the past few years, the usefulness of transient expression assays has continuously increased for the characterization of unknown gene function and metabolic pathways. In grapevine (Vitis vinifera L.), one of the most economically important fruit crops in the world, recent systematic sequencing projects produced many gene data sets that require detailed analysis. Due to their rapid nature, transient expression assays are well suited for large‐scale genetic studies. Although genes and metabolic pathways of any species can be analysed by transient expression in model plants, a need for homologous systems has emerged to avoid the misinterpretation of results due to a foreign genetic background. Over the last 10 years, various protocols have thus been developed to apply this powerful technology to grapevine. Using cell suspension cultures, somatic embryos, leaves or whole plantlets, transient expression assays enabled the study of the function, regulation and subcellular localization of genes involved in specific metabolic pathways such as the biosynthesis of phenylpropanoids. Disease resistance genes that could be used for marker‐assisted selection in conventional breeding or for stable transformation of elite cultivars have also been characterized. Additionally, transient expression assays have proved useful for shaping new tools for grapevine genetic improvement: synthetic promoters, silencing constructs, minimal linear cassettes or viral vectors. This review provides an update on the different tools (DNA constructs, reporter genes, vectors) and methods (Agrobacterium‐mediated and direct gene transfer methods) available for transient gene expression in grapevine. The most representative results published thus far are then described.     

发根农杆菌Ri质粒rol基因研究进展及在林木改良上的应用

Ri质粒上携带的诱根基因的表达不仅能导致植物被感染部位形成大量的毛根,而且由毛根容易获得再生的转化植株,这些植株可表现出许多能稳定遗传的表型变异,在植物遗传改良中有着广阔的应用前景。20世纪80年代以来,国内外学者对发根农杆菌Ri质粒及其rol基因进行了广泛深入的研究。本文重点综述了农杆碱型发根农杆菌Ri质粒的结构与功能,rol基因的位点与特征,Ri质粒的转化与rol基因的表达对植物生长发育的影响及在林木遗传改良上应用等方面的研究现状,并讨论了Ri质粒rol基因在林木遗传改良应用上存在的问题与应用前景。     

Genetic Engineering of Plants to Enhance Selenium Phytoremediation

Referee: Dr. Dean A. Martens, USDAARS Southwest Watershed, Research Center, 200 E. Allen Road, Tucson, AZ 85719 Phytoremediation is the use of plants to remove, contain, or render harmless environmental pollutants. In recent years, much attention has been focused on the improvement of such technologies for this purpose. In this review, we introduce selenium phytoremediation and describe the attempts made to enhance it through genetic engineering. Initial efforts have taken advantage of the knowledge of the enzymatic pathways for selenium assimilation and volatilization, especially by overexpressing genes of rate-limiting enzymes in plants. Another possible approach is to introduce additional metabolic pathways from selenium hyperaccumulators or organisms other than plants that can help detoxify selenium compounds. In this way the capacity of plants to take up, accumulate, and volatilize compounds can be increased beyond that of any naturally occurring plant species. Here we report on the progress that has been made in overexpressing potentially important enzymes involved in the selenium/sulfur pathways and discuss possible future directions in the enhancement of phytoremediation through genetic engineering.