Multifunctional grains for the future: genetic engineering for enhanced and novel cereal quality

Cereals provide more than half the world population’s calorific intake, and have a variety of other important uses as food and beverage ingredients, livestock feeds, and as sources of renewable energy and industrial components. The technology to genetically modify many important cereals is now well-established, thereby presenting new opportunities to produce cereals with enhanced quality and novel properties. In 2007, GM (genetically modified) maize with insect and herbicide resistance was grown on over 30 million hectares worldwide, yet to date, there are no GM cereals with enhanced or novel grain (end-use) qualities being grown in commercial farmers’ fields. This review will discuss some of the latest GM technology developments reported to enhance the quality of cereals for food and other uses. Developments and opportunities involving gene manipulation for starch and protein quality, as well as non-starch polysaccharides, phenolic compounds and micronutrients will also be discussed. The current paucity of GM cereals with enhanced grain quality is not related to the absence of technological progress, rather it is the regulatory and consumer acceptance issues that have slowed the release of these crops.     

Recent advances in genetic engineering for improvement of fruit crops

Fruits are one of the major sources of vitamins, essential nutrients, antioxidants and fibers in human diet. During the last two–three decades, genetic engineering methods based on the use of transgenes have been successfully adopted to improve fruit plants and focused mainly on enhanced tolerance to biotic and abiotic stresses, increased fruit yield, improved post harvest shelf life of fruit, reduced generation time and production of fruit with higher nutritional value. However, the development of transgenic fruit plants and their commercialization are hindered by many regulatory and social hurdles. Nowadays, new genetic engineering approaches i.e. cisgenesis or intragenesis receive increasing interest for genetic modification of plants. The absence of selectable marker gene in the final product and the introduced gene(s) derived from the same plant or plants sexually compatible with the target crop should increase consumer’s acceptance. In this article, we attempt to summarize the recent progress achieved on the genetic engineering in fruit plants and their applications in crop improvement. Challenges and opportunities for the deployment of genetic engineering in crop improvement programs of fruit plants are also discussed.     

The role of cuticle in fruit shelf-life

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Genetic architecture of apple fruit quality traits following storage and implications for genetic improvement

Accurate prediction of genetic potential and response to selection in breeding requires knowledge of genetic parameters for important selection traits. Data from breeding trials can be used to obtain estimates of these parameters so that predictions are directly relevant to the improvement program. Here, a factor allocation diagram was developed to describe the sampling design used to assess the quality of fresh and post-storage (2 months) fruit from advanced selection trial in an apple breeding program from which models for analyses were developed. Genetic variation was the largest source of variation for the fruit size, red colour type, proportion of red skin colour and lenticels, and instrumentally assessed fruit diameter, mass, puncture force and titratable acidity. In contrast, residual variation was the largest for fruit shape, juiciness, sweetness, aromatic flavour, eating and overall quality, and instrumental crispness. Genetic effects for traits were generally stable over fixed effects, except for a significant interaction with storage duration for firmness. Genetic correlations among traits were generally weak except between fruit mass (and diameter) and sensory size (0.98), titratable acidity and sensory acidity (0.97), puncture force and sensory firmness (0.96–0.90), crispness and juiciness (0.87), sweetness and aromatic flavour (0.84) and instrumental and sensory crispness (0.75). Predictions of the performance for seven commercial cultivars are presented. This study suggests that the Washington State apple production area can be treated as a single target environment and sufficient diversity exists to generate new elite cultivars. In addition, options for evaluating the efficiency of apple breeding are discussed.     

Both additivity and epistasis control the genetic variation for fruit quality traits in tomato

The effect of a gene involved in the variation of a quantitative trait may change due to epistatic interactions with the overall genetic background or with other genes through digenic interactions. The classical populations used to map quantitative trait loci (QTL) are poorly efficient to detect epistasis. To assess the importance of epistasis in the genetic control of fruit quality traits, we compared 13 tomato lines having the same genetic background except for one to five chromosome fragments introgressed from a distant line. Six traits were assessed: fruit soluble solid content, sugar content and titratable acidity, fruit weight, locule number and fruit firmness. Except for firmness, a large part of the variation of the six traits was under additive control, but interactions between QTL leading to epistasis effects were common. In the lines cumulating several QTL regions, all the significant epistatic interactions had a sign opposite to the additive effects, suggesting less than additive epistasis. Finally the re-examination of the segregating population initially used to map the QTL confirmed the extent of epistasis, which frequently involved a region where main effect QTL have been detected in this progeny or in other studies.     

BioModel engineering for multiscale Systems Biology

We discuss some motivational challenges arising from the need to model and analyse complex biological systems at multiple scales (spatial and temporal), and present a biomodel engineering framework to address some of these issues within the context of multiscale Systems Biology. Our methodology is based on a structured family of Petri net classes which enables the investigation of a given system using various modelling abstractions: qualitative, stochastic, continuous and hybrid, optionally in a spatial context. We illustrate our approach with case studies demonstrating hierarchical flattening, treatment of space, and hierarchical organisation of space.     

Phytohormones in fruit development and maturation

Phytohormones are integral to the regulation of fruit development and maturation. This review expands upon current understanding of the relationship between hormone signaling and fruit development, emphasizing fleshy fruit and highlighting recent work in the model crop tomato (Solanum lycopersicum) and additional species. Fruit development comprises fruit set initiation, growth, and maturation and ripening. Fruit set transpires after fertilization and is associated with auxin and gibberellic acid (GA) signaling. Interaction between auxin and GAs, as well as other phytohormones, is mediated by auxin-responsive Aux/IAA and ARF proteins. Fruit growth consists of cell division and expansion, the former shown to be influenced by auxin signaling. While regulation of cell expansion is less thoroughly understood, evidence indicates synergistic regulation via both auxin and GAs, with input from additional hormones. Fruit maturation, a transitional phase that precipitates ripening, occurs when auxin and GA levels subside with a concurrent rise in abscisic acid (ABA) and ethylene. During fruit ripening, ethylene plays a clear role in climacteric fruits, whereas non-climacteric ripening is generally associated with ABA. Recent evidence indicates varying requirements for both hormones within both ripening physiologies, suggesting rebalancing and specification of roles for common regulators rather than reliance upon one. Numerous recent discoveries pertaining to the molecular basis of hormonal activity and crosstalk are discussed, while we also note that many questions remain such as the molecular basis of additional hormonal activities, the role of epigenome changes, and how prior discoveries translate to the plethora of angiosperm species.     

双歧杆菌发酵果蔬汁营养成分分析及保质期观察

目的分析双歧杆菌发酵果蔬汁的营养成分及保质期观察。方法采用各种营养分析方法对双歧杆菌发酵果蔬汁进行主要营养成分的分析测定。结果双歧杆菌发酵果蔬汁营养丰富,含有蛋白质、脂肪、糖、水溶性维生素和多种微量元素,含有18种氨基酸,8种人体营养必需氨基酸。结论双歧杆菌发酵果蔬汁营养成分丰富,保质期长,作为一种营养食品饮料值得推广应用。     

Successes and prospects for genetic engineering]

The review of literature (1970-1976) on problems of gene engineering is given. Gene engineering is pointed out to be a new method of modern biology and a new page of modern molecular genetics. Gene engineering detected a real possibility of artificial creating living hybrid organisms, i.e. constructing functional recombinant DNA molecules according to a project of investigator, but not to possibilities of crossing. The determination of gene engineering (in contrast with genetical engineering) is given in the first division of the article. Genetical engineering is a construction of hybrid organisms on the basis of recombination between non-homologous chromosomes cy crossing. Genetical engineering is based on sex crossing, thus the application of this method is restricted by crossability (i.e. experiments in vivo), which possibilities are determined by taxonomical limits. Gene engineering is a new method of operating directly with genes. It permits constructing in vitro any hybrid genomes desirable. There is no limits of combining ability for gene engineering. Three main stages of constructing hybrid genomes should be taken into account for the proper determination of gene engineering as a method of genome constructing: 1) the gene isolation; 2) their cross-linking in vitro; 3) the transfer of hybrid DNA into recipient cell or its genome. The cardinal stage of gene engineering is the construction of hybrid DNA, cross-linking any initial DNAs from any remote animals, plants and bacteria. All the methods known of gene isolation are described. The chemical method of gene isolation is based on that case, when DNA of some gene differs in its physico-chemical characteristics from total DNA, for example, DNAs of genes coding ribosomal RNAs or sea urchine histone DNA. Isolation of promotors and operators using DNA dependent RNA polymerase, which recognizes promotors, repressor and operator DNA, should also be considered as the chemical method of gene isolation. Restrictase method, which is also well known, is convenuent because the restricts have long enough sticky ends, which is important for the following gene cross-linking. The method of total restriction, reported by Lederberg et al. and Debabov et al., is described. The phage method (in particular, Shimada method) is given, permitting the direct integration of lambda phage into a number of sites of Escherichia coli chromosome. Gene engineering method of gene isolation is mentioned, in particular, the data of Kameron et al. on hybrid phages carrying DNA ligase gene, and Clark a. Carbon on hybrid plasmids carrying triptophane and arabinose operons genes. These methods are called "shot gun". Methods of gene isolation from higher organisms are less developed. A method of gene isolation using so called colony hybridization (according to Grünstein and Hognes) is also given...     

Journalists and genetic engineering

Mass media coverage of genetic engineering is considered as an essential cause of the public image which this technology has. Because most people have only few experiences with this technology, the influence of journalists, who report on genetic engineering, seems to be obviously high. Which attitudes do these journalists have? How do they inform themselves? These and other questions are to be answered by a standardized survey among German journalists. For the first time the results of this study reveal the methods of investigation and source selection of 'genetic engineering journalists' and afford an insight into the journalistic climate of opinion on genetic engineering and its applications. There is clear evidence of an altogether positive global judgement of journalists reporting on this technology, which finds support in their immediate professional social environment.     

Significance of flower and fruit thinning on fruit quality

The effects of mechanical or chemical flower and fruit thinning on fruitquality were primarily by altering crop load. However, there were alsodirect effects of thinning agents. Fruit size was directly related tothinning intensity. In addition to crop load, age of wood, flower budquality, competition within clusters and canopy were important factorsaffecting the response to thinning. Short- and long-term thinningstudies identified two groups of quality components: Group 1characteristics include size, colour, skin performance, firmness andsugar and acid content of the fruit. Group 2 characteristics wererepresented by inorganic components, especially calcium and potassiumwhich are implicated in the susceptibility of fruit to physiologicaldisorders. While group 1 characteristics were improved by increasingthinning intensity, storability of the fruit was better at high than atlow crop loads. Therefore, a compromise between all quality requirementsmust be found for a good economic return. Establishing the trends ofthinning on the different quality parameters can help to select athinning strategy for local or regional conditions typically beingdetermined by growing and market conditions.     

Rational strain improvement for enhanced clavulanic acid production by genetic engineering of the glycolytic pathway in Streptomyces clavuligerus

Clavulanic acid is a potent beta-lactamase inhibitor used to combat resistance to penicillin and cephalosporin antibiotics. There is a demand for high-yielding fermentation strains for industrial production of this valuable product. Clavulanic acid biosynthesis is initiated by the condensation of L-arginine and D-glyceraldehyde-3-phosphate (G3P). To overcome the limited G3P pool and improve clavulanic acid production, we genetically engineered the glycolytic pathway in Streptomyces clavuligerus. Two genes (gap1 and gap2) whose protein products are distinct glyceraldehyde-3-phosphate dehydrogenases (GAPDHs) were inactivated in S. clavuligerus by targeted gene disruption. A doubled production of clavulanic acid was consistently obtained when gap1 was disrupted, and reversed by complementation. Addition of arginine to the cultured mutant further improved clavulanic acid production giving a greater than 2-fold increase over wild type, suggesting that arginine became limiting for biosynthesis. This is the first reported application of genetic engineering to channel precursor flux to improve clavulanic acid production.     

Biology of cord blood cells and future prospects for enhanced clinical benefit

Cord blood (CB) has served as a clinically beneficial source of hematopoietic stem (HSC) and progenitor (HPC) cells for transplantation and correction of a large number of malignant and non-malignant disorders. The capacity of CB to perform these functions is intimately related to the quality and quantity of HSC and HPC present in CB. This review covers the biology of HSC and HPC, efforts to expand these cells ex vivo for enhanced clinical utility that has thus far not been very successful, and recent studies on attempts to enhance the homing and engrafting capability of HSC as an alternative means for more effective use of the limited numbers of CB cells collected. This review also highlights the presence in CB of mesenchymal stem cells, unrestricted somatic stem cells, endothelial progenitor cells and immune cells. The presence and biology of these non-HSC/HPC may open up future possibilities for additional clinical benefit of CB, a product considered mainly for discard before its clinical transplantation potential was realized in the late 1980s.     

Programmable genetic circuits for pathway engineering

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Techniques for genetic engineering in mycobacteria

The study of mycobacterial genetics has experienced quick technical developments in the past ten years, despite a relatively slow start, caused by difficulties in accessing these recalcitrant species. The study of mycobacterial pathogenesis is important in the development of new ways of treating tuberculosis and leprosy, now that the emergence of antibiotic-resistant strains has reduced the effectiveness of current therapies. The tuberculosis vaccine strain M. bovis BCG might be used as a vector for multivalent vaccination. Also, non-pathogenic mycobacterial strains have many possible biotechnological applications. After giving a historical overview of methods and techniques, we will discuss recent developments in the search for alternative host strains and DNA transfer systems. Special attention will be given to the development of vectors and techniques for stabilizing foreign DNA in mycobacteria.