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(More customer reviews)This book gives a useful and fascinating overview of the status of transgenic strategies in insects as it was known in the year 2000. Written by experts in the field, it will introduce both biologists and non-biologists to many of the techniques used for the introduction of transgenes in insects. Readers are expected to have a fairly strong background in molecular genetics, but it could still be profitably read by anyone who is curious about this exciting technology. Due to space constraints, only a few of the articles will be reviewed here.
The first article gives a historical introduction to gene transfer in insects. The P-Element transformation was the first transposon-based system for transforming the germline in D. melanogaster efficiently and stably. This transposon is an example of the Class II short inverted terminal repeat transposons, and its high mobility made it a successful for Drosophila transformation. The P vector however was not successful in non-drosophilid insects, and therefore other choices for vector-mediated transfer were researched. Some of these are discussed in this article, such as the hobo transposon, Hermes, Minos (first to successfully transform a non-drosophilid, the medfly), piggyBac (second successful transformation agent in medflies), and the mariner element. Approaches to creating transient systems, employing viral and symbiont vectors, are also discussed.
In article 7, pantropic retroviral vectors for gene transfer in insects are discussed. These arose from the genetic modification of the Moloney murine leukemia virus in order that it contain the G envelope protein from the vesicular stomatitis virus (VSV-G). These vectors are considered to be stable once inserted into the genome and are incapable of self-propagation. Most importantly, these vectors are now extensively used for human gene therapy protocols. The somatic infection of larvae using these vectors has been accomplished in D. melanogaster, Aedes triseriatus, Culex tarsalis (the western encephalitis mosquito), Anopholes gambiae (the malaria mosquito), and Manduca sexta (the tobacco hawkmoth).
Article 8 overviews densonucleosis viruses as transducing systems for insects. These viruses are linear single-stranded DNA molecules between 4000 and 6000 nucleotides in length that it seems are restricted to arthropods. The primary application of these vectors has been to deliver genes into mosquitoes for the laboratory study of gene expression. It is hoped that they will be instrumental in control programs against mosquitoes. These viruses have a limited host range however, being restricted to the Aedes, Culex, and Culiseta mosquitoes. They are also considered to be limited in scope as gene-transfer vectors due to their small genome size and due to their (icosahedral) shape.
In the ninth article, RNA virus expression systems based on the Sindbis virus for efficiently transducing mosquito cells and allowing stable gene expression in various species of mosquitos, such as the yellow fever mosquito (Aedes aegypti), the eastern treehole mosquito (Aedes triseriatus), the northern house mosquito (Culex pipiens), and Anopholes gambiae, are discsussed. The Sindbis virus is an alphavirus, with a single-stranded RNA genome. The article discusses the protein expression in the saliva of Culex pipiens, in the midgut of Aedes aegypti, and the expression of antiviral RNAs in Aedes aegypti and Aedes triseriatus.
In article 11, the role of polydnaviruses in insect transgenic strategies is discussed. These viruses are multisegmented DNA viruses that are found exclusively in the female reproductive tracts of some wasps. Segmentation in the polydnavirus genomes is thought to have evolved in order to increase the copy number of essential viral genes. They are known to integrate stably into the chromosomal DNA of the cell line of a gypsy moth, and to infect and integrate in lepidopteran and coleopteran cell cultures. They are apparently difficult to engineer however, and but the author of the article believes that their impact may lie in pointing the way to other methods for performing transgenesis.
Article 12 discusses the Hermes vector for transforming insects other than D. melanogaster. First discovered in M. domestica (the common housefly), cell lines of Anopheles gambiae were stably transformed by Hermes, and Hermes has been transposed in the embryos of Aedes aegypti. It is described in the article as having a wide host range, with accurate transposition occurring in twelve species of insects.
In article 13, the genetic engineering of insects with mariner transposons is discussed, The mariner element was first isolated from Drosophila mauritiana, and the mariner family of transposons is known to be widespread in animal genomes. This has caused some to be concerned about the risks involved for active mariners released in insect control programs could invade other genomes, such as human genomes. The article describes the evidence of recent and ancient horizontal gene transfers between animal hosts as being "overwhelming." The authors of the article though believe that one should not be concerned about releasing transgenic insects created with mariners into the environment. They give several reasons for not being concerned, one being that when nonautonomous mariners are used using a transient transposase, the resultant transformants are stable. In addition, the timescales involved are too long for horizontal gene transfer to be a significant risk, with over 100, 000 years being quoted as the most recent event for its occurrence. Only two mariner elements have invaded the human genome in the last 100 million years.
In the fourteenth article, the tagalong (TFP3) and piggyBac elements, both transposable elements of the TTAA-specific family, are reviewed in regards to their utility in the transformation of insects. The piggyBac element was first isolated from a nucleopolyhedrosis virus which infects cell cultures of the cabbage looper moth (Trichoplusia ni). The authors discusses several successful piggyBac transformations, such as in D. melanogaster, Aedes aegypti, Anopholes Gambiae, Bombyx mori (the domestic silk moth), Pectinophora gossypiella (the pink bollworm), and Tribolium castaneum (the red flour beetle). The horizontal transmission of piggyBac among species is considered to be a viable possibility for the authors, and they therefore devote a section to the safety concerns involved with the release of transgenic insects.
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Imagine scientists controlling the transmission of certain diseases through the genetic modification of mosquitoes. Eradicating harmful insects without the use of pesticides. Or increasing the fertility of some insects who in turn eat harmful arthropods or even a plant pathogen. Those are just a few of the real-world applications of insect transgenesis, which offers substantial benefits to humankind-whether it be in improving agricultural productivity or reducing the spread of insect-vectored diseases.Insect Transgenesis: Methods and Applications is the first publication to describe in a comprehensive manner the various methodologies available, possible applications, and the risk assessment and regulatory issues involved in this fascinating area of research.Divided into several areas of interest, the book starts with an overview of the history and methodology of insect gene transfer. The book then examines gene targeting by homologous recombination and recombination systems, and systems for transgenic selection, including visible eye color markers, chemical resistance, and fluorescent proteins. Other sections consider the use of various vector systems to integrate DNA into a host genome or to express foreign genes in a host organism.The work concludes with strategies for the use of transgenic insects, including examples for agricultural pests and vectors of disease. Of particular interest are the final chapters that discuss risk assessment considerations and governmental regulatory procedures for the transport and release of transgenic insects.
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