Plant DNA Infectious Agents

Zusatztext

There has been recent rapid progress in the transformation of plants with foreign DNA, making use either of the natural routes of genetic invasion that viruses and bacteria have developed, or of chemical, mechanical and electrical tricks to make plant protoplast membranes permeable to nucleic acids. Genes integrated into plant virus genomes can be carried systemi cally from the initial site of infection into the rest of the plant. Genes placed between the borders of Agrobacterium tumefaciens T-DNA can be transferred into single cells or plant tissue, which then divides to produce wound calli, or as in the case of an Agrobacterium rhizogenes infection, grow out into new roots. Calli and roots can be grown into whole plants. If virus genomes are placed between the T-DNA borders, a very effective infectious route, termed "agroinfection", is established. Once inside a pro toplast, DNA finds its way into the nucleus where it can finally integrate into the resident chromosome and be expressed. Whether it can also find its way into chloroplasts is not yet clear, but at least translation products can be targeted into this organelle. Regeneration of whole organisms from single cells is a special feature of plants and offers a unique tool to study genes in a multicellular organism. In addition, as in animal cells, transcription and translation of trans forming genes can be studied in plant cells during "transient expression".

Autorenportrait

Inhaltsangabe1 The Molecular Biology of Cauliflower Mosaic Virus and Its Application as Plant Gene Vector.- I. Introduction.- II. The Biology of Cauliflower Mosaic Virus.- A. The Virus Particle.- B. The DNA of CaMV.- C. The Genetic Organisation of the CaMV.- 1. The Genes of CaMV.- 2. Transcripts of CaMV.- D. The Replication of CaMV.- E. Structural Homologies Between CaMV and Retroid Elements.- III. The Development of CaMV into a Plant Gene Vector.- A. Mutants of CaMV.- 1. Mutations in ORF II.- 2. Mutations in Other Regions of the CaMV Genome.- B. Translational Polarity.- C. Transducing Cauliflower Mosaic Virus Variants.- D. Defective Complementing Mutants of CaMV.- IV. Elements of CaMV as Tools in Plant Genetic Engineering.- V. Vector Based on Other Plant Viruses.- VI. Conclusion and Outlook.- VII. References.- 2 The Structure, Expression, Functions and Possible Exploitation of Geminivirus Genomes.- I. Introduction.- II. Genome Organisation.- A. Coding Regions.- B. Non-coding Regions.- III. Gene Expression.- IV. Gene Functions.- V. The Potential of Geminiviruses as Gene Vectors.- VI. References.- 3 cDNA Cloning of Plant RNA Viruses and Viroids.- I. General Introduction.- II. Construction of Full-Length cDNA Clones.- A. Introduction.- B. Synthesis of Double-Stranded cDNA.- C. Cloning Strategies.- D. Cloning in Transcription Vectors.- III. DNA Copies as Tools to Study the Molecular Biology of Plant RNA Viruses.- A. Introduction.- B. Infectivity of cDNA Clones.- i) Infectivity of DNA Copies.- ii) Infectivity of in vitro Transcripts from DNA Copies.- C. RNA Replication.- D. RNA Recombination.- E. Genetic Organisation and Gene Expression.- IV. Viroids and Satellites.- A. Introduction.- B. Molecular Cloning of Viroids.- C. Application of cDNA Clones.- i) Viroids.- ii) Satellite Viruses.- V. Diagnosis of Plant Diseases Using DNA Copies of Plant Viruses and Viroids.- A. Introduction.- B. Spot Hybridisation.- VI. Conclusions and Future Aspects.- VII. References.- 4 Agroinfection.- I. Introduction.- II. Potential Applications of Agroinfection.- A. Agrobacterium as an Organism for the Experimental Storage and Transmission of Plant Viruses.- 1. Storage and Safety.- 2. Efficiency and Flexibility.- 3. Release of Viral Genomes from the T-DNA.- 4. Analysis of T-DNA Transfer.- B. Transformation of Plant Cells with Viral Genetic Information.- 1. Transient Expression.- 2. Expression of Viral Genes in Host and Non-Host Plants.- 3. Transgenic Plants Containing Oligomers of Viral Genomes or Genome Components.- i) Complementation Between Different Components of a Multi-Component System.- ii) Analysis of in vitro Produced Mutant Viral Strains.- iii) Development of Proviral Vectors.- 4. Super-Infection of Plants Transgenic for Viral Sequences.- i) Cross-Protection.- ii) Complementation of Defective Viral Genes with Integrated Wild-Type-Genes; Development of Complementation Vectors.- III. Perspectives.- IV. References.- 5 The Mechanism of T-DNA Transfer from Agrobacterium tumefaciens to the Plant Cell.- I. General Introduction.- A. Scope of the Review.- B. Crown Gall Disease.- C. Molecular Basis of Neoplastic Transformation.- a) The Ti Plasmid and Its Organisation.- b) Functional Organisation of the T-DNA.- II. Early Events of Transformation.- A. Virulence Functions.- a) Chromosomal Virulence Region.- b) Organisation of the Virulence Region.- c) Regulation of vir Region Expression.- d) Nature of the Inducer.- B. T-DNA-Transfer.- a) The 25-bp Terminal Sequence.- b) Overdrive.- c) Analysis of the T-DNA/Plant DNA Junctions.- d) T-DNA Localisation and Structure Within the Plant Genome.- III. T-DNA Processing.- A. The Search of Processing Intermediates.- a) Genetic Assays.- b) Physical Assays.- c) Summary and Discussion.- B. Proteins Involved in T-DNA Processing.- a) Vir D Locus.- b) Vir C Locus.- c) Vir E Locus.- d) Vir F Locus.- IV. Conclusions.- V. References.- 6 Molecular Analysis of Root Induction by Agrobacterium rhizogenes.- I. Introduction.- II. Taxonomy.- III.

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