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Interdependence between species is a law of nature. The degree of this interdependence is vividly evident in the plant-microbial world. Indeed, there is no axenic plant in nature and one finds various forms of interac tions between these two kingdoms ranging from completely innocuous to obligate parasitic. Most of these interactions are poorly understood at the molecular and physiological levels. Only those few cases for which a molecular picture is emerging are discussed in this volume. With the advent of recombinant DNA technology and the realization that some of these interactions are very beneficial to the host plant, a spate of activity to understand and manipulate these processes is occurring. Microbes interact with plants for nutrition. In spite of the large number of plant-microbe interactions, those microbes that cause harm to the plants (i. e. , cause disease) are very few. It is thus obvious that plants have evolved various defense mechanisms to deal with the microbial world. The mecha nisms for protection are highly diverse and poorly understood. Some pathogens have developed very sophisticated mechanisms to parasitize plants, an excellent example for this being crown gall caused by a soil bac terium, Agrobacterium tumefaciens. A remarkable ingenuity is exhibited by this bacterium to manipulate its host to provide nitrogenous compounds which only this bacterium can catabolize. This is carried out by a direct gene transfer mechanism from bacteria to plants.
List of contents
Section I. Recognition.- 1 Host Specificity in Rhizobium-Legume Interactions.- 2 Interaction of Agrobacterium tumefaciens with the Plant Cell Surface.- Section II. Symbiosis.- 3 Legume-Rhizobium-Symbiosis: Host's Point of View.- 4 Rhizobium-Leguminosae Symbiosis: The Bacterial Point of View.- 5 Nitrogen Assimilation in the Legume-Rhizobium Symbiosis: A Joint Endeavour.- 6 Hydrogenase and Energy Efficiency in Nitrogen Fixing Symbionts.- 7 Symbiotic Relationships in Actinorhizae.- 8 Host-Fungus Specificity, Recognition and Compatibility in Mycorrhizae.- 9 Molecular Biology of Stem Nodulation.- Section III. Plant Tumor Induction.- 10 Induction of Cell Proliferation by Agrobacterium tumefaciens and A. Rhizogenes: A Parasite's Point of View.- 11 Gene Organization of the Ti-Plasmid.- 12 Phytohormone-Mediated Tumorigenesis by Plant Pathogenic Bacteria.- Section IV. Plant Pathogens and Defence Mechanisms.- 13 Genetic and Biochemical Basis of Virulence in Plant Pathogens.- 14 Defense Responses of Plants.
