Molecular Genetics Of Plant Microbe Interactions 1988

Gene-for-gene recognition. Characterization of avirulence genes from pseudomonas syringae pathovars and races. Search for new symbiotic genes in rhizobium meliloti genome involved in the infection process of alfafa nodules. A molecular analysis of the host range genes of rhizobium trifolii. Signal recognition responses in the rhizobium trifolii-whith clover symbiosis. Genetic analysis of the role of exopolysaccharides in rhizobium symbiosis. Characterization of polysaccharides of rhizobium meliloti succinoglycan mutants, and properties of the second exopolysaccharide EPSb.Signal exchange and metabolic interaction. Symbiosis. Pathogenicity. Plant genetics.

Increased interest in the basic biology of plants and microorganisms stems from the fact that crop productivity is directly affected by plant-microbe interactions. In spite of the fact that plants exist in the environment amongst diverse species of microorganisms, only a few ever establish a direct relationship. Emerging awareness concerning the indirect effect of microbial association on plant growth and the possibility of using one microbe against another for controlling pathogenic interactions is at the genesis of new fields of studies. The primary reason for a microbe to associate with· photoautotrophic organisms (plants) is to tap its nutritional requirements, fixed carbon, as a source of energy. By hook or by crook, a microbe must survive. Some have evolved mechanisms to exploit plants to develop a niche for their biotropic demands. When in contact with a living plant, microorganisms may live in a passive association using exudates from the plant, invade it pathogenically or coexist with it in symbiosis. The plant responds to the interloper, either reacting in a hypersensitive manner to contain the invasion of pathogens, or by inducing a set of genes that leads toward symbiosis, or by simply succumbing to the invader. Thus, prior to contact wi th the plant, mic roorganism is able to sense the presence of the host and activate accordingly a set of genes required for the forthcoming interaction, whether symbiotic or pathogenic.

Several fundamental advances were announced at the Seventh International Symposium on Molecular Plant--Microbe Interactions held in Edinburgh in 1994. These included the cloning and identification of plant resistance genes involved in recognition of pathogens; the description of genetically engineered plants with novel resistance to pathogens; characterization of the molecular basis of pathogenicity of fungal and bacterial plant pathogens; and the mechanisms of communication used during recognition between symbiotic rhizobia and their host legumes. Participants in the Symposium contributed a series of papers that represent the leading edge of research in this important area of plant and microbial science. These articles are brought together to form this book, which will be essential reading for research workers, advanced students and others interested in keeping abreast of this rapidly developing area.

Overview. Concepts and terminology in plant-microbe interactions. Factors in pathogenesis. Microbial enzyne regulation and its importance for pathogenicity. Genetics of host-parasite systems: a prospectus for molecular biology. Approaches and tools for research. Diagnostic approaches for the rapid and specific detection of plant viruses and viroids. Theory and practice of genetic engineering. Development of plant vectors. Mutant selection. Molecular biology of recognition. Concepts and experimental approaches in host-microbe recognition. Adsorption of bacteria to plant surfaces. Plant response to the environment. Genetics of rhizobium nodulation. Systemic responses to wounding. Genetic and molecular aspects of resitance induced by infections or chemicals. Plant tumorigenesis. Biological control. Epiphytic microbes as biological control agents. Hypovirulence. A model to explain the "Cross protection" phenomenson shown by plant viruses and viroids.

Proceedings of the 5th International Symposium on the Molecular Genetics of Plant-Microbe Interactions; Interlaken, Switzerland, September 9-14, 1990