Recognition in Microbe-Plant Symbiotic and Pathogenic Interactions

This volume comprises the lectures of the speakers at the NATO Advanced Research Workshop held at the Congress Centre The Flevohof at Biddinghuizen, The Netherlands, May 11-16, 1986. The purpose of the workshop was to bring together experts in symbiosis, plant pathology and plant molecular biology in order to discuss recent progress in the field of microbe -plant re­ cognition at the molecular level, to promote integration of various disciplines, and to define recommendations for future research and applications. Plants have developed a variety of sophisticated defence mechanisms to cope with an environment in which many different microbes live. Most microbes which colonize plant tissues are harmless. Some microbes have developed ways to attack plants successfully, resulting in enormous losses of crop yields. Other microbes have reached an agreement with the host plant which is beneficial for both: these microbes live in symbiosis with the plant and provide their host plant for example with substantial amounts of atmospheric nitrogen. Chemical protection of crops is a necessity in modern crop management but this treatment has some negative effects as well. Therefore scientists are looking for alternative, biological, ways to control crop pests. Against this background specialists from eleven countries discussed the results of their most recent work on the molecular background of microbe -plant interactions. It appeared that, in order to capitalize the recent rapid progress made in the mole­ cular genetical studies on Rhizobium-legume and pathogen-host plant interactions, a multidisciplinary approach is required.

I. Recognition in Nodulation by Rhizobium.- Genetic analysis of Rhizobium-plant interactions.- Respective roles of common and specific Rhizobium meliloti nod genes in the control of lucerne infection.- Infection mutants of Rhizobium meliloti are altered in acidic exopolysaccharide production.- Intercellular communication and recognition in the Rhizobium-legume symbiosis.- Promoters and operon structure of the nodulation region of the Rhizobium leguminosarum symbiosis plasmid pRL1JI.- Manipulation of nodulation specificity in the pea-Rhizobium leguminosarum symbiosis.- Bradyrhizobium japonicum genes involved in soybean root-nodule development.- Nodulation of soybean: Bradyrhizobium japonicum physiology and genetics.- Attachment of Rhizobium leguminosarum to pea root hair tips.- Specificity of Rhizobium(Galega) ― Galega-interaction.- Flavones induce expression of the nodulation genes in Rhizobium.- Induction of Rhizobium nod genes by flavonoids: differential adaptation of promoter, nodD gene and inducers for various cross-inoculation groups.- Induction of Rhizobium leguminosarumnod genes by flavonoids is antagonized by other plant-specified aromatic compounds.- Fractionation of Rhizobium leguminosarum cells into outer membrane, cytoplasmic membrane, periplasmic and cytoplasmic components.- A study of surface interactions between Rhizobium bacteroids and the peribacteroid membrane using monoclonal antibodies.- Nodulins involved in early stages of pea root nodule development.- II. Recognition in Pathogen ― Plant Interaction.- Pathogenic strategies of fungi.- The molecular basis of the Agrobacterium-plant interaction ― Characteristics of Agrobacterium virulence genes and their possible occurrence in other plant-associated bacteria.- T-region transfer from Agrobacterium tumefaciens to plant cells: functional characterization of border repeats.- Cloning of DNA sequences from Azospirillum brasilense, homologous to Rhizobium nod genes and Agrobacterium vir genes.- Attachment of Agrobacterium tumefaciens to plant host cells.- Role of fimbriae and pili in the attachment of Klebsiella, Enterobacter and Pseudomonas to plant surfaces.- Race specific resistance to Bremia lactucae is expressed by lettuce cells in suspension culture.- Interaction of fungal polygalacturonase with plant proteins in relation to specificity and regulation of plant defense response.- A model system for the study of fungus ― host surface interactions: adhesion of Phytophthora megasperma to protoplasts and mesophyll cells of soybean.- Ultrastructural studies of surface interactions during adhesion and infection by ericoid endomycorrhizal fungi.- Structural modifications of the fungal wall before and during VAM symbiosis.- III. Recognition in Plant Defence.- Occurrence of race-specific elicitors in the host pathogen interaction tomato-Cladosporium fulvum.- Studies on the role of carbohydrates in host-microbe interactions.- Biochemical interactions of plants with potentially pathogenic fungi.- Stimulation of phytoalexin formation in fungus-infected plants and elicitor-treated cell cultures of parsley.- Recognition and response in plant: pathogen interactions.- Phytoalexin synthesis in soybean following infection of roots with Phytophthora megasperma or treatment of cell cultures with fungal elicitor.- Elicitation of indole alkaloid biosynthesis in periwinkle.- Expression of plant genes in the hypersensitive reaction of French bean (Phaseolus vulgaris) to the plant pathogenic bacterium Pseudomonas syringae pv. phaseolicola.- Hydroxyproline-rich glycoproteins (HRGPs) in infected plants: signaling, accumulation and gene expression.- IV. Recognition in Biological Crop Pest Control.- A model genetically engineered pesticide: cloning and expression of the Bacillus thuringiensis subsp. Kurstaki ? -endotoxin into Pseudomonas fluorescens.- Molecular aspects of plant growth affecting Pseudomonas species.- The iron-uptake system of the plant-growth-stimulating Pseudomonas putida WCS358: genetic analysis and properties and structure analysis of its siderophore.- Role of flagella of the plant growth stimulating Pseudomonas fluorescens isolate WCS374 in the colonization of potato roots.- Conditions in the rhizosphere in relation to microbial development.- V. Recommendations for Future Research and Applications.- Consensus and perspective on Rhizobium.- Prospects for novel plant disease control rationales.- Plant-Agrobacterium interaction.- Recognition, elicitors and the hypersensitive reaction.- Molecular analysis of plant defence mechanisms.