Advances In Molecular Genetics Of Plant Microbe Interactions Vol 2

Research on the interaction between plants and microbes continues to attract increasing attention, both within the field as well as in the scientific community at large. Many of the major scientific journals have recently reviewed various aspects of the field. Several papers dealing with plant-microbe interactions have been featured on the covers of scientific publications in the past several months, and the lay press have recently presented feature articles of this field. An additional sign of the interest in this field is that the International Society of Molecular Plant-Microbe Interactions has almost 500 members. This book is a collection of the papers that were given at the Sixth Inlernational Symposium on the Molecular Genetics of Plant-Microbe Interactions which was held in Seattle, Washington in July, 1992. Approximately 650 scientists attended and approximately 50 lectures covering the topics of Agrobacterium-plant interactions, Rhizobium-plant interactions, bacteria-plant interactions, fungal-plant interactions and new aspects of biotechnology were presented. In addition, many sessions were devoted to the plant response to the microbe. Over 400 posters were presented of which the authors of 20 were selected to give an oral presentation. These papers are included in this volume as well. The symposium also included speakers whose research interests are not directly related to plant-microbe interactions but who are at the cutting edge of research areas that impact on the theme of the symposium. These individuals kindly agreed to summarize their talks and their papers are also included.

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.

Research on the interaction between plants and microbes has attracted considerable attention in recent years. The use of modem genetic techniques has now made possible a detailed analysis both of plant and of microbial genes involved in phytopathogenic and beneficial interactions. At the biochemical level, signal molecules and their receptors, either of plant or of microbial origins, have been detected which act in signal transduction pathways or as co-regulators of gene expression. We begin to understand the molecular basis of classical concepts such as gene-for-gene relationships, hypersensitive response, induced resistance, to name just a few. We realize, and will soon exploit, the tremendous potential of the results of this research for practical application, in particular to protect crop plants against diseases and to increase crop yield and quality. This exclung field of research, which is also of truly interdisciplinary nature, is expanding rapidly. A Symposium series has been devoted to it which began in 1982. Recently, the 5th International Symposium on the Molecular Genetics of Plant-Microbe Interactions was held in Interlaken, Switzerland. It brought together 640 scientists from almost 30 different countries who reported their latest research progress in 47 lectures, 10 short oral presentations, and on over 400 high-quality posters. This book presents a collection of papers that comprehensively reflect the major areas under study, explain novel experimental approaches currently in use, highlight significant advances made over the last one or two years but also emphasize the obstacles still ahead of us.

This volume presents the latest research findings in molecular plant-microbe interactions, based on presentations of leading international scientists at the Sixth International Symposium on this subject. From these presentations it is clear that the field has made enormous advances in the past several years. In addition to the text on plant-microbe interactions, a number of experts in fields peripherally related to the main subject of the symposium also participated, and these individuals have also contributed to the present volume. This published material is very up-to-date, representing the cutting edge of current research. For anyone interested in learning of the latest advanced in this rapidly moving field, this volume is required reading.

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.

Plant-Microbe Interactions, Volume 2 Volume 1 of this series has made its appearance and dealt forcefully with impor tant current topics in the field of plant-microbe interactions. We believe that the quality of those chapters was high and should serve as a focal point for the state of the art as well as an enduring reference. Volume 2 builds upon these accom plishments. Chapter 1 discusses the fascinating lipo-chitin signal molecules from Rhizo bium, aspects regarding their biosynthesis, and the basis for host specificity. These molecules are a cardinal example of how microorganisms influence plant development and stimulate speculation that they have identified a previously un known aspect of plant hormone activity. Chapter 2 continues the discussion of Rhizobium by considering the trafficking of carbon and nitrogen in nodules. Al though the ostensible advantage of nodules to plants is the fixation of atmos pheric nitrogen, the actual process involved in supplying reduced nitrogen to the plant host is complex.