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Polyploidy – whole-genome duplication (WGD) – is a fundamental driver of biodiversity with significant consequences for genome structure, organization, and evolution. Once considered a speciation process common only in plants, polyploidy is now recognized to have played a major role in the structure, gene content, and evolution of most eukaryotic genomes. In fact, the diversity of eukaryotes seems closely tied to multiple WGDs. Polyploidy generates new genomic interactions – initially resulting in “genomic and transcriptomic shock” – that must be resolved in a new polyploid lineage. This process essentially acts as a “reset” button, resulting in genomic changes that may ultimately promote adaptive speciation. This book brings together for the first time the conceptual and theoretical underpinnings of polyploid genome evolution with syntheses of the patterns and processes of genome evolution in diverse polyploid groups. Because polyploidy is most common and best studied in plants, the book emphasizes plant models, but recent studies of vertebrates and fungi are providing fresh perspectives on factors that allow polyploid speciation and shape polyploid genomes. The emerging paradigm is that polyploidy – through alterations in genome structure and gene regulation – generates genetic and phenotypic novelty that manifests itself at the chromosomal, physiological, and organismal levels, with long-term ecological and evolutionary consequences.
Polyploidy – whole-genome duplication (WGD) – is a fundamental driver of biodiversity with significant consequences for genome structure, organization, and evolution. Once considered a speciation process common only in plants, polyploidy is now recognized to have played a major role in the structure, gene content, and evolution of most eukaryotic genomes. In fact, the diversity of eukaryotes seems closely tied to multiple WGDs. Polyploidy generates new genomic interactions – initially resulting in “genomic and transcriptomic shock” – that must be resolved in a new polyploid lineage. This process essentially acts as a “reset” button, resulting in genomic changes that may ultimately promote adaptive speciation. This book brings together for the first time the conceptual and theoretical underpinnings of polyploid genome evolution with syntheses of the patterns and processes of genome evolution in diverse polyploid groups. Because polyploidy is most common and best studied in plants, the book emphasizes plant models, but recent studies of vertebrates and fungi are providing fresh perspectives on factors that allow polyploid speciation and shape polyploid genomes. The emerging paradigm is that polyploidy – through alterations in genome structure and gene regulation – generates genetic and phenotypic novelty that manifests itself at the chromosomal, physiological, and organismal levels, with long-term ecological and evolutionary consequences.
Polyploidy plays an important role in biological diversity, trait improvement, and plant species survival. Understanding the evolutionary phenomenon of polyploidy is a key challenge for plant and crop scientists. This book is made up of contributions from leading researchers in the field from around the world, providing a truly global review of the subject. Providing broad-ranging coverage, and up-to-date information from some of the world’s leading researchers, this book is an invaluable resource for geneticists, plant and crop scientists, and evolutionary biologists.
Plant molecular biology has produced an ever-increasing flood of data about genes and genomes. Evolutionary biology and systematics provides the context for synthesizing this information. This book brings together contributions from evolutionary biologists, systematists, developmental geneticists, biochemists, and others working on diverse aspects of plant biology whose work touches to varying degrees on plant molecular evolution. The book is organized in three parts, the first of which introduces broad topics in evolutionary biology and summarizes advances in plant molecular phylogenetics, with emphasis on model plant systems. The second segment presents a series of case studies of gene family evolution, while the third gives overviews of the evolution of important plant processes such as disease resistance, nodulation, hybridization, transposable elements and genome evolution, and polyploidy.
This second of two volumes on Plant Genome Diversity provides, in 20 chapters, insights into the structural evolution of plant genomes with all its variations. Starting with an outline of plant phylogeny and its reconstruction, the second part of the volume describes the architecture and dynamics of the plant cell nucleus, the third examines the evolution and diversity of the karyotype in various lineages, including angiosperms, gymnosperms and monilophytes. The fourth part presents the mechanisms of polyploidization and its biological consequences and significance for land plant evolution. The fifth part deals with genome size evolution and its biological significance. Together with Volume I, this comprehensive book on the plant genome is intended for students and professionals in all fields of plant science, offering as it does a convenient entry into a burgeoning literature in a fast-moving field.
This volume brings together the disciplines of plant and animal genome research, and serves as an opportunity for scientists from both fields to compare results, problems and prospects.
It is said that "necessity is the mother of invention". To be sure, wheels and pulleys were invented out of necessity by the tenacious minds of upright citi zens. Looking at the history of mankind, however, one has to add that "Ieisure is the mother of cultural improvement". Man's creative genius flourished only when his mind, freed from the worry of daily toils, was permitted to entertain apparently useless thoughts. In the same manner, one might say with regard to evolution that "natural selection mere(y tnodifted, while redundanry created". Natural selection has been extremely effective in policing alleHe mutations which arise in already existing gene loci. Because of natural selection, organisms have been able to adapt to changing environments, and by adaptive radiation many new species were created from a common ancestral form. Y et, being an effective policeman, natural selection is extremely conservative by nature. Had evolution been entirely dependent upon natural selection, from a bacterium only numerous forms of bacteria would have emerged. The creation of metazoans, vertebrates and finally mammals from unicellular organisms would have been quite impos sible, for such big leaps in evolution required the creation of new gene loci with previously nonexistent functions. Only the cistron which became redun dant was able to escape from the relentless pressure of natural selection, and by escaping, it accumulated formerly forbidden mutations to emerge as a new gene locus.
The Genetics and Genomics of the Brassicaceae provides a review of this important family (commonly termed the mustard family, or Cruciferae). The family contains several cultivated species, including radish, rocket, watercress, wasabi and horseradish, in addition to the vegetable and oil crops of the Brassica genus. There are numerous further species with great potential for exploitation in 21st century agriculture, particularly as sources of bioactive chemicals. These opportunities are reviewed, in the context of the Brassicaceae in agriculture. More detailed descriptions are provided of the genetics of the cultivated Brassica crops, including both the species producing most of the brassica vegetable crops (B. rapa and B. oleracea) and the principal species producing oilseed crops (B. napus and B. juncea). The Brassicaceae also include important “model” plant species. Most prominent is Arabidopsis thaliana, the first plant species to have its genome sequenced. Natural genetic variation is reviewed for A. thaliana, as are the genetics of the closely related A. lyrata and of the genus Capsella. Self incompatibility is widespread in the Brassicaceae, and this subject is reviewed. Interest arising from both the commercial value of crop species of the Brassicaceae and the importance of Arabidopsis thaliana as a model species, has led to the development of numerous resources to support research. These are reviewed, including germplasm and genomic library resources, and resources for reverse genetics, metabolomics, bioinformatics and transformation. Molecular studies of the genomes of species of the Brassicaceae revealed extensive genome duplication, indicative of multiple polyploidy events during evolution. In some species, such as Brassica napus, there is evidence of multiple rounds of polyploidy during its relatively recent evolution, thus the Brassicaceae represent an excellent model system for the study of the impacts of polyploidy and the subsequent process of diploidisation, whereby the genome stabilises. Sequence-level characterization of the genomes of Arabidopsis thaliana and Brassica rapa are presented, along with summaries of comparative studies conducted at both linkage map and sequence level, and analysis of the structural and functional evolution of resynthesised polyploids, along with a description of the phylogeny and karyotype evolution of the Brassicaceae. Finally, some perspectives of the editors are presented. These focus upon the Brassicaceae species as models for studying genome evolution following polyploidy, the impact of advances in genome sequencing technology, prospects for future transcriptome analysis and upcoming model systems.
Polyploidy as a dramatic mutational event in the process of evolution has wide implications in nature and for the generation of new and improved crops. The three day Conference on POLYPLOIDY: BIOLOGICAL RELEVANCE focused on three aspects of this natural phenomenon: the first emphasized the characteristics of polyploidy, the second described the occurrence of polyploidy among plants and animals, and the third considered past and future areas of both fundamental and pragmatic research that involve polyploidy. New information relative to origin, cytogenetics, ecology, physiology, biochemistry, and populational studies stress the need to reexamine current views on the origins of polyploidy and its significance among both plants and animals. There are major differences in the occurrence of polyploidy between. plant groups and it is proving a much more common event among bisexual vertebrates than heretofore considered possible. Crop development and improvement must utilize approaches based fundamentally on more natural systems; in fact future research should focus more on polyploidy as a natural phenomenon that needs study at all levels of endeavor from field-oriented populational aspects to sophisticated molecular analyses and genome manipulations. This volume provides a summary of current knowledge of polyploidy pertinent to botanists, zoologists, and agriculturists who are interested in the evolution o~natural systems and who are concerned with the contribution that crop improvement can make to human well-being. Walter H. Lewis St. Louis, Missouri October, 1979 v ACKNOWLEDGMENTS The Host Committee thanks all speakers and moderators for their generous contribution to the Conference and to this volume.