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Evolution & Development,
1999]
Developmental constraints have been defined as biases on the production of variant phenotypes or limitations on phenotypic variability caused by the structure, character, composition, or dynamics of developmental systems". The term has widely been discussed, but is far from being generally accepted. One reason might be that is has so far not been possible to test experimentally the concept of restraint. Experimental tests are difficult because the hypothesis is supported only by the failure or the limitation of seeing phenotypic variation, which can always hypothetically be explained by stabilizing selection. This article suggests an approach to study the potential molecular basis for developmental constraints.
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Bioessays,
1997]
To understand how morphological characters change during evolution, we need insight into the evolution of developmental processes. Comparative developmental approaches that make use of our fundamental understanding of development in certain model organisms have been initiated for different animal systems and flowering plants. Nematodes provide a useful experimental system with which to investigate the genetic and molecular alterations underlying evolutionary changes of cell fate specification in development, by comparing different species to the genetic model system Caenorhabditis elegans. In this review, I will first discuss the different types of evolutionary alterations seen at the cellular level by focusing mainly on the analysis of vulva development in different species. The observed alterations involve changes in cell lineage, cell migration and cell death, as well as induction and cell competence. I then describe a genetic approach in the nematode Pristionchus pacificus that might identify those genetic and molecular processes that cause evolutionary changes of cell fate specification.
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Curr Opin Genet Dev,
2000]
Multiple evolutionary variations occur in the cellular and genetic programming of nematode development. Many changes involve alterations of inductive interactions. Surprisingly, inductive processes vary during evolution, irrespective of changes in the final cell lineages and morphological structures. Genetic studies in some nematodes also shed light on the underlying mechanisms of evolutionary change.
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Nat Rev Genet,
2009]
There has been a recent trend in evolutionary developmental biology (evo-devo) towards using increasing numbers of model species. I argue that, to understand phenotypic change and novelty, researchers who investigate evo-devo in animals should choose a limited number of model organisms in which to develop a sophisticated methodological tool kit for functional investigations. Furthermore, a synthesis of evo-devo with population genetics and evolutionary ecology is needed to meet future challenges.
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Dev Biol,
1996]
Nematodes provide a useful experimental system with which to investigate the evolution of development at the cellular, genetic, and molecular levels. Building on an understanding of vulval development in Caenorhabditis elegans, analysis of vulval development has been extended to a number of other species in three families of the Nematode phylum. Changes have occurred in most aspects of vulval development: alteration in the number of cells competent to participate in vulval development by changes in apoptosis; changes in the relative contributions of position-dependent predisposition toward particular fates (prepattern), inductive signaling and lateral signaling; and in the specific lineages generated by vulval precursor cells. Genetic analysis of one species in which only three vulval precursor cells are present identified a mutation that increases the number of vulva precursor cells toward that found in C. elegans.
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Wiley Interdiscip Rev Dev Biol,
2012]
The free-living nematode Caenorhabditis elegans is one of the most important model organisms in all areas of modern biology. Using the knowledge about C. elegans as a baseline, nematodes are now intensively studied in evolution and development. Evolutionary developmental biology or for short, 'evo-devo' has been developed as a new research discipline during the last two decades to investigate how changes in developmental processes and mechanisms result in the modification of morphological structures and phenotypic novelty. In this article, we review the concepts that make nematode evo-devo a successful approach to evolutionary biology. We introduce selected model systems for nematode evo-devo and provide a detailed discussion of four selected case studies. The most striking finding of nematode evo-devo is the magnitude of developmental variation in the context of a conserved body plan. Detailed investigation of early embryogenesis, gonad formation, vulva development, and sex determination revealed that molecular mechanisms evolve rapidly, often in the context of a conserved body plan. These studies highlight the importance of developmental systems drift and neutrality in evolution.
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Curr Biol,
2011]
Phenotypic plasticity refers to the ability of an organism to adopt different phenotypes depending on environmental conditions. In animals and plants, the progression of juvenile development and the formation of dormant stages are often associated with phenotypic plasticity, indicating the importance of phenotypic plasticity for life-history theory. Phenotypic plasticity has long been emphasized asa crucial principle in ecology and as facilitator of phenotypic evolution. In nematodes, several examples of phenotypic plasticity have been studied at the genetic and developmental level. In addition, the influence of different environmental factors has been investigated under laboratory conditions. These studies have provided detailed insight into the molecular basis of phenotypic plasticity and itsecological and evolutionary implications. Here, we review recent studies on the formation of dauer larvae in Caenorhabditis elegans, the evolution of nematode parasitism and the generation of a novel feeding trait in Pristionchus pacificus. These examples reveal a conserved and co-opted role of an endocrine signaling module involving the steroid hormone dafachronic acid. We will discuss how hormone signaling might facilitate life-history and morphological evolution.
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Annu Rev Genet,
2011]
Nematodes are found in virtually all habitats on earth. Many of them are parasites of plants and animals, including humans. The free-living nematode, Caenorhabditis elegans, is one of the genetically best-studied model organisms and was the first metazoan whose genome was fully sequenced. In recent years, the draft genome sequences of another six nematodes representing four of the five major clades of nematodes were published. Compared to mammalian genomes, all these genomes are very small. Nevertheless, they contain almost the same number of genes as the human genome. Nematodes are therefore a very attractive system for comparative genetic and genomic studies, with C. elegans as an excellent baseline. Here, we review the efforts that were made to extend genetic analysis to nematodes other than C. elegans, and we compare the seven available nematode genomes. One of the most striking findings is the unexpectedly high incidence of gene acquisition through horizontal gene transfer (HGT).
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Curr Opin Cell Biol,
2001]
Cells are important modules of biological systems, and many evolutionary alterations involve changes in cell determination and cell proliferation. Genetic and molecular comparisons of nematode vulva development between Caenorhabditis, Pristionchus and Oscheius indicate that although the vulva is a stable organ, cell determination and proliferation change dramatically during nematode evolution.
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Annu Rev Cell Dev Biol,
2015]
The evolutionary conservation of developmental mechanisms is a truism in biology, but few attempts have been made to integrate development with evolutionary theory and ecology. To work toward such a synthesis, we summarize studies in the nematode model Pristionchus pacificus, focusing on the development of the dauer, a stress-resistant, alternative larval stage. Integrative approaches combining molecular and genetic principles of development with natural variation and ecological studies in wild populations have identified a key role for a developmental switch mechanism in dauer development and evolution, one that involves the nuclear hormone receptor DAF-12. DAF-12 is a crucial regulator and convergence point for different signaling inputs, and its function is conserved among free-living and parasitic nematodes. Furthermore, DAF-12 is the target of regulatory loops that rely on novel or fast-evolving components to control the intraspecific competition of dauer larvae. We propose developmental switches as paradigms for understanding the integration of development, evolution, and ecology at the molecular level.