-
[
WormBook,
2007]
Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) mutually associated with the enteric bacterium, Photorhabdus luminescens, used globally for the biological control of insects. Much of the previous research concerning H. bacteriophora has dealt with applied aspects related to biological control. However, H. bacteriophora is an excellent model to investigate fundamental processes such as parasitism and mutualism in addition to its comparative value to Caenorhabditis elegans. In June 2005, H. bacteriophora was targeted by NHGRI for a high quality genome sequence. This chapter summarizes the biology of H. bacteriophora in common and distinct from C. elegans, as well as the status of the genome project.
-
[
Genetics,
2020]
Sustaining a healthy proteome is a lifelong challenge for each individual cell of an organism. However, protein homeostasis or proteostasis is constantly jeopardized since damaged proteins accumulate under proteotoxic stress that originates from ever-changing metabolic, environmental, and pathological conditions. Proteostasis is achieved via a conserved network of quality control pathways that orchestrate the biogenesis of correctly folded proteins, prevent proteins from misfolding, and remove potentially harmful proteins by selective degradation. Nevertheless, the proteostasis network has a limited capacity and its collapse deteriorates cellular functionality and organismal viability, causing metabolic, oncological, or neurodegenerative disorders. While cell-autonomous quality control mechanisms have been described intensely, recent work on <i>Caenorhabditis elegans</i> has demonstrated the systemic coordination of proteostasis between distinct tissues of an organism. These findings indicate the existence of intricately balanced proteostasis networks important for integration and maintenance of the organismal proteome, opening a new door to define novel therapeutic targets for protein aggregation diseases. Here, we provide an overview of individual protein quality control pathways and the systemic coordination between central proteostatic nodes. We further provide insights into the dynamic regulation of cellular and organismal proteostasis mechanisms that integrate environmental and metabolic changes. The use of <i>C. elegans</i> as a model has pioneered our understanding of conserved quality control mechanisms important to safeguard the organismal proteome in health and disease.
-
[
WormBook,
2005]
Ubiquitin is a highly conserved 76 amino acid polypeptide, which is covalently attached to target proteins to signal their degradation by the 26S proteasome or to modify their function or localization. Regulated protein degradation, which is associated with many dynamic cellular processes, occurs predominantly via the ubiquitin-proteasome system. Ubiquitin is conjugated to target proteins through the sequential actions of a ubiquitin-activating enzyme, ubiquitin-conjugating enzymes, and ubiquitin-protein ligases. The nematode Caenorhabditis elegans has one ubiquitin-activating enzyme, twenty putative ubiquitin-conjugating enzymes, and potentially hundreds of ubiquitin-protein ligases. Research in C. elegans has focused on the cellular functions of ubiquitin pathway components in the context of organismal development. A combination of forward genetics, reverse genetics, and genome-wide RNAi screens has provided information on the loss-of-function phenotypes for the majority of C. elegans ubiquitin pathway components. Additionally, detailed analysis of several classes of ubiquitin-protein ligases has led to the identification of their substrates and the molecular pathways that they regulate. This review presents a comprehensive overview of ubiquitin-mediated pathways in C. elegans with a description of the known components and their identified molecular, cellular, and developmental functions.
-
[
WormBook,
2006]
There are two sexes in C. elegans, hermaphrodite and male. While there are many sex-specific differences between males and hermaphrodites that affect most tissues, the basic body plan and many of its structures are identical. However, most structures required for mating or reproduction are sexually dimorphic and are generated by sex-specific cell lineages. Thus to understand cell fate specification in hermaphrodites, one must consider how the body plan, which is specified during embryogenesis, influences the fates individual cells. One possible mechanism may involve the asymmetric distribution of POP-1 /Tcf, the sole C. elegans Tcf homolog, to anterior-posterior sister cells. Another mechanism that functions to specify cell fates along the anterior-posterior body axis in both hermaphrodites and males are the Hox genes. Since most of the cell fate specifications that occur in hermaphrodites also occur in males, the focus of this chapter will be on those that only occur in hermaphrodites. This will include the cell fate decisions that affect the HSN neurons, ventral hypodermal P cells, lateral hypodermal cells V5 , V6 , and T ; as well as the mesodermal M, Z1 , and Z4 cells and the intestinal cells. Both cell lineage-based and cell-signaling mechanisms of cell fate specification will be discussed. Only two direct targets of the sex determination pathway that influence cell fate specification to produce hermaphrodite-specific cell fates have been identified. Thus a major challenge will be to learn additional mechanisms by which the sex determination pathway interacts with signaling pathways and other cell fate specification genes to generate hermaphrodite-specific cell fates.