Molecular evolution of the crustacean hyperglycemic hormone family in ecdysozoans

<p>Abstract</p> <p>Background</p> <p>Crustacean Hyperglycemic Hormone (CHH) family peptides are neurohormones known to regulate several important functions in decapod crustaceans such as ionic and energetic metabolism, molting and reproduction. The structural conservation of these peptides, together with the variety of functions they display, led us to investigate their evolutionary history. CHH family peptides exist in insects (Ion Transport Peptides) and may be present in all ecdysozoans as well. In order to extend the evolutionary study to the entire family, CHH family peptides were thus searched in taxa outside decapods, where they have been, to date, poorly investigated.</p> <p>Results</p> <p>CHH family peptides were characterized by molecular cloning in a branchiopod crustacean, <it>Daphnia magna</it>, and in a collembolan, <it>Folsomia candida</it>. Genes encoding such peptides were also rebuilt <it>in silico </it>from genomic sequences of another branchiopod, a chelicerate and two nematodes. These sequences were included in updated datasets to build phylogenies of the CHH family in pancrustaceans. These phylogenies suggest that peptides found in Branchiopoda and Collembola are more closely related to insect ITPs than to crustacean CHHs. Datasets were also used to support a phylogenetic hypothesis about pancrustacean relationships, which, in addition to gene structures, allowed us to propose two evolutionary scenarios of this multigenic family in ecdysozoans.</p> <p>Conclusions</p> <p>Evolutionary scenarios suggest that CHH family genes of ecdysozoans originate from an ancestral two-exon gene, and genes of arthropods from a three-exon one. In malacostracans, the evolution of the CHH family has involved several duplication, insertion or deletion events, leading to neuropeptides with a wide variety of functions, as observed in decapods. This family could thus constitute a promising model to investigate the links between gene duplications and functional divergence.</p

Diversification, evolution and sub-functionalization of 70kDa heat-shock proteins in two sister species of Antarctic krill: differences in thermal habitats, responses and implications under climate change

A comparative thermal tolerance study was undertaken on two sister species of Euphausiids (Antarctic krills) Euphausia superba and Euphausia crystallorophias. Both are essential components of the Southern Ocean ecosystem, but occupy distinct environmental geographical locations with slightly different temperature regimes. They therefore provide a useful model system for the investigation of adaptations to thermal tolerance. Methodology/Principal Finding Initial CTmax studies showed that E. superba was slightly more thermotolerant than E. crystallorophias. Five Hsp70 mRNAs were characterized from the RNAseq data of both species and subsequent expression kinetics studies revealed notable differences in induction of each of the 5 orthologues between the two species, with E. crystallorophias reacting more rapidly than E. superba. Furthermore, analyses conducted to estimate the evolutionary rates and selection strengths acting on each gene tended to support the hypothesis that diversifying selection has contributed to the diversification of this gene family, and led to the selective relaxation on the inducible C form with its possible loss of function in the two krill species. Conclusions The sensitivity of the epipelagic species E. crystallorophias to temperature variations and/or its adaptation to cold is enhanced when compared with its sister species, E. superba. These results indicate that ice krill could be the first of the two species to be impacted by the warming of coastal waters of the Austral ocean in the coming years due to climate change

Recherche de substances hormonales actives sur la croissance d'invertebres marins d'interet aquacole

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Evolution moléculaire d'une famille de neuropeptides au sein des arthropodes (l'exemple de la CHH (Crustacean Hyperglycemic Hormone))

Les peptides de la famille de la CHH sont des neurohormones connues chez les Crustacés Décapodes pour réguler plusieurs grandes fonctions. Ces hormones ont été peu étudiées en-dehors des Décapodes mais sont supposées être présentes chez l ensemble des Arthropodes, voire des Ecdysozoaires. Afin de confirmer cette hypothèse et de progresser dans la reconstitution d un scénario évolutif de la famille de la CHH, des peptides ont été recherchés et caractérisés dans de nouveaux taxons. Des ADNc codant des CHH ont ainsi été clonés pour la première fois chez un pagure et chez une galathée (Anomoures), et la présence des peptides dans le système nerveux a été confirmée par spectrométrie de masse et immunohistochimie. Des peptides de la famille de la CHH ont ensuite été clonés chez un branchiopode, Daphnia magna, et chez un collembole, Folsomia candida, et des gènes codant de tels peptides ont également été reconstitués in silico chez six insectes, un branchiopode, un chélicérate et quatre nématodes. Les phylogénies réalisées, ajoutées aux informations sur les structures de gènes, ont conduit à proposer pour la première fois un scénario évolutif de la famille de la CHH.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Biogenesis of d-amino acid containing peptides/proteins: where, when and how?

International audiencePeptides and proteins are chiral molecules with their structure determined by the composition and configuration of the amino acids constituting them. Natural amino acids (except glycine) display two chiral types (l- and d-enantiomers). For example, the presence of octopine, a derivative of l-arginine and d-alanine in octopus, or peptidyl poly-d-glutamic acid in a bacterial cell wall was demonstrated in the 1920s and 1930s, respectively. Nevertheless, an old dogma in biology was that proteins (in a strict sense) are composed of amino acids in the l-configuration exclusively, until a d-alanyl residue was reported in a frog skin opioid peptide in the early 1980s, and since, numerous d-amino acid containing peptides (DAACPs) have been discovered in multicellular organisms. Several hypotheses may be formulated to explain the origin of a d-residue in the peptide/protein chain. It may result from different mechanisms such as incorporation of a d-amino acid, non-enzymatic racemisation associated with ageing or diseases and enzymatic posttranslational modification. In the last case, the DAACPs are synthesised via a ribosome-dependent manner, and a normal codon for l-amino acid is present in the mRNA at the position where the d-residue is processed in the mature peptide by peptidyl aminoacyl l-d isomerisation, a peculiar and subtle posttranslational modification. In this review, the different pathways of biogenesis of DAACPs not only in bacteria but also in multicellular organisms are discussed, along with the description of the cellular specificity, the enzyme specificity and the substrate specificity of peptidyl aminoacyl l-d isomerisation

The Crustacean Hyperglycemic Hormone Superfamily: Progress Made in the Past Decade

International audienceEarly studies recognizing the importance of the decapod eyestalk in the endocrine regulation of crustacean physiology-molting, metabolism, reproduction, osmotic balance, etc.-helped found the field of crustacean endocrinology. Characterization of putative factors in the eyestalk using distinct functional bioassays ultimately led to the discovery of a group of structurally related and functionally diverse neuropeptides, crustacean hyperglycemic hormone (CHH), molt-inhibiting hormone (MIH), gonad-inhibiting hormone (GIH) or vitellogenesis-inhibiting hormone (VIH), and mandibular organ-inhibiting hormone (MOIH). These peptides, along with the first insect member (ion transport peptide, ITP), constitute the original arthropod members of the crustacean hyperglycemic hormone (CHH) superfamily. The presence of genes encoding the CHH-superfamily peptides across representative ecdysozoan taxa has been established. The objective of this review is to, aside from providing a general framework, highlight the progress made during the past decade or so. The progress includes the widespread identification of the CHH-superfamily peptides, in particular in non-crustaceans, which has reshaped the phylogenetic profile of the superfamily. Novel functions have been attributed to some of the newly identified members, providing exceptional opportunities for understanding the structure-function relationships of these peptides. Functional studies are challenging, especially for the peptides of crustacean and insect species, where they are widely expressed in various tissues and usually pleiotropic. Progress has been made in deciphering the roles of CHH, ITP, and their alternatively spliced counterparts (CHH-L, ITP-L) in the regulation of metabolism and ionic/osmotic hemostasis under (eco)physiological, developmental, or pathological contexts, and of MIH in the stimulation of ovarian maturation, which implicates it as a regulator for coordinating growth (molt) and reproduction. In addition, experimental elucidation of the steric structure and structure-function relationships have given better understanding of the structural basis of the functional diversification and overlapping among these peptides. Finally, an important finding was the first-ever identification of the receptors for this superfamily of peptides, specifically the receptors for ITPs of the silkworm, which will surely give great impetus to the functional study of these peptides for years to come. Studies regarding recent progress are presented and synthesized, and prospective developments remarked upon

Thermal constraints on the metabolic rates of krill from Kongsfjorden, West-Spitsbergen

The high Arctic Kongsfjorden (79°N) is influenced mainly by cold Arctic but also warmer Atlantic water masses. In recent years, the proportion of Atlantic inflow increased, attributed to climate change. Concurrently, two boreal and one subtropical krill species are now being found regularly in Kongsfjorden – in addition to the previously prevailing arcto-boreal species Thysanoessa inermis and T. raschii. Generally, krill occupy a central trophic position as secondary producers linking primary production to higher trophic levels. Many adult fish, seabirds and marine mammals rely on them as a food source. Although a change in a krill population may have a significant impact on the ecosystem, knowledge on the physiological performance of the species inhabiting Arctic waters is still scarce. We aim at determining the ecophysiology of this key group within the challenging Arctic ecosystem. Using non-invasive optical oxygen sensors, respiration measurements helped to characterize the species’ metabolic reaction to temperature variation, i.e. to reveal the thermal limits of metabolic adaptability. Thysanoessa spp. appear more stenotherm than the boreal and the subtropical krill species: the upper level of respiration is reached at temperatures < 12°C while mortality increases and the animals are less tolerant to ambient oxygen concentrations. The species’ thermal limit of adaptive capacity found may explain its current arcto-boreal distribution. In contrast, the other boreal and a subtropical krill species show a higher tolerance to temperature changes, which may support the species’ success in northward expansion as reported through increasing abundances at lower latitudes. Accordingly, at least one of the latter species may profit from the increasing “Atlantification” of the Kongsfjord ecosystem due to its superior physiological plasticity

Comparative Population Transcriptomics Provide New Insight into the Evolutionary History and Adaptive Potential of World Ocean Krill

Genetic variation is instrumental for adaptation to changing environments but it is unclear how it is structured and contributes to adaptation in pelagic species lacking clear barriers to gene flow. Here, we applied comparative genomics to extensive transcriptome datasets from 20 krill species collected across the Atlantic, Indian, Pacific, and Southern Oceans. We compared genetic variation both within and between species to elucidate their evolutionary history and genomic bases of adaptation. We resolved phylogenetic interrelationships and uncovered genomic evidence to elevate the cryptic Euphausia similis var. armata into species. Levels of genetic variation and rates of adaptive protein evolution vary widely. Species endemic to the cold Southern Ocean, such as the Antarctic krill Euphausia superba, showed less genetic variation and lower evolutionary rates than other species. This could suggest a low adaptive potential to rapid climate change. We uncovered hundreds of candidate genes with signatures of adaptive evolution among Antarctic Euphausia but did not observe strong evidence of adaptive convergence with the predominantly Arctic Thysanoessa. We instead identified candidates for cold-adaptation that have also been detected in Antarctic fish, including genes that govern thermal reception such as TrpA1. Our results suggest parallel genetic responses to similar selection pressures across Antarctic taxa and provide new insights into the adaptive potential of important zooplankton already affected by climate change

Experimental strategies for the analysis of d-amino acid containing peptides in crustaceans: A review.

International audienceDetection of d-amino acids in natural peptides has been, and remains a challenging task, as peptidyl isomerization is a peculiar and subtle posttranslational modification that does not induce any change in primary sequence or in physicochemical properties of the molecule such as molecular mass or pI. Therefore, the presence of a d-amino acid residue in a peptide chain is generally transparent to classical methods of peptide analysis (electrophoresis, chromatography, mass spectrometry, molecular biology). In this article, we will review the various experimental strategies and analytical techniques, which have been used to characterize and to study d-amino acid containing peptides in crustaceans