Dramatic expansion and developmental expression diversification of the methuselah gene family during recent Drosophila evolution

Destructive effects of UVC radiation on Drosophila melanogaster: Mortality, fertility, mutations, and molecular mechanisms

The detrimental effects of ultraviolet C (UVC) radiation on living organisms, with a specific focus on the fruit fly Drosophila melanogaster, were examined. This study investigated the impact of heightened UVC radiation exposure on D. melanogaster by assessing mortality and fertility rates, studying phenotypic mutations, and investigating the associated molecular mechanisms. The findings of this study revealed that UVC radiation increases mortality rates and decreases fertility rates in D. melanogaster. Additionally, phenotypic wing mutations were observed in the exposed flies. Furthermore, the study demonstrated that UVC radiation downregulates the expression of antioxidant genes, including superoxide dismutase (SOD), manganese-dependent superoxide dismutase (Mn-SOD), zinc-dependent superoxide dismutase (Cu-Zn-SOD), and the G protein-coupled receptor methuselah (MTH) gene. These results suggest that UVC radiation exerts a destructive effect on D. melanogaster by inducing oxidative stress, which is marked by the overexpression of harmful oxidative processes and a simultaneous reduction in antioxidant gene expression. In conclusion, this study underscores the critical importance of comprehending the deleterious effects of UVC radiation, not only to safeguard human health on Earth, but also to address the potential risks associated with space missions, such as the ongoing Emirate astronaut program.

Identification of G Protein-Coupled Receptors (GPCRs) Associated with Lambda-Cyhalothrin Detoxification in Cydia pomonella

While previous studies have reported G protein-coupled receptor (GPCR)-mediated insecticide resistance in various arthropods, the understanding of GPCR-associated resistance mechanisms in Cydia pomonella remains limited. In this study, a total of 95 CpGPCR genes categorized into four families were identified in C. pomonella. Results revealed high expression levels of the majority of the CpGPCRs during the first larval stage and in the head of C. pomonella. Exposure to lambda-cyhalothrin significantly increased the expression of 15 CpGPCRs, including CpGPCR70, which is highly expressed in all larval stages and shows the highest expression in the midgut. RNA interference (RNAi) demonstrated that downregulation of CpGPCR70 leads to reduced expression of key resistance-related genes and a decreased tolerance of larvae to lambda-cyhalothrin. These findings indicate that CpGPCR70 plays a crucial role in regulating the expression of detoxifying genes involved in lambda-cyhalothrin resistance, offering valuable insights for the development of more effective pest control strategies.

Chromosome-level genome assembly of Monochamus saltuarius reveals its adaptation and interaction mechanism with pine wood nematode

Monochamus saltuarius (Coleoptera: Cerambycidae) was reported as the vector beetle of the pine wood nematode (PWN, Bursaphelenchus xylophilus) in Japan and Europe. It was first reported to transmitted the PWN to native Pinus species in 2018 in Liaoning Province, China. However, the lack of genomic resources has limited the in-depth understanding of its interspecific relationship with PWN. Here, we obtained a chromosome-level reference genome of M. saltuarius combining Illumina, Nanopore and Hi-C sequencing technologies. We assembled the scaffolds into ten chromosomes (including an X chromosome) and obtained a 682.23 Mb chromosome-level genome with a N50 of 73.69 Mb. In total, 427.67 Mb (62.69 %) repeat sequences were identified and 14, 492 protein-coding genes were predicted, of which 93.06 % were annotated. We described the mth/mthl, P450, OBP and OR gene families associated with the vector beetle's development and resistance, as well as the host selection and adaptation, which serve as a valuable resource for understanding the host adaptation in insects during evolution. This high quality reference genome of M. saltuarius also provide new avenues for researching the mechanism of this synergistic damage between vector beetles and PWN.

Identification and characterization of G protein-coupled receptors in Spodoptera frugiperda (Insecta: Lepidoptera)

Spodoptera frugiperda (Insecta: Lepidoptera) is a destructive invasive pest feeding on various plants and causing serious damage to several economically-important crops. G protein-coupled receptors (GPCRs) are cellular receptors that coordinate diverse signaling processes, associated with many physiological processes and disease states. However, less information about GPCRs had been reported in S. frugiperda, limiting the recognition of signaling system and in-depth studies of this pest. Here, a total of 167 GPCRs were identified in S. frugiperda. Compared with other insects, the GPCRs of S. frugiperda were significantly expanded. A large of tandem duplication and segmental duplication events were observed, which may be the key factor to increase the size of GPCR family. In detail, these expansion events mainly concentrate on biogenic amine receptors, neuropeptide and protein hormone receptors, which may be involved in feeding, reproduction, life span, and tolerance of S. frugiperda. Additionally, 17 Mth/Mthl members were identified in S. frugiperda, which may be similar to the evolutionary pattern of 16 Mth/Mthl members in Drosophila. Moreover, the expression patterns across different developmental stages of all GPCR genes were also analyzed. Among these, most of the GPCR genes are poorly expressed in S. frugiperda and some highly expressed GPCR genes help S. frugiperda adapt to the environment better, such as Rh6 and AkhR. In this study, all GPCRs in S. frugiperda were identified for the first time, which provided a basis for further revealing the role of these receptors in the physiological and behavioral regulation of this pest.

G protein-coupled receptors that influence lifespan of human and animal models

Humanity has always sought to live longer and for this, multiple strategies have been tried with varying results. In this sense, G protein-coupled receptors (GPCRs) may be a good option to try to prolong our life while maintaining good health since they have a substantial participation in a wide variety of processes of human pathophysiology and are one of the main therapeutic targets. In this way, we present the analysis of a series of GPCRs whose activity has been shown to affect the lifespan of animal and human models, and in which we put a special interest in describing the molecular mechanisms involved. Our compilation of data revealed that the mechanisms most involved in the role of GPCRs in lifespan are those that mimic dietary restriction, those related to insulin signaling and the AMPK and TOR pathways, and those that alter oxidative homeostasis and severe and/or chronic inflammation. We also discuss the possibility of using agonist or antagonist drugs, depending on the beneficial or harmful effects of each GPCR, in order to prolong people's lifespan and healthspan.

Identification and Functional Analysis of G Protein-Coupled Receptors in 20-Hydroxyecdysone Signaling From the Helicoverpa armigera Genome

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors in animals and humans, which transmit various signals from the extracellular environment into cells. Studies have reported that several GPCRs transmit the same signal; however, the mechanism is unclear. In the present study, we identified all 122 classical GPCRs from the genome of Helicoverpa armigera, a lepidopteran pest species. Twenty-four GPCRs were identified as upregulated at the metamorphic stage by comparing the transcriptomes of the midgut at the metamorphic and feeding stages. Nine of them were confirmed to be upregulated at the metamorphic stage. RNA interference in larvae revealed the prolactin-releasing peptide receptor (PRRPR), smoothened (SMO), adipokinetic hormone receptor (AKHR), and 5-hydroxytryptamine receptor (HTR) are involved in steroid hormone 20-hydroxyecdysone (20E)-promoted pupation. Frizzled 7 (FZD7) is involved in growth, while tachykinin-like peptides receptor 86C (TKR86C) had no effect on growth and pupation. Via these GPCRs, 20E regulated the expression of different genes, respectively, including Pten (encoding phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase), FoxO (encoding forkhead box O), BrZ7 (encoding broad isoform Z7), Kr-h1 (encoding Krüppel homolog 1), Wnt (encoding Wingless/Integrated) and cMyc, with hormone receptor 3 (HHR3) as their common regulating target. PRRPR was identified as a new 20E cell membrane receptor using a binding assay. These data suggested that 20E, via different GPCRs, regulates different gene expression to integrate growth and development.

Extensive crosstalk of G protein-coupled receptors with the Hedgehog signalling pathway

Hedgehog (Hh) ligands orchestrate tissue patterning and growth by acting as morphogens, dictating different cellular responses depending on ligand concentration. Cellular sensitivity to Hh ligands is influenced by heterotrimeric G protein activity, which controls production of the second messenger 3',5'-cyclic adenosine monophosphate (cAMP). cAMP in turn activates Protein kinase A (PKA), which functions as an inhibitor and (uniquely in Drosophila) as an activator of Hh signalling. A few mammalian Gαi- and Gαs-coupled G protein-coupled receptors (GPCRs) have been shown to influence Sonic hedgehog (Shh) responses in this way. To determine whether this is a more-general phenomenon, we carried out an RNAi screen targeting GPCRs in Drosophila. RNAi-mediated depletion of more than 40% of GPCRs tested either decreased or increased Hh responsiveness in the developing Drosophila wing, closely matching the effects of Gαs and Gαi depletion, respectively. Genetic analysis indicated that the orphan GPCR Mthl5 lowers cAMP levels to attenuate Hh responsiveness. Our results identify Mthl5 as a new Hh signalling pathway modulator in Drosophila and suggest that many GPCRs may crosstalk with the Hh pathway in mammals.

The role of G protein-coupled receptor-related genes in cytochrome P450-mediated resistance of the house fly, Musca domestica (Diptera: Muscidae), to imidacloprid

Ninety-four putative G protein-coupled receptors (GPCRs) were identified in the Musca domestica genome. They were annotated and compared with their homologues in Drosophila melanogaster. Phylogenetic analyses of the GPCRs from both species revealed that several family members shared a closer relationship based on the domain architecture. The expression profiles of these genes were examined by quantitative real-time PCR amongst three strains of the house fly, a near-isogenic line strain with imidacloprid resistance (N-IRS), the corresponding susceptible strain (CSS) and another strain derived from field populations with imidacloprid resistance (IRS). We found that five GPCR genes were upregulated in the N-IRS and eight GPCR genes were upregulated in the IRS strains compared to the CSS strain. The transgenic lines of D. melanogaster with the GPCR genes (LOC101899380 in the N-IRS strain and LOC101895664 in the IRS strain) exhibited significantly increased tolerance to imidacloprid, and higher expression of cytochrome P450 genes. Bioinformatic analysis of LOC101899380 was carried out based on its full-length nucleic acid sequence and putative amino acid sequence, and it was named Methuselah-like10 (Mthl10) owing to its homology with D. melanogaster Mthl10. A cell-base cell counting kit-8 toxicity assay demonstrated that the expression of the GPCR gene LOC101899380 in Spodoptera frugiperda (Sf9) cells using a baculovirus-mediated expression system can elevate the cell tolerance to imidacloprid, indirectly supporting the hypothesis that the GPCR gene LOC101899380 plays some role in imidacloprid resistance. These results should be useful for furthering understanding of the regulatory pathway by which house flies develop resistance.

Physiological functions of a methuselah-like G protein coupled receptor in Lymantria dispar Linnaeus

Insect G protein coupled receptors (GPCRs) have been identified as a highly attractive target for new generation insecticides discovery due to their critical physiological functions. However, few insect GPCRs have been functionally characterized. Here, we cloned the full length of a methuselah-like GPCR gene (Ldmthl1) from the Asian gypsy moth, Lymantria dispar. We then characterized the secondary and tertiary structures of Ldmthl1. We also predicted the global structure of this insect GPCR protein which is composed of three major domains. RNA interference of Ldmthl1 resulted in a reduction of gypsy moths' resistance to deltamethrin and suppressed expression of downstream stress-associated genes, such as P450s, glutathione S transferases, and heat shock proteins. The function of Ldmthl1 was further investigated using transgenic lines of Drosophila melanogaster. Drosophila with overexpression of Ldmthl1 showed significantly longer lifespan than control flies. Taken together, our studies revealed that the physiological functions of Ldmthl1 in L. dispar are associated with longevity and resistance to insecticide stresses. Potentially, Ldmthl1 can be used as a target for new insecticide discovery in order to manage this notorious forest pest.

Genomic signatures of G-protein-coupled receptor expansions reveal functional transitions in the evolution of cephalopod signal transduction

Coleoid cephalopods show unique morphological and neural novelties, such as arms with tactile and chemosensory suckers and a large complex nervous system. The evolution of such cephalopod novelties has been attributed at a genomic level to independent gene family expansions, yet the exact association and the evolutionary timing remain unclear. In the octopus genome, one such expansion occurred in the G-protein-coupled receptors (GPCRs) repertoire, a superfamily of proteins that mediate signal transduction. Here, we assessed the evolutionary history of this expansion and its relationship with cephalopod novelties. Using phylogenetic analyses, at least two cephalopod- and two octopus-specific GPCR expansions were identified. Signatures of positive selection were analysed within the four groups, and the locations of these sequences in the Octopus bimaculoides genome were inspected. Additionally, the expression profiles of cephalopod GPCRs across various tissues were extracted from available transcriptomic data. Our results reveal the evolutionary history of cephalopod GPCRs. Unexpanded cephalopod GPCRs shared with other bilaterians were found to be mainly nervous tissue specific. By contrast, duplications that are shared between octopus and the bobtail squid or specific to the octopus' lineage generated copies with divergent expression patterns devoted to tissues outside of the brain. The acquisition of novel expression domains was accompanied by gene order rearrangement through either translocation or duplication and gene loss. Lastly, expansions showed signs of positive selection and some were found to form tandem clusters with shared conserved expression profiles in cephalopod innovations such as the axial nerve cord. Altogether, our results contribute to the understanding of the molecular and evolutionary history of signal transduction and provide insights into the role of this expansion during the emergence of cephalopod novelties and/or adaptations.

Characterization of G-protein coupled receptors from the blackback land crab Gecarcinus lateralis Y organ transcriptome over the molt cycle

BACKGROUND

G-protein coupled receptors (GPCRs) are ancient, ubiquitous, constitute the largest family of transducing cell surface proteins, and are integral to cell communication via an array of ligands/neuropeptides. Molt inhibiting hormone (MIH) is a key neuropeptide that controls growth and reproduction in crustaceans by regulating the molt cycle. It inhibits ecdysone biosynthesis by a pair of endocrine glands (Y-organs; YOs) through binding a yet uncharacterized GPCR, which triggers a signalling cascade, leading to inhibition of the ecdysis sequence. When MIH release stops, ecdysone is synthesized and released to the hemolymph. A peak in ecdysone titer is followed by a molting event. A transcriptome of the blackback land crab Gecarcinus lateralis YOs across molt was utilized in this study to curate the list of GPCRs and their expression in order to better assess which GPCRs are involved in the molt process.

RESULTS

Ninety-nine G. lateralis putative GPCRs were obtained by screening the YO transcriptome against the Pfam database. Phylogenetic analysis classified 49 as class A (Rhodopsin-like receptor), 35 as class B (Secretin receptor), and 9 as class C (metabotropic glutamate). Further phylogenetic analysis of class A GPCRs identified neuropeptide GPCRs, including those for Allatostatin A, Allatostatin B, Bursicon, CCHamide, FMRFamide, Proctolin, Corazonin, Relaxin, and the biogenic amine Serotonin. Three GPCRs clustered with recently identified putative CHH receptors (CHHRs), and differential expression over the molt cycle suggests that they are associated with ecdysteroidogenesis regulation. Two putative Corazonin receptors showed much higher expression in the YOs compared with all other GPCRs, suggesting an important role in molt regulation.

CONCLUSIONS

Molting requires an orchestrated regulation of YO ecdysteroid synthesis by multiple neuropeptides. In this study, we curated a comprehensive list of GPCRs expressed in the YO and followed their expression across the molt cycle. Three putative CHH receptors were identified and could include an MIH receptor whose activation negatively regulates molting. Orthologs of receptors that were found to be involved in molt regulation in insects were also identified, including LGR3 and Corazonin receptor, the latter of which was expressed at much higher level than all other receptors, suggesting a key role in YO regulation.

Massive parallel expansions of Methuselah/Methuselah-like receptors in schizophoran Diptera

The Methuselah/Methuselah-like (Mth/Mthl) family of G-protein coupled receptors (GPCRs) is represented by 16 homologs in the fruit fly Drosophila melanogaster. Three of them have thus far been functionally characterized and found to play critical roles in cell adhesion, immunity, lifespan, and oxidative stress regulation. Evolutionary studies have shown that the large number of D. melanogaster Mth/Mthl GPCRs arose by at least two rounds of gene duplications. The first produced the "mth superclade" subfamily and was followed by the expansion of the "melanogaster subgroup" cluster within the "mth superclade" of Mth/Mthl GPCRs. The adaptive significance of the Mth/Mthl receptor repertoire expansion in Drosophila remains elusive. Studying the Mth/Mthl gene family content in newly available dipteran genomes, we find that the first expansion of the mthl superclade predates the diversification of schizophoran Diptera approximately 65 million years ago. Unexpectedly, we further find that the subsequent expansion of the melanogaster subgroup cluster was paralleled by independent mth superclade Mth/Mthl GPCR expansions in other schizophoran clades (Muscidae and Tephritidae). Our study thus reveals an even more dynamic diversification of mth superclade GPCRs than previously appreciated and linked to the emergence of schizophoran flies, the most dramatic radiation in the dipteran tree of life.

The Drosophila cytokine, GBP: A model that illuminates the yin-yang of inflammation and longevity in humans?

Our laboratories have determined that the Drosophila cytokine, Growth-blocking peptide (GBP), mediates its biological effects through the Mthl10 G-protein coupled receptor. In this Cytokine Stimulus, we discuss the functional plasticity of the GBP/Mthl10 axis, and we propose that conserved components of this regulatory network may be relevant to human health.

Cytokine signaling through Drosophila Mthl10 ties lifespan to environmental stress

A systems-level understanding of cytokine-mediated, intertissue signaling is one of the keys to developing fundamental insight into the links between aging and inflammation. Here, we employed Drosophila, a routine model for analysis of cytokine signaling pathways in higher animals, to identify a receptor for the growth-blocking peptide (GBP) cytokine. Having previously established that the phospholipase C/Ca²⁺ signaling pathway mediates innate immune responses to GBP, we conducted a dsRNA library screen for genes that modulate Ca²⁺ mobilization in Drosophila S3 cells. A hitherto orphan G protein coupled receptor, Methuselah-like receptor-10 (Mthl10), was a significant hit. Secondary screening confirmed specific binding of fluorophore-tagged GBP to both S3 cells and recombinant Mthl10-ectodomain. We discovered that the metabolic, immunological, and stress-protecting roles of GBP all interconnect through Mthl10. This we established by Mthl10 knockdown in three fly model systems: in hemocyte-like Drosophila S2 cells, Mthl10 knockdown decreases GBP-mediated innate immune responses; in larvae, Mthl10 knockdown decreases expression of antimicrobial peptides in response to low temperature; in adult flies, Mthl10 knockdown increases mortality rate following infection with Micrococcus luteus and reduces GBP-mediated secretion of insulin-like peptides. We further report that organismal fitness pays a price for the utilization of Mthl10 to integrate all of these various homeostatic attributes of GBP: We found that elevated GBP expression reduces lifespan. Conversely, Mthl10 knockdown extended lifespan. We describe how our data offer opportunities for further molecular interrogation of yin and yang between homeostasis and longevity.

Diversification of spatiotemporal expression and copy number variation of the echinoid hbox12/pmar1/micro1 multigene family

Changes occurring during evolution in the cis-regulatory landscapes of individual members of multigene families might impart diversification in their spatiotemporal expression and function. The archetypal member of the echinoid hbox12/pmar1/micro1 family is hbox12-a, a homeobox-containing gene expressed exclusively by dorsal blastomeres, where it governs the dorsal/ventral gene regulatory network during embryogenesis of the sea urchin Paracentrotus lividus. Here we describe the inventory of the hbox12/pmar1/micro1 genes in P. lividus, highlighting that gene copy number variation occurs across individual sea urchins of the same species. We show that the various hbox12/pmar1/micro1 genes group into three subfamilies according to their spatiotemporal expression, which ranges from broad transcription throughout development to transient expression in either the animal hemisphere or micromeres of the early embryo. Interestingly, the promoter regions of those genes showing comparable expression patterns are highly similar, while differing from those of the other subfamilies. Strikingly, phylogenetic analysis suggests that the hbox12/pmar1/micro1 genes are species-specific, exhibiting extensive divergence in their noncoding, but not in their coding, sequences across three distinct sea urchin species. In spite of this, two micromere-specific genes of P. lividus possess a TCF/LEF-binding motif in a similar position, and their transcription relies on Wnt/β-catenin signaling, similar to the pmar1 and micro1 genes, which in other sea urchin species are involved in micromere specification. Altogether, our findings suggest that the hbox12/pmar1/micro1 gene family evolved rather rapidly, generating paralogs whose cis-regulatory sequences diverged following multiple rounds of duplication from a common ancestor.

Gene Ages, Nomenclatures, and Functional Diversification of the Methuselah/Methuselah-Like GPCR Family in Drosophila and Tribolium

Affecting lifespan regulation and oxidative stress resistance, the G-protein coupled receptor (GPCR) gene methuselah (mth) plays important roles in the life history of Drosophila melanogaster. Substantial progress has been made in elucidating the molecular pathways by which mth affects these traits, yet conflicting ideas exist as to how old these genetic interactions are as well as how old the mth gene itself is. Root to these issues is the complex gene family history of the Mth/Mthl GPCR family, which experienced independent expansions in a variety of animal clades, leading to at least six subfamilies in insects. Within insects, drosophilid flies stand out by possessing up to three times more Mth/Mthl receptors due to the expansion of a single subfamily, the mth superclade subfamily, which contains an even younger subfamily introduced here as the melanogaster subgroup subfamily. As a result, most of the 16 Mth/Mthl receptors of D. melanogaster are characterized by n:1 orthology relationships to singleton mth superclade homologs in nondrosophilid species. This challenge is exacerbated by the inconsistent naming of Mth/Mthl orthologs across species. To consolidate this situation, we review established ortholog relationships among insect Mth/Mthl receptors, clarify the gene nomenclatures in two important satellite model species, the fruit fly relative D. virilis and the red flour beetle Tribolium castaneum, and discuss the genetic and functional evolution of the D. melanogaster Mth GPCR.

Identification, Characterization and Expression of Methuselah-Like Genes in Dastarcus helophoroides (Coleoptera: Bothrideridae)

Dastarcus helophoroides, which has a relatively longer lifespan compared to other insects, is one of the most effective natural enemies of many large-body long-horned beetles. Methuselah (Mth) is associated with the lifespan, stress resistance, and reproduction in Drosophila melanogaster, but Mth is not present in non-drosophiline insects. A number of methuselah-like genes (mth-likes, mthls) have been identified in non-drosophiline insects, but it is still unknown whether they are present in Dastarcus helophoroides. We identified three novel mth-like genes in D. helophoroides: mth-like1, mth-like2, and mth-like5, and carried out bioinformatic analysis based on the full-length nucleic acid sequences and deduced amino acid sequences. Real-time quantitative polymerase chain reaction (RT-qPCR) showed variations in expression patterns of mth-like genes in different tissues (highly expressed in reproductive systems) and at different developmental stages, indicating that mth-likes were likely be involved in reproduction and development. The altered mRNA expression in aging adults and under oxidation, high temperature, and starvation stress, indicated that mth-like genes were likely to be involved in aging and the resistance of oxidation, high temperature, and starvation. These results characterize, for the first time, the basic properties of three mth-like genes from D. helophoroides that probably play important roles in development, aging, reproduction, and stress resistance.

Gia/Mthl5 is an aorta specific GPCR required for Drosophila heart tube morphology and normal pericardial cell positioning

G-protein signaling is known to be required for cell-cell contacts during the development of the Drosophila dorsal vessel. However, the identity of the G protein-coupled receptor (GPCR) that regulates this signaling pathway activity is unknown. Here we describe the identification of a novel cardiac specific GPCR, called Gia, for "GPCR in aorta". Gia is the only heart-specific GPCR identified in Drosophila to date and it is specifically expressed in cardioblasts that fuse at the dorsal midline to become the aorta. Gia is the only Drosophila gene so far identified for which expression is entirely restricted to cells of the aorta. Deletion of Gia led to a broken-hearted phenotype, characterized by pericardial cells dissociated from cardioblasts and abnormal distribution of cell junction proteins. Both phenotypes were similar to those observed in mutants of the heterotrimeric cardiac G proteins. Lack of Gia also led to defects in the alignment and fusion of cardioblasts in the aorta. Gia forms a protein complex with G-αo47A, the alpha subunit of the heterotrimeric cardiac G proteins and interacts genetically with G-αo47A during cardiac morphogenesis. Our study identified Gia as an essential aorta-specific GPCR that functions upstream of cardiac heterotrimeric G proteins and is required for morphological integrity of the aorta during heart tube formation. These studies lead to a redefinition of the bro phenotype, to encompass morphological integrity of the heart tube as well as cardioblast-pericardial cell spatial interactions.

In silico prediction of the G-protein coupled receptors expressed during the metamorphic molt of Sagmariasus verreauxi (Crustacea: Decapoda) by mining transcriptomic data: RNA-seq to repertoire

Against a backdrop of food insecurity, the farming of decapod crustaceans is a rapidly expanding and globally significant source of food protein. Sagmariasus verreauxi spiny lobster, the subject of this study, are decapods of underdeveloped aquaculture potential. Crustacean neuropeptide G-protein coupled receptors (GPCRs) mediate endocrine pathways that are integral to animal fecundity, growth and survival. The potential use of novel biotechnologies to enhance GPCR-mediated physiology may assist in improving the health and productivity of farmed decapod populations. This study catalogues the GPCRs expressed in the early developmental stages, as well as adult tissues, with a view to illuminating key neuropeptide receptors. De novo assembled contiguous sequences generated from transcriptomic reads of metamorphic and post metamorphic S. verreauxi were filtered for seven transmembrane domains, and used as a reference for iterative re-mapping. Subsequent putative GPCR open reading frames (ORFs) were BLAST annotated, categorised, and compared to published orthologues based on phylogenetic analysis. A total of 85 GPCRs were digitally predicted, that represented each of the four arthropod subfamilies. They generally displayed low-level and non-differential metamorphic expression with few exceptions that we examined using RT-PCR and qPCR. Two putative CHH-like neuropeptide receptors were annotated. Three dimensional structural modelling suggests that these receptors exhibit a conserved extracellular ligand binding pocket, providing support to the notion that these receptors co-evolved with their ligands across Decapoda. This perhaps narrows the search for means to increase productivity of farmed decapod populations.

Methuselah/Methuselah-like G protein-coupled receptors constitute an ancient metazoan gene family

Inconsistent conclusions have been drawn regarding the phylogenetic age of the Methuselah/Methuselah-like (Mth/Mthl) gene family of G protein-coupled receptors, the founding member of which regulates development and lifespan in Drosophila. Here we report the results from a targeted homolog search of 39 holozoan genomes and phylogenetic analysis of the conserved seven transmembrane domain. Our findings reveal that the Mth/Mthl gene family is ancient, has experienced numerous extinction and expansion events during metazoan evolution, and acquired the current definition of the Methuselah ectodomain during its exceptional expansion in arthropods. In addition, our findings identify Mthl1, Mthl5, Mthl14, and Mthl15 as the oldest Mth/Mthl gene family paralogs in Drosophila. Future studies of these genes have the potential to define ancestral functions of the Mth/Mthl gene family.

Transcription factors, chromatin proteins and the diversification of Hemiptera

Availability of complete genomes provides a means to explore the evolution of enormous developmental, morphological, and behavioral diversity among insects. Hemipterans in particular show great diversity of both morphology and life history within a single order. To better understand the role of transcription regulators in the diversification of hemipterans, using sequence profile searches and hidden Markov models we computationally analyzed transcription factors (TFs) and chromatin proteins (CPs) in the recently available Rhodnius prolixus genome along with 13 other insect and 4 non-insect arthropod genomes. We generated a comprehensive collection of TFs and CPs across arthropods including 303 distinct types of domains in TFs and 139 in CPs. This, along with the availability of two hemipteran genomes, R. prolixus and Acyrthosiphon pisum, helped us identify possible determinants for their dramatic morphological and behavioral divergence. We identified five domain families (i.e. Pipsqueak, SAZ/MADF, THAP, FLYWCH and BED finger) as having undergone differential patterns of lineage-specific expansion in hemipterans or within hemipterans relative to other insects. These expansions appear to be at least in part driven by transposons, with the DNA-binding domains of transposases having provided the raw material for emergence of new TFs. Our analysis suggests that while R. prolixus probably retains a state closer to the ancestral hemipteran, A. pisum represents a highly derived state, with the emergence of asexual reproduction potentially favoring genome duplication and transposon expansion. Both hemipterans are predicted to possess active DNA methylation systems. However, in the course of their divergence, aphids seem to have expanded the ancestral hemipteran DNA methylation along with a distinctive linkage to the histone methylation system, as suggested by expansion of SET domain methylases, including those fused to methylated CpG recognition domains. Thus, differential use of DNA methylation and histone methylation might have played a role in emergence of polyphenism and cyclic parthenogenesis from the ancestral hemipteran.

Multispecies Analysis of Expression Pattern Diversification in the Recently Expanded Insect Ly6 Gene Family

Gene families often consist of members with diverse expression domains reflecting their functions in a wide variety of tissues. However, how the expression of individual members, and thus their tissue-specific functions, diversified during the course of gene family expansion is not well understood. In this study, we approached this question through the analysis of the duplication history and transcriptional evolution of a rapidly expanding subfamily of insect Ly6 genes. We analyzed different insect genomes and identified seven Ly6 genes that have originated from a single ancestor through sequential duplication within the higher Diptera. We then determined how the original embryonic expression pattern of the founding gene diversified by characterizing its tissue-specific expression in the beetle Tribolium castaneum, the butterfly Bicyclus anynana, and the mosquito Anopheles stephensi and those of its duplicates in three higher dipteran species, representing various stages of the duplication history (Megaselia abdita, Ceratitis capitata, and Drosophila melanogaster). Our results revealed that frequent neofunctionalization episodes contributed to the increased expression breadth of this subfamily and that these events occurred after duplication and speciation events at comparable frequencies. In addition, at each duplication node, we consistently found asymmetric expression divergence. One paralog inherited most of the tissue-specificities of the founder gene, whereas the other paralog evolved drastically reduced expression domains. Our approach attests to the power of combining a well-established duplication history with a comprehensive coverage of representative species in acquiring unequivocal information about the dynamics of gene expression evolution in gene families.

Methuselah-like genes affect development, stress resistance, lifespan and reproduction in Tribolium castaneum

Methuselah (Mth) is associated with lifespan, stress resistance and reproduction in Drosophila melanogaster, but Mth is not present in nondrosophiline insects. A number of methuselah-likes (mthls) have been identified in nondrosophiline insects, but it is unknown whether the functions of mth are shared by mthls or are divergent from them. Five mthls have been identified in Tribolium castaneum. Although they have different developmental expression patterns, they all enhance resistance to starvation. Only mthl1 and mthl2 enhance resistance to high temperature, whereas mthl4 and mthl5 negatively regulate oxidative stress in T. castaneum. Unlike in the fly with mth mutation, knockdown of mthls, except mthl3, shortens the lifespan of T. castaneum. Moreover, mthl1 and mthl2 are critical for Tribolium development. mthl1 plays important roles in larval and pupal development and adult eclosion, while mthl2 is required for eclosion. Moreover, mthl1 and mthl2 silencing reduces the fertility of T. castaneum, and mthl1 and mthl4 are also essential for embryo development. In conclusion, mthls have a significant effect on insect development, lifespan, stress resistance and reproduction. These results provide experimental evidence for functional divergence among mthls/mth and clues for the signal transduction of Mthls.

Drosophila americana as a model species for comparative studies on the molecular basis of phenotypic variation

Understanding the molecular basis of within and between species phenotypic variation is one of the main goals of Biology. In Drosophila, most of the work regarding this issue has been performed in D. melanogaster, but other distantly related species must also be studied to verify the generality of the findings obtained for this species. Here, we make the case for D. americana, a species of the virilis group of Drosophila that has been diverging from the model species, D. melanogaster, for approximately 40 Myr. To determine the suitability of this species for such studies, polymorphism and recombination estimates are presented for D. americana based on the largest nucleotide sequence polymorphism data set so far analyzed (more than 100 data sets) for this species. The polymorphism estimates are also compared with those obtained from the comparison of the genome assembly of two D. americana strains (H5 and W11) here reported. As an example of the general utility of these resources, we perform a preliminary study on the molecular basis of lifespan differences in D. americana. First, we show that there are lifespan differences between D. americana populations from different regions of the distribution range. Then, we perform five F2 association experiments using markers for 21 candidate genes previously identified in D. melanogaster. Significant associations are found between polymorphism at two genes (hep and Lim3) and lifespan. For the F2 association study involving the two sequenced strains (H5 and W11), we identify amino acid differences at Lim3 and Hep that could be responsible for the observed changes in lifespan. For both genes, no large gene expression differences were observed between the two strains.

The Drosophila melanogaster methuselah gene: a novel gene with ancient functions

The Drosophila melanogaster G protein-coupled receptor gene, methuselah (mth), has been described as a novel gene that is less than 10 million years old. Nevertheless, it shows a highly specific expression pattern in embryos, larvae, and adults, and has been implicated in larval development, stress resistance, and in the setting of adult lifespan, among others. Although mth belongs to a gene subfamily with 16 members in D. melanogaster, there is no evidence for functional redundancy in this subfamily. Therefore, it is surprising that a novel gene influences so many traits. Here, we explore the alternative hypothesis that mth is an old gene. Under this hypothesis, in species distantly related to D. melanogaster, there should be a gene with features similar to those of mth. By performing detailed phylogenetic, synteny, protein structure, and gene expression analyses we show that the D. virilis GJ12490 gene is the orthologous of mth in species distantly related to D. melanogaster. We also show that, in D. americana (a species of the virilis group of Drosophila), a common amino acid polymorphism at the GJ12490 orthologous gene is significantly associated with developmental time, size, and lifespan differences. Our results imply that GJ12490 orthologous genes are candidates for developmental time and lifespan differences in Drosophila in general.

More than two decades of research on insect neuropeptide GPCRs: an overview

This review focuses on the state of the art on neuropeptide receptors in insects. Most of these receptors are G protein-coupled receptors (GPCRs) and are involved in the regulation of virtually all physiological processes during an insect's life. More than 20 years ago a milestone in invertebrate endocrinology was achieved with the characterization of the first insect neuropeptide receptor, i.e., the Drosophila tachykinin-like receptor. However, it took until the release of the Drosophila genome in 2000 that research on neuropeptide receptors boosted. In the last decade a plethora of genomic information of other insect species also became available, leading to a better insight in the functions and evolution of the neuropeptide signaling systems and their intracellular pathways. It became clear that some of these systems are conserved among all insect species, indicating that they fulfill crucial roles in their physiological processes. Meanwhile, other signaling systems seem to be lost in several insect orders or species, suggesting that their actions were superfluous in those insects, or that other neuropeptides have taken over their functions. It is striking that the deorphanization of neuropeptide GPCRs gets much attention, but the subsequent unraveling of the intracellular pathways they elicit, or their physiological functions are often hardly examined. Especially in insects besides Drosophila this information is scarce if not absent. And although great progress made in characterizing neuropeptide signaling systems, even in Drosophila several predicted neuropeptide receptors remain orphan, awaiting for their endogenous ligand to be determined. The present review gives a précis of the insect neuropeptide receptor research of the last two decades. But it has to be emphasized that the work done so far is only the tip of the iceberg and our comprehensive understanding of these important signaling systems will still increase substantially in the coming years.