Identification of gamma-interferon-inducible lysosomal thiol reductase (GILT) homologues in the fruit fly Drosophila melanogaster

Post-Transcriptional Induction of the Antiviral Host Factor GILT/IFI30 by Interferon Gamma

Gamma-interferon-inducible lysosomal thiol reductase (GILT) plays pivotal roles in both adaptive and innate immunities. GILT exhibits constitutive expression within antigen-presenting cells, whereas in other cell types, its expression is induced by interferon gamma (IFN-γ). Gaining insights into the precise molecular mechanism governing the induction of GILT protein by IFN-γ is of paramount importance for adaptive and innate immunities. In this study, we found that the 5' segment of GILT mRNA inhibited GILT protein expression regardless of the presence of IFN-γ. Conversely, the 3' segment of GILT mRNA suppressed GILT protein expression in the absence of IFN-γ, but it loses this inhibitory effect in its presence. Although the mTOR inhibitor rapamycin suppressed the induction of GILT protein expression by IFN-γ, the expression from luciferase sequence containing the 3' segment of GILT mRNA was resistant to rapamycin in the presence of IFN-γ, but not in its absence. Collectively, this study elucidates the mechanism behind GILT induction by IFN-γ: in the absence of IFN-γ, GILT mRNA is constitutively transcribed, but the translation process is hindered by both the 5' and 3' segments. Upon exposure to IFN-γ, a translation inhibitor bound to the 3' segment is liberated, and a translation activator interacts with the 3' segment to trigger the initiation of GILT translation.

The immune factors involved in the rapid clearance of bacteria from the midgut of the tick Ixodes ricinus

Ticks are obligate hematophagous arthropods that transmit a wide range of pathogens to humans as well as wild and domestic animals. They also harbor a non-pathogenic microbiota, although our previous study has shown that the diverse bacterial microbiome in the midgut of Ixodes ricinus is quantitatively poor and lacks a core. In artificial infections by capillary feeding of ticks with two model bacteria (Gram-positive Micrococcus luteus and Gram-negative Pantoea sp.), rapid clearance of these microbes from the midgut was observed, indicating the presence of active immune mechanisms in this organ. In the current study, RNA-seq analysis was performed on the midgut of I. ricinus females inoculated with either M. luteus or Pantoea sp. or with sterile water as a control. While no immune-related transcripts were upregulated by microbial inoculation compared to that of the sterile control, capillary feeding itself triggered dramatic transcriptional changes in the tick midgut. Manual curation of the transcriptome from the midgut of unfed I. ricinus females, complemented by the proteomic analysis, revealed the presence of several constitutively expressed putative antimicrobial peptides (AMPs) that are independent of microbial stimulation and are referred to here as 'guard' AMPs. These included two types of midgut-specific defensins, two different domesticated amidase effector 2 (Dae2), microplusin/ricinusin-related molecules, two lysozymes, and two gamma interferon-inducible lysosomal thiol reductases (GILTs). The in vitro antimicrobial activity assays of two synthetic mature defensins, defensin 1 and defensin 8, confirmed their specificity against Gram-positive bacteria showing exceptional potency to inhibit the growth of M. luteus at nanomolar concentrations. The antimicrobial activity of midgut defensins is likely part of a multicomponent system responsible for the rapid clearance of bacteria in the tick midgut. Further studies are needed to evaluate the role of other identified 'guard' AMPs in controlling microorganisms entering the tick midgut.

mosGILT controls innate immunity and germ cell development in Anopheles gambiae

Gene-edited mosquitoes lacking a gamma-interferon-inducible lysosomal thiol reductase-like protein, namely (mosGILTnull) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILTnull Anopheles gambiae was therefore compared to wild type (WT) mosquitoes by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILTnull A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg, an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILTnull mosquitoes. These results provide a crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

Functional of tongue sole (Cynoglossus semilaevis) gamma-interferon-inducible lysosomal thiol reductase with implications in innate immune reponse depend on CXXC active site

The enzyme gamma-interferon-inducible lysosomal thiol reductase (GILT) plays an important role in promoting the processing and presentation of major histocompatibility complex (MHC) class II-restricted antigens. It is also involved in MHC I-restricted antigens catalyzing disulfide bond reduction in fishes' adaptive immunity. The open reading frame of tongue sole (Cynoglossus semilaevis) GILT (tsGILT) gene is 771 bp long, encoding 257 amino acids, with a calculated molecular weight of 28.465 kDa and isoelectric point (pI) of 5.35. After induction with lipopolysaccharide, the expression of tsGILT mRNA was upregulated in spleen and kidney and recombinant tsGILT protein transferred to late endosomes and lysosomes in HeLa cells. The refolded tsGILT was capable of catalyzing the reduction of the interchain disulfide bonds against an IgG substrate depend on the active site CXXC motif at residues 75-78. The process of immune response to bacteria challenge needs GILT to catalyze the reduction of disulfide bond and unfolding native protein antigens, promoting their hydrolysis by proteases. Whether a single mutation or a double mutation of active site CXXC at residues75-78, the 3D structure of tsGILT protein has undergone major changes and lost its activity of catalyzing the reduction of the interchain disulfide bonds.

A Drosophila glial cell atlas reveals a mismatch between transcriptional and morphological diversity

Morphology is a defining feature of neuronal identity. Like neurons, glia display diverse morphologies, both across and within glial classes, but are also known to be morphologically plastic. Here, we explored the relationship between glial morphology and transcriptional signature using the Drosophila central nervous system (CNS), where glia are categorised into 5 main classes (outer and inner surface glia, cortex glia, ensheathing glia, and astrocytes), which show within-class morphological diversity. We analysed and validated single-cell RNA sequencing data of Drosophila glia in 2 well-characterised tissues from distinct developmental stages, containing distinct circuit types: the embryonic ventral nerve cord (VNC) (motor) and the adult optic lobes (sensory). Our analysis identified a new morphologically and transcriptionally distinct surface glial population in the VNC. However, many glial morphological categories could not be distinguished transcriptionally, and indeed, embryonic and adult astrocytes were transcriptionally analogous despite differences in developmental stage and circuit type. While we did detect extensive within-class transcriptomic diversity for optic lobe glia, this could be explained entirely by glial residence in the most superficial neuropil (lamina) and an associated enrichment for immune-related gene expression. In summary, we generated a single-cell transcriptomic atlas of glia in Drosophila, and our extensive in vivo validation revealed that glia exhibit more diversity at the morphological level than was detectable at the transcriptional level. This atlas will serve as a resource for the community to probe glial diversity and function.

Viruses in Laboratory Drosophila and Their Impact on Host Gene Expression

Drosophila melanogaster has one of the best characterized antiviral immune responses among invertebrates. However, relatively few easily transmitted natural virus isolates are available, and so many Drosophila experiments have been performed using artificial infection routes and artificial host-virus combinations. These may not reflect natural infections, especially for subtle phenotypes such as gene expression. Here, to explore the laboratory virus community and to better understand how natural virus infections induce changes in gene expression, we have analysed seven publicly available D. melanogaster transcriptomic sequencing datasets that were originally sequenced for projects unrelated to virus infection. We have found ten known viruses-including five that have not been experimentally isolated-but no previously unknown viruses. Our analysis of host gene expression revealed that numerous genes were differentially expressed in flies that were naturally infected with a virus. For example, flies infected with nora virus showed patterns of gene expression consistent with intestinal vacuolization and possible host repair via the upd3 JAK/STAT pathway. We also found marked sex differences in virus-induced differential gene expression. Our results show that natural virus infection in laboratory Drosophila does indeed induce detectable changes in gene expression, suggesting that this may form an important background condition for experimental studies in the laboratory.

Anopheles gambiae mosGILT regulates innate immune genes and zpg expression

Gene-edited mosquitoes lacking a g amma-interferon-inducible lysosomal thiol reductase-like protein, namely ( mosGILT null ) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILT null A. gambiae was therefore compared to wild type (WT) by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILT null A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg , an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILT null mosquitoes. These results provide the crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

The venom composition and parthenogenesis mechanism of the parasitoid wasp Microctonus hyperodae, a declining biocontrol agent

A biocontrol system in New Zealand using the endoparasitoid Microctonus hyperodae is failing, despite once being one of the most successful examples of classical biocontrol worldwide. Though it is of significant economic importance as a control agent, little is known about the genetics of M. hyperodae. In this study, RNA-seq was used to characterise two key traits of M. hyperodae in this system, the venom, critical for the initial success of biocontrol, and the asexual reproduction mode, which influenced biocontrol decline. Expanded characterisation of M. hyperodae venom revealed candidates involved in manipulating the host environment to source nutrition for the parasitoid egg, preventing a host immune response against the egg, as well as two components that may stimulate the host's innate immune system. Notably lacking from the venom-specific expression list was calreticulin, as it also had high expression in the ovaries. In-situ hybridisation revealed this ovarian expression was localised to the follicle cells, which may result in the deposition of calreticulin into the egg exochorion. Investigating the asexual reproduction of M. hyperodae revealed core meiosis-specific genes had conserved expression patterns with the highest expression in the ovaries, suggesting M. hyperodae parthenogenesis involves meiosis and that the potential for sexual reproduction may have been retained. Upregulation of genes involved in endoreduplication provides a potential mechanism for the restoration of diploidy in eggs after meiosis.

Antibacterial responses and functional characterization of the interferon gamma inducible lysosomal thiol reductase (GILT) protein in Chinese mitten crab (Eriocheir sinensis)

The inducible reductase of interferon gamma (IFN- γ), IFN-γ-induced lysosomal thiol reductase (GILT) is important in antiviral immunity, but its mechanism in invertebrate antimicrobial immunity is unclear. We determined that GILT protein was involved in the antibacterial immunity of Chinese mitten crab (Eriocheir sinensis). GILT protein was highly expressed in crab hemocytes and was significantly upregulated 6 h after bacterial stimulation. Recombinant E. sinensis GILT (rEsGILT) contained a CXXS active site that catalyzed disulfide bond reduction. Vibrio parahaemolyticus and Staphylococcus aureus were bound through interaction with peptidoglycan and lipopolysaccharide, respectively, and bacterial agglutination and clearance in the crabs was markedly promoted. Nevertheless, EsGILT exhibited no direct antibacterial or bactericidal activity. EsGILT also promoted crab hemocyte phagocytosis and played an anti-bacterial role, and inhibited hemocyte apoptosis. In summary, EsGILT promoted bacterial agglutination, clearance, and phagocytosis by recognizing and agglutinating pathogenic microorganisms and reduced the apoptosis level, indirectly participating in antibacterial reactions.

Proteotranscriptomic Integration analyses reveals new mechanistic insights regarding Bombyx mori fluorosis

The commercial value of silkworms has been widely explored and the effects of fluoride exposure on silkworms' breeding and silk production cannot be ignored. Bombyx mori is a commonly used model to explore the mechanisms of fluorosis. In the present study, we analyzed the differences in physiological and biochemical indicators after exposing larva to NaF, then evaluated differential genes and proteins. Compared to control, larvae exposed to 600 mg L^-1 NaF presented decreased bodyweight, damaged midgut tissue, and were accompanied by oxidative stress. The RNA-seq showed 1493 differentially expressed genes (574 upregulated and 919 downregulated). Meanwhile, the TMT detected 189 differentially expressed proteins (133 upregulated and 56 downregulated). The integrative analysis led to 4 upregulated and 9 downregulated genes and proteins. Finally, we hypothesized that fluoride exposure might affect the intestinal digestion of silkworms, inhibit the gene expression of detoxification enzymes and stimulate cellular immune responses. Our current findings provided new insights into insect fluorosis.

Antivirus activity, but not thiolreductase activity, is conserved in interferon-gamma-inducible GILT protein in arthropod

We have previously reported that gamma-interferon inducible lysosomal thiolreductase (GILT) functions as a host defense factor against retroviruses by digesting disulfide bonds on viral envelope proteins. GILT is widely conserved even in plants and fungi as well as animals. The thiolreductase active site of mammalian GILT is composed of a CXXC amino acid motif, whereas the C-terminal cysteine residue is changed to serine in arthropods including shrimps, crabs, and flies. GILT from Penaeus monodon (PmGILT) also has the CXXS motif instead of the CXXC active site. We demonstrate here that a human GILT mutant (GILT C75S) with the CXXS motif and PmGILT significantly inhibit amphotropic murine leukemia virus vector infection in human cells without alterning its expression level and lysosomal localization, showing that the C-terminal cysteine residue of the active site is not required for the antiviral activity. We have reported that human GILT suppresses HIV-1 particle production by digestion of disulfide bonds on CD63. However, GILT C75S mutant and PmGILT did not digest CD63 disulfide bonds, and had no effect on HIV-1 virion production, suggesting that they do not have thiolreductase activity. Taken together, this study found that antiviral activity, but not thiolreductase activity, is conserved in arthropod GILT proteins. This finding provides a new insight that the common function of GILT is antiviral activity in many animals.

Developmental Alcohol Exposure in Drosophila: Effects on Adult Phenotypes and Gene Expression in the Brain

Fetal alcohol exposure can lead to developmental abnormalities, intellectual disability, and behavioral changes, collectively termed fetal alcohol spectrum disorder (FASD). In 2015, the Centers for Disease Control found that 1 in 10 pregnant women report alcohol use and more than 3 million women in the USA are at risk of exposing their developing fetus to alcohol. Drosophila melanogaster is an excellent genetic model to study developmental effects of alcohol exposure because many individuals of the same genotype can be reared rapidly and economically under controlled environmental conditions. Flies exposed to alcohol undergo physiological and behavioral changes that resemble human alcohol-related phenotypes. Here, we show that adult flies that developed on ethanol-supplemented medium have decreased viability, reduced sensitivity to ethanol, and disrupted sleep and activity patterns. To assess the effects of exposure to alcohol during development on brain gene expression, we performed single cell RNA sequencing and resolved cell clusters with differentially expressed genes which represent distinct neuronal and glial populations. Differential gene expression showed extensive sexual dimorphism with little overlap between males and females. Gene expression differences following developmental alcohol exposure were similar to previously reported differential gene expression following cocaine consumption, suggesting that common neural substrates respond to both drugs. Genes associated with glutathione metabolism, lipid transport, glutamate and GABA metabolism, and vision feature in sexually dimorphic global multi-cluster interaction networks. Our results provide a blueprint for translational studies on alcohol-induced effects on gene expression in the brain that may contribute to or result from FASD in human populations.

Planarian gamma-interferon-inducible lysosomal thiol reductase (GILT) is required for gram-negative bacterial clearance

The powerful regenerative ability of planarians has long been a concern of scientists, but recently, their efficient immune system has attracted more and more attention from researchers. Gamma-interferon-inducible lysosomal thiol reductase (GILT) is related not only to antigen presentation but also to bacteria invasions. But the systematic studies are not yet to be conducted on the relationship between bacterial infection. Our study reveals for the first time that GILT of planarian (DjGILT) plays an essential role in the clearance of Gram-negative bacteria by conducting H₂O₂ concentration in planarians. In animals that DjGILT was silenced, it persisted for up to 9 days before all bacteria were cleared, compared with 6 days of the control group. When infected with E. coli and V. anguillarum, the level of H₂O₂ was significantly increased in DjGILT-silenced planarians, and concomitantly, mRNA level of C-type lectin DjCTL, which modulates agglutination and clearance efficiency of invading bacteria, was decreased. Further study showed that the decrease of H₂O₂ level led to a significant increase in DjCTL transcripts. Collectively, we proposed a mechanism model for the involvement of GILT gene in bacterial elimination. We have for the first time revealed the specific mechanism of GILT in innate immune response against bacterial infection.

A physiologic overview of the organ-specific transcriptome of the cattle tick Rhipicephalus microplus

To further obtain insights into the Rhipicephalus microplus transcriptome, we used RNA-seq to carry out a study of expression in (i) embryos; (ii) ovaries from partially and fully engorged females; (iii) salivary glands from partially engorged females; (iv) fat body from partially and fully engorged females; and (v) digestive cells from partially, and (vi) fully engorged females. We obtained > 500 million Illumina reads which were assembled de novo, producing > 190,000 contigs, identifying 18,857 coding sequences (CDS). Reads from each library were mapped back into the assembled transcriptome giving a view of gene expression in different tissues. Transcriptomic expression and pathway analysis showed that several genes related in blood digestion and host-parasite interaction were overexpressed in digestive cells compared with other tissues. Furthermore, essential genes for the cell development and embryogenesis were overexpressed in ovaries. Taken altogether, these data offer novel insights into the physiology of production and role of saliva, blood digestion, energy metabolism, and development with submission of 10,932 novel tissue/cell specific CDS to the NCBI database for this important tick species.

A physiologic overview of the organ-specific transcriptome of the cattle tick Rhipicephalus microplus

To further obtain insights into the Rhipicephalus microplus transcriptome, we used RNA-seq to carry out a study of expression in (i) embryos; (ii) ovaries from partially and fully engorged females; (iii) salivary glands from partially engorged females; (iv) fat body from partially and fully engorged females; and (v) digestive cells from partially, and (vi) fully engorged females. We obtained > 500 million Illumina reads which were assembled de novo, producing > 190,000 contigs, identifying 18,857 coding sequences (CDS). Reads from each library were mapped back into the assembled transcriptome giving a view of gene expression in different tissues. Transcriptomic expression and pathway analysis showed that several genes related in blood digestion and host-parasite interaction were overexpressed in digestive cells compared with other tissues. Furthermore, essential genes for the cell development and embryogenesis were overexpressed in ovaries. Taken altogether, these data offer novel insights into the physiology of production and role of saliva, blood digestion, energy metabolism, and development with submission of 10,932 novel tissue/cell specific CDS to the NCBI database for this important tick species.

Development on Citrus medica infected with 'Candidatus Liberibacter asiaticus' has sex-specific and -nonspecific impacts on adult Diaphorina citri and its endosymbionts

Huanglongbing (HLB) is a deadly, incurable citrus disease putatively caused by the unculturable bacterium, 'Candidatus Liberibacter asiaticus' (CLas), and transmitted by Diaphorina citri. Prior studies suggest D. citri transmits CLas in a circulative and propagative manner; however, the precise interactions necessary for CLas transmission remain unknown, and the impact of insect sex on D. citri-CLas interactions is poorly understood despite reports of sex-dependent susceptibilities to CLas. We analyzed the transcriptome, proteome, metabolome, and microbiome of male and female adult D. citri reared on healthy or CLas-infected Citrus medica to determine shared and sex-specific responses of D. citri and its endosymbionts to CLas exposure. More sex-specific than shared D. citri responses to CLas were observed, despite there being no difference between males and females in CLas density or relative abundance. CLas exposure altered the abundance of proteins involved in immunity and cellular and oxidative stress in a sex-dependent manner. CLas exposure impacted cuticular proteins and enzymes involved in chitin degradation, as well as energy metabolism and abundance of the endosymbiont 'Candidatus Profftella armatura' in both sexes similarly. Notably, diaphorin, a toxic Profftella-derived metabolite, was more abundant in both sexes with CLas exposure. The responses reported here resulted from a combination of CLas colonization of D. citri as well as the effect of CLas infection on C. medica. Elucidating these impacts on D. citri and their endosymbionts contributes to our understanding of the HLB pathosystem and identifies the responses potentially critical to limiting or promoting CLas acquisition and propagation in both sexes.

Transcriptomics reveals specific molecular mechanisms underlying transgenerational immunity in Manduca sexta

The traditional view of innate immunity in insects is that every exposure to a pathogen triggers an identical and appropriate immune response and that prior exposures to pathogens do not confer any protective (i.e., adaptive) effect against subsequent exposure to the same pathogen. This view has been challenged by experiments demonstrating that encounters with sublethal doses of a pathogen can prime the insect's immune system and, thus, have protective effects against future lethal doses. Immune priming has been reported across several insect species, including the red flour beetle, the honeycomb moth, the bumblebee, and the European honeybee, among others. Immune priming can also be transgenerational where the parent's pathogenic history influences the immune response of its offspring. Phenotypic evidence of transgenerational immune priming (TGIP) exists in the tobacco moth Manduca sexta where first-instar progeny of mothers injected with the bacterium Serratia marcescens exhibited a significant increase of in vivo bacterial clearance. To identify the gene expression changes underlying TGIP in M. sexta, we performed transcriptome-wide, transgenerational differential gene expression analysis on mothers and their offspring after mothers were exposed to S. marcescens. We are the first to perform transcriptome-wide analysis of the gene expression changes associated with TGIP in this ecologically relevant model organism. We show that maternal exposure to both heat-killed and live S. marcescens has strong and significant transgenerational impacts on gene expression patterns in their offspring, including upregulation of peptidoglycan recognition protein, toll-like receptor 9, and the antimicrobial peptide cecropin.

A single-cell atlas of adult Drosophila ovary identifies transcriptional programs and somatic cell lineage regulating oogenesis

Oogenesis is a complex developmental process that involves spatiotemporally regulated coordination between the germline and supporting, somatic cell populations. This process has been modeled extensively using the Drosophila ovary. Although different ovarian cell types have been identified through traditional means, the large-scale expression profiles underlying each cell type remain unknown. Using single-cell RNA sequencing technology, we have built a transcriptomic data set for the adult Drosophila ovary and connected tissues. Using this data set, we identified the transcriptional trajectory of the entire follicle-cell population over the course of their development from stem cells to the oogenesis-to-ovulation transition. We further identify expression patterns during essential developmental events that take place in somatic and germline cell types such as differentiation, cell-cycle switching, migration, symmetry breaking, nurse-cell engulfment, egg-shell formation, and corpus luteum signaling. Extensive experimental validation of unique expression patterns in both ovarian and nearby, nonovarian cells also led to the identification of many new cell type-and stage-specific markers. The inclusion of several nearby tissue types in this data set also led to our identification of functional convergence in expression between distantly related cell types such as the immune-related genes that were similarly expressed in immune cells (hemocytes) and ovarian somatic cells (stretched cells) during their brief phagocytic role in nurse-cell engulfment. Taken together, these findings provide new insight into the temporal regulation of genes in a cell-type specific manner during oogenesis and begin to reveal the relatedness in expression between cell and tissues types.

Development of the transcriptome for a sediment ecotoxicological model species, Chironomus dilutus

Chironomus dilutus is a prominent model species in conventional sediment toxicity testing and sediment contamination diagnosis. However, lack of genomic data significantly limited its application in identifying toxicological mode of action (MOA) and molecular biomarkers of toxicants. Here the transcriptome of C. dilutus in full life span and both sexes (1st, 2nd, 3rd and 4th instar larvae, pupae, and adults) were developed and temporal gene expression across adjacent life stages were investigated to understand the regulation of development. Furthermore, transcriptional response of Midges (the 4th instar larvae) exposed to chemicals of different MOAs (CdCl₂, nonylphenol and triclosan) were profiled based on the reference transcriptome. Consequently, a complete transcriptome of 31132 unigenes with N50 of 3117bp, covering 98.8% of the arthropod single-copy orthologs were assembled. While 364 genes were differentially expressed among adjacent larval stages, 7142 and 2127 of transcripts were significantly changed for the transition of larvae-pupae and pupae-adults, respectively. Finally, chemical-specific gene expression profile were identified in the midges, showed its potential in classifying distinct contaminants. Overall, the comprehensive transcriptome of C. dilutus developed here could not only facilitate the mechanistic understanding of environmental toxicants during critical life stage of aquatic insects, but also provide molecular diagnostic tools in sediment ecotoxicology.

Identification and Characterization of an OSH1 Thiol Reductase from Populus Trichocarpa

Interferon gamma-induced lysosomal thiol reductase (GILT) is abundantly expressed in antigen-presenting cells and participates in the treatment and presentation of antigens by major histocompatibility complex II. Also, GILT catalyzes the reduction of disulfide bonds, which plays an important role in cellular immunity. (1) Background: At present, the studies of GILT have mainly focused on animals. In plants, GILT homologous gene (Arabidopsis thalianaOSH1: AtOSH1) was discovered in the forward screen of mutants with compromised responses to sulphur nutrition. However, the complete properties and functions of poplar OSH1 are unclear. In addition, CdCl2 stress is swiftly engulfing the limited land resources on which humans depend, restricting agricultural production. (2) Methods: A prokaryotic expression system was used to produce recombinant PtOSH1 protein, and Western blotting was performed to identify its activity. In addition, a simplified version of the floral-dip method was used to transform A. thaliana. (3) Results: Here, we describe the identification and characterization of OSH1 from Populus trichocarpa. The deduced PtOSH1 sequence contained CQHGX2ECX2NX4C and CXXC motifs. The transcript level of PtOSH1 was increased by cadmium (Cd) treatment. In addition, recombinant PtOSH1 reduced disulfide bonds. A stress assay showed that PtOSH1-overexpressing (OE) A. thaliana lines had greater resistance to Cd than wild-type (WT) plants. Also, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in PtOSH1-OE plants were significantly higher than those in WT A. thaliana. These results indicate that PtOSH1 likely plays an important role in the response to Cd by regulating the reactive oxygen species (ROS)-scavenging system. (4) Conclusions: PtOSH1 catalyzes the reduction of disulfide bonds and behaves as a sulfhydryl reductase under acidic conditions. The overexpression of PtOSH1 in A. thaliana promoted root development, fresh weight, and dry weight; upregulated the expression levels of ROS scavenging-related genes; and improved the activity of antioxidant enzymes, enhancing plant tolerance to cadmium (Cd) stress. This study aimed to provide guidance that will facilitate future studies of the function of PtOSH1 in the response of plants to Cd stress.

Penaeus monodon GILT enzyme restricts WSSV infectivity by reducing disulfide bonds in WSSV proteins

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is involved in the adaptive immune response via its effects on major histocompatibility complex (MHC)-restricted antigen presentation. In addition to antigen presentation, GILT exerts its antiviral activity by reducing disulfide bonds in proteins involved in viral infection and assembly, thereby inhibiting viral envelope-mediated infection and viral progeny production. In black tiger shrimp, Penaeus monodon GILT (PmGILT) was cloned and characterized, and found to be involved in the shrimp innate immune response and to exert neutralizing activity against white spot syndrome virus (WSSV) infection. However, the anti-WSSV mechanism of PmGILT in the shrimp innate immune response has not been defined. To explore the anti-WSSV activity of PmGILT, a yeast 2-hybrid (Y2H) assay was performed to identify WSSV proteins targeted by PmGILT. The assay revealed 4 potential PmGILT-interacting WSSV proteins: WSSV002, WSSV164, WSSV189, and WSSV471. Three of these 4 WSSV proteins (WSSV002, WSSV164 and WSSV189) were successfully produced and confirmed to interact with PmGILT in in vitro pull-down assays. WSSV189 and WSSV471 were previously identified as structural proteins, whereas WSSV164 is an immediate-early protein which has anti-melanization activity, and WSSV002 is an unknown. Because of the thiol reductase activity of PmGILT, WSSV164 and WSSV189, both of which are cysteine-containing WSSV proteins, were chosen for disulfide bond reduction assays. PmGILT reduced intrachain disulfide bonds in both WSSV proteins, suggesting that PmGILT exerts its anti-WSSV activity via its thiol reductase activity to disrupt the WSSV protein complex and restore the melanization activity of PmproPO1 and PmproPO2.

Identification and functional characterization of interferon-γ-inducible lysosomal thiol reductase (GILT) gene in common Chinese cuttlefish Sepiella japonica

Interferon-γ-inducible lysosomal thiol reductase (GILT) is a pivotal enzyme involved in the histocompatibility complex (MHC) class II-restricted antigen processing whereby it catalyzes the disulfide bond reduction in the endocytic pathway. Here, a novel GILT homologue termed as SjGILT firstly identified from common Chinese cuttlefish Sepiella japonica. SjGILT shared domain topology containing a signal peptide, a signature sequence CQHGX₂ECX₂NX₄C, an activate-site CXXC motif, two potential N-glycosylation sites and six conserved cysteins with its counterparts in other animals. SjGILT transcripts were constitutively expressed in all examined tissues in S. japonica, with the higher expression levels in immune-related tissues such as pancreas, intestines, liver and gills. Upon lipopolysaccharide (LPS) challenge, SjGILT transcripts were significantly induced in liver and gill tissues, and SjGILT protein transferred to late endosomes and lysosomes in HeLa cells. Further study showed that recombinant SjGILT had obvious thiol reductase activity demonstrated by reducing the interchain disulfide bonds of IgG under acidic conditions. Taken together, these results suggested that SjGILT may be involved in the immune response to bacteria challenge, and then might play an important role in the processing of MHC class II-restricted antigens in S. japonica.

Two Phytoplasmas Elicit Different Responses in the Insect Vector Euscelidius variegatus Kirschbaum

Phytoplasmas are plant-pathogenic bacteria transmitted by hemipteran insects. The leafhopper Euscelidius variegatus is a natural vector of chrysanthemum yellows phytoplasma (CYp) and a laboratory vector of flavescence dorée phytoplasma (FDp). The two phytoplasmas induce different effects on this species: CYp slightly improves whereas FDp negatively affects insect fitness. To investigate the molecular bases of these different responses, transcriptome sequencing (RNA-seq) analysis of E. variegatus infected with either CYp or FDp was performed. The sequencing provided the first de novo transcriptome assembly for a phytoplasma vector and a starting point for further analyses on differentially regulated genes, mainly related to immune system and energy metabolism. Insect phenoloxidase activity, immunocompetence, and body pigmentation were measured to investigate the immune response, while respiration and movement rates were quantified to confirm the effects on energy metabolism. The activation of the insect immune response upon infection with FDp, which is not naturally transmitted by E. variegatus, confirmed that this bacterium is mostly perceived as a potential pathogen. Conversely, the acquisition of CYp, which is naturally transmitted by E. variegatus, seems to increase the insect fitness by inducing a prompt response to stress. This long-term relationship is likely to improve survival and dispersal of the infected insect, thus enhancing the opportunity of phytoplasma transmission.

A proteomics approach to identify targets of the ubiquitin-like molecule Urm1 in Drosophila melanogaster

By covalently conjugating to target proteins, ubiquitin-like modifiers (UBLs) act as important regulators of target protein localization and activity, thereby playing a critical role in the orchestration of cellular biology. The most ancient and one of the least studied UBLs is Urm1, a dual-function protein that in parallel to performing similar functions as its prokaryotic ancestors in tRNA modification, also has adopted the capacity to conjugate to cellular proteins analogous to ubiquitin and other UBL modifiers. In order to increase the understanding of Urm1 and its role in multicellular organisms, we have used affinity purification followed by mass spectrometry to identify putative targets of Urm1 conjugation (urmylation) at three developmental stages of the Drosophila melanogaster lifecycle. Altogether we have recovered 79 Urm1-interacting proteins in Drosophila, which include the already established Urm1 binding partners Prx5 and Uba4, together with 77 candidate urmylation targets that are completely novel in the fly. Among these, the majority was exclusively identified during either embryogenesis, larval stages or in adult flies. We further present biochemical evidence that four of these proteins are covalently conjugated by Urm1, whereas the fifth verified Urm1-binding protein appears to interact with Urm1 via non-covalent means. Besides recapitulating the previously established roles of Urm1 in tRNA modification and during oxidative stress, functional clustering of the newly identified Urm1-associated proteins further positions Urm1 in protein networks that control other types of cellular stress, such as immunological threats and DNA damage. In addition, the functional characteristics of several of the candidate targets strongly match the phenotypes displayed by Urm1n123 null animals, including embryonic lethality, reduced fertility and shortened lifespan. In conclusion, this identification of candidate targets of urmylation significantly increases the knowledge of Urm1 and presents an excellent starting point for unravelling the role of Urm1 in the context of a complex living organism.

Molecular structure and functional characterization of the gamma-interferon-inducible lysosomal thiol reductase (GILT) gene in largemouth bass (Microptenus salmoides)

The enzyme gamma-interferon-inducible lysosomal thiol reductase (GILT) plays a role in facilitating the processing and presentation of major histocompatibility complex (MHC) class II-restricted antigens and is also involved in MHC I-restricted antigens in adaptive immunity catalyzing disulfide bond reduction in mammals. In this study, we cloned a GILT gene homolog from largemouth bass (designated 'lbGILT'), a freshwater fish belonging to Perciformes and known for its nutritive value. We obtained the full-length cDNA of lbGILT by reverse transcription PCR and rapid amplification of cDNA ends. This cDNA is comprised of a 5'-untranslated region (UTR) of 87 bp, a 3'-UTR of 189 bp, and an open reading frame of 771 bp. It encodes a protein of 256 amino acids with a deduced molecular weight of 28.548 kDa and a predicted isoelectric point of 5.62. The deduced protein possesses the typical structural features of known GILTs, including an active site motif, two potential N-linked glycosylation sites, a GILT signature sequence, and six conserved cysteines. Tissue-specific expression of lbGILT was shown by real-time quantitative PCR. The expression of lbGILT mRNA was obviously up regulated in spleen and kidney after induction with lipopolysaccharide. Recombinant lbGILT was produced as an inclusion body with a His6 tag in ArcticExpress (DE3), and the protein was then washed, solubilized, and refolded. The refolded lbGILT showed reduction activity against an IgG substrate. These results suggest that lbGILT plays a role in innate immunity.

Predator strike shapes antipredator phenotype through new genetic interactions in water striders

How novel genetic interactions evolve, under what selective pressures, and how they shape adaptive traits is often unknown. Here we uncover behavioural and developmental genetic mechanisms that enable water striders to survive attacks by bottom-striking predators. Long midlegs, critical for antipredator strategy, are shaped through a lineage-specific interaction between the Hox protein Ultrabithorax (Ubx) and a new target gene called gilt. The differences in leg morphologies are established through modulation of gilt differential expression between mid and hindlegs under Ubx control. Furthermore, short-legged water striders, generated through gilt RNAi knockdown, exhibit reduced performance in predation tests. Therefore, the evolution of the new Ubx–gilt interaction contributes to shaping the legs that enable water striders to dodge predator strikes. These data show how divergent selection, associated with novel prey–predator interactions, can favour the evolution of new genetic interactions and drive adaptive evolution.

Understanding the mechanism underlying the evolution of ecologically relevant traits is challenging. Here the authors show that changes in the Hox protein Ultrabithorax and its target gene gilt contribute to the evolution of long-mid-legs in water striders, a critical trait to escape predators.

The first echinoderm gamma-interferon-inducible lysosomal thiol reductase (GILT) identified from sea cucumber (Stichopus monotuberculatus)

Gamma-interferon-inducible lysosomal thiol reductase (GILT) has been described as a key enzyme that facilitating the processing and presentation of major histocompatibility complex class II-restricted antigen in mammals. In this study, the first echinoderm GILT named StmGILT was identified from sea cucumber (Stichopus monotuberculatus). The StmGILT cDNA is 1529 bp in length, containing a 5'-untranslated region (UTR) of 87 bp, a 3'-UTR of 674 bp and an open reading frame (ORF) of 768 bp that encoding a protein of 255 amino acids with a deduced molecular weight of 27.82 kDa and a predicted isoelectric point of 4.73. The putative StmGILT protein possesses all the main characteristics of known GILT proteins, including a signature sequence, a reductase active site CXXC, twelve conserved cysteines, and two potential N-linked glycosylation sites. For the gene structure, StmGILT contains four exons separated by three introns. In the promoter region of StmGILT gene, an NF-κB binding site and an IFN-γ activation site were found. The thiol reductase activity of recombinant StmGILT protein was also demonstrated in this study. In addition, the highest level of mRNA expression was noticed in coelomocytes of S. monotuberculatus. In in vitro experiments performed in coelomocytes, the expression of StmGILT mRNA was significantly up-regulated by lipopolysaccharides (LPS), inactivated bacteria or polyriboinosinic polyribocytidylic acid [poly (I:C)] challenge, suggested that the sea cucumber GILT might play critical roles in the innate immune defending against bacterial and viral infections.