Expression of Ixodes scapularis antifreeze glycoprotein enhances cold tolerance in Drosophila melanogaster

Physics of Ice Nucleation and Antinucleation: Action of Ice-Binding Proteins

Ice-binding proteins are crucial for the adaptation of various organisms to low temperatures. Some of these, called antifreeze proteins, are usually thought to inhibit growth and/or recrystallization of ice crystals. However, prior to these events, ice must somehow appear in the organism, either coming from outside or forming inside it through the nucleation process. Unlike most other works, our paper is focused on ice nucleation and not on the behavior of the already-nucleated ice, its growth, etc. The nucleation kinetics is studied both theoretically and experimentally. In the theoretical section, special attention is paid to surfaces that bind ice stronger than water and thus can be "ice nucleators", potent or relatively weak; but without them, ice cannot be nucleated in any way in calm water at temperatures above -30 °C. For experimental studies, we used: (i) the ice-binding protein mIBP83, which is a previously constructed mutant of a spruce budworm Choristoneura fumiferana antifreeze protein, and (ii) a hyperactive ice-binding antifreeze protein, RmAFP1, from a longhorn beetle Rhagium mordax. We have shown that RmAFP1 (but not mIBP83) definitely decreased the ice nucleation temperature of water in test tubes (where ice originates at much higher temperatures than in bulk water and thus the process is affected by some ice-nucleating surfaces) and, most importantly, that both of the studied ice-binding proteins significantly decreased the ice nucleation temperature that had been significantly raised in the presence of potent ice nucleators (CuO powder and ice-nucleating bacteria Pseudomonas syringae). Additional experiments on human cells have shown that mIBP83 is concentrated in some cell regions of the cooled cells. Thus, the ice-binding protein interacts not only with ice, but also with other sites that act or potentially may act as ice nucleators. Such ice-preventing interaction may be the crucial biological task of ice-binding proteins.

Protein regulation mechanism of cold tolerance in Haemaphysalis longicornis

Ticks are external parasitic arthropods that can transmit a variety of pathogens by sucking blood. Low-temperature tolerance is essential for ticks to survive during the cold winter. Exploring the protein regulation mechanism of low-temperature tolerance of Haemaphysalis longicornis could help to explain how ticks survive in winter. In this study, the quantitative proteomics of several tissues of H. longicornis exposed to low temperature were studied by data independent acquisition technology. Totals of 3 699, 3 422, and 1 958 proteins were identified in the salivary gland, midgut, and ovary, respectively. The proteins involved in energy metabolism, cell signal transduction, protein synthesis and repair, and cytoskeleton synthesis changed under low-temperature stress. The comprehensive analysis of the protein regulation of multiple tissues of female ticks exposed to low temperature showed that maintaining cell homeostasis, maintaining cell viability, and enhancing cell tolerance were the most important means for ticks to maintain vital signs under low temperature. The expression of proteins involved in and regulating the above cell activities was the key to the survival of ticks under low temperatures. Through the analysis of a large amount of data, we found that the expression levels of arylamine N-acetyltransferase, inositol polyphosphate multikinase, and dual-specificity phosphatase were up-regulated under low temperature. We speculated that they might have important significance in low-temperature tolerance. Then, we performed RNA interference on the mRNA of these 3 proteins, and the results showed that the ability of female ticks to tolerate low temperatures decreased significantly.

Cold-induced immune activation in chill-susceptible insects

Chilling injuries in chill-susceptible insects, like the model dipteran Drosophila melanogaster, have been well-documented as a consequence of stressful low temperature exposures. Cold stress also causes upregulation of genes in the insect immune pathways, some of which are also upregulated following other forms of sterile stress. The adaptive significance and underlying mechanisms surrounding cold-induced immune activation, however, are still unclear. Here, we review recent work on the roles of ROS, DAMPs, and AMPs in insect immune signalling or function. Using this emerging knowledge, we propose a conceptual model linking biochemical and molecular causes of immune activation to its consequences during and following cold stress.

Comparative analysis of cadmium-induced toxicity and survival responses in the wolf spider Pirata subpiraticus under low-temperature treatment

Cadmium (Cd) pollution is a serious heavy metal pollution in paddy fields, but its effect and underlying mechanism on soil arthropod overwintering and cold resistance are still unclear. In the present study, adult females of the wolf spider Pirata subpiraticus exposed to Cd stress underwent a simulated temperature process (25℃ → 16℃ → 8℃ → 4℃). The mortality rate and content of nutrients in the Cd-treated spiders were dramatically elevated after low-temperature treatment compared to those in the Cd-free control spiders under the same temperature condition. To uncover the putative modulatory mechanism of Cd on cold tolerance in P. subpiraticus, we employed an in-depth RNA sequencing analysis and yielded a total of 888 differentially expressed genes (DEGs). Besides, we characterized genes that participate in multiple cryoprotectant syntheses, including arginine, cysteine, glucose, glycerol, heat shock protein, and mannose. The enrichment analyses found that most of the DEGs involved in biological processes and pathways were related to carbohydrate, lipid, and protein metabolism. Notably, ten Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, such as starch and sucrose metabolism, arachidonic acid metabolism, amino acid metabolism, mineral absorption, and vitamin digestion and absorption, were distinctively enriched with downregulated genes. Meanwhile, we also identified that seven DEGs might inhibit the KEGG pathway of ovarian steroidogenesis and potentially cripple ovarian function and fecundity in the spider. The decreased egg sac weight, number of hatched spiderlings, and vitellin concentration further supported the view that Cd exposure vitiates the overwintering spider's fecundity. Collectively, the comparative analysis provides a novel perspective regarding the survival response and fecundity on the cold tolerance of spiders under Cd stress and offers a profound insight for evaluating Cd-induced toxicity on overwintering arthropods.

Comparative N-glycoproteomic analysis of Tibetan and lowland chicken fertilized eggs: Implications on proteins biofunction and species evolution

The characterization and functionality of protein glycosylation among different related species are of common interest. Herein, non-standard quantification and N-glycosylation enrichment technology combined with ultra-high liquid chromatography-tandem mass spectrometry were used to establish detailed N-glycoproteomics of fertilized eggs, and quantitatively compared between Tibetan and lowland chicken. A total of 396N-glycosites from 143 glycoproteins were found. Specifically, compared with lowland chicken egg white, 32N-glycosites of 22 glycoproteins were up-regulated and 57N-glycosites of 25 glycoproteins were down-regulated in Tibetan chicken egg white. Also, 137N-glycosites in 72 glycoproteins showed much higher-degree glycosylation and 36N-glycosites in 15 glycoproteins displayed lower-degree glycosylation in Tibetan chicken egg yolk than those in lowland chicken egg yolk. Through bioinformatic analysis, these varied glycoproteins were highly associated with antifreeze activity, hypoxia adaptation, coagulation cascade, and binding/immunity activities, which may be related to plateau hypoxia and cold stress. PRACTICAL APPLICATIONS: These findings provide a new insight on the role of biological egg N-glycoproteins related to environmental adaptation and evolution, which may be further applied in improving egg processing and human health, by developing biomolecules for food and medical industry.

Precise levels of the Drosophila adaptor protein Dreadlocks maintain the size and stability of germline ring canals

Intercellular bridges are essential for fertility in many organisms. The developing fruit fly egg has become the premier model system to study intercellular bridges. During oogenesis, the oocyte is connected to supporting nurse cells by relatively large intercellular bridges, or ring canals. Once formed, the ring canals undergo a 20-fold increase in diameter to support the movement of materials from the nurse cells to the oocyte. Here, we demonstrate a novel role for the conserved SH2/SH3 adaptor protein Dreadlocks (Dock) in regulating ring canal size and structural stability in the germline. Dock localizes at germline ring canals throughout oogenesis. Loss of Dock leads to a significant reduction in ring canal diameter, and overexpression of Dock causes dramatic defects in ring canal structure and nurse cell multinucleation. The SH2 domain of Dock is required for ring canal localization downstream of Src64 (also known as Src64B), and the function of one or more of the SH3 domains is necessary for the strong overexpression phenotype. Genetic interaction and localization studies suggest that Dock promotes WASp-mediated Arp2/3 activation in order to determine ring canal size and regulate growth.

This article has an associated First Person interview with the first author of the paper.

Summary:Drosophila Dock likely functions downstream of WASp and the Arp2/3 complex to regulate the size and stability of the germline ring canals in the developing egg chamber.

A brief review of applications of antifreeze proteins in cryopreservation and metabolic genetic engineering

Antifreeze proteins (AFPs) confer the ability to survive at subzero temperatures and are found in many different organisms, including fish, plants, and insects. They prevent the formation of ice crystals by non-colligative adsorption to the ice surface and are essential for the survival of organisms in cold environments. These proteins are also widely used for cryopreservation, food technology, and metabolic genetic engineering over a range of sources and recipient cell types. This review summarizes successful applications of AFPs in the cryopreservation of animals, insects, and plants, and discusses challenges encountered in cryopreservation. Applications in metabolic genetic engineering are also described, specifically with the overexpression of AFP genes derived from different organisms to provide freeze protection to sensitive crops seasonally exposed to subzero temperatures. This review will provide information about potential applications of AFPs in the cryopreservation of animals and plants as well as in plant metabolic genetic engineering in hopes of furthering the development of cold-tolerant organisms.

Targeted substrate degradation by Kelch controls the actin cytoskeleton during ring canal expansion

During Drosophila oogenesis, specialized actin-based structures called ring canals form and expand to accommodate growth of the oocyte. Previous work demonstrated that Kelch and Cullin 3 function together in a Cullin 3-RING ubiquitin ligase complex (CRL3^Kelch) to organize the ring canal cytoskeleton, presumably by targeting a substrate for proteolysis. Here, we use tandem affinity purification followed by mass spectrometry to identify HtsRC as the CRL3^Kelch ring canal substrate. CRISPR-mediated mutagenesis of HtsRC revealed its requirement in the recruitment of the ring canal F-actin cytoskeleton. We present genetic evidence consistent with HtsRC being the CRL3^Kelch substrate, as well as biochemical evidence indicating that HtsRC is ubiquitylated and degraded by the proteasome. Finally, we identify a short sequence motif in HtsRC that is necessary for Kelch binding. These findings uncover an unusual mechanism during development wherein a specialized cytoskeletal structure is regulated and remodeled by the ubiquitin-proteasome system.

Arthropod transcriptional activator protein-1 (AP-1) aids tick-rickettsial pathogen survival in the cold

Ixodes scapularis ticks transmit several pathogens to humans including rickettsial bacterium, Anaplasma phagocytophilum. Here, we report that A. phagocytophilum uses tick transcriptional activator protein-1 (AP-1) as a molecular switch in the regulation of arthropod antifreeze gene, iafgp. RNAi-mediated silencing of ap-1 expression significantly affected iafgp gene expression and A. phagocytophilum burden in ticks upon acquisition from the murine host. Gel shift assays provide evidence that both the bacterium and AP-1 influences iafgp promoter and expression. The luciferase assays revealed that a region of approximately 700 bp upstream of the antifreeze gene is sufficient for AP-1 binding to promote iafgp gene expression. Furthermore, survival assays revealed that AP-1-deficient ticks were more susceptible to cold in comparison to the mock controls. In addition, this study also indicates arthropod AP-1 as a global regulator for some of the tick genes critical for A. phagocytophilum survival in the vector. In summary, our study defines a novel mode of arthropod signaling for the survival of both rickettsial pathogen and its medically important vector in the cold.

From ice-binding proteins to bio-inspired antifreeze materials

Ice-binding proteins (IBP) facilitate survival under extreme conditions in diverse life forms. IBPs in polar fishes block further growth of internalized environmental ice and inhibit ice recrystallization of accumulated internal crystals. Algae use IBPs to structure ice, while ice adhesion is critical for the Antarctic bacterium Marinomonas primoryensis. Successful translation of this natural cryoprotective ability into man-made materials holds great promise but is still in its infancy. This review covers recent advances in the field of ice-binding proteins and their synthetic analogues, highlighting fundamental insights into IBP functioning as a foundation for the knowledge-based development of cheap, bio-inspired mimics through scalable production routes. Recent advances in the utilisation of IBPs and their analogues to e.g. improve cryopreservation, ice-templating strategies, gas hydrate inhibition and other technologies are presented.

A Tick Antivirulence Protein Potentiates Antibiotics against Staphylococcus aureus

New strategies are needed to combat antibiotic resistance, especially against pathogens such as methicillin-resistant Staphylococcus aureus A tick antifreeze glycoprotein, IAFGP, possesses potent antibiofilm properties against a variety of clinical pathogens, including S. aureus Synergy between IAFGP, or a peptide (P1) representative of a repeat region of the protein, with different antibiotics was assessed in vitro Antibiotics that synergized with either IAFPG or P1 were further evaluated in vivo using vertebrate and invertebrate infection models. IAFGP readily enhanced the efficacy of antibiotics against S. aureus Synergy with daptomycin, an antibiotic used to treat methicillin-resistant S. aureus, was observed in vitro and in vivo using iafgp-transgenic mice and flies. Furthermore, synergy with ciprofloxacin or gentamicin, antibiotics not generally used to treat S. aureus, was also perceived. The combined effect of the antibiotic and IAFGP was associated with improved permeation of the antibiotic into the cell. Our results highlight that synergy of IAFGP with antibiotics traditionally used to treat this pathogen, and enhancement of the potency of antibiotics not commonly used against this microbe, can provide novel alternative therapeutic strategies to combat bacterial infections.

Thermal reactionomes reveal divergent responses to thermal extremes in warm and cool-climate ant species

Background

The distributions of species and their responses to climate change are in part determined by their thermal tolerances. However, little is known about how thermal tolerance evolves. To test whether evolutionary extension of thermal limits is accomplished through enhanced cellular stress response (enhanced response), constitutively elevated expression of protective genes (genetic assimilation) or a shift from damage resistance to passive mechanisms of thermal stability (tolerance), we conducted an analysis of the reactionome: the reaction norm for all genes in an organism’s transcriptome measured across an experimental gradient. We characterized thermal reactionomes of two common ant species in the eastern U.S, the northern cool-climate Aphaenogaster picea and the southern warm-climate Aphaenogaster carolinensis, across 12 temperatures that spanned their entire thermal breadth.

Results

We found that at least 2 % of all genes changed expression with temperature. The majority of upregulation was specific to exposure to low temperatures. The cool-adapted A. picea induced expression of more genes in response to extreme temperatures than did A. carolinensis, consistent with the enhanced response hypothesis. In contrast, under high temperatures the warm-adapted A. carolinensis downregulated many of the genes upregulated in A. picea, and required more extreme temperatures to induce down-regulation in gene expression, consistent with the tolerance hypothesis. We found no evidence for a trade-off between constitutive and inducible gene expression as predicted by the genetic assimilation hypothesis.

Conclusions

These results suggest that increases in upper thermal limits may require an evolutionary shift in response mechanism away from damage repair toward tolerance and prevention.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2466-z) contains supplementary material, which is available to authorized users.

Frostbite protection in mice expressing an antifreeze glycoprotein

Ectotherms in northern latitudes are seasonally exposed to cold temperatures. To improve survival under cold stress, they use diverse mechanisms to increase temperature resistance and prevent tissue damage. The accumulation of anti-freeze proteins that improve cold hardiness occurs in diverse species including plants, arthropods, fish, and amphibians. We previously identified an Ixodes scapularis anti-freeze glycoprotein, named IAFGP, and demonstrated its cold protective function in the natural tick host and in a transgenic Drosophila model. Here we show, in a transgenic mouse model expressing an anti-freeze glycoprotein, that IAFGP protects mammalian cells and mice from cold shock and frostbite respectively. Transgenic skin samples showed reduced cell death upon cold storage ex vivo and transgenic mice demonstrated increased resistance to frostbite injury in vivo. IAFGP actively protects mammalian tissue from freezing, suggesting its application for the prevention of frostbite, and other diseases associated with cold exposure.

Antivirulence properties of an antifreeze protein

As microbial drug-resistance increases, there is a critical need for new classes of compounds to combat infectious diseases. The Ixodes scapularis tick antifreeze glycoprotein, IAFGP, functions as an antivirulence agent against diverse bacteria, including methicillin-resistant Staphylococcus aureus. Recombinant IAFGP and a peptide, P1, derived from this protein bind to microbes and alter biofilm formation. Transgenic iafgp-expressing flies and mice challenged with bacteria, as well as wild-type animals administered P1, were resistant to infection, septic shock, or biofilm development on implanted catheter tubing. These data show that an antifreeze protein facilitates host control of bacterial infections and suggest therapeutic strategies for countering pathogens.

Methods for studying oogenesis

Drosophila oogenesis is an excellent system for the study of developmental cell biology. Active areas of research include stem cell maintenance, gamete development, pattern formation, cytoskeletal regulation, intercellular communication, intercellular transport, cell polarity, cell migration, cell death, morphogenesis, cell cycle control, and many more. The large size and relatively simple organization of egg chambers make them ideally suited for microscopy of both living and fixed whole mount tissue. A wide range of tools is available for oogenesis research. Newly available shRNA transgenic lines provide an alternative to classic loss-of-function F2 screens and clonal screens. Gene expression can be specifically controlled in either germline or somatic cells using the Gal4/UAS system. Protein trap lines provide fluorescent tags of proteins expressed at endogenous levels for live imaging and screening backgrounds. This review provides information on many available reagents and key methods for research in oogenesis.