RNA-sequencing indicates high hemocyanin expression as a key strategy for cold adaptation in the Antarctic amphipod Eusirus cf.giganteus clade g3

We here report the de novo transcriptome assembly and functional annotation of Eusirus cf.giganteus clade g3,providing the first database of expressed sequences from this giant Antarctic amphipod.RNA-sequencing,carried out on the whole body of a single juvenile individual likely undergoing molting,revealed the dominant expression of hemocyanins.The mRNAs encoding these oxygen-binding proteins cumulatively accounted for about 40%of the total transcriptional effort,highlighting the key biological importance of high hemocyanin production in this Antarctic amphipod species.We speculate that this observation may mirror a strategy previously described in Antarctic cephalopods,which compensates for the decreased ability to release oxygen to peripheral tissues at sub-zero temperatures by massively increasing total blood hemocyanin content compared with temperate species.These preliminary results will undoubtedly require confirmation through proteomic and biochemical analyses aimed at characterizing the oxygen-binding properties of E.cf.giganteus clade g3 hemocyanins and at investigating whether other Antarctic arthropod species exploit similar adaptations to cope with the challenges posed by the extreme conditions of the polar environment.

Psychrotolerant methanogenic archaea:Diversity and cold adaptation mechanisms

Because of their diversity and abundance in a wide range of environments, particularly in cold regions, cold-adaptive archaea are expected to play a pivotal role in material recycling in cold environments. Methanogenic archaea are ubiquitous on earth and produce a large amount of methane （CH4） as their main carbon metabolite. Methanogens are the most laboratory amenda- ble archaea. The few psychrophilic archaea that have been cultured to date are mainly affiliated with methanogens, thus make them a good model for investigating mechanisms of archaeal cold adaptation. Studies of psychrotolerant methanogens have been ongoing since the 1990s. Using Methanocoecoides burtonii, a methanogen isolated from Ace Lake in Antarctica, exten- sive studies on the genomic characteristics associated with cold adaptation have been carried out by the Cavicchioli laboratory. We recently analyzed the genome of another psychrophilic methanogen and identified the gene repertoire associated with cold adaptation. This review summarizes recent studies of psychroactive methanogens, particularly their diversity, the genomics and proteomics associated with their cold adaptation, and the cellular components and proteins likely involved in their cold protec- tion.

Cold adaptation strategy of psychrophilic bacteria:an in-silico analysis of isocitrate dehydrogenase

Non-specific electrostatics is crucial for structure and stability;recently,it has been argued that psychrophilic proteins may also utilize specific electrostatic interactions.Do psychrophilic proteins increase the number of salt bridges for cold adaptation?Are there any changes that occur in their sequence,which helps them to adapt in an extreme environment?Do intra-protein interactions affect their stability?Is there any special type of intra-protein interaction present in psychrophilic protein structure?This study will give all those answers.Sequences(n~100)and structures of psychrophilic isocitrate dehydrogenase and mesophilic isocitrate dehydrogenase extracted from databases.Sequences had been analyzed in BLOCK and non-BLOCK format.The sequences of psychrophiles and mesophiles create two separate clades.The number of charged and uncharged polar residues is very much high in psychrophilic proteins.The formation of long network aromatic-aromatic interactions and network aromatic-sulfur interactions are very crucial for psychrophilic protein stability.Identification of these types of interactions is also a novelty of this study.Favorable mutation of charged residues with high-energy contributions affects the protein stability.This study will help in protein engineering.

Genome-wide scan for selective footprints and genes related to cold tolerance in Chantecler chickens

The Chantecler chicken,a unique Canadian indigenous breed,is well adapted to extremely cold environments.However,its genetic characteristics have not been well studied.Here,we analyzed the whole genomes of 10 Chantecler chickens and 121 worldwide chickens,which indicated that Chantecler chickens were derived from commercial chickens and exhibit a high level of inbreeding.Based on a genome-wide scan,we identified two vital candidate regions containing ME3 and ZNF536,which are related to fat metabolism and nervous system in cold adaptation,respectively.We also found that the genetic mechanism of cold adaptation in Chantecler chickens differed from that of chickens from other cold regions,such as northern China.Our study indicated that specialized commercial chickens in the early 20th century contained sufficient genetic diversity to adapt to extreme cold environments over a very short time.These findings enrich our understanding of the adaptive potential of commercial species.

Structure and function of a novel cold regulated cold shock domain containing protein from an obligate psychrophilic yeast,Glaciozyma antarctica

Cold shock domain(CSD)-containing proteins are one of the groups of the evolutionarily conserved nucleic acid-binding proteins in all three domains of life consisting of an ancient beta-barrel fold that serves to bind nucleic acids.The c DNA of a novel protein-coding gene containing CSD was cloned from Glaciozyma antarctica designated as Ga16676.The full length of Ga16676 gene with the size of 1335 bp encodes for an N-terminal CSD with conserved nucleic acids binding motif RNP1 and RNP2.The Ga16676 gene was cloned in p ET30 Ek/LIC,sequenced,expressed and its resistance towards cold was characterized.Recombinant protein expression of Ga16676 showed overexpressed soluble expression in both supernatant and pellet forms at 20℃.The effects of recombinant CSD protein overexpression on colony formation shows that E.coli cells were able to grow at 37℃and 20℃but not at 4℃while E.coli_Ga16676 cells were able to grow at all temperatures tested.In addition,E.coli_Ga16676 cells showed higher growth rate compared to empty E.coli cells at 10℃.Structural analysis of Ga16676 reveals some interesting findings such as more aromatic interactions for efficient binding in low energy environment,a longer loop that may contribute to structural flexibility and clustering of charged amino acids on the protein surface that is important for protein stability and flexibility.

Structural basis for the cold activation and adaptation of anα-agarase from marine bacterium Catenovulum agarivorans STB13

Enzymes have high activity at low temperatures are defined as cold-adapted enzymes,but few enzymes show an activation effect after low-temperature incubation.In this study,we cloned an agarase from the marine bacte-rium Catenovulum agarivorans STB13(Ca-AGA)and expressed the protein in Bacillus subtilis.The enzyme exhibited a peculiar cold activation,which was enhanced by 5-fold after incubation at-20℃ or 4℃ for 6 h.Fluorescence and CD spectra studies confirmed the secondary and tertiary structural changes in Ca-AGA at low temperature,which formed compact protein structures after low-temperature treatment.The enzyme also showed outstanding cold adaptation,retaining approximately 60%of its maximum activity at 10℃.Based on a bioinformatics analysis,the carbohydrate-binding modules(CBMs)and long linker region were presumed to play a crucial role in cold adaptation due to a relatively high percentage of acidic residues and a negative charge density compared to the catalytic domain.A mutation that truncated the linker-CBM region resulted in a 59.97%reduction of the activity at 10℃.This study describes anα-agarase of cold activation and adaptation in detail,which may have great potential for producing functional agaro-oligosaccharides in food and pharmaceutical industrial applications at ambient temperature.

Transposon mutagenesis of Psychrobacter cryohalolentis PAMC 21807 by tri-parental conjugation

Random mutagenesis is commonly used to study gene function. The screening of mutants exhibiting specific pheno- types assists in the identification of phenotype-related genes. In the current study, we isolated Antarctic bacteria, and developed a transposon Tn5 mutagenesis system. A total of 26 strains were isolated from seawater and freshwater near Antarctic King Sejong Research Station, King George Island. Six Psychrobacter strains were identified as psychrophilic, with optimal growth tempera- tures of 10~C or 15~C Psychrobacter cryohalolentis PAMC 21807 with a high growth rate at 4~C was selected for transposon mutagenesis. Tri-parental conjugation with a plasmid containing Tn5 produced 13 putative recombinants containing the selectable marker. Genomic Southern hybridization confirmed Tn5 existed as episomes for seven recombinants, and for a single recombinant, Tn5 was integrated into the genome of Psychrobacter cryohalolentis PAMC 21807. The result indicates that the mutagenesis method, although successful, has a relatively low rate. The psychrophilic bacteria isolated in this study may be a useful resource for studying cold adaptation mechanisms, and the mutagenesis method can be applied to genetic analysis.

The impact of low ambient temperature on cardiovascular health

Extreme weather events and climate change have witnessed a substantial increase in recent years,leading to heightened concerns.The rise in abnormal ambient temperatures,both in intensity and frequency,directly and indirectly impacts cardiovascular health.While the impact of high ambient temperatures on cardiovascular response is a common concern in the context of global warming,the significance of low temperatures cannot be overlooked.The challenges posed by low temperatures contribute to increased cardiovascular morbidity and mortality,posing a significant threat to global public health.This review aims to provide an overview of the relationship between low ambient temperature and cardiovascular health,encompassing the burden of cardiovascular outcomes and underlying mechanisms.Additionally,the review explores strategies for cold adaptation and cardioprotection.We posit that to optimize cold adaptation strategies,future research should delve deeper into the underlying mechanisms of cardiovascular health in response to low ambient temperature exposure.

Cold tolerance and cold hardening strategy of the Japanese pine sawyer Monochamus alternatus （Coleoptera： Cerambycidae）

The Japanese pine sawyer, Monochamus alternatus, is an important pine forest pest and vector transmitting the pine wilt nematode that causes pine wilt disease. Low temperatures in autumn, winter and spring often differentially affect mortality of M. alternatus larvae. In this paper, we mainly compared the differences of mortality and cold hardening of larvae from different seasons, based on supercooling point （SCP） and cumulative probability of individuals freezing （CPIF）. The cold hardening of the larvae from autumn, winter and spring seasons were largely different. Correlations between mortality and CPIF of autumn and spring larvae were highest on day 1/4, and gradually decreased with prolonged exposure duration. This beetle＇s death mainly resulted from freezing in short exposure duration. However, the correlation between mortality and CPIF of winter larvae increased gradually with the prolonged exposure duration. Death did not mainly result from freezing in long exposure duration. Autumn larvae are more susceptible and adaptable than winter and spring larvae. Winter larvae have a slight freeze-tolerance trend. Our research showed that M. alternatus came into complex cold-hardening strategies under natural selection. Freeze avoidance is the primary strategy; with prolonged exposure duration to above SCP or 〈 0℃, chill tolerance is more important; this is followed by freeze tolerance during harsh winters.

Individual thermal comfort prediction using classification tree model based on physiological parameters and thermal history in winter

Individual thermal comfort models based on physiological parameters could improve the efficiency of the personal thermal comfort control system.However,the effect of thermal history has not been fully addressed in these models.In this study,climate chamber experiments were conducted in winter using 32 subjects who have different indoor and outdoor thermal histories.Two kinds of thermal conditions were investigated:the temperature dropping(24-16℃)and severe cold(12℃)conditions.A simplified method using historical air temperature to quantify the thermal history was proposed and used to predict thermal comfort and thermal demand from physical or physiological parameters.Results show the accuracies of individual thermal sensation prediction was low to about 30%by using the PMV index in cold environments of this study.Base on the sensitivity and reliability of physiological responses,five local skin temperatures(at hand,calf,head,arm and thigh)and the heart rate are optimal input parameters for the individual thermal comfort model.With the proposed historical air temperature as an additional input,the general accuracies using classification tree model C5.0 were increased up by 15.5%for thermal comfort prediction and up by 29.8%for thermal demand prediction.Thus,when predicting thermal demands in winter,the factor of thermal history should be considered.

Up-regulation of Long Non-coding RNA TUG1 in Hibernating Thirteen-lined Ground Squirrels

Mammalian hibernation is associated with multiple physiological, biochemical, and molecular changes that allow animals to endure colder temperatures. We hypothesize that long non-coding RNAs（lnc RNAs）, a group of non-coding transcripts with diverse functions, are differentially expressed during hibernation. In this study, expression levels of lncRNAs H19 and TUG1 were assessed via qRT-PCR in liver, heart, and skeletal muscle tissues of the hibernating thirteen-lined ground squirrels（Ictidomys tridecemlineatus）. TUG1 transcript levels were significantly elevated 1.94-fold in skeletal muscle of hibernating animals when compared with euthermic animals. Furthermore, transcript levels of HSF2 also increased 2.44-fold in the skeletal muscle in hibernating animals. HSF2 encodes a transcription factor that can be negatively regulated by TUG1 levels and that influences heat shock protein expression. Thus, these observations support the differential expression of the TUG1-HSF2 axis during hibernation. To our knowledge, this study provides the first evidence for differential expression of lnc RNAs in torpid ground squirrels, adding lnc RNAs as another group of transcripts modulated in this mammalian species during hibernation.