Studies of cold tolerance.
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Acclimatization↗
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Cold tolerance and the regulation of cardiac performance and hemolymph distribution in Maja squinado (Crustacea: decapoda).
Elevated Mg(2+) levels in the hemolymph ([Mg(2+)](HL)) of brachyuran crabs have recently been demonstrated to limit cold tolerance by reducing motor and circulatory activity. Therefore, the limiting function of elevated [Mg(2+)](HL) on circulatory performance and arterial hemolymph flow was investigated by the pulsed-Doppler technique in the spider crab Maja squinado during progressive cooling from 12 degrees to 0 degrees C. [Mg(2+)](HL) were reduced from control levels of 39.9 mmol L(-1) to levels of 6.1 mmol L(-1) by incubation in magnesium reduced seawater. At 12 degrees C cardiac output was 13.9+/-2.4 mL kg(-1) min(-1) and stroke volume 0.2+/-0.04 mL kg(-1) min(-1) in control animals. In [Mg(2+)](HL)-reduced animals cardiac output increased to 43.6+/-5.0 mL kg(-1) min(-1) and stroke volume rose to 0.6+/-0.1 mL kg(-1) min(-1). Temperature reduction in control animals revealed a break point at 8 degrees C linked to a major redirection of hemolymph flow from lateral to sternal and hepatic arteries. Cardiac output and heart rate dropped sharply during cooling until transiently constant values were reached. Further heart rate reduction occurred below 4.5 degrees C. Such a plateau was not detected in [Mg(2+)](HL)-reduced animals where the break point decreased to 6 degrees C, also indicated by a sharp drop in heart rate and cardiac output and the redirection of hemolymph flow. It is concluded that progressive cooling brings the animals from a temperature range of optimum cardiac performance into a deleterious range when aerobic scope for activity falls before critical temperatures are reached. Reduction of [Mg(2+)](HL) shifts this transition to lower temperatures. These findings support a limiting role for [Mg(2+)](HL) in thermal tolerance.
Acclimatization↗
Ability of cold-tolerant plants to grow in hydrocarbon-contaminated soil.
Phytoremediation of hydrocarbons in soil involves plants and their associated microorganisms. Differences in environmental conditions and restrictions on species importation mean that each country may need to identify indigenous plants to use for phytoremedation. Screening plants for hydrocarbon tolerance before screening for degradation ability may prove more economical than screening directly for degradation. Thirty-nine cold-tolerant plants native, or exotic and naturalized, in western Canada were assessed for their ability to survive in crude oil-contaminated soil. Four naturalized grasses (i.e., Agropyron pectiniforme, Bromus inermis, Phleum pratense, and Poa pratensis), three naturalized legumes (i.e., Medicago sativa, Melilotus officinalis, and Trifolium repens), two native forbs (i.e., Artemisia frigida and Potentilla pensylvanica), one native grass (i.e., Bromus ciliatus) and two native legumes (i.e., Glycyrrhiza lepidota and Psoralea esculenta) exhibited phytoremediation potential, based on survival. We determined the effect of increasing crude oil concentrations on total and root biomass, and relative growth rate of those species with the highest survival. The addition of 0.5%, 1%, and 5% (crude oil wt/fresh soil wt) crude oil to soil significantly decreased both the total biomass by at least 22% of the control and the relative growth rate of all species except P. esculenta. Root biomass significantly decreased by at least 22% with crude oil addition in all species except P. esculenta and A. frigida. Total biomass production in contaminated soil had a significant negative correlation with the relative growth rate in uncontaminated soil.
Acclimatization↗
Some preliminary studies on the ability of Africanized honey bees (Apis mellifera L.) to tolerate cold temperatures when placed inside a refrigerator.
Cold is often suggested as an ecological mechanism to prevent the migration of Africanized honey bees. The ability of Africanized honey bees to tolerate cold temperatures was investigated. In one study an observation hive was placed inside a refrigerator at 25 degrees C. The study was conceptualized as a choice experiment in which the colony could remain in a cold environment or leave for a warm environment. Analysis indicated that the bees remained at 9 +/- 1 degrees C for 14 days before leaving. In a second series of studies, testing the tolerance to 0 degree C, 280 bees were placed individually in small metal tubes. The data gathered included survival rate, time to regain consciousness, and ability to feed. Analysis indicated that Africanized bees can survive for up to 3 hr. at 0 degree C with few ill effects. At 4 hr., however, the survival rate is low. Limitations of the study, the use of cold as a possible deterrent to honey bee mites, and suggestions for additional research are discussed.
Animals↗
Transgenic tall fescue containing the Agrobacterium tumefaciens ipt gene shows enhanced cold tolerance.
Embryogenic calli of Festuca arundinacea were transformed with the Agrobacterium tumefaciens isopentenyl transferase (ipt) gene driven by a maize ubiquitin promoter. Tillering ability, levels of chlorophyll a and b, and cold tolerance were greatly increased in the transgenic turfgrass, which resulted in the plants remaining more vigorous and staying green longer under lower temperatures.
Acclimatization↗
Effects of lifestyle, body composition, and physical fitness on cold tolerance in humans.
In the present study, we attempted to clarify the effects of lifestyle and body compositions on basal metabolism and to clarify the effects of physical training on thermoregulatory responses to cold. Basal metabolism, body compositions, and questionnaires regarding lifestyle were evaluated in 37 students. From multiple linear regression analysis, sex, muscle weight, fat intake, and diurnal temperature were selected as significant explanatory variables. In a second experiment, rectal and the skin temperature at 7 different points as well as the oxygen uptake of eight males were measured at 10 degrees C for 90 min before and after training. The decline in rectal temperature that was observed before training was not observed after training. In addition, rectal temperature was significantly higher at post-training than at pre-training. These results suggest that some lifestyle factors affect cold tolerance; in particular, daily activity might improve our ability to control heat radiation and basal heat production.
Adaptation, Physiological↗
Genetic Enhancement of Cold Tolerance by Expression of a Gene for Chloroplast [omega]-3 Fatty Acid Desaturase in Transgenic Tobacco.
The increased production of trienoic fatty acids, hexadecatrienoic (16:3) and linolenic (18:3) acids, is a response connected with cold acclimation of higher plants and is thought to protect plant cells against cold damage. Transgenic tobacco (Nicotiana tabacum cv SR1) plants that contain increased levels of 16:3 and 18:3 fatty acids, and correspondingly decreased levels of their precursors, hexadecadienoic and linoleic acids, were engineered by introduction of a chloroplast [omega]-3 fatty acid desaturase gene (the fad7 gene) isolated from Arabidopsis thaliana. When exposed to 1[deg]C for 7 d and then cultured at 25[deg]C, the suppression of leaf growth observed in the wild-type plants was significantly alleviated in the transgenic plants with the fad7 gene. The low-temperature- induced chlorosis was also much reduced in the plants transformed with the fad7 gene. These results indicate that increased levels of trienoic fatty acids in genetically engineered plants enhance cold tolerance.
Journal Article↗
Exogenous ABA enhances cold tolerance of Rhododendron yedoense var. poukhanense under subzero temperature: integrating physiology, transcriptome, and proteome.
Low temperature limits the growth and ornamental value of evergreen shrubs. Rhododendron yedoense var. poukhanense, an important ornamental shrub from Northeast China, frequently suffers freezing damage during winter. While exogenous abscisic acid (ABA) enhances cold tolerance in many plants, its molecular mechanisms at subzero temperatures remain poorly understood in non-model species lacking chromosome-level reference genomes. This study investigated the effects of exogenous ABA on freezing tolerance in R. yedoense var. poukhanense at -4 °C using an integrated physiological, transcriptomic, and proteomic approach. Cutting seedlings were subjected to four treatments: CK (22°C control), A (22°C + ABA), LT (-4°C), and ALT (-4°C + ABA). Photosynthetic pigments, osmotic regulation substances, antioxidant enzyme activities, and malondialdehyde (MDA) content were measured. Transcriptome sequencing and quantitative proteomics were performed, and transcriptome data were validated by quantitative real-time PCR (qRT-PCR) of 15 selected genes. ABA pretreatment reduced visible cold injury severity, partially preserved photosynthetic pigments, decreased MDA content by 28.7%, and promoted recovery of catalase (+43.6%), superoxide dismutase (+31.1%), and peroxidase (+20.0%) activities under freezing stress. Transcriptome analysis revealed 8, 444 differentially expressed genes (DEGs) in LT versus CK and 6, 481 DEGs in ALT versus CK, representing a 23% reduction in transcriptional reprogramming scope attributable to ABA priming. The ALT versus LT comparison identified only 1, 690 additional DEGs, indicating that most cold-responsive genes were pre-activated during the ABA priming phase. Proteome analysis identified 1, 461 differentially expressed proteins (DEPs) in ALT versus CK. Integrated analysis revealed extensive post-transcriptional regulation, with transcript-protein concordance of only 1.0-4.1%, and co-enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in both omics layers. qRT-PCR validation confirmed high reliability of the transcriptome data (R2 = 0.8500). These findings demonstrate that exogenous ABA enhances freezing tolerance through multi-layered molecular regulation encompassing transcriptional buffering, translational reprogramming, and functional reallocation from photosynthesis to stress protection. This study provides the first integrated physiology-transcriptome-proteome framework for ABA-mediated freezing tolerance in an evergreen ornamental shrub and offers theoretical support for ABA-based winter protection strategies.
Rhododendron yedoense var. Poukhanense↗
Antifreeze protein does not confer cold tolerance to transgenic Drosophila melanogaster.
Fish antifreeze proteins (AFPs) have been reported by some researchers to prolong the viability of tissues, organs, and embryos under hypothermic conditions, while others have observed no such effect or even AFP-mediated cryotoxicity. We examined the influence of Type III AFP from Atlantic wolffish on cold tolerance in a whole animal model system, transgenic Drosophila. The activity of the AFP, transgenically expressed under the transcriptional control of the female-specific yp1 and yp2 promoters and secreted into fly hemolymph, was confirmed through thermal hysteresis and differential scanning calorimetry measurements as well as through observations of ice crystal morphology. In cold exposure trials, at 0 degrees C and at -7 degrees C, transgenic adult flies of both sexes exhibited greater survival than nontransgenic controls even though the antifreeze was only produced in females. We attribute these observations to the expression of the xanthine dehydrogenase marker gene used to identify transgenics, rather than the production of AFP. Type III AFP therefore appears unable to enhance survival of adult Drosophila under hypothermic conditions.
Animals↗
Molecular and metabolic characterization of cold-tolerant alpine soil Pseudomonas sensu stricto.
Alpine soils undergo dramatic temporal changes in their microclimatic properties, suggesting that the bacteria there encounter uncommon shifting selection gradients. Pseudomonads constitute important members of the alpine soil community. In order to characterize the alpine Pseudomonas community and to assess the impact of shifting selection on this community, we examined the ability of cold-tolerant Pseudomonas isolates to grow on a variety of carbon sources, and we determined their phylogenetic relationships based on 16S ribosomal DNA sequencing. We found a high prevalence of Pseudomonas in our soil samples, and isolates from these soils exhibited extensive metabolic diversity. In addition, our data revealed that many of our isolates form a unique cold-adapted clade, representatives of which are also found in the Swedish tundra and Antarctica. Our data also show a lack of concordance between the metabolic properties and 16S phylogeny, indicating that the metabolic diversity of these organisms cannot be predicted by phylogeny.
Altitude↗
Lactic acid inhibition of the growth of spoilage bacteria and cold tolerant pathogens on pork.
The antibacterial effects of a 3% solution of lactic acid at 55 degrees C were assessed, by examining aerobic bacterial growth on artificially-inoculated pork fat and lean tissue. Discs of fat or lean tissues, each of 10 cm2 surface area, were aseptically excised from pork Longissimus dorsi muscle and inoculated with the cold tolerant pathogens Listeria monocytogenes 4b Scott A no. 3, Yersinia enterocolitica 0:4,32 or Aeromonas hydrophila ATCC 7966, or with the wild type spoilage bacteria Pseudomonas fragi or Brochothrix thermosphacta. After inoculation, each meat disc was immersed in water or lactic acid for 15 s and aerobic bacterial growth followed during 15 days of storage at 4 degrees C. P. fragi and B. thermosphacta grew on both fat and lean, but the pathogens grew on fat tissue only and A. hydrophila did not survive on lean. Lactic acid reduced all test bacteria on fat to below detectable levels within 4 days of treatment and no bacteria could be recovered from acid-treated fat surfaces for the remainder of the 15-day storage interval. Bacteria attached to lean were generally more resistant to lactic acid. In some instances the acid was bacteriostatic (P. fragi, L. monocytogenes) while in others the population declined at a greatly reduced rate as compared with a similar population on fat (B. thermosphacta, Y. enterocolitica). A. hydrophila was equally sensitive to lactic acid on lean and fat. Depending upon the tested strain, tissue type and storage time, maximum reductions in the number of bacteria recovered from acid treated pork ranged from 1 to 8 log cycles. The high bactericidal efficacy of lactic acid applied to pork fat was attributable to a low tissue pH, which varied from 3.49 to 4.41 during the 15 days of aerobic storage.
Adipose Tissue↗
Cloning of heat shock protein genes (hsp90 and hsc70) and their expression during larval diapause and cold tolerance acquisition in the rice stem borer, Chilo suppressalis Walker.
The complete cDNA sequences of heat shock protein 90 (hsp90) and of heat shock cognate protein 70 (hsc70) were cloned by reverse transcription polymerase chain reaction from the rice stem borer, Chilo suppressalis Walker. They potentially encode a 717-amino-acids (hsp90) and a 652-amino-acids (hsc70) protein, with calculated molecular weight of 82.5 and 71.3 kDa, respectively. The deduced amino acid sequence of hsp90 showed the highest homology of 97.2% to Spodoptera frugiperda hsp90. The closest match of C. suppressalis hsc70 was with Manduca sexta hsc70 at 98.0% identity. Expression of hsp90 in diapausing larvae was higher than that in non-diapausing larvae. No such up-regulation in diapausing larvae was observed for hsc70. In non-diapausing larvae, but not in diapausing ones, hsp90 expression was up-regulated by cold acclimation. Hsc70 expression slightly decreased during cold acclimation irrespective of the state of diapause. Involvement of hsp90 and hsc70 in larval diapause and cold tolerance acquisition in C. suppressalis is discussed.
Amino Acid Sequence↗
Electrophysiological evidence of an increase in cold tolerance of cardiac muscles in mice after energy restriction.
Life-prolonging energy restriction (ER) has been known to extend longevity. The heart was selected as the target organ of ER and the electrophysiological properties of ER on the heart were investigated. Action potential parameters were measured on ventricular papillary muscles of C57BL/6 mice (2-6 months of age). Resting membrane potential (Rm) did not change even when the temperature was lowered to 20 degrees C in ER mice (-67.5 +/- 0.8 mV), however, the membrane was depolarized in the control (-61.1 +/- 1.1 mV). Action potential duration measured at 30 and 50% repolarization was significantly prolonged in ER mice at 20-35 degrees C. Ouabain (10 microM) decreased Rm in ER mice at 20 degrees C (-68.6 +/- 1.0 to -63.6 +/- 0.8 mV), but failed to decrease Rm in the control (-60.6 +/- 1.8 to -62.1 +/- 1.2 mV). There were no significant differences in extracted Na, K-ATPase activity or affinity and binding capacity of ouabain between ER and control hearts. These results indicate that in ER mice the lack of effect of temperature on Rm was not due to a change in the physicochemical properties of Na, K-ATPase. The present study collectively suggests that ER increases cold tolerance in the heart of mice.
Acclimatization↗
Winter warming facilitates range expansion: cold tolerance of the butterfly Atalopedes campestris.
Our ability to predict ecological and evolutionary responses to climate change requires an understanding of the mechanistic links between climate and range limits. The warming trend over the past half-century has generated numerous opportunities to develop much-needed case studies of these links. Species that are only limited by climatic factors are likely to shift range quickly during periods of warming. Such species directly impact recipient communities and indicate trends that will become more widespread. Because minimum temperature (T (min)) is rising at twice the rate of maximum temperature, species with this range-limiting factor may be especially responsive to global warming. In this study, I test the hypothesis that rising T (min) has directly affected the range of a skipper butterfly. Atalopedes campestris has moved northward rapidly this century, recently colonizing eastern Washington where January T (min) has risen 3 degrees C in 50 years. The results show that: 1. A. campestris' range lies completely within the -4 degrees C January average minimum isotherm, and that recently colonized areas were below this threshold earlier this century. 2. In acute cold stress experiments, -4 to -7 degrees C proved to be a critical thermal limit: median supercooling point was -6.3 degrees C, and minimum lethal temperature (LT50 with 12-h exposure) was -5.7 degrees C. 3. In chronic cold stress experiments, survivorship declined sharply in diurnally fluctuating thermal regimes typical of the current range edge. High mortality occurred under constant 0 degrees C conditions as well as in fluctuating regimes, implying that thermal insulation from snow would not protect A. campestris. 4. There was no evidence of evolution in cold tolerance at the range margin, despite strong selection. Thus, winter warming was apparently a prerequisite for the range expansion. Characteristics of this species that seem to be associated with its rapid response are that it is an opportunistic species, it is not habitat or dispersal limited, and it is constrained by T (min).
Acclimatization↗
Vitamin A increases cold tolerance in goldfish.
As body stores of vitamin A, represented in the liver, are high in cold adapted animals, we hypothesized this phenomenon confers a survival value by increasing tolerance to cold. We injected retinol palmitate into goldfishes and found they tolerated cooler temperatures (4.6 degrees C more) and survived longer at 0 degree C (43 min 50% survival rate) compared to controls (28 min 50% survival rate). The resistance to cold is associated with the appearance of hepatic antifreeze protein(s) in the injected fishes.
Acclimatization↗
Drought acclimation confers cold tolerance in the soil collembolan Folsomia candida.
It has been noted that both summer drought and sub-zero winter temperatures induce the synthesis of sugars and polyols in invertebrate tissues. This has led several authors to suggest that many of the adaptations, previously viewed as a response to cold, might be part of a more universal desiccation tolerance mechanism. Here we show that acclimation of the soil dwelling collembolan Folsomia candida to a sublethal desiccation stress confers tolerance to cold shock and a significant increase in the molar percent of membrane fatty acids with a mid-chain double bond. These changes in membrane fatty acids are interpreted as conferring a significant reduction in the transition temperature of cell membranes, as would be expected in acclimation to cold, and these changes are therefore interpreted as contributing to the cross-tolerance. Drought acclimation was also shown to trigger the synthesis of the 70kDa family of heat-shock proteins (Hsp70). This group of heat shock proteins is implicated in the reestablishment of the normal three-dimensional structure of partially unfolded proteins and therefore are also likely to contribute to the observed cross-tolerance. This study provides evidence that the stresses exerted by desiccation and cold at the cellular level have sufficient similarities to induce overlapping adaptations.
Journal Article↗
Enhancement of cold tolerance and inhibition of lipid peroxidation by citrus dehydrin in transgenic tobacco.
Citrus ( Citrus unshiu Marcov.) dehydrin in response to chilling stress was overexpressed in tobacco ( Nicotiana tabacum L.), and the cold stress tolerance of transgenics at low temperature was analyzed. The freezing at -4 degrees C for 3 h of 24 independent lines indicated that a phenotype expressing citrus dehydrin showed less electrolyte leakage than the control. Dehydrin protein content was correlated with freezing tolerance in transgenics. Dehydrin-expressing tobacco exhibited earlier germination and better seedling growth than the control at 15 degrees C. Cell fractionation experiments suggested that the protein was predominantly expressed in mitochondria and the soluble fraction. Malondialdehyde production enhanced by chilling stress was lower in tobacco plants expressing citrus dehydrin than in control phenotypes. Dehydrin protein, purified from Escherichia coli expressing citrus dehydrin cDNA, prevented peroxidation of soybean ( Glycine max L.) liposomes in vitro. The inhibitory activity of dehydrin against liposome oxidation was stronger than that of albumin, glutathione, proline, glycine betaine, and sucrose. These results suggest that dehydrin facilitates plant cold acclimation by acting as a radical-scavenging protein to protect membrane systems under cold stress.
Adaptation, Physiological↗
Cold tolerance in Drosophila: adaptive variations revealed by the analysis of starvation survival reaction norms.
Three species of Drosophila were investigated for their capacity to survive without food (starvation tolerance) at seven different temperatures ranging from 0 to 25 degrees C. In all cases biphasic response curves (reaction norms) were observed, corresponding either to special deleterious effects of cold or to a progressive exhaustion of reserves proportional to metabolic rate. The temperature at which survival was longest was called the threshold temperature. The position of the threshold exhibited adaptive changes, either due to acclimation in the same species, or to genetic variations evidenced between species. In D. melanogaster, adults grown at lower temperature (12 degrees C) were more tolerant to cold than adults grown at higher temperatures (21, 25 or 30 degrees C). This acclimation process shifted, in an adaptive way, the position of the threshold temperature from 6.2 to 7.5 degrees C. A comparison of three different species grown at a single developmental temperature (21 degrees C) revealed similar but greater adaptive differences in their threshold temperature: 4.8 degrees C in the temperate D. subobscura, 7 degrees C in the cosmopolitan D. melanogaster and 14.6 degrees C in the tropical D. ananassae.
Journal Article↗