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This document is an editorial published in the journal Frontiers in Plant Science. It discusses the topic of plant adaptation and resistance to cold temperature stress. The editorial highlights the importance of understanding the mechanisms behind plant responses to cold stress, as it can significantly impact crop productivity and survival. The document also provides a brief summary of six research papers included in the Research Topic, which cover various aspects of plant adaptation to cold stress. The findings presented in these papers contribute to our understanding of plant responses to environmental stresses and can inform efforts to enhance crop resilience in the face of changing climatic conditions. [Extracted from the article]

Tolerance to freezing and seedling diseases caused by Microdochium spp. is an essential trait for the wintering of triticale (×Triticosecale Wittmack) and other cereals. Preceding multi-year studies indicate that after long-term exposure to the low temperature, cereal seedlings acquire a genotype-dependent cross-tolerance to other subsequent stresses. This paper presents the first non-gel protein profiling performed via high performance liquid chromatography coupled with Mass Spectrometry as well as Fourier Transform-Raman spectroscopy measurements performed directly on leaves of triticale seedlings growing under different conditions. The research used doubled haploid lines selected from the mapping population, with extreme tolerance/susceptibility to freezing and M. nivale infection. These non-targeted methods led to the detection of twenty two proteins cold-accumulated in the most tolerant seedlings in relation to susceptible ones, classified as involved in protein biosynthesis, response to different stimuli, energy balancing, oxidative stress response, protein modification, membrane structure and anthocyanin synthesis. Additionally, in seedlings of the most freezing- and M. nivale-tolerant line, cold-hardening caused decrease of the carotenoid and chlorophyll content. Moreover, a decrease in the band intensity typical for carbohydrates as well as an increase in the band intensity characteristic for protein compounds were detected. Both studied lines revealed a different answer to stress in the characteristics of phenolic components. [ABSTRACT FROM AUTHOR]

The aim of this study was verification whether an 8-week-long swimming exercise training would induce adaptive changes in body weight in rats and whether possible changes would depend on aquatic environment temperature and animal sex. The exercisetrained groups swam 4 minutes a day, five days a week during eight week of housing. Exercise was performed by swimming in glass tanks containing tap water maintained according to group at 5 ±2°C (cold group) and 36 ±2°C (thermal neutral group). Before and after each week of the experiment, rats were weighed. When comparing the nature of changes in the body weight of rats exposed to swimming exercise training in cold water, attention should be paid to their dependence on sex. There were statistically significant changes in the nature of changes in body weight between male rats and female rats of the cold group (5°C) as early as experimental week 2 until the end of the experiment (p < 0.001). Interestingly, the females exposed to swimming exercise training at 5°C were the only group in which an increase in body weight occurred during experimental week 8 in relation to baseline values.

Key points Muscle-derived thermogenesis during acute cold exposure in humans consists of a combination of cold-induced increases in skeletal muscle proton leak and shivering., Daily cold exposure results in an increase in brown adipose tissue oxidative capacity coupled with a decrease in the cold-induced skeletal muscle proton leak and shivering intensity., Improved coupling between electromyography-determined muscle activity and whole-body heat production following cold acclimation suggests a maintenance of ATPase-dependent thermogenesis and decrease in skeletal muscle ATPase independent thermogenesis., Although daily cold exposure did not change the fibre composition of the vastus lateralis, the fibre composition was a strong predictor of the shivering pattern evoked during acute cold exposure., Abstract We previously showed that 4 weeks of daily cold exposure in humans can increase brown adipose tissue (BAT) volume by 45% and oxidative metabolism by 182%. Surprisingly, we did not find a reciprocal reduction in shivering intensity when exposed to a mild cold (18°C). The present study aimed to determine whether changes in skeletal muscle oxidative metabolism or shivering activity could account for these unexpected findings. Nine men participated in a 4 week cold acclimation intervention (10°C water circulating in liquid-conditioned suit, 2 h day-1, 5 days week-1). Shivering intensity and pattern were measured continuously during controlled cold exposure (150 min at 4 °C) before and after the acclimation. Muscle biopsies from the m. vastus lateralis were obtained to measure oxygen consumption rate and proton leak of permeabilized muscle fibres. Cold acclimation elicited a modest 21% ( P < 0.05) decrease in whole-body and m. vastus lateralis shivering intensity. Furthermore, cold acclimation abolished the acute cold-induced increase in proton leak. Although daily cold exposure did not change the fibre composition of the m. vastus lateralis, fibre composition was a strong predictor of the shivering pattern evoked during acute cold. We conclude that muscle-derived thermogenesis during acute cold exposure in humans is not only limited to shivering, but also includes cold-induced increases in proton leak. The efficiency of muscle oxidative phosphorylation improves with cold acclimation, suggesting that reduced muscle thermogenesis occurs through decreased proton leak, in addition to decreased shivering intensity as BAT capacity and activity increase. These changes occur with no net difference in whole-body thermogenesis. [ABSTRACT FROM AUTHOR]

Introduction Abiotic stress is a major cause of yield loss in plant culture. Miscanthus, a perennial C4 grass, is now considered a major source of renewable energy, especially for biofuel production. During the first year of planting in Northern Europe, Miscanthus was exposed to frost temperature, which generated high mortality in young plants and large loss of yield. One strategy to avoid such loss is to apply cold-acclimation, which confers on plants a better resistance to low temperature. Objectives The aim of this study is to describe the effect of a cold-acclimation period on the metabolome of two Miscanthus genotypes that vary in their frost sensitivity at the juvenile stage. Miscanthus × giganteus (GIG) is particularly sensitive to frost, whereas Miscanthus sinensis August Feder (AUG) is tolerant. Materials and methods Polar metabolite extraction was performed on Miscanthus, grown in non-acclimated or cold-acclimated conditions. Extracts were analysed by 1H-NMR followed by multivariate statistical analysis. Discriminant metabolites were identified. Results More than 40 metabolites were identified in the two Miscanthus genotypes. GIG and AUG showed a different metabolic background before cold treatment, probably related to their genetic background. After cold-acclimation, GIG and AUG metabolomes remained different. The tolerant genotype showed notably higher levels of accumulation in proline, sucrose and maltose when subjected to cold. Conclusion These two genotypes seem to have a different adaptation strategy in cold conditions. The studied change in the metabolome concerns different types of molecules related to the cold-tolerant behaviour of Miscanthus. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study was aimed to investigate the possibility of regulating free proline content and ethylene production in the resistant to abiotic stress cv. 'Hornet H' and the tolerant to stress cv. 'Sunday' of winter rapeseed seedlings by pretreatment with exogenous L-proline and L-glutamine in non-acclimated and cold-acclimated seedlings in relation to freezing tolerance. The ratio of proline content in acclimated (at 4°C) versus non-acclimated (18°C) 'Hornet H' seedlings increased 2.12-fold and in 'Sunday' seedlings 1.95-fold. Exogenously applied, proline and glutamine produced a positive effect on free proline content in both cold-acclimated and non-acclimated seedlings. At a temperature of -1°C the proline content significantly increased in non-acclimated and especially in cold-acclimated seedlings. At an intensified freezing temperature (−3°C, −5°C, −7°C), the proline content decreased in comparison with that at −1°C, but glutamine, especially proline, in cold-acclimated seedlings takes part in free proline level increase and in seedlings' resistance to freezing. Ethylene production increased in cold-acclimated conditions and under the effect of exogenous proline and glutamine. In freezing conditions, ethylene production decreased, but in cold-acclimated seedlings and under pretreatment of proline and glutamine the ethylene synthesis was intensive. Thus, free proline content and ethylene production increase in cold-acclimated winter rapeseed seedlings and under pretreatment with glutamine and especially with proline. Free proline is involved in the response to cold stress, and its level may be an indicator of cold-hardening and freezing tolerance, but the role of ethylene in the regulation of cold tolerance remains not quite clear. [ABSTRACT FROM AUTHOR]

Masson pine (Pinus massoniana Lamb.), a native species widely distributed in temperate forests in central China, and Loblolly pine (Pinus taeda L.), an exotic tree species introduced to China from southeastern United States, are dominant evergreen conifers that play a pivotal role in maintaining forest structure and functions for the region. We examined the effects of freezing on these species with chlorophyll fluorescence and electrolyte leakage using both field- and laboratory-based experiments in September 2009 and January 2010, respectively. We found that freezing could cause a greater impact on the Loblolly pine than the Masson pine. Although the two species showed similar values of F v /F m and electrolyte leakage before freezing, the Masson pine needles showed lower F v /F m and higher electrolyte leakage ratios than those of the Loblolly pine when treated in low temperatures (−15 to 0°C). We also found that cold-acclimation was crucial for both species to adapt to low temperatures with the F v /F m ratio decreased approximately by 80% in the first freezing hour for the non-acclimated needles of both species while the cold-acclimated needles showed little changes in the F v /F m ratio. This finding is also supported by our measurements of electrolyte leakage. These results suggest that the Loblolly pine could be more susceptible to freezing damages than the Masson pine in central China. [ABSTRACT FROM AUTHOR]

In this study, the effects of l-arginine-nitric-oxide (NO)-producing pathway on protein content of ubiquitin, as an important component of ubiquitin-proteasome system for protein removal, were investigated. We showed that l-arginine markedly decreased ubiquitin protein content in interscapular brown adipose tissue, both in thermogenic inactive (at room temperature) and thermogenic active (on cold) states; while in l-NAME-treated groups this effect was abolished. This result suggests that nitric oxide (NO), besides well established roles, is involved in this aspect of structure remodeling, as well. [ABSTRACT FROM AUTHOR]

Analysis of metabolomics data often goes beyond the task of discovering biomarkers and can be aimed at recovering other important characteristics of observed metabolomic changes. In this paper we explore different methods to detect the presence of distinctive phases in seasonal-responsive changes of metabolomic patterns of Siberian spruce ( Picea obovata) during cold acclimation occurred in the period from mid-August to January. Multivariate analysis, specifically orthogonal projection to latent structures discriminant analysis (OPLS-DA), identified time points where the metabolomic patterns underwent substantial modifications as a whole, revealing four distinctive phases during acclimation. This conclusion was re-examined by a univariate analysis consisting of multiple pair-wise comparisons to identify homogeneity intervals for each metabolite. These tests complemented OPLS-DA, clarifying biological interpretation of the classification: about 60% of metabolites found responsive to the cold stress indeed changed at one or more of the time points predicted by OPLS-DA. However, the univariate approach did not support the proposed division of the acclimation period into four phases: less than 10% of metabolites altered during the acclimation had homogeneous levels predicted by OPLS-DA. This demonstrates that coupling the classification found by OPLS-DA and the analysis of dynamics of individual metabolites obtained by pair-wise multicomparisons reveals a more correct characterization of biochemical processes in freezing tolerant trees and leads to interpretations that cannot be deduced by either method alone. The combined analysis can be used in other 'omics'-studies, where response factors have a causal dependence (like the time in the present work) and pair-wise multicomparisons are not conservative. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effect of chilling on both cold-acclimated and non-acclimated chickpea ( Cicer arietinum L.) cultivars (Gökçe and Canıtez 87). Chickpea seedlings grown in soil culture for 12 days were subjected to chilling temperatures (2 and 4°C for 12 days) after maintaining in cold-acclimation (10°C, 7 days) or non-acclimation (25°C, 7 days) periods. The lowest values of growth parameters were obtained with cold-acclimated plants, whereas non-acclimated plants exhibited the lowest water content values, especially at 2°C. There was no effect of cold-acclimation period on chlorophyll fluorescence parameters. Plants subjected to chilling temperatures after cold-acclimation were more tolerant with respect to chlorophyll fluorescence parameters, and Gökçe had better photosystem II (PSII) photochemical activity. In the chilling treatments, total chlorophyll ( a + b) content reduced, especially at 2°C, while anthocyanin and flavonoid contents increased to a greater extent in Gökçe and carotenoid content of the cultivars did not change. Malondialdehyde (MDA) content was higher for Canıtez 87, mostly at 2°C, while proline accumulation was greater for Gökçe. The cold-acclimation period led to a remarkable increase in antioxidant enzyme activities of both cultivars. The superoxide dismutase (SOD) activity was much higher in Gökçe for both chilling temperatures and the ascorbate peroxidase (APX) activity increased only in the cold-acclimated 4°C treatments. Similarly, with APX activity, the glutathione reductase (GR) and peroxidase (POD) activities of cultivars were higher in cold-acclimated plants at both the chilling temperatures, mostly in Gökçe. The results of this study indicate that cold-acclimation increased the cultivars ability to withstand the chilling temperatures. The lower MDA content and higher antioxidant and photochemical activities in Gökçe indicated an enhanced chilling tolerance capacity of this cultivar to protect the plant from oxidative damage. [ABSTRACT FROM AUTHOR]

To assess the changes in thermoregulatory characteristics that accompany the seasonal expression of torpor we measured seasonal differences in body mass adjustments, body temperature ( Tb) and metabolic rate (MR) in both summer- and winter-acclimated individuals from a species of food-storing hibernator, the Eastern chipmunk ( Tamias striatus). Torpor occurred only in the winter and was associated with lower normothermic Tb, during inter-bout arousal periods than in the summer. Chipmunks increased body mass before the initiation of torpor in winter, and steadily lost mass as the hibernation season progressed. Torpor expression was correlated to initial mass gain, with the individuals who showed the largest mass increase in the fall showing the highest degree of torpor. Acclimation to winter-like conditions produced a decline in normothermic MR at all ambient temperatures examined. The findings indicate that torpor expression is accompanied by a decrease in Tb and MR during normothermy, indicating that a conservation of energy metabolism occurs, not only in torpor, but also during the inter-bout arousal periods. [ABSTRACT FROM AUTHOR]

A proportion of Helicoverpa armigera collected from fields in Okayama Prefecture (Western Japan; 34.6°N, 134.1°E) does not enter diapause when reared under a short days at 20 °C during the larval stages. However, diapause in such photo-insensitive individuals can be induced when they are reared at moderately low temperatures, such as 15 °C, regardless of photoperiod. To determine whether such photo-insensitive individuals can survive overwintering in fields, the present study compares the cold hardiness and sugar content between nondiapausing and diapausing pupae of photo-insensitive individuals selected over several generations at 20 °C under a short day photoperiod (LD 10 : 14 h). Diapausing and nondiapausing pupae are obtained under the short days by rearing at 15 and 20 °C, respectively, during larval and pupal stages. These pupae are stepwise acclimated at a reduction of 5 °C every 5 days to 0 °C. Maximum survival periods of nondiapausing and diapausing pupae at 0 °C are approximately 30 and 90 days, respectively. Trehalose content in diapausing pupae increases, reaches a maximum level (1.95 mg 100 mg−1 in males and 2.1 mg 100 mg−1 in females) 28 days after exposure to 0 °C and then decreases. On the other hand, glucose content in diapausing pupae increases (maximum level: 0.32 mg 100 mg−1 in males and 0.21 mg 100 mg−1 in females) with decreasing trehalose content 42 days after exposure to 0°C. The decrease in trehalose content and the increase in glucose content may be linked to termination of diapause in H. armigera. These results suggest that, in Japan, the photo-insensitive individuals can only survive in the mild winters of southern regions, and not in the severe winters of northern regions. [ABSTRACT FROM AUTHOR]

Abstract: An equation to calculate the percentage of water remaining unfrozen at any temperature due to colligative properties of solutions was derived from the freezing point depression equation. The accuracy of the equation was demonstrated with a 0.1M sucrose solution frozen at temperatures from −0.5 to −6°C in an isothermal calorimeter. Empirical measurements using latent heat as a measure of the amount of water frozen were within 1% of the expected values calculated from the equation. The extent to which percentages of water freezing in oat crown tissue at varying temperatures follows the expected freezing curve indicates how closely the system follows colligative freezing processes. The freezing curve for non-acclimated crowns followed a colligative freezing pattern more closely than did the curve for crowns from cold-acclimated plants. This suggests that water in crowns from non-acclimated plants may remain unfrozen primarily by colligative means while other mechanisms of keeping water unfrozen are important in cold-acclimated crowns. This may help explain contradictory results of studies that attempt to correlate carbohydrate concentrations with freezing tolerance. [Copyright &y& Elsevier]

Abstract: Overwintering freeze-tolerant larvae of Chilo suppressalis can survive at −25°C, but non-diapausing larvae cannot. We reported earlier that to prevent intracellular freezing, which causes death in overwintering larvae of the Saigoku ecotype distributed in southwestern Japan, water leaves and glycerol enters fat body cells through water channels during freezing. However, it is still unclear how diapause and low-temperature exposure are related to the acquisition of freeze tolerance. We compared the extent of tissue damage, accumulation of glycerol, and transport of glycerol and water in fat body tissues between cold-acclimated and non-acclimated non-diapausing and diapausing larvae. The tissue from cold-acclimated diapausing larvae could survive only when frozen in Grace''s insect medium with 0.25M glycerol at −20°C. The protection provided by glycerol was offset by mercuric chloride, which is a water-channel inhibitor. Fat body tissue isolated from non-acclimated diapausing larvae was injured by freezing even though glycerol was added to the medium, but the level of freezing injury was significantly lower than in non-diapausing larvae. Radiotracer assays in cold-acclimated diapausing larvae showed that during freezing, water left the cells into the medium and glycerol entered the cells from the medium at the same time. Therefore, in Saigoku ecotype larvae of the rice stem borer, both diapause and cold-acclimation are essential to accumulate glycerol and activate aquaporin for the avoidance of freezing injury. [Copyright &y& Elsevier]

Abstract: The suitability of using Arabidopsis as a model plant to investigate freezing tolerance was evaluated by observing similarities to winter cereals in tissue damage following controlled freezing and determining the extent to which Arabidopsis undergoes subzero-acclimation. Plants were grown and frozen under controlled conditions and percent survival was evaluated by observing re-growth after freezing. Paraffin embedded sections of plants were triple stained and observed under light microscopy. Histological observations of plants taken 1 week after freezing showed damage analogous to winter cereals in the vascular tissue of roots and leaf axels but no damage to meristematic regions. The LT50 of non-acclimated Arabidopsis decreased from about −6°C to a minimum of about −13°C after 7 days of cold-acclimation at 3°C. After exposing cold-acclimated plants to −3°C for 3 days (subzero-acclimation) the LT50 was lowered an additional 3°C. Defining the underlying mechanisms of subzero-acclimation in Arabidopsis may provide an experimental platform to help understand winter hardiness in economically important crop species. However, distinctive histological differences in crown anatomy between Arabidopsis and winter cereals must be taken into account to avoid misleading conclusions on the nature of winter hardiness in winter cereals. [Copyright &y& Elsevier]

Abstract: Cold-acclimation did not alter uncoupling (state 4 respiration) in rat liver or skeletal muscle mitochondria. Palmitate significantly uncoupled mitochondria, but neither the magnitude of this uncoupling nor the contribution of different inner mitochondrial membrane transporters to uncoupling was altered by cold-acclimation. Guanosine diphosphate did not reduce uncoupling, suggesting no role for uncoupling protein homologues. The adenine nucleotide transporter and the permeability transition pore, either alone or in combination, appear to contribute significantly to free fatty-acid (FFA)-induced uncoupling. Evidence suggests that these two elements may be working together, as components of the same mechanism, to mediate FFA uncoupling. [Copyright &y& Elsevier]

Abstract: Adults of warm- and cold-acclimated tropical cockroaches, Nauphoeta cinerea were exposed to low temperatures of 0 or 5 °C for various time intervals (hours to days). Development of chilling-injury (defects in crawling and uncoordinated movements) and mortality during the exposure were assessed and correlated with the changes in concentrations of metal ions (Na+, K+ and Mg2+) in the haemolymph and coxal muscle tissue. Warm-acclimated insects entered chill-coma at both low temperatures. In their haemolymph, the [Na+] and [Mg2+] linearly decreased and [K+] increased with the increasing time of exposure. The rate of concentration changes was higher at 0 than at 5 °C. The concentration changes resulted in gradually dissipating equilibrium potentials across the muscle cell membranes. For instance, E K decreased from −49.8 to −20.7 mV during 7 days at 5 °C. Such a disturbance of ion homeostasis was paralleled by the gradual development of chilling-injury and mortality. Most of the cockroaches showed chilling-injury when the molar ratio of [Na+]/[K+] in their haemolymph decreased from an initial of 4.4 to 2.1–2.5. In contrast, the cold-acclimated cockroaches did not enter chill-coma. They maintained constant concentrations of ions in their haemolymph, constant equilibrium potentials across muscle cell membranes and the development of chilling-injury was significantly suppressed at 5 °C for 7 days. [Copyright &y& Elsevier]

Abstract: In temperate climates, plants are more frequently exposed to sudden and strong decrease of temperature combined with high light intensity that compromise the photosynthetic efficiency and, often, the development and their survival. To investigate deeper the effects of such a photo-oxidative cold shock on photosynthesis of mandarin (Citrus reticulata Blanco) we used transient fluorescence analysis and gas exchange techniques. Mandarin plants were acclimated at 13°C or grown at 25°C for 30 days, then single leaves were exposed for 6h at 5°C and 1200μmolphotonsm-2s-1 and again exposed for 72h under growth conditions. Acclimated leaves showed lower photosynthesis and higher total carotenoid contents than non-acclimated leaves. The photo-oxidative cold shock inhibited photosystem II (PSII) efficiency, as suggested by the reduction of Fv/Fm ratios, in all leaves. Carotenoid content was reduced in non-acclimated leaves. A time-dependent increase in the initial fluorescence level (F0) and a faster decline in Fv/Fm ratio indicated a stronger PSII inhibition in non-acclimated leaves in comparison with acclimated leaves. The chlorophyll a fluorescence kinetic showed in all leaves complex changes in the O–J, J–I and I–P phases. The I and P steps of the fluorescence rise were particularly affected in non-acclimated leaves. Photosynthesis, fluorescence and pigment contents, measured in leaves maintained for 2h in the dark and then returned for 72h to growth conditions, showed a different pattern of recovery between leaves. Photosynthesis and fluorescence completely recovered in acclimated leaves after 72h under growth conditions. On the contrary, non-acclimated leaves still showed very low values of photosynthesis and Fv/Fm, suppression of the sigmoidal shape of fluorescent transients and further reduction of chlorophyll contents, indicating the presence of irreversible damages to PSII and, probably, an anticipated senescence. It is suggested that carotenoids have a relevant role in protecting leaves of mandarin from the effects of a photo-oxidative cold shock. [Copyright &y& Elsevier]

Suppression subtractive hybridization and differential display polymerase chain reactions were used to identify genes that were differentially expressed in cold-hardened and dehardened leaves of winter rye (Secale cerealeL.). The transcripts of nine genes declined during dehardening at 22°C of cold-hardened 4°C-grown leaves, indicating some role in cold-acclimation. Among the genes that were strongly expressed in cold-hardened leaves were five genes of photosynthetic metabolism, the gene of the antioxidative enzyme peptide methionine sulfoxide reductase (PMSR) and three genes of RNA and protein metabolism. Four genes were identified that were more strongly expressed during dehardening of cold-hardened leaves at 22°C. A full-length cDNA for a presumed cytosolic PMSR (EC 1.8.4.6) of rye leaves was identified. After heterologous expression inEscherichia coli, an antiserum against the ScPMSR was produced. The content of the ScPMSR protein, visualized by immunoblotting, was much higher in cold-hardened than in non-hardened leaves and declined during dehardening. In non-hardened leaves the mRNA of ScPMSR increased only slowly during exposures to 4°C in light and was not affected by exposure to 4°C in darkness. However, the ScPMSR mRNA was also induced by prolonged exposure (48 h) to high light at 22°C, or by treatment with 2 µM paraquat. Consequently, the induction of cytosolic ScPMSR is a late response to prolonged photooxidative stress conditions, as expected during growth at low temperature in light. In cold-hardened leaves, PMSR may protect proteins from photodamage and thus prevent their degradation and the need for repair. [ABSTRACT FROM AUTHOR]

Abstract: The influence of fasting and winter-acclimatization (cold and short-day acclimatization) on mouse plasma leptin, ghrelin, growth hormone (GH) and melatonin concentrations was determined from blood samples taken at mid-day and midnight. A 16-h fast decreased the plasma leptin but almost doubled the plasma ghrelin concentrations which contribute to energy saving, appetite stimulation and, in the case of leptin, to inhibition of reproduction. Winter-acclimatization did not affect plasma ghrelin concentrations, whereas leptin decreased to the same level as in fasting. The low leptin concentrations possibly enable an increased caloric intake for the purpose of thermogenesis. Fasting and winter-acclimatization seemed to abolish the diurnal leptin rhythm, but had no effect on that of ghrelin. Plasma melatonin concentration correlated negatively with ghrelin, suggesting a possible role for melatonin in the regulation of ghrelin concentration. SNS-activity and insulin appear to be the main regulators of leptin plasma concentration in the mouse, rather than melatonin as in some seasonal mammals. Interestingly, endogenous ghrelin did not stimulate GH secretion, which is a well-documented reaction to exogenous ghrelin injections. [Copyright &y& Elsevier]

As sessile organisms, plants must adapt to their environment. One approach toward understanding this adaptation is to investigate environmental regulation of gene expression. Our focus is on the environmental regulation of EARLI1, which is activated by cold and long-day photoperiods. Cold activation of EARLI1 in short-day photoperiods is slow, requiring several hours at 4 °C to detect an increase in mRNA abundance. EARLI1 is not efficiently cold-activated in etiolated seedlings, suggesting that photomorphogenesis is necessary for its cold activation. Cold activation of EARLI1 is inhibited in the presence of the calcium channel blocker lanthanum chloride or the calcium chelator EGTA. Addition of the calcium ionophore Bay K8644 results in cold-independent activation of EARLI1. These data suggest that EARLI1 is not an immediate target of the cold response, and that calcium flux affects its expression. EARLI1 is a putative secreted protein and has motifs found in lipid transfer proteins. Over-expression of EARLI1 in transgenic plants results in reduced electrolyte leakage during freezing damage, suggesting that EARLI1 may affect membrane or cell wall stability in response to low temperature stress. [ABSTRACT FROM AUTHOR]

Marsupials lack brown adipose tissue, and therefore rely exclusively on other tissues for thermogenesis. To determine the magnitude of phenotypic plasticity of the liver in response to changing metabolic demand, gray short-tailed opossums (M. domestica) were exposed to thermoneutral (28 °C) or cold (9–12 °C) conditions continuously for 6 weeks. Half of each group was also endurance trained with a treadmill program during their respective temperature exposure. Mass specific summit metabolism (V˙O2summit) increased 11% following cold acclimation, though there was no significant main effect by training on V˙O2summit. To estimate the contribution of the liver to whole animal oxidative activity, we determined liver mass, mitochondrial volume density, and total mitochondrial volume. Relative liver mass was 48% greater in cold-acclimated animals, whereas training had no effect on liver mass. The stereological analysis of hepatocyte ultrastructure suggests the percentage of intracellular volumes remained unchanged in response to either aerobic challenge. Thus, following cold-acclimation, there is a 20% increase in the total mitochondrial volume of the liver. This increase could account for nearly half (44%) of the observed increase in whole animal V˙O2summit following cold exposure. [Copyright &y& Elsevier]

The hypothesis that the extracellular concentration of sugars helps regulate the acclimation of plant cells to cold was tested in this work. Suspension cultures were used to control the concentration of sugars in the medium supplied to barley cell cultures (Hordeum vulgare L. cv. Igri), replacing the medium daily to help maintain the concentration. Freezing tolerance and the levels of mRNA expression of the stress‐response genes blt4.9 (coding for a non‐ specific lipid transfer protein) and dhn1 (coding for a dehydrin) were measured. Similar levels of freezing‐tolerance and gene expression were obtained in the experiments as occur during cold‐acclimation in the crown of the whole plant. In the cell cultures, cold (6/2 °C) did not induce an increase in freezing tolerance or in the expression of detectable levels of blt4.9 or dhn1 mRNAs when only 1 g l–1 sucrose was supplied. However, the cells in this low sucrose medium in the cold were not sugar‐starved, indicating that this did not explain the failure of the cells to acclimate when grown in the cold environment. Ten g l–1 sucrose supplied to cells grown in the warm (25 °C) induced acclimation to freezing and up‐regulation of expression of blt4.9 and dhn1 mRNAs. Osmolality of the medium did not explain this. Thirty g l–1 sucrose induced yet higher levels of freezing tolerance and of blt4.9 and dhn1 mRNAs in cultures grown in either the cold or the warm environment. The results implicate sugars in the regulation of cold acclimation [ABSTRACT FROM PUBLISHER]

In cold‐hardened leaves (CHL) of winter rye (Secale cereale L.) much higher levels of malate were detected by 13C‐NMR than in non‐hardened leaves (NHL). As this was not observed previously, malate metabolism of CHL was studied in more detail by biochemical assays. The activities of several enzymes of malate metabolism, NADP‐malate dehydrogenase, NAD‐malate dehydrogenase, phosphoenolpyruvate carboxylase, and NADP‐malic enzyme, were also increased in CHL. Short exposures to low temperature of 1–3 d did not induce increases in the malate content or in the activities of enzymes of malate metabolism in mature NHL. The malate content and the enzyme activities declined within 1–2 d after a transfer of CHL from their growing temperature of 4 °C to 22 °C. The malate content was further increased when CHL were exposed to a higher light intensity at 4 °C. In CO2‐free air the malate content of CHL strongly declined at 4 °C. Malate may thus serve as an additional carbon sink and as a CO2‐store in CHL. It may further function as a vacuolar osmolyte balancing increased concentrations of soluble sugars previously observed in the cytosol of CHL. Malate was not used as a source of reductants when CHL were exposed to photo‐oxidative stress by treatment with paraquat. However, the activities of enzymes of the oxidative pentose phosphate pathway were markedly increased in CHL and may serve as non‐photosynthetic sources of NADPH and thus contribute to the previously observed superior capacity of CHL of winter rye to maintain their antioxidants in a reduced state in the presence of paraquat. [ABSTRACT FROM PUBLISHER]

Two high mountain plants Soldanella alpina (L.) and Ranunculus glacialis (L.) were transferred from their natural environment to two different growth conditions (22 °C and 6 °C) at low elevation in order to investigate the possibility of de‐acclimation to light and cold and the importance of antioxidants and metabolite levels. The results were compared with the lowland crop plant Pisum sativum (L.) as a control. Leaves of R. glacialis grown for 3 weeks at 22 °C were more sensitive to light‐stress (defined as damage to photosynthesis, reduction of catalase activity (EC 1.11.1.6) and bleaching of chlorophyll) than leaves collected in high mountains or grown at 6 °C. Light‐stress tolerance of S. alpina leaves was not markedly changed. Therefore, acclimation is reversible in R. glacialis leaves, but constitutive or long‐lasting in S. alpina leaves. The different growth conditions induced significant changes in non‐photochemical fluorescence quenching (qN) and the contents of antioxidants and xanthophyll cycle pigments. These changes did not correlate with light‐stress tolerance, questioning their role for light‐ and cold‐acclimation of both alpine species. However, ascorbate contents remained very high in leaves of S. alpina under all growth conditions (12–19% of total soluble carbon). In cold‐acclimated leaves of R. glacialis, malate represented one of the most abundant compounds of total soluble carbon (22%). Malate contents declined significantly in de‐acclimated leaves, suggesting a possible involvement of malate, or malate metabolism, in light‐stress tolerance. Leaves of the lowland plant P. sativum were more sensitive to light‐stress than the alpine species, and contained only low amounts of malate and ascorbate. [ABSTRACT FROM PUBLISHER]

The naked mole-rat (Heterocephalus glaber) lives communally in a thermally buffered underground habitat. Here, it relies primarily on ectothermic (behavioral) mechanisms to maintain body temperature (Tb). Outside this milieu, it is unable to effectively regulate Tb and Tb tracks that of ambient temperature (Ta). Although naked mole-rats, in their natural habitat have little need for cold-tolerance, we questioned whether or not thermogenic capacity would change with prolonged (>1 year) exposure to cooler conditions. We hypothesized that these rodents would not conform to common mammalian patterns and that non-shivering thermogenic (NST) capacity would be unchanged with chronic cold exposure. The capacity for NST was assessed following noradrenaline administration (0.8 mg/kg, s.c.) to lightly anesthetized (pentobarbital 6% m/v 40 mg/kg) animals and monitoring the concomitant changes in oxygen consumption and Tb. Results concur with the null hypothesis in that prolonged cold exposure did not elicit any increase in NST capacity (1.52±0.17 ml O2/g/h, cold-acclimated; 1.73±0.31 ml O2/g/h, control; P>0.05). Rapid heat loss across their uninsulated integument may necessitate continuous maximal stimulation of brown adipose tissue (BAT), and as such, prevent any further increase in thermogenic capacity following cold exposure. [Copyright &y& Elsevier]

Summary In a search for cold-regulated genes that are differentially expressed in alfalfa genotypes of contrasting freezing tolerance, we screened 1036 arrayed cDNA clones. The screening resulted in isolation of cDNA clones, which demonstrated dramatic differences in expression between hardy and un-hardy alfalfa varieties. Detailed analysis revealed that these cDNAs represent parts of novel non-coding repetitive elements carrying long-terminal repeats (LTR) and other retroelement-like features. Despite strong expression under low temperatures, DNA templates remained highly methylated, and a drug-induced decrease in methylation did not activate transcription under normal temperatures. We identified that these repetitive elements represent a large family and could insert into, or be adjacent to, the unrelated polyprotein sequences of putative retrotransposons. These retrotransposons also showed low temperature-induced transcriptional activation; however, this activation was not genotype-dependent. The retroelements described in this study are the first retroelement characterized in the Medicago genus. Furthermore, they represent the only known example of genotype-specific cold-induced transcriptional activation of multiple copies of a repetitive element whose expression is associated with a genotype difference in cold acclimation. [ABSTRACT FROM AUTHOR]

Physiological studies have shown that glucagon is a potential mediator of nonshivering thermogenesis (NST) in birds. The present work was undertaken in order to investigate whether the observed thermogenesis results from a direct action of glucagon on avian thermoregulatory mechanisms or in fact requires the participation of other agents such as catecholamines. Our experiments were performed using cold-acclimated (CA) ducklings which developed muscle NST. A comparison was made with thermoneutral (TN) ducklings of the same age. Our principal results showed that: (1) at ambient temperature (25°C), circulating norepinephrine (NE) was markedly decreased in CA ducklings (–42%), while circulating epinephrine (E) did not undergo any consistent change; (2) in CA and TN ducklings, an intraperitoneal injection of glucagon (360 µg.kg–1) was followed after 10 min by prominent lipolysis and a large increase in circulating NE (4- to 6-fold) and E (14- to 17-fold), which was sustained for at least 1 h. The elevation of circulating NE was less pronounced in CA ducklings. The thermogenic action of glucagon in birds is probably indirect and involves at least the mobilization of lipids and sympatho-adrenal stimulation. The changes in peripheral noradrenergic activity during cold acclimation could be associated with adaptive changes leading to NST. [ABSTRACT FROM AUTHOR]

Cold hardiness and in vitro regeneration are closely related traits in selected alfalfa and red clover germplasms. We investigated the cold-induction of three genes, MsaCIA, MsaCIB and MsaCIC, implicated in the cold tolerance of alfalfa, in non-regenerative and regenerative somaclonal variants of red clover by Northern blot analysis using alfalfa cDNA clones as hybridization probes. Only the MsaCIA gene exhibited increased steady-state mRNA levels in cold-acclimated red clover. We observed, however, enhanced-cold induction of steady-state levels of MsaCIA gene transcripts in all regenerative somaclonal variants compared to non-regenerative red clover lines. Moreover, these two traits, regeneration and enhanced cold-induction of MsaCIA, were concomitantly transmitted to progeny suggesting that enhanced expression of MsaCIA and the regenerative trait are either linked, or the expression of both traits are regulated by a ‘master’ gene whose expression is modified by somatic embryogenesis. [ABSTRACT FROM AUTHOR]

The present study was designed to determine whether norepinephrine (NE) mediate endothelium-dependent relaxations in arteries of the pulmonary vasculature of cold-acclimated rats. Twenty male Sprague-Dawley rats comprising two groups (Cold-acclimated for 12 weeks at 6°C, CA; Warm-acclimated for 12 weeks at 24 °C, WA) were used. After anesthesia, the pulmonary artery (4 mm long) was isolated. Pulmonary artery with and without endothelium were suspended for isometric force measurements in a buffered salt solution. The doseresponse relations for the vascular responses to the isolated pulmonary artery to norepinephrine (NE), phenylephrine (PE) and acetylcholine (Ach) were determined and compared in the CA group and the WA group. In the CA group, the vascular sensitivities to NE and PE-induced contraction in the pulmonary artery was significantly lowered than that in the WA group. NE and PE-induced contractions were significandy greater in endotheliumdenuded compared with endothelium-intact arteries. These differences of contraction responses to NE and PE between arteries with widiout endothelium were significantly greater in the CA group than in the WA group. There was no significant difference between the pulmonary arterial response to Ach in the CA group and that in the WA group. Our data suggest that chronic exposure to cold show decreased NE and PE-induced contraction responses in isolated pulmonary arteries and may decrease NE-induced contraction responses due to enhancing NE-induced endodielium derived relaxing factor release via up-regulating endothelial α-adrenoceptors. [ABSTRACT FROM AUTHOR]

Cereal plants become more resistant to freezing when first exposed to a period of cold-acclimation. Many physiological and molecular changes have been shown to occur at low temperatures, but the role and the contribution of each to frost resistance is still poorly understood. Two cultivars of barley (Hordeum vulgare L.), the winter barley Onice and the spring barley Gitane, were acclimated under controlled conditions under an 8-h photoperiod at 4°C (light) and 2°C (dark) for 21 days. Changes in free proline, ABA, water-soluble carbohydrates and free fatty acids were measured to assess their involvement in cold-acclimation and to explain the different frost-resistant capacities of the two cultivars. Exposure of barley plants to low temperature resulted in an equal increase in proline in both cultivars. During the first days of cold acclimation, ABA levels showed a peak in the frost-resistant cultivar, lasting about 24 h, followed by a decrease. The water soluble carbohydrates reached their highest content after 3 days of hardening, although after 14 to 21 days of acclimation the carbohydrate content was similar to that of unhardened plants. The frost-resistant Onice had a much higher free fatty acid content than the frost-sensitive Gitane. Furthermore in Onice 86% of free fatty acids was represented by unsaturated molecular species, linolenic acid alone being 71%. In contrast, in the frost-sensitive cultivar only 31% of free fatty acids was unsaturated and a large amount of 9-oxo-nonanoic acid, a product present in the linolenic acid cascade, was also detected. The ABA content after 2 days of hardening and the free fatty acid composition were clearly different between the two cultivars and may explain, at least in part, the different frost-resistant capacities of Onice and Gitane. [ABSTRACT FROM AUTHOR]

Leaf discs from spinach were exposed to a photon flux density of 1 250 µmol m-2 s-1 at 5°C for 2 or 3 h in ambient air. Photoinhibition of photosystem II (PS II) was measured by means of chlorophyll fluorescence. Recovery of photosystem II was followed at 6°C and 20°C in low light or darkness for periods up to 12 h. The experimental setup allowed kinetic resolution of different phases of recovery. The experiments revealed a temperature dependent dark recovery phase and two distinct light- and temperature dependent phases: (1) A relatively fast, light dependent recovery phase occurred in parallel with partial recovery of basic fluorescence at 6°C and 20°C. A population of PS II centers with very slow fluorescence induction kinetics, which had accumulated during photoinhibition treatment, disappeared during this phase. This fast recovery phase is proposed to represent reactivation of photoinhibited PS II, without dissassembly or incorporation of new D1-protein. (2) A relatively slow light-dependent recovery phase took place at 20°C, but not at 6°C. In the presence of the chloroplast translation inhibitor streptomycin, part of the 2nd phase was inhibited. This phase is proposed to involve assembly of new Photosystem II centers, which is partly dependent on de novo synthesis of D1-reaction center protein, but presumably is also using a preexisting pool of D1-protein. Cold acclimation of the leaves resulted in a decreased sensitivity for photoinhibition of photosystem II. Recovery of photoinhibited photosystem II at 6°C of the cold-acclimated leaves was faster than in non-acclimated leaves, but this effect can be ascribed to diminished photoinhibitory damage. [ABSTRACT FROM AUTHOR]

bIt4 is a barley gene which,as measured by steady state mRNA levels, Is induced by a low positive temperature treatment of shoot meristems. The gene is also Induced in shoot meristems by drought stress. We now report the response of this gene to foliar applications of abscisic acid. The striking similarity between the predicted amino acid sequence of blt4 and two maize phosphoilpid transfer proteins indicates a biochemical function for the blt4 gene product. This homology also demonstrates the hitherto unreported environmental regulation of expression of a phospholipid transfer protein which may involve abscisic acid in the signal transduction pathway. [ABSTRACT FROM AUTHOR]