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PubMed2025

Integrated 16 S rRNA and transcriptome analysis reveal molecular and microbial mechanisms of cold-tolerant germination in hulless barley.

BACKGROUND: Elucidating the mechanisms underlying cold-tolerant germination is crucial for enhancing crop resilience to low temperatures. Hulless barley (Hordeum vulgare var. coeleste L.), with remarkable natural cold adaptation, serves as an ideal model to study cold stress tolerance mechanisms in gramineous crops. In this study, cold-tolerant variety 37 and cold-sensitive variety 44 were screened and used to investigate the molecular mechanisms of cold-tolerant germination, via seed germination assays, combined with phytohormone determination, transcriptome sequencing and 16 S rRNA amplicon sequencing. RESULTS: Low temperature significantly inhibited hulless barley seed germination: the germination rate of cold-sensitive variety 44 decreased by 69%, while that of cold-tolerant variety 37 only decreased by 2%. Transcriptome analysis identified 2,647 and 2,392 differentially expressed genes (DEGs) in variety 37 and 44, respectively. Weighted gene co-expression network analysis (WGCNA) revealed a green module significantly positively correlated with gibberellic acid (GA) content, containing 10 core genes such as late embryogenesis abundant protein (LEA) and Homeobox genes. 16 S rRNA sequencing showed that the cold-tolerant variety 37 had enriched abundances of dominant endophytes including Sphingomonas and Pelomonas, with correlation coefficients of 0.70 and 0.87 with GA content, respectively. Additionally, exogenous GA treatment significantly increased germination rates under cold stress by 176.67% in cold-sensitive variety 44. CONCLUSIONS: This study confirms that the enhanced cold tolerance of hulless barley during seed germination originates from the synergistic interaction between beneficial endophytes (Sphingomonas, Pelomonas), GA, and core genes (e.g., LEA, Homeobox). Exogenous GA application can significantly restore the germination ability of cold-sensitive varieties. These findings provide a critical theoretical basis for improving cold tolerance in hulless barley germplasm.

Hordeum↗
PubMed2004

Degradation of phenol and toxicity of phenolic compounds: a comparison of cold-tolerant Arthrobacter sp. and mesophilic Pseudomonas putida.

Phenol degradation efficiency of cold-tolerant Arthrobacter sp. AG31 and mesophilic Pseudomonas putida DSM6414 was compared. The cold-tolerant strain was cultivated at 10 degrees C, while the mesophile was grown at 25 degrees C. Both strains degraded 200 mg and 400 mg phenol/l within 48-72 h of cultivation, but the cold-tolerant strain produced more biomass than the mesophile. Both strains oxidized catechol by the ortho type of ring fission. Catechol 1,2 dioxygenase (C1,2D) activity was found intra- and extracellularly in the absence and in the presence of phenol. In the presence of 200 mg phenol/l, C1,2D activity of the mesophile was about 1.5- to 2-fold higher than that of the cold-tolerant strain. However, an initial phenol concentration of 400 mg/l resulted in a comparable enzyme activity of the cold-tolerant and the mesophilic strain. The two strains differed significantly in their toxicity pattern towards 12 aromatic (mostly phenolic) compounds at different growth temperatures, which was determined via growth inhibition in the presence of nutrients and toxicants. For the cold-tolerant strain, toxicity was significantly lower at 10 degrees C than at 25 degrees C. The mesophile showed a significantly lower susceptibility to high hydrocarbon concentrations when grown at 25 degrees C compared to 10 degrees C.

Arthrobacter↗
PubMed2000

Effect of ginseng saponins on cold tolerance in young and elderly rats.

Acute systemic injection of ginseng saponin (GS) significantly elevated both the total and maximum heat production in young rats (3-6 months) and improved their cold tolerance under severe cold (-10 degrees C under helium-oxygen). However, pretreating the animal with the optimal dose (10 mg/kg) of GS devoid of Rg1 and Rb1 failed to elicit any beneficial effect in improving the cold tolerance. Pretreating the animal with Rb1, but not Rg1, increased thermogenesis as well as cold tolerance in young rats. A similar beneficial effect in improving cold tolerance was also observed when old rats (26-28 months) were pretreated with the same doses of Rb1 (2.5 and 5.0 mg/kg). Our results indicate that Rb1 is the key ingredient in GS-mediated enhancement in thermogenic capacity and that both young and old rats can benefit from this treatment for enhanced cold tolerance.

Adaptation, Physiological↗
PubMed1985

Improving cold tolerance in elderly rats by aminophylline.

During severe cold exposure, old rats (23-26 months) were less capable in maintaining normal body temperature as compared to young rats (6-9 months) due to lower rate of heat production (HP). Single injection of optimal doses of aminophylline (AMPY; 10 and 18.7 mg/kg, i.p.), a phosphodiesterase inhibitor which enhances the intracellular cyclic AMP concentration, significantly increased the rate of HP in old rats to levels beyond the control values observed in young rats. Consequently, cold tolerance of the old rats was significantly improved. This AMPY-improved cold tolerance is apparently not due to increased non-shivering thermogenesis (NST) since AMPY failed to enhance norepinephrine-stimulated NST in the old rats. It is likely that AMPY increased substrate mobilization and/or conversion, thereby circumventing the limiting role of substrate availability for shivering thermogenesis. Thus, the age-dependent decrease in cold tolerance may be due to a reduced capacity for substrate mobilization when challenged by cold.

Aging↗
PubMed1998

Geographical and diapause-related cold tolerance in the blow fly, Calliphora vicina.

Three geographical strains of the blow fly, Calliphora vicina, were tested for cold tolerance at 0 degrees, -4 degrees and -8 degrees C. Survival to eclosion after 1 to 18 days of cold exposure was greater for diapause-destined larvae than for nondiapause-destined larvae of the two northern strains (Nallikari, Finland 65 degrees N and Edinburgh, Scotland 55 degrees N) but not for the southernmost strain (Barga, Italy 44 degrees N) where no clear differences were apparent. Diapause-destined larvae of the Edinburgh strain were more cold tolerant than those from Nallikari, at both -4 degrees and -8 degrees C, a difference possibly attributable to the long-lasting snow cover in the more northern locality, which might insulate the overwintering soil microclimate. At 0 degrees C, however, Nallikari larvae were more cold tolerant than Edinburgh or Barga. This was also the case for nondiapause-destined larvae, indicating that cold tolerance may occur, in part, independently of the diapause programme. In all three strains diapausing larvae were more cold tolerant than same-age (nondiapausing) pupae. For Nallikari, but not Barga, wandering larvae from short-day exposed flies, therefore initially programmed for diapause, but diverted from the diapause pathway by larval breeding at 19 degrees C, were significantly more cold tolerant than nondiapause larvae from long-day parents, indicating some maternal regulation of larval cold tolerance. There was, however, no evidence for an additional cold hardiness in larvae acclimatised to cold by a gradual reduction of temperature.

Journal Article↗
PubMed1991

Effect of aging on cold tolerance and thyroid activity in CBA/Ca inbred mice.

Relationships between cold tolerance, serum levels of thyroxine (T4), thyronine (T3), and thyrotropine (TSH), and thyroid morphometry have been investigated in male CBA/Ca inbred mice at various ages through their life span. From the data obtained it appeared that there was an age-related decrease in cold tolerance up to 18 months of age which was followed by an increase, the age effect being most apparent in relation to cold resistance and cold tolerance during the recovery period following cold exposure. The age-related changes in cold tolerance appeared to be associated with changes in the serum concentrations of T3, T4, and TSH. In contrast to the T3 serum levels which showed a decrease at 36 months, the thyroxine contents showed a perceptible decrease from the age of 12-18 months onwards. A similar pattern was observed for the TSH levels, with a peak at 21 months, followed by a decline at 30 months. A relationship with age between serum T4 level and thyroid weight was indicated together with structural changes in the thyroid gland, particularly during senescence, for example the size and number of thyroid epithelial cells had become enlarged by 30 months of age.

Acclimatization↗
PubMed2004

Physical mapping and putative candidate gene identification of a quantitative trait locus Ctb1 for cold tolerance at the booting stage of rice.

Norin-PL8 is a cold-tolerant variety of rice (Oryza sativa L.) that was developed by introgressing chromosomal segments from a cold-tolerant tropical japonica variety, Silewah, into a template japonica variety, Hokkai241. We previously identified two closely linked quantitative trait loci, Ctb1 and Ctb2, for cold tolerance at the booting stage of Norin-PL8 in the long arm of chromosome 4. We report here the physical mapping of Ctb1 and the identification of the candidate genes. A total of 2,008 segregating individuals were screened for recombination in the Ctb1 region by a PCR-based screening, and a series of near-isogenic lines (NILs) were developed from progenies of recombinants. A comparison of the degrees of cold tolerance of the NILs indicated that Ctb1 is located in the 56-kb region covered by a bacterial artificial chromosome clone, OSJNBa0058 K23, that had been sequenced by the International Rice Genome Sequence Project. We found seven open reading frames (ORFs) in the 56-kb region. Two ORFs encoded receptor-like protein kinases that are possibly involved in signal transduction pathways. Proteins that may be associated with a ubiquitin-proteasome pathway were encoded by three ORFs, two of which encoded F-box proteins and one of which encoded a protein with a BAG domain. The other two ORFs encoded a protein with an OTU domain and an unknown protein. We were also able to show that Ctb1 is likely to be associated with anther length, which is one of major factors in cold tolerance at the booting stage.

Blotting, Southern↗
PubMed2004

Genetic analysis of cold-tolerance of photosynthesis in maize.

The genetic basis of cold-tolerance was investigated by analyzing the quantitative trait loci (QTL) of an F2:3 population derived from a cross between two lines bred for contrasting cold-tolerance using chlorophyll fluorescence as a selection tool. Chlorophyll fluorescence parameters, CO2 exchange rate, leaf greenness, shoot dry matter and shoot nitrogen content were determined in plants grown under controlled conditions at 25/22 degrees C or 15/13 degrees C (day/night). The analysis revealed the presence of 18 and 19 QTLs (LOD > 3.5) significantly involved in the variation of nine target traits in plants grown at 25/22 degrees C and 15/13 degrees C, respectively. Only four QTLs were clearly identified in both temperatures regimes for the same traits, demonstrating that the genetic control of the performance of the photosynthetic apparatus differed, depending on the temperature regime. A major QTL for the cold-tolerance of photosynthesis was identified on chromosome 6. This QTL alone explained 37.4 of the phenotypic variance in the chronic photoinhibition at low temperature and was significantly involved in the expression of six other traits, including the rate of carbon fixation and shoot dry matter accumulation, indicating that the tolerance to photoinhibition is a key factor in the tolerance of maize to low growth temperature. An additional QTL on chromosomes 2 corresponded to a QTL identified previously in another population, suggesting some common genetic basis of the cold-tolerance of photosynthesis in different maize germplasms.

Adaptation, Physiological↗
PubMed1998

How Drosophila species acquire cold tolerance--qualitative changes of phospholipids.

Phospholipids of many cold-tolerant organisms have been reported to contain more unsaturated fatty acids than cold-susceptible organisms, a phenomenon known to maintain membrane fluidity at low temperature. However, we have obtained results to the contrary through a comparison of the membrane phospholipids of six temperate and subtropical species belonging to the Drosophila melanogaster species group. With enhancement of cold tolerance, the percentages of monoenoic acids increased but the percentages of dienoic acids decreased, that is, the number of double bonds in the phospholipid decreased without a marked variation in the percentages of unsaturated fatty acids. Concomitantly, the percentage of fatty acids containing 16 carbon atoms increased, while that of fatty acids with 18 carbon atoms decreased. Since phosphatidylethanolamine is a dominant phospholipid in Drosophila, these changes probably contribute to keeping the homeoviscosity of the cellular membranes in a manner different to that in phosphatidylcholine-rich membranes, thereby increasing cold tolerance.

Acclimatization↗
PubMed1986

The effect of cold acclimation and exercise training on cold tolerance in aged C57BL/6J mice.

We investigated whether intermittent cold acclimation and low intensity exercise training, two interventions known to improve thermoregulatory function in young rodents, enhanced cold tolerance in aged C57BL/6J mice. Mice, aged 18 to 20 months, were randomly assigned to four treatment conditions: (a) intermittent cold acclimation (CA) (50 min per day, 5 times per week for 3 weeks at 5 degrees C), (b) submaximal treadmill exercise (EX) (15 m min-1 for 30 min, 5 times per week for 8 weeks, (c) sequential treatment of CA + EX, and (d) control group. Mice were exposed to a 3-hr cold stress test (15 degrees C) prior to and following treatment. CA aged mice maintained normothermia and demonstrated significant increases in oxygen consumption and brown adipose tissue protein concentration compared with controls; enhanced cold tolerance was probably due to increased utilization of nonshivering thermogenesis. EX aged mice had elevated O2 consumption and increased skeletal muscle enzyme activity compared with controls; however, cold tolerance was not enhanced compared with CA mice. The data suggest that intermittent CA effectively reduces hypothermia during cold challenge in aged mice.

Acclimatization↗
PubMed2000

Expression of cold-adapted beta-tubulins confer cold-tolerance to human cellular microtubules.

Isolated microtubule proteins from the cold-adapted fish, Atlantic cod (Gadus morhua), assemble at temperatures between 8 and 30 degrees C, while avian and mammalian microtubules normally do not assemble at temperatures below 20 degrees C. Tubulin, the main component in microtubules, is expressed as many isotypes. Microtubules with different isotype composition have been shown to have different dynamic properties in vitro. Our hypothesis was that cold-tolerance of microtubules is caused by tubulin isotypes that differ in the primary sequence compared to mammalian tubulins. Here we show that transfection of human HepG2 cells with cod beta-tubulin induced cold-adaptation of the endogenous microtubules. Incorporation of one single tubulin isotype can induce cold-tolerance to cold-intolerant microtubules. Three cod beta-tubulin isotypes were tested and two of these (beta1 and beta2) transferred cold-tolerance to HepG2 microtubules, thus not all cod beta-tubulins were able to confer cold-stability.

Acclimatization↗
PubMed2004

Partial link between the seasonal acquisition of cold-tolerance and desiccation resistance in the goldenrod gall fly Eurosta solidaginis (Diptera: Tephritidae).

Possible links between seasonal increases in cold-tolerance and desiccation resistance were examined in field-collected larvae of the goldenrod gall fly, Eurosta solidaginis. From 20 September to 30 October 2001, larvae exhibited a gradual increase in cold-tolerance culminating in 100% survival of freezing at -20 degrees C for 24 h. The increase in cold-tolerance was probably due to a concomitant increase in cryoprotectants as measured by hemolymph osmolality (488-695 mOsmol kg(-1)). In contrast to the gradual increase in cold-tolerance, larvae exhibited two distinct phases of reduced rates of water loss. The first phase was an abrupt sixfold decrease to 0.57 microg mm(-2) h(-1) between 3 and 16 October. The first phase of reduced rates of water loss was not correlated with changes in cold-tolerance; nor was it correlated with hemolymph osmolality and body water content, which remained constant throughout the study. The reduction in rates of water loss during the first phase were probably the result of decreased respiratory water loss as the larvae entered diapause, and possibly reduced cuticular water loss as larvae increased the amount of their cuticular hydrocarbons. Interestingly, the first phase of reduced water loss was associated with, and may have been cued by, a reduction in the water potential of the gall tissues surrounding the larvae. The second phase was a more subtle fourfold reduction in rates of water loss occurring between 16 October and 11 December. In contrast to the first phase, the second phase of increased desiccation resistance correlated closely with increases in hemolymph osmolality (568-870 mOsmol kg(-1)). The correlation between seasonal increases in hemolymph osmolality and reduction in rates of water loss may represent a link between desiccation resistance and cold-tolerance in this species.

Acclimatization↗
PubMed1996

Cold-induced vasodilatation response of finger skin blood vessels in older men observed by using a modified local cold tolerance test.

The time of onset and magnitude of cold-induced vasodilatation (CIVD) in six older men (62-70 years) were compared with those of seven younger men (20-29 years) by using a modified local cold tolerance test. This test consisted of a 10-min immersion of the left middle finger in cold water at 10 degrees C, and was substituted for a conventional test (30-min immersion in ice water at 0 degrees C). Vasodilatation occurred significantly later in the older group, and the magnitude of their response was significantly lower during the immersion. No vasodilatation occurred in two of the older men. As the finger skin temperature before the test was not significantly different between the two age groups, the difference of CIVD response in the two age groups was thought to reflect the age-related changes of peripheral vascular reactivity to a local cold stimulus. Considering the fact that no subjects complained a great deal of cold pain during the immersion, our modified local cold tolerance test seems to be a useful method for detecting the age-related degradation of local cold tolerance and peripheral vascular reactivity in older workers.

Adult↗
PubMed1994

Effect of exercise on cold tolerance and metabolic heat production in adult and aged C57BL/6J mice.

Two groups of adult (12-mo-old) and two groups of aged (24-mo-old) C57BL/6J male mice were subjected to a standardized cold stress test (3-h partial restraint at 6 degrees C). One group from each age group was tested in the morning, and the other was tested in the afternoon. Half of the mice were subjected to running exercise on a treadmill during 1 h before the cold stress test. The other half were placed on a nonoperational treadmill for 1 h before the cold stress test. One hour of exercise resulted in improvement of cold tolerance during the subsequent cold exposure in both age groups but only during afternoon testing. Improvement in cold tolerance was not accompanied by an elevation of cold-induced metabolic heat production in adult mice. Metabolic heat production in aged mice showed only modest elevation. The discrepancy between improvement in cold tolerance and lack of elevation of metabolic heat production suggests that the primary mechanism for augmentation of cold tolerance after exercise in the afternoon is an improvement in cold-induced vasoconstriction of skin vessels, which is probably normally compromised in the afternoon.

Age Factors↗
PubMed1996

Identification of the amino acid residues responsible for cold tolerance in Flaveria brownii pyruvate,orthophosphate dikinase.

Pyruvate,orthophosphate dikinase (PPDK), an enzyme important in C4 photosynthesis, is typically a cold-sensitive enzyme. However, a cold-tolerant form of the enzyme has been isolated from the leaves of Flaveria brownii. Using an Escherichia coli expression system and the PPDK cDNAs from F. brownii (cold-tolerant), F. bidentis (cold-sensitive) and maize (intermediate cold tolerance), site-directed mutagenesis studies indicated that as few as three amino acids residues (of 880 residues) strongly influence the cold sensitivity of Flaveria PPDK. Gel filtration analysis of the PPDK expressed in E. coli showed that subunit association and cold tolerance are closely linked.

Amino Acid Sequence↗
PubMed1997

Identification of the amino acid residues responsible for cold tolerance in Flaveria brownii pyruvate,orthophosphate dikinase.

Pyruvate,orthophosphate dikinase (PPDK), an enzyme important in C4 photosynthesis, is typically a cold-sensitive enzyme. However, a cold-tolerant form of the enzyme has been isolated from the leaves of Flaveria brownii. Using an E. coli expression system and the PPDK cDNAs from F. brownii (cold-tolerant), F. bidentis (cold-sensitive) and maize (intermediately cold-tolerant), site-directed mutagenesis studies indicated that as few as three amino acids residues (of 880 residues) strongly influence the cold sensitivity of Flaveria PPDK. Gel filtration analysis of the PPDK expressed in E. coli showed that subunit association and cold tolerance are closely linked.

Amino Acid Sequence↗
PubMed1990

Seedling growth, mitochondrial characteristics, and alternative respiratory capacity of corn genotypes differing in cold tolerance.

Four maize (Zea mays L.) inbreds representing genetic differences in seedling cold tolerance were used to determine the effect of growth temperatures on dry weight accumulation and mitochondrial properties, especially the alternative oxidase capacity. Seedlings were grown in darkness at 30 degrees C (constant), 14 degrees C (constant), and 15 degrees C for 16 hours and 8 degrees C for 8 hours. Inbreds B73 and B49 were characterized as cold tolerant while G50 and G84 were cold sensitive. Shoot growth rate of cold-sensitive inbreds in the lower temperatures was slower relative to the tolerant inbreds. Mesocotyl tissue was particularly sensitive to low temperatures during growth after germination. There were no significant differences in relative rates of mitochondrial respiration in the cold-tolerant compared to cold-sensitive inbreds measured at 25 degrees C. Mitochondria from all seedlings grown at all temperatures had the ability to phosphorylate as indicated by the observation of respiratory control. This result indicated that differences in low temperature growth were probably not related to mitochondrial function at low temperatures. Alternative oxidase capacity was higher in mitochondria from seedlings of all inbreds grown at 14 degrees C compared to 30 degrees C. Capacities in seedlings of 14 degrees C-grown B73 and G50 were higher than in B49 and G84. Capacities in seedlings grown for 16 hours at 15 degrees C and 8 hours at 8 degrees C were similar to those from 14 degrees C-grown except in G50 which was lower and similar to those grown at 30 degrees C. Mesocotyl tissue was the most responsive tissue to low growth temperature. Coleoptile plus leaf tissue responded similarly but contained lower capacities. Antibody probing of western blots of mitochondrial proteins confirmed that differences in alternative oxidase capacities were due to differences in levels of the alternative oxidase protein. Male sterile lines of B73 were also grown under the three different temperature regimes. These lines grew equally as well as the normal B73 at all temperatures and the response of alternative oxidase capacity and protein to low growth temperature was similar to normal B73.

Journal Article↗
PubMedDate not supplied

Are mummy characteristics reliable indicators of diapause and cold tolerance in the parasitoid wasp Aphidius rhopalosiphi (Braconidae, aphidiinae) ?

Many insect species have evolved different overwintering survival strategies such as cold tolerance or diapause. This study investigated the relationship between Aphidius rhopalosiphi mummy colour and cold tolerance and diapause. Mummy colour was insufficient to discriminate diapausing from non-diapausing individuals. This phenotypic character seems to reflect environmental conditions rather than direct developmental time and cocoon thickness (identification criteria of diapause). There is, however, a relationship between cold tolerance and mummy colour. Dark mummies exhibited significantly higher water content, survival at low temperature and lower supercooling point values than pale mummies. Mummy colour in Aphidius rhopalosiphi seems to be a phenotypic indicator of the cold tolerance.

Adaptation, Physiological↗