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At least 19 recordsLinked to original sources
PubMed2026

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↗
PubMed2026

The Absence of E. coli Nucleoid-Associated Protein FIS at Low Temperature Leads to an Adaptation Response That Causes a Shift Towards Genome Compaction in Small Rods.

In contrast to the rod shape at 37°C, the morphology of Escherichia coli cells at temperatures just above the minimum temperature of growth is small rods. A study was initiated to determine the requirement of nucleoid-associated protein FIS for growth and genome compaction in the small rods at low temperature. Growth and nucleoid staining analyses revealed that the fis null mutant displayed decreased growth and initially formed filaments containing decondensed nucleoids at 12°C, indicating that FIS facilitates production of small rods with condensed nucleoids at low temperature. However, characterized by biphasic growth at low temperature, the fis null mutant exhibited increased growth, cell division, and nucleoid condensation following an acclimation phase. Therefore, the absence of FIS with nucleoid decondensation leads to an adaptation mechanism, termed FIS Null Adaptation Response, that causes a shift towards nucleoid condensation resulting in genome compaction in small rods. Furthermore, overproduction of the HsIVU protease suppressed the cold-sensitive phenotypes of the fis null mutant indicating that degradation of a natural substrate of the protease alleviates the requirement of FIS at low temperature. In addition, null mutations of genes encoding natural substrates of HsIVU (exoribonuclease RNAse R, and cell division inhibitor SulA) were identified as extragenic suppressors of the fis null mutation.

Escherichia coli↗
PubMed1978

Resonance Raman spectroscopy of the retinylidene chromophore in bacteriorhodopsin (bR570), bR560, M421, and other intermediates: structural conclusions based on kinetics, analogues, models, and isotopically labeled membranes.

Resonance Raman spectra of various intermediates in the bacteriorhodopsin proton pumping cycle have been obtained at physiological and low temperatures. To interpret these data, spectra of modél compounds, bacteriorhodopsin analogues, and isotopically labeled membranes have been measured. These results demonstrate that a protein group interacts with the Schiff base proton and, thus, the chromophore in protonated bacteriorhodopsin species is not a simple protonated Schiff base. This accounts for the abnormally low frequency of the C=N+H vibrational mode in bacteriorhodopsin and other failures to model the chromophore in bR570 with a simple butylamine protonated Schiff base of all-trans-retinal. To obtain the resonance Raman spectrum of M412 at physiological pH and temperatures, a dual beam kinetic technique was developed. We demonstrate that in the fingerprint region of the resonance Raman spectrum M412 is modeled accurately by a simple unprotonated butylamine Schiff base of all-trans-retinal. Spectral resolution and the solution environment of the membrane suspensions play important roles in this conclusion. Kinetic resonance Raman techniques are also used to monitor the time evolution of the M412 species and the intermediates which precede it. We find spectral features in our kinetic data which can be assigned to L550, and we present evidence for a new unprotonated species (X) which occurs before M412. Single pass flow resonance Raman spectra of bR560 also have been obtained, and, although bR570 and M412 appear to have all-trans chromophores, there are 13-cis-like features in the spectra of bR560, L550, and X.

Bacteriorhodopsins↗
PubMed1979

Comparison of formation, activation, and nuclear translocation of receptor . estradiol (R . E2) complex at 0 degrees C and 37 degrees C in intact uterine cells.

The present study was undertaken to establish whether molecular events leading to binding, transformation-activation, and nuclear translocation of cytoplasmic uterine estrogen receptor described for cell-free systems also occur in intact uterine cells. Cell suspensions were incubated at 0 degrees C or 37 degrees C with estradiol (E2) and specific binding to intracellular receptors was measured. The data demonstrate that saturation of specific estrogen binding sites occurs within 60 min at 37 degrees C and within 22 h at 0 degrees C, with a total of approximately 24,000 to 30,000 receptor sites per cell. At equilibrium, the total number and subcellular distribution of receptor . estradiol (R . E2) complexes formed in cells incubated at 0 degrees C or 37 degrees C were identical. Scatchard analysis of the equilibrium binding data yielded the same association constants for cytoplasmic and nuclear R . E2 formed in intact cells incubated at either temperature. Sucrose density gradient analysis of nuclear and cytoplasmic R . E2 formed in intact cells at 0 degrees C or 37 degrees C showed that at both temperatures, the nuclear R . E2 had a 5 S sedimentation coefficient; at both temperatures, a 5 S cytosol R . E2 was detected; only in the 0 degrees C incubation, an additional 4 S cytosol R . E2 was found. These results suggest that the molecular interactions regulating the dynamics of estrogen binding in the intact cell are similar at both physiological and low temperatures.

Animals↗
PubMed1976

Kinetics of bicarbonate-chloride exchange across the human red blood cell membrane.

The kinetics of bicarbonate-chloride exchange across the human red cell membrane was studied by following the time course of extracellular pH in a stopped-flow rapid-reaction apparatus during transfer of H+ into the cell by the CO2 hydration-dehydration cycle, under conditions where the rate of the process was determined by HCO3--Cl- exchange flux across the membrane. The flux of bicarbonate increased linearly with [HCO3-] gradient from 0.6 to 20 mM across the red cell membrane at both 37 degrees C and 2 degrees C, and decreased as transmembrane potential was increased by decreasing extracellular [Cl-]. An Arrhenius plot of the rate constants for the exchange indicates that the Q10 is strongly dependent on temperature, being about 1.7 between 24 degrees C and 42 degrees C and about 7 between 2 degrees C and 12 degrees C. These data agree well with the published values for Q10 of 1.2 between 24 degrees C and 40 degrees C and of 8 between 0 degrees C and 10 degrees C. The results suggest that different processes may determine the rate of HCO3--Cl- exchange at low vs. physiological temperatures, and that the functional (and/or structural) properties of the red cell membrane vary markedly with temperature.

Bicarbonates↗
PubMed1978

The role of hormones in the acclimation of fish to low temperatures.

The known cases elucidating the role of hormones in the regulation of physiological and biochemical changes which occur when fish are acclimated to low temperatures are sparse, but evidence is accumulating to implicate prolactin, glucagon, insulin and perhaps thyroxine and cortisol in at least some of the physiological adjustments observed in some species. The need for further research on hormonal control mechanisms at work during low-temperature acclimation is discussed, with special emphasis placed on neuroendocrine relationships.

Adaptation, Physiological↗
PubMed1976

D-Mannitol dehydrogenase from Absidia glauca. Purification, metabolic role, and subunit interactions.

When Absidia glauca was grown in minimal media with D-mannitol as the only source of carbon, an NAD+ specific D-mannitol dehydrogenase (EC 1.1.1.67) was induced. The crude extract also gave evidence of mannitol kinase, mannitol-1-phosphate dehydrogenase, phosphofructokinase, and L-iditol dehydrogenase activity. The heat labile purified preparation was judged enzymically homogeneous based on evidence derived from substrate specificity studies and activity staining, following disc gel electrophoresis. The enzymic monomer, with a weight of about 67000 daltons, slowly polymerizes when stored at -20 degrees C, giving a multiplicity of protein bands on electrophoresis distributed predominantly across a spectrum from dimer to pentamer, with enzymic activity resident predominantly in even multiples of the monomer. Depolymerization occurred rapidly (hours) when a frozen preparation was brought to and held between 4 and 20 degrees C. Aggregate fragmentation with sodium dodecyl sulfate showed a time-temperature dependence, terminating in a subunit component of 13000 daltons. pH optimum for polyol oxidation occurs at 9.6 (NaOH-glycine buffer) while ketose reduction proceeded most rapidly at pH 7.0-7.2 (phosphate buffer). A regulatory role is suggested for this enzyme based on dead-end inhibition by mannitol 1-phosphate, multiple enzyme forms, and its locus at the initiation site for mannitol utilization. The physiological relevance of low-temperature aggregation to regulatory control remains to be established.

Electrophoresis, Disc↗
PubMed1977

[Contractility and epithelization in the chick embryo axial mesoderm].

The still unsegemented axial mesoderm was cross cut at different distances form the last somite under the normal physiological conditions, at the low temperature and under the effect of cytochalasin B. Under the normal conditions the inner cells of the axial mesoderm formed a lens-shaped cleft immediately after the operation; this movement was suppressed at the low temperature and absent under the effect of cytochalasin B. This suggests the active contractility of the mesodermal syncytium. The wound margin near the last somite acquired the epithelial structure already within several minutes after the cut, whereas in the more caudal regions it preserved the connective tissue character for a long time. The importance of the axial mesoderm contractility and its ability of epithelization for the somitogenesis is discussed.

Animals↗
PubMed1978

Repeated feeding of Amblyomma herbraeum (Acarina: Ixodidae) immatures on laboratory hosts. Host effects on tick yield, engorged weight and engorgement period.

Rabbits and sheep are unable to acquire a resistance to larvae and nymphs of Amblyomma hebraeum. After repeated infestation of hosts there is no progressive decline in either the tick yield or the engorged weight of fed ticks. Seasonal fluctuations in engorged weights do occur however, with the weight declining in early to midwinter and increasing in early to midsummer. Changes in hose physiology as a result of low temperature acclimatization appear to be responsible for the fluctuations. Tick yield is determined by the amount of grooming undertaken by hosts. The feedings periods of larvae and nymphs are dependent on the skin temperature of the host.

Animals↗
PubMed1979

Physical modifications of rhodopsin boundary lipids in lecithin-rhodopsin complexes: a spin-label study.

The microviscosity of rhodopsin boundary lipids was studied with a spin-labeled fatty acid covalently attached to rhodopsin, in rhodopsin-egg lecithin vesicles. When the lipid-to-protein ratio was high (500:1, mole to mole), only narrow peaks were visible in electron paramagnetic resonance spectrum at 37 degrees C. This enabled us to show that, under these conditions, not more than 10% of the probes have their motion strongly restricted by the proximity of the protein. When the temperature was reduced, a second component characteristic of strong immobilization appeared. It corresponds to 50% of the signal at -5 degrees C. At all temperatures reduction of the lipid-to-protein ratio also resulted in an increase of the amount of immobilized lipid. These results show that the rhodopsin boundary layer under physiological conditions is associated with low microviscosity. However, low temperatures, low lipid-to-protein ratios, or combinations of the two can induce dramatic modifications of the physical state of the boundary lipids, which under these conditions may no longer be representative of the functional biological system. These results are relevant to the general theory of lipid-protein interaction.

Animals↗
PubMed1978

Lipid adaptation in liver mitochondrial membranes of carp acclimated to different environmental temperatures: phospholipid composition, fatty acid pattern and cholesterol content.

The lipid fraction of liver mitochondria has been studied in carp acclimated to high and low environmental temperatures. Evidence is provided for a temperature-induced lipid adaptation which might control membrane fluidity. This supports suggestions made in a recent communication on temperature-induced changes in the Arrhenius functions of mitochondrial oxidase systems from carp liver ((Wodtke, E. (1976) J. Comp. Physiol. 110, 145--157). The results of the analysis of lipid composition are: the ratio of phospholipid to protein does not differ at cold and warm acclimation temperatures. Fish kept at low environmental temperature show a decreased molar ratio of cholesterol : phospholipid in mitochondrial membrane lipids; the diminished complexation renders phospholipids more sensitive to fluidity control by fatty acid substitution. A decrease of mitochondrial phosphatidylcholine at low acclimation temperature is observed, which is compensated by increased amounts of phosphatidylethanolamine and phosphatidylinositol. This means there is an increase in the acidic character of the phospholipids at low environmental temperature, and might be the cause of fluidization of the membrane and a decrease in transition temperature. The fatty acid pattern of carp mitochondria differs markedly from that of mammalian mitochondria; it is not identical for total lipids, phosphatidylcholine and phosphatidylethanolamine, and is roughly characterized by high amounts in n--3, but low amounts in n--6 and mono-unsaturated fatty acids. Low environmental temperature decreases the proportion of saturated species and markedly lowers the ratio of the alpha-linolenic acid family, the latter perhaps being caused by the increased activity of delta6-desaturase, as calculated for low acclimation temperature. An increase in mean unsaturation and in the proportion of 1,2-diunsaturated phospholipids most probably increases membrane fluidity at low acclimation temperature.

Adaptation, Physiological↗
PubMed1977

Neurofibrillar changes in goldfish (Carassius auratus L.) brain in relation to environmental temperature.

Neurofibrillar changes occur in the brains of goldfish, Carassius auratus L., maintained at 5 degrees C for 177 days or more under a 12-hour photoperiod. In paraffin sections impregnated by the silver method of Holmes, the light microscopic appearance of the neurofibrillary change was evidenced by black rings 1 micrometer to 2 micrometer in outside diameter. A quantitative study showed the mean number of rings to be: optic tectum layer 3, 1.34 X 10(2)/mm(3), layer 5, 1.14 X 10(2)/MM(3), nucleus prerotundus 4.63 X 10(2)/mm(3), olfactory bulbs, 6.2 X 10(2)/mm3. In the brains of fish kept at 15 degrees C a few rings are found only in some olfactory bulbs and not in any other region of the brain. The brain wet weight also changes and was found to be significantly (p less than 0.01) less in 5 degrees C than in 15 degrees C fish, the mean values being 0.1588 g and 0.2091 g respectively. The significance of the observed changes is discussed. It is suggested that the smaller brain wet weight may reflect a change in the vasculature of the brain and be related to the acclimation process. It is hypothesized that the rings are a morphological expression of a physiological change caused by prolonged exposure to low temperatures; a neuronal response reflecting either early degeneration or a functional adaptation which may involve an alteration in axoplasmic transport. It is suggested that this system is a useful model for the study of relationships between neurofibrillar disturbances and neuronal function.

Animals↗
PubMedDate not supplied

Tripartite and bipartite models of the photochemical apparatus of photosynthesis.

Tripartite and bipartite models for the photochemical apparatus of photosynthesis are presented and examined. It is shown that the equations for the yields of fluorescence from the different parts of the photochemical apparatus of the tripartite model transform into the simple equations of the bipartite formulation when the probability for energy transfer from the light-harvesting chlorophyll a/b complex to photosystem II is unity. The nature of the 695 and 735 nm fluorescence bands which appear in the emission spectrum of chloroplasts at low temperature is examined. It is proposed that these bands are due to fluorescence from energy-trapping centres which form in the antenna chlorophyll of photosystem II and photosystem I on cooling to low temperature. Even though these fluorescence emissions can be regarded as low temperature artifacts since they are not present at physiological temperatures, they nevertheless are proportional to the excitation energy in the two photosystems and can be used to monitor energy distribution in the photochemical apparatus. However, the question of their artifactual nature is crucial to the interpretation of fluorescence-lifetime measurements at low temperature.

Chlorophyll↗
PubMed1978

Sphingomyelin multiple phase behavior as revealed by multinuclear magnetic resonance spectroscopy.

31P and 13C nuclear magnetic resonance (NMR) spectra are employed to study the phase behavior of bovine brain sphingomyelin as a function of temperature. The 31P NMR data suggest that, while at low temperatures sphingomyelin can form a lamellar phase, at physiological temperatures and higher the lamellar phase is unstable, and a new phase, best described as a hexagonal phase, is formed. Egg phosphatidylcholine is suggested to play an important role in stabilizing bilayers in natural membranes. Cholesterol also exhibits a sphingomyelin bilayer-stabilizing ability. The 13C NMR spectra suggest a gelling of the hydrocarbon chains of sphingomyelin at low temperature. Thus, bovine brain sphingomyelin undergoes both a gel to liquid-crystalline phase transition and a lamellar to nonlamellar transition.

Animals↗
PubMed1979

Effect of a low protein diet during pregnancy of the rhesus monkey. II. Physiological adaptation of the infant.

Heart rate, respiratory rate, and ability to maintain body temperature were evaluated in six infants born to rhesus monkeys that had been fed a low protein diet throughout pregnancy. All infants were kept in incubations equipped with a "servo" control thermal unit that maintained the infants' skin temperature at 37.0 C (98.6 F). The thermal units were disconnected and the infants were exposed to room temperature (approximately 27 C) for 6-hr periods each day after 24 hr of age in order to determine the efficiency of thermal control mechanism. The thermal servo control units were "on" for a longer period of time in experimental animals than in control animals during the first 24 hr of life. Infants from mothers fed the low protein diets were also less able to maintain their own body temperatures after exposure to room temperature. This function was seriously compromised in two of the six experimental infants. The compromised temperature control mechanism seen in these infant monkeys is a serious and potentially lethal side-effect of protein-calorie malnutrition during pregnancy. The possible relationship of inadequate maternal nutrition to the inefficient thermal mechanism of certain "high risk" human newborns should be reevaluated.

Adaptation, Physiological↗
PubMed1976

The mechanism of the aminoacylation of transfer ribonucleic acid: enzyme-product dissociation is not rate limiting.

It has been proposed that the rate-limiting step in the synthesis of aminoacyl-tRNA is the rate at which the product dissociates from the enzyme. The experimental evidence supporting this hypothesis comes from work at low pH and low temperature (although the reaction has been argued to have the same mechanism under physiological conditions). We have reexamined the binding assay by which M. Yarus and P. Berg (1969) (J. Mol. Biol. 42, 171-189) measured the kd for dissociation of Enz-(Ile-tRNA). We find that when overall reaction and dissociation are measured under identical conditions the two rates are not the same. Moreover, while an increase in ionic strength greatly stimulates dissociation, the same increased ionic strength slows aminoacylation. Spermine accelerates overall aminoacylation without affecting dissociation. Because any change in a rate-limiting step must, by definition, cause a parallel change in the overall reaction, these observations prove that under these conditions the synthesis of Ile-tRNA is not limited by the rate of dissociation of Enz-(Ile-tRNA). Entirely similar observations were made for the dissociation of Enz-(Val-tRNA) and the overall synthesis of Val-tRNA at 0 degrees C, PH 5.0. In addition, valine enzyme isolated by nitrocellulose filtration during the course of an aminoacylation was shown not to be saturated with recently synthesized Val-tRNA. The enzyme was in equilibrium with uncharged substrate tRNA and with product Val-tRNA. E. W. Eldred and P. R. Schimmel ((1972) Biochemistry 11, 17-23) report that the formation of Ile-tRNA proceeds at two rates: (a) k = 2 X 10(-2)S(-1) until the enzyme is saturated with the first mole of product, and (b) k = 2 X 10(-3)S(-1) for subsequent cycles. We did not observe this behavior at any pH or temperature with four different amino acid:tRNA ligases. Because aminoacylation proceeds more rapidly than "dissociation" under some conditions, we believe that the binding assay measures not only enzyme-product dissociation but also other slower reactions such as aggregation or disaggregation of Enz-(AA-tRNA). In conjunction with recent studies from other laboratories, this work makes it unlikely that enzyme-product dissociation is the rate-limiting step in the synthesis of aminoacyl-tRNA either at low temperature and pH or under more nearly physiological conditions. From the effect of salt, it would appear that the rate of aminoacylation of tRNA is largely limited by the rate or extent of formation of Enz-(tRNA) (Loftfield, R. B., and Eigner, E. A. (1967), J. Biol. Chem. 242, 5355-5359). Using the binding assay of M. Yarus ((1972) Biochemistry 11, 2050-2060), we find the Kass for Enz-(Ile-tRNA) varies linearly with the Debye-Hückel function at ionic strengths of 0.1-0.4 from 10(8) to 10(6).

Amino Acyl-tRNA Synthetases↗