Incubation temperature induced developmental plasticity of cold responsive physiological phenotypes in Japanese Quails

Embryonic development is a critical period for phenotype formation.Environmental variation during embryonic development can induce changes in postnatal phenotypes of animals.The thyroxine secretion and aerobic metabolic activity of small birds are important phenotypes closely related to their winter survival.In the context of climate change,it is necessary to determine whether temperature variation during incubation in birds leads to developmental plasticity of these cold responsive phenotypes.We incubated Japanese Quail(Coturnix japonica)eggs at 36.8℃,37.8℃,and 38.8℃,and raised the chicks to 35-day old at 22℃with same raising conditions,then all the quails were exposed to gradually temperature dropping environment(from 15℃to 0℃).After cold treatment,serum T3 level,resting metabolic rate,skeletal muscle and liver metabolomes of the birds were measured.The serum T3 levels were significantly lower in the 38.8℃group and significantly higher in the 36.8℃group compared to the 37.8℃group.The metabolic rate in the 38.8℃group was significantly lower compared to the 37.8℃group.Compared with the 37.8℃group,metabolites involved in the tricarboxylic acid cycle in the liver were significantly lower in the 38.8℃group,and metabolites related to lipid oxidation metabolism and fatty acid biosynthesis were significantly lower in the skeletal muscles in the 38.8℃group but significantly higher in the 36.8℃group.These results indicate that incubation temperature variation can lead to developmental plasticity in cold responsive physiological phenotypes.Higher incubation temperature may impair the capacity of birds coping with cold challenge.

COR27 and COR28 encode nighttime repressors integrating Arabidopsis circadian clock and cold response

Summary It was noted that circadian components function in plant adaptation to diurnal temperature cycles and freezing tolerance. Our genome-wide transcriptome analysis revealed that evening-phased COR27 and COR28 mainly repress the transcription of clockassociated evening genes PRRS, ELF4 and cold-responsive genes. Chromatin immunoprecipitation indicated that CCAI is recruited to the site containing EE elements of COR27 and COR28 promoters in a temperaturedependent way. Further genetic analysis shows COR28 is essential for the circadian function of PRR9 and PRRT. Together, our results support a role of COR27 and COR28 as nighttime repressors integrating circadian clock and plant cold stress responses.

Endocrine response of early-hatching Asian Short-toed Lark nestlings exposed to cold temperature in a high-latitude grassland habitat

Background:In high latitude grassland habitats,altricial nestlings hatching in open-cup nests early in the breeding season must cope with cold temperature challenges.Thyroid hormones(triiodothyronine,T_(3)and thyroxine,T_(4))and corticosterone play a crucial role in avian thermoregulation response to cold.Investigating the endocrine response of altricial nestlings to temperature variation is important for understanding the adaptive mechanisms of individual variation in the timing of breeding in birds.Methods:We compared nest temperature,ambient temperature,body temperature,plasma T_(3),T_(4)and corticosterone levels in Asian Short-toed Lark(Alaudala cheleensis)nestlings hatching in the early-,middle-,and late-stages of the breeding season in Hulunbuir grassland,northeast China.Results:Mean nest temperature in the early-,middle-and late-stage groups was-1.85,3.81 and 10.23℃,respectively,for the 3-day-old nestlings,and 6.83,10.41 and 11.81℃,respectively,for the 6-day-old nestlings.The nest temperature significantly correlated with body temperature,plasma T_(3),T_(4)and corticosterone concentrations of nestlings.Body temperature of 3-day-old nestlings in the early and middle groups was significantly lower than that of the late group,but there was no significant difference between the nestlings in the early and middle groups.The T_(4)and T_(3)concentrations and the ratio of T_(3)/T_(4)of both 3-and 6-day-old nestlings in the early-stage group were significantly higher compared to the middle and late groups.The corticosterone levels of 3-day-old nestlings were significantly higher in the early-stage group compared to the middle-and late-stage groups.Conclusion:Nestlings hatching early responded to cold temperature by increasing thyroid hormones and corticosterone levels even in the early days of post hatching development when the endothermy has not been established.These hormones may play a physiological role in neonatal nestlings coping with cold temperature challenges.

Physiological Changes in Leaves of Medicago falcata Under Low-Temperature Stress

Low temperature significantly restricts crop yield and quality.Medicago falcata(M.falcata)is a typical legume species that exhibits great capacity of tolerance to low temperature.To understand the low-temperature responses in M.falcata,the electrolyte leakage and lipid peroxidation level,and activities of superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD),and contents of reduced glutathione(GSH),soluble protein,soluble sugar and proline were investigated in low-temperature-stressed M.falcata leaves.The electrolyte leakage and malondialdehyde(MDA)content increased,and could be used to quantify low-temperature damage at cellular level.And then,the significant change of SOD,POD and CAT activities,and GSH content reflected the higher reactive oxygen species(ROS)scavenging capacity in M.falcata.In addition,the significant change of soluble protein,soluble sugar and proline contents helped to maintain osmotic equilibrium,energy supply and protein functions.These nine physiological traits were analyzed by gray relational grade analysis and ranked from the highest to the lowest as follows:electrolyte leakage,GSH,proline,soluble protein,MDA,soluble sugar,SOD,CAT and POD,and illustrated that the electrolyte leakage level,GSH and proline contents should be selected and measured priority in M.falcata low-temperature tolerance to improve measurement efficiency.

The calcium-dependent kinase OsCPK24 functions in cold stress responses in rice

Calcium-dependent protein kinases（CPKs）are serine/threonine protein kinases that function in plant stress responses. Although CPKs are recognized as key messengers in signal transduction, the specific roles of CPKs and the molecular mechanisms underlying their activity remain largely unknown. Here, we characterized the function of Os CPK_（24）, a cytosol-localized calciumdependent protein kinase in rice. Os CPK_（24） was universally and highly expressed in rice plants and was induced by cold treatment. Whereas Os CPK_（24） knockdown plants exhibited increased sensitivity to cold compared to wild type（WT）, Os CPK_（24）-overexpressing plants exhibited increased cold tolerance. Plants overexpressing Os CPK_（24） exhibited increased accumulation of proline（an osmoprotectant） and glutathione（an antioxidant） and maintained a higher GSH/GSSG（reduced glutathione to oxidized glutathione） ratio during cold stress compared to WT. In addition to these effects in response to cold stress, we observed the kinase activity of Os CPK_（24） varied under different calcium concentrations. Further,Os CPK_（24） phosphorylated Os Grx_（10）, a glutathionedependent thioltransferase, at rates modulated by changes in calcium concentration. Together, our results support the hypothesis that Os CPK_（24） functions as a positive regulator of cold stress tolerance in rice, a process mediated by calcium signaling and involving phosphorylation and the inhibition of Os Grx_（10） to sustain higher glutathione levels.

Proteomics Analysis Reveals Post-Translational Mechanisms for Cold-Induced Metabolic Changes in Arabidopsis

Cold-induced changes of gene expression and metabolism are critical for plants to survive freezing. Largely by changing gene expression, exposure to a period of non-freezing low temperatures increases plant tolerance to freezing--a phenomenon known as cold acclimation. Cold also induces rapid metabolic changes, which provide instant protection before temperature drops below freezing point. The molecular mechanisms for such rapid metabolic responses to cold remain largely unknown. Here, we use two-dimensional difference gel electrophoresis （2-D DIGE） analysis of sub-cellular fractions ofArabidopsis thaliana proteome coupled with spot identification by tandem mass spectrometry to identify early cold-responsive proteins in Arabidopsis. These proteins include four enzymes involved in starch degradation, three HSP100 proteins, several proteins in the tricarboxylic acid cycle, and sucrose metabolism. Upon cold treatment, the Disproportio- nating Enzyme 2 （DPE2）, a cytosolic transglucosidase metabolizing maltose to glucose, increased rapidly in the centrifugation pellet fraction and decreased in the soluble fraction. Consistent with cold-induced inactivation of DPE2 enzymatic activity, the dpe2 mutant showed increased freezing tolerance without affecting the C-repeat binding transcription factor （CBF） transcriptional pathway. These results support a model that cold-induced inactivation of DPE2 leads to rapid accumulation of maltose, which is a cold-induced compatible solute that protects cells from freezing damage. This study provides evidence for a key role of rapid post-translational regulation of carbohydrate metabolic enzymes in plant protection against sudden temperature drop.

Holocene vegetation succession and responses to climate change in the northern sector of Northeast China

Sediment pollen samples from the Huola Basin in the northern sector of northeast China, and surface pollen samples from its environs, were analyzed to reconstruct accurately the historical response of vegetation to climate change since 9100 cal yr BP. Pollen analysis of the Huola Section indicates that vegetation experienced a transformation from early-mid Holocene warm-cold mixed vegetation to late Holocene cold-temperate vegetation. From 9100 to 6000 cal yr BP, the study area was warmer and moister than at present, developing Corylus, Carpinus, Pinus, Picea, Betula and Larix-dominated forests. Two cooling events at 6000–5000 and 3500–2500 cal yr BP led to a decrease in Corylus, Carpinus and other warmth-loving vegetation, whereas cold temperate forests composed of Larix and Betula expanded. After 2500 cal yr BP, Larix and Betula dominated cold-temperate vegetated landscapes. The Holocene warm period in NE China(9100–6000 cal yr BP) suggests that such warming could have resulted in a strengthening of the influence from East Asian Summer Monsoon on northernmost NE China and would have benefited the development of warm-temperate forest vegetation and an improved plant load, which also provides the similarity model for the possible global warming in the future.