134,893 research outputs found
Effects of chronic cold treatment on root elongation and gene expression in "Arabidopsis thaliana"
No full textLow temperature is a major limitation of plant growth. Cold adaptation is important for the survival and distribution of plant species at high elevations and high latitudes. Much is known about the molecular basis for cold acclimation and freezing tolerance, which are triggered by acute cold treatment. The causes of growth limitation at low, non-freezing temperatures are largely unexplored. To better understand the mechanisms limiting plant growth in cold environments, I studied the elongation-growth of roots and patterns of gene expression in Arabidopsis accessions from diverse habitats. Arabidopsis thaliana (L.) Heyhn is a small, annual weed that is widely distributed in different growth environments and is well-suited for molecular genetic studies. My initial study of 23 accessions failed to detect ecotypic differentiation for root elongation rates at low, nonfreezing temperatures (10 °C); however, evidence was obtained implicating the cell-cycle gene CYCB1;1 as part of a compensatory mechanism for maintaining proliferation under these conditions. I used microarray technology to obtain a global picture of cold-responsive gene expression in the temperate Col-0 accession and the high-altitude (3400 m) Sha accession, which is expected to be adapted for a cold environment. I compared the effects of acute-cold treatment (4 h at 10 °C) and chronic-cold treatment (6 weeks at 10 °C) using plants grown at 21 °C as a control. Cold-treatment had major effects on gene expression at the mRNA level: 11% of the 24,000 genes represented on the Affymetrix ATH1 GeneChip responded by at least 2-fold to either or both cold treatments. A substantial fraction of cold-responsive genes, 35%, responded specifically to chronic cold treatment. This suggests there are fundamental differences in the response of plants to acute-cold treatment and growth at low, nonfreezing temperatures. Datasets of annotated genes were screened for significant, non-redundant enrichment for Gene Ontology (GO) terms to identify functional groups and processes. GO-term enrichment provided a rough picture of major trends in gene expression associated with coldresponses, which were then verified by examining the expression patterns of individual genes. Flavonoid biosynthesis, particularly the activation of anthocyanin biosynthesis, was the only major function induced by both acute- and chronic-cold treatment. In contrast, genes concerned with electron transport and light-reactions in photosynthesis were repressed by both cold treatments. This is consistent with the well-documented, general reduction of these functions associated with growth at low temperatures. Thus,
regulation at the mRNA level appears to be an important mechanism for down-regulating
energy metabolism in cold environments.
Acute-cold treatment induced numerous genes concerned with responses to
pathogen infection, cold, drought, salt stress, and UV damage. The breadth of these
stress responses emphasizes that brief exposure to cold, even at temperatures as high
as 10 °C, is perceived by plants as a form of stress. Unexpectedly, global induction of
stress-related genes was restricted primarily to the acute-cold response. This strongly
suggests that in contrast to “cold shock,” growth at low, non-freezing temperatures is not
recognized by Arabidopsis plants as a stress per se. Therefore, mechanisms exist for
suppressing prolonged stress responses in the cold. This implies that general stress
responses are not essential for growth of Arabidopsis at low temperatures.
Several other processes and pathways responded primarily to chronic- cold
treatment and are likely to be relevant to growth at low temperatures. Sha-specific,
chronic-cold induction of genes encoding ion transporters; genes concerned with
compensation for Pi deprivation; and, genes required for formation of root hairs,
comprised the only major functional group showing ecotypic differentiation. Induction of
genes encoding primary wall constituents and enzymes concerned with cell enlargement
and pectin metabolism were induced specifically by chronic-cold treatment, while those
genes important for secondary wall formation such as those encoding cellulose synthase
and laccase required for lignification were repressed. These findings and the coldrepression
of genes concerned with fiber and vascular tissue formation suggest as a
working hypothesis that chronic cold treatment increases the flexibility of roots and cell
wall extensibility as a compensatory response to the reduced root growth in the cold. In
summary, the present study identified several functional groups of genes showing novel
regulation by chronic cold treatment. These findings provide the starting point for future
studies using informative mutants and biochemical profiling to establish causal
relationships between gene expression and adaptations for growth in cold environments
Can we improve the identification of cold homes for targeted home energy-efficiency improvements?
No full textObjective: To investigate the extent to which homes with low indoor-temperatures can be identified from dwelling and household characteristics.Design: Analysis of data from a national survey of dwellings, occupied by low-income households, scheduled for home energy-efficiency improvements. Setting: Five urban areas of England: Birmingham, Liverpool, Manchester, Newcastle and Southampton.Methods: Half-hourly living-room temperatures were recorded for two to four weeks in dwellings over the winter periods November to April 2001-2002 and 2002-2003. Regression of indoor on outdoor temperatures was used to identify cold-homes in which standardized daytime living-room and/ or nighttime bedroom-temperatures were < 16 degrees C (when the outdoor temperature was 5 degrees C). Tabulation and logistic regression were used to examine the extent to which these cold-homes can be identified from dwelling and household characteristics.Results: Overall, 21.0% of dwellings had standardized daytime living-room temperatures < 16 degrees C and 46.4% had standardized nighttime bedroom-temperatures below the same temperature. Standardized indoor-temperatures were influenced by a wide range of household and dwelling characteristics, but most strongly by the energy efficiency (SAP) rating and by standardized heating costs. However, even using these variables, along with other dwelling and household characteristics in a multi-variable prediction model, it would be necessary to target more than half of all dwellings in our sample to ensure at least 80% sensitivity for identifying dwellings with cold living-room temperatures. An even higher proportion would have to be targeted to ensure 80% sensitivity for identifying dwellings with cold-bedroom temperatures.Conclusion: Property and household characteristics provide only limited potential for identifying dwellings where winter indoor temperatures are likely to be low, presumably because of the multiple influences on home heating, including personal choice and behaviour. This suggests that the highly selective targeting of energy-efficiency programmes is difficult to achieve if the primary aim is to identify dwellings with cold-indoor-temperatures. (c) 2006 Published by Elsevier Ltd
Transcription factors involved in cold response in plants.
No full textStudies in Arabidopsis have shown cold stress tolerance can be enhanced by manipulation of the CBF/DREB and ICE transcription factor genes. To date, few studies have investigated CBF and ICE genes in crops species such as barley. Using a C-repeat element as bait, two CBF genes were isolated from a cold-stressed barley cDNA library, HvCBF16 and HvCBF23. HvCBF16 was induced by cold treatment but not by other abiotic stresses. HvCBF23 was constitutively expressed and was not induced by cold treatment. The analysis of transgenic plants expressing these genes will determine their importance in cold tolerance.
Transgenic barley plants expressing the barley gene HvCBF2A were found to be more cold tolerant in controlled temperature trials, and hence were assayed to determine the basis of their acquired phenotype. Northern and qRT-PCR analysis showed that four genes known to be involved in cold tolerance were significantly upregulated. Importantly the increased expression was proportional to the level of transgene expression and levels were higher following cold treatment.
A homolog of the Arabidopsis ICE transcription factor was isolated from a freezing-tolerant barley variety (Hordeum vulgare L. cv. Haruna Nijo) and transcript analysis of HvICE2 under various abiotic stresses showed that expression of HvICE2 was induced at low temperatures, particularly in floral tissues. HvICE2 was over-expressed using the maize ubiquitin constitutive promoter in transgenic barley. Expression analysis of putative downstream genes, including various COR genes, in the transgenic plants before and during cold treatment did not reveal any alteration in expression. This suggests HvICE2 that the COR genes studied are not targets of HvICE2 or that additional factors or conditions are required for effective function of HvICE2. Transgenic Arabidopsis plants were produced with over- or reduced-expression of the uncharacterised ICE gene, AtICE2. The cold tolerance of the AtICE2 transgenic lines was not significantly different from wild type plants.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 201
Effects of cold rolling on phase precipitation and phase transformation in a 2507 SDSS
No full textIn the present work 7 samples of UNS S32750 was cold rolled at different rates, analyzed in this state and also after the ageing for 2400s at 400 and 900°C.\nInvestigation was carry out with: OM SEM ( EBSD EDS) Magnetic tests: Forster, Permeameter, Stablein steinitz, ferrite tester.\nWas found that in this SDSS that no enhancements of magnetic properities took place, therefore, there was not transformation of phase (γ α ') due to cold deformation. After the treatment at 900°C big amount of sigma phase precipitated in all the samples, but this phenomena was more accentued in the most deformed samples than in the others, so, it 's possible to say that the cold deformation improve the quantity of sigma phase that precipitate. Again, it seems that the decomposition process results significantly more secondary austenite than sigma phase but this require further investigatio
Cold & fire
No full text"Cold & Fire", a song by the Australian band Dear Anonymous, was produced as part of the Indie 100 research intensive project within the Independent Music Project (IMP). The IMP is an ongoing, interdisciplinary research arm within QUT. The song's author is Julia Kourtidis
WSN based intelligent cold chain management
No full textThis paper presents a cold chain monitoring system which is implemented by using ubiquitous computing technologies, Radio Frequency Identification (RFID) & Wireless Sensor Network (WSN). In this paper, we discuss how cold supply chain works and how we can monitor and control cold supply chain by using wireless tracking and sensing technologies. We propose a prototype design which will provide a well controlled and transparent cold chain system, which could help the users to manage their products’ environmental data in real time during the life cycle. Moreover, we highlight how the availability of product trace data in combination with historical condition-monitoring data can facilitate decision-making processes enhancing supply chain’s performance. Finally we discuss the integration works of these two technologies together in the cold supply chain management system. Hardware and software platform of WSN used in this system are also described in this paper
Low Fatigue Response of Crest-Fixed Cold-Formed Steel Drape Curved Roof Claddings
No full textCold-formed steel roof claddings are subjected to significant suction/uplift pressures during high wind events. In New Zealand, the strong prevailing winds makes this a common occurrence. Suction pressures are generated by the turbulence of the wind flow around the building which can vary both spatially and temporally. The weakest link in the roofing system is the connection between roof sheeting and screw fasteners, which if fails, can lead to progressive collapse of the whole roofing assembly. Fluctuating high wind suction pressures can result in either static or fatigue pull-through failure of the roof sheeting at its screw fastener connections. Current literature has covered the static and fatigue wind uplift performance of crest-fixed corrugated and trapezoidal roof claddings. However, no research has been undertaken to understand the wind uplift performance of the typical crest-fixed cold-formed steel drape curved roof claddings used in New Zealand. This issue is addressed herein. In total, 35 large scale experimental tests are presented for crest-fixed drape curved steel roof claddings subjected to static and cyclic wind suction/uplift loads applied using a Pressure Loading Actuator. The material properties of claddings were determined using tensile coupon tests while the initial geometric imperfections of claddings were measured using a laser scanner. The critical fastener reactions were determined using a three axis load cell. Crack initiation, propagation of cracks, crack patterns and the number of load cycles to failure are discussed for such claddings under different load levels. Tests showed that the drape curved roof claddings are also subjected to localised dimpling and pull-through failures at their screw connections under static and cyclic wind uplift loads with the occurrence of low cycle fatigue failures under cyclic loading
Electrophysiological characterisation of neuronal components of cold sensitivity
No full textAberrant cold sensitivity is apparent in several neuropathies of peripheral and central origin, and is poorly treated by currently available drugs. In an attempt to understand the mechanisms of cold evoked hyperalgesia and analgesia, these studies examined the dual pro- and anti-nociceptive roles of TRPM8, a cold temperature gated channel, and the role of calcium channels within cold sensitive pathways through a combination of in vivo electrophysiology, behavioural measures and gene ablation. Blocking TRPM8 with novel antagonists revealed lamina V/VI neuronal responses to innocuous and noxious cold stimulation were conserved in naïve rats. However, under neuropathic conditions inhibition of TRPM8 decreased neuronal responses to innocuous and noxious cold stimuli. This corresponded with an attenuation of behavioural hypersensitivity to innocuous cooling. Remarkably, systemically activating TRPM8 with a novel agonist resulted in identical neuronal and behavioural effects in neuropathic rats. Menthol is known to relieve various pain conditions as well as inducing hyperalgesia. Unlike in human subjects, menthol fails to induce central sensitisation in naïve rats, whereas in neuropathic rats topical menthol exerts some similar effects to the systemically dosed TRPM8 agonist. Gene ablation identifies a role of α2δ-1, an auxiliary calcium channel subunit, in cold and mechanical sensory pathways, likely dependent on impaired trafficking of calcium channels. Furthermore, α2δ-1 knockout mice exhibit a delay in the development of neuropathic like behaviours after injury. In neuropathic rats, systemic and spinal delivery of an activation state dependent Cav2 antagonist suppresses neuronal responses to mechanical stimuli but reveals no change in channel function within cold sensitive pathways. These findings expand the understanding of the neural basis of cold sensitivity and demonstrate TRPM8 is not essential to all forms of cold transduction in naïve rats, and that both inhibiting and activating TRPM8 have similar selective modality related inhibitory effects on cold transduction in neuropathic rats
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Enhanced levels of cold shock proteins in Listeria monocytogenes LO28 upon exposure to low temperature and high hydrostatic pressure
No full textListeria monocytogenes is a psychrotrophic food-borne pathogen that is problematic for the food industry
because of its ubiquitous distribution in nature and its ability to grow at low temperatures and in the presence
of high salt concentrations. Here we demonstrate that the process of adaptation to low temperature after cold
shock includes elevated levels of cold shock proteins (CSPs) and that the levels of CSPs are also elevated after
treatment with high hydrostatic pressure (HHP). Two-dimensional gel electrophoresis combined with Western
blotting performed with anti-CspB of Bacillus subtilis was used to identify four 7-kDa proteins, designated Csp1,
Csp2, Csp3, and Csp4. In addition, Southern blotting revealed four chromosomal DNA fragments that reacted
with a csp probe, which also indicated that a CSP family is present in L. monocytogenes LO28. After a cold shock
in which the temperature was decreased from 37°C to 10°C the levels of Csp1 and Csp3 increased 10- and
3.5-fold, respectively, but the levels of Csp2 and Csp4 were not elevated. Pressurization of L. monocytogenes
LO28 cells resulted in 3.5- and 2-fold increases in the levels of Csp1 and Csp2, respectively. Strikingly, the level
of survival after pressurization of cold-shocked cells was 100-fold higher than that of cells growing exponentially
at 37°C. These findings imply that cold-shocked cells are protected from HHP treatment, which may affect
the efficiency of combined preservation techniques
Studies on the cold hardiness of the peach-potato aphid Myzus persicae (Sulzer)
No full textA system incorporating a prototype automatic thermoelectric cooling method with computer-based recording of aphid supercooling points was developed and formed the basis of cold hardiness assessment.
Under laboratory culture all developmental stages of Myzus persicae had a mean inherent supercooling potential below -20°C, with first instar nymphs the most cold hardy. When maintained at 5°C, younger instars demonstrated acclimation ability unlike adult aphids, and in an insecticide
resistant strain, adults lost cold hardiness. When in contact with surface moisture, the majority of aphids did not experience inoculative nucleation. Sexual morphs of M. persicae possessed supercooling ability comparable with
laboratory maintained parthenogenetic morphs; eggs supercooled to below -30°C.
Seasonal studies of supercooling ability demonstrated that all aphid stages were most cold hardy in summer. Younger instars showed natural acclimatisation and were cold hardy throughout the year. Overall adults lost cold hardiness as winter progressed, exhibiting bimodal supercooling
point distributions in two winters, with distinct high (HG) and low (LG) groups and mean supercooling points of approximately -20°C and -10 oe respectively. Clonal differences and adult age did not account for this
pattern. Following experimental starvation at 5°C, first instars of M. persicae maintained extensive supercooling potential but adults exhibited losses of cold hardiness comparable with those in natural overwintering populations, suggesting that feeding may be necessary to maintain adult cold hardiness levels during winter. Subsequent starvation
experiments did not reproduce the dramatic losses of cold hardiness implying that the feeding influence was more complex than the availability of food per se. In a series of host transfer experiments the mean supercooling point of Aphis fabae adults could be shifted by over 10°C, increasing when they fed on beans and reduced when transferred back to spindle; the LG (spindle/poor supercoolers) to HG (bean/good supercoolers) shift was more difficult to achieve and suggested a nucleating agent in
spindle sap.
Trimethylsilyl derivatised carbohydrate extracts of M. persicae and A. fabae were analysed by capillary gas-liquid chromatography. Glucose, glycerol, fructose, mannitol, sucrose, and trehalose were detected in samples of both species, together with trace amounts of unidentified
carbohydrates in M. persicae samples. Dulcitol was present in spindle-fed A. fabae only. There was no obvious correlation between carbohydrate content and supercooling ability but high total percentage body carbohydrate levels were revealed and may have a solute effect, enhancing
inherent supercooling potential and dependent on carbohydrate-rich sap intake.
Laboratory cultured A. fabae were capable of extensive supercooling, as were individuals collected from summer herbaceous hosts; first instars were the most cold hardy. When associated with the primary host, spindle, all aphids showed poor supercooling potential, less than -15°C;
overwintering eggs were capable of supercooling to below -30°C and acclimatised in winter. Eggs and oviparae were not subject to inoculative nucleation. Preliminary experiments to relate supercooling ability to mortality at sub-zero temperatures proved inconclusive and were terminated
when temperature shock and/or desiccation were thought to have induced premature mortality.
The results demonstrate that the cold hardiness characteristics of M. persicae are atypical of those observed in other freezing-susceptible arthropods. It is proposed that continued feeding during mild winters
maintains cold hardiness levels in adult M. persicae and this influence may provide a possible explanation for the successful anholocyclic overwintering of this aphid during such winters. Avenues of research to further investigate this proposal are suggested
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