Thermal Induction Research Articles

Spt6 enhances the elongation rate of RNA polymerase II in vivo

Several eukaryotic transcription factors have been shown to modulate the elongation rate of RNA polymerase II (Pol II) on naked or chromatin-reconstituted templates in vitro. However, none of the tested factors have been shown to directly affect the elongation rate of Pol II in vivo. We performed a directed RNAi knock-down (KD) screen targeting 141 candidate transcription factors and identified multiple factors, including Spt6, that alter the induced Hsp70 transcript levels in Drosophila S2 cells. Spt6 is known to interact with both nucleosome structure and Pol II, and it has properties consistent with having a role in elongation. Here, ChIP assays of the first wave of Pol II after heat shock in S2 cells show that KD of Spt6 reduces the rate of Pol II elongation. Also, fluorescence recovery after photobleaching assays of GFP-Pol II in salivary gland cells show that this Spt6-dependent effect on elongation rate persists during steady-state-induced transcription, reducing the elongation rate from approximately 1100 to 500 bp/min. Furthermore, RNAi depletion of Spt6 reveals its broad requirement during different stages of development.

Thermal Facilitation of Lymphocyte Trafficking Involves Temporal Induction of Intravascular ICAM‐1

Fever is associated with improved survival, although its beneficial mechanisms are poorly understood. Previous studies indicate that the thermal element of fever augments lymphocyte migration across high endothelial venules (HEVs) of lymphoid organs by increasing the intravascular display of a gatekeeper trafficking molecule, intercellular adhesion molecule-1 (ICAM-1). Here, we evaluated the spatio-temporal relationship between the thermal induction of intravascular ICAM-1 and lymphocyte trafficking. Intravascular ICAM-1 density was quantified by immunofluorescence staining in mice exposed to fever-range whole-body hyperthermia (39.5+/-0.5 degrees C). ICAM-1-dependent lymphocyte trafficking was measured in short-term homing assays. A linear relationship was observed between the duration of heat treatment and intravascular ICAM-1 density in HEVs with maximal responses requiring sustained (i.e., five hours) thermal stress. Circulating lymphocytes were found to sense incremental changes in ICAM-1 on HEVs, such that trafficking is proportional to the intravascular density of ICAM-1. We further identified a hydroxamate-sensitive shedding mechanism that restores ICAM-1 expression to homeostatic levels following the cessation of thermal stress. The time-dependent response to thermal stress indicates that ICAM-1 density governs the efficiency of lymphocyte interactions with HEVs in vivo. These studies highlight the dynamic role of the microcirculation in promoting immune surveillance during febrile inflammatory responses.

Thermal Induction of 9t12t Linoleic Acid: a New Pathway for the Formation of Conjugated Linoleic Acids

Accepted version of an article published in the journal: International Journal of Engineering and Technology Published version available at: http://www.ijetch.org/papers/066.pdf

The Fabrication of Nano-Particles in Aqueous Solution From Oxyfluoride Glass Ceramics by Thermal Induction and Corrosion Treatment

An innovative route is reported to fabricate nano-particles in aqueous solution from oxyfluoride glass by the thermal induction and corrosion treatment in this letter. The investigations of X-ray diffraction and transmission electron microscope based on nano-particles in glass ceramics (GCs) and aqueous solution indicate that the nano-particles formed in glass matrix during the thermal induction process are released to aqueous solution and their structure, shape and luminescent properties in glass host can be kept. Owing to the designable composition of the nano-particles during glass preparation process, the method is a novel way to obtain nano-particles in aqueous solution from GCs.

INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING IN AN OPEN LOW-FIELD MAGNETIC RESONANCE IMAGING SYSTEM

The intraoperative combination of an open magnetic resonance imaging (MRI) system with neurophysiological localization and continuous monitoring techniques allows for the best available anatomic and physiological orientation as well as real-time functional monitoring. Methodological aspects and technical adaptations for this combination of methods and the experience in 29 patients with tumors in the central region are reported. MRI-compatible platinum/iridium electrodes for intraoperative neuromonitoring were attached to the patient's head. All other electrodes located outside the magnet were stainless steel needle-electrodes for recording of motor evoked potentials and for stimulating somatosensory evoked potentials. Intraoperative MRI was performed using a 0.15-T intraoperative magnetic resonance scanner (PoleStar N20; Medtronic Surgical Navigation Technologies, Louisville, KY). The calculated and measured values of the maximum induced magnetic field (2 x 10(-6) T), induced voltage (0.1 V), and force (0.01 N) by the static or changing magnetic field within all attached electrodes were negligible and proved the method's safety. In 29 patients, platinum/iridium electrodes with low susceptibility showed no interference with the imaging quality. Furthermore, neurophysiological monitoring could be performed with unaffected recording quality. Side effects (e.g., thermal induction) were not observed. Neurophysiological monitoring for evoked potentials and direct cortical stimulation can be performed with standard quality within a low-field intraoperative MRI system. Electrodes fixed to the head should be of low magnetic susceptibility to guarantee optimal imaging quality. The combined use of an open ultra low-field MRI system and intraoperative monitoring allows for resection control and continuous functional monitoring.

Effect of Armature Design on Thermal and Electromagnetic Distribution of an Electromagnetic Launcher

The purpose of this study is to investigate the effect of armature design on the thermal and magnetic induction distribution of the rails and the armature in an electromagnetic launcher. In our formulation of governing, non-linear differential equations, Maxwell equations coupled with energy equation are applied to the rails and the armatures. To solve the non-linear governing differential equations, a finite difference code based on alternative directional implicit method is utilized. For different armatures, the length, shape, and input current of the rails stay the same. In addition, armature-melting latent heat and the friction force between the armatures and the rails are considered. First, armature speed is calculated; then, temperature and magnetic induction distribution is calculated by the energy equation. Temperature and magnetic induction distribution obtained for the rails and different armatures show that the maximum temperature occurs at the trailing edge of each armature. The best design shows the lowest temperature, which is about 600 K. This is due to aerodynamic shape and stability of this armature. However, for all armatures, the temperature of one meter rail stays around 360 K.

Investigation of Magnetic Nanoparticle−Polymer Composites for Multiple-controlled Drug Delivery

We present preliminary results obtained in the development of multiple-controlled drug delivery vehicles using magnetic nanoparticle-polymer composites. Two types of magnetic nanoparticle−polymer composites were prepared and tested for their potential as drug delivery systems with multiple controls (magnetically and thermally induced controlled delivery). These studies focused on the release of fluorescein isothiocyanate (FITC) from poly(methylmethacrylate) (PMMA), containing either magnetite or cobalt nanoparticles, by changing the sample temperature or by exposing it to an oscillating magnetic field. The magnetite−PMMA and cobalt−PMMA composites were 250 μm or less in size and were superparamagnetic. The investigations reported here demonstrated that the release of FITC from magnetite−PMMA particles can be induced thermally but not magnetically. There was no release of FITC from cobalt−PMMA composites either through thermal or magnetic induction. Characterization of the composites included transmission ...

Evidence for Importance of tRNA-Dependent Cytokinin Biosynthetic Pathway in the Moss Physcomitrella patens

To study cytokinin biosynthesis, we characterized a temperature-sensitive cytokinin-overproducing mutant, oveST25, of the moss Physcomitrella patens with respect to changes in cytokinin content during thermal induction in comparison to wild type. Our findings, based on combined liquid chromatography-mass spectrometry (LC-MS) analyses, show that thermoinduction caused a strong increase of extracellular N 6-(Δ2-isopentenyl)adenine (iP), N 6-(Δ2-isopentenyl)adenosine (iPR), cis-zeatin (cZ), cis-zeatin riboside (cZR) and its O-glucoside cZROG in oveST25. In contrast, no significant changes were measured in the wild type. To investigate the relevance of tRNA for cytokinin production in Physcomitrella, we determined cytokinins in tissue and culture medium as well as in tRNA hydrolysates. The analysis of cytokinins from whole-culture extracts of wild type revealed 56% of iP-type, 32% of cZ-type, and 11% of trans-zeatin (tZ)-type forms. In tRNA, 90% of cytokinins were represented by cZ-type and 8% by iP-type forms; tZ-type cytokinins were found only in trace amounts. The finding that the major free cytokinins are, albeit with altered proportions, also major forms in tRNA is compatible with the hypothesis of a strong tRNA-mediated biogenesis of cytokinins in this plant. Our RT-PCR-based studies on the expression of the tRNA-IPT gene, PpIPT1, revealed enhanced transcription levels in the cytokinin-overproducing oveST25 mutant at the inducing temperature of 25°C, but not at noninducing conditions (15°C). A wild-type transgenic line with cytokinin deficiency due to heterologous cytokinin oxidase/dehydrogenase overexpression (AtCKX2) also exhibited enhanced PpIPT1 expression levels, indicating that cytokinin deficiency might upregulate tRNA-mediated cytokinin biosynthesis. The evidence that the tRNA-mediated pathway might be mainly responsible for biosynthesis of isoprenoid cytokinins in Physcomitrella is strongly supported by the recent release of the Physcomitrella genomic sequence where only tRNA-IPTs but no adenylate-IPTs are present.

Heritability of responses to painful stimuli in women: a classical twin study

There is as yet no conclusive evidence for the heritability of pain sensitivity in humans. We performed a classical twin study to evaluate the relative contributions of genetic and environmental factors on responses to painful stimuli in women. Ninety-eight pairs of twins, 51 monozygotic (MZ) and 47 dizygotic (DZ), were recruited from the TwinsUK adult registry held at St Thomas' Hospital, London. The correlation of quantitative sensory testing scores for the different responses to painful stimuli were compared between the MZ and DZ twin pairs and structural equation modelling was used to provide an estimate of the heritability. Statistically significant genetic components (varying between 22 and 55%) were seen for the responses to the majority of painful stimuli including: heat pain threshold (HPT), the pain rating during induction of a thermal burn, the secondary areas of punctate hyperalgesia and brush evoked allodynia following the induction of a 45 degrees C thermal burn, and the pain ratings during the iontophoresis of adenosine triphosphate (ATP) and acid. The area of skin flare following thermal burn induction did not have a significant genetic component; rather common environmental factors provided the greatest contribution (65%). In our experiment neither shared genetic nor environmental features were significant in determining the extent of thermal sensitisation. In summary we show that sensitivity to a variety of experimental thermal, mechanical and chemical pain-producing stimuli has a genetic contribution. Our study demonstrates the importance of genetic factors in determining human experimental pain sensitivity, and opens the way for its use as a phenotype in gene discovery. Since experimental pain sensitivity is known to be a predictor for pathological pain, our data imply that genetic factors have an important aetiological contribution towards clinical pain states.

Influence of climatic conditions on antiperspirant efficacy determined at different test areas

The efficacy of antiperspirants is a current topic among the developers of cosmetic products. According to the Food and Drug Administration (FDA) for the US market, efficacy testing performed in the axilla of human volunteers is mandatory. Another method is yet available, which enables comparison of more than one antiperspirant formula in a single study by performing the test on the backs of volunteers. However, how reproducible are these methods, comparing between the back and axilla? Do they differ as a result of seasonal variation? Is a correlation between the results of the two methods possible? To answer these questions, the antiperspirant efficacy of aluminium chlorohydrate (ACH) aqueous solutions was investigated in the axilla and on the backs of volunteers, in four separate clinical studies covering cold and warm seasons. Four days of product application were followed by thermal sweat induction on the fifth day, using a sauna. The amount of sweat recovered by weighing cotton pads before and after sweat induction was used to calculate sweat reduction. Testing in the axilla and on the back was performed on the same volunteers simultaneously to achieve the best comparable data. For this reason, the FDA guideline was slightly modified to thermal stimulation in a sauna instead of in a hot room. Increasing concentrations of ACH in aqueous solutions on the backs of volunteers showed a saturation for 8% ACH with a sweat reduction of approximately 50%. The antiperspirant efficacy of solutions containing 4%, 8% or 12% ACH was repeatedly found at the same levels, when tested on the backs during summer, autumn and winter time. Axilla tests, with an 8% ACH aqueous solution, showed strongly varying results for summer and winter time, represented by sweat reduction values of -2% to 25%. As an assumption, these high variations might result from reduced gel formation in cold seasons due to low humidity in the axillae during the application phase. On the back, this effect was avoided by applying occlusive foils after product application. To gain further insight, a study, during which summer conditions were artificially simulated by thermal stimulation during the application phase, again showed decreased antiperspirant efficacy in the axilla for winter conditions with sweat reduction values of 2%, compared with 25% under simulated summer conditions. These strongly varying values of sweat reduction in the axilla under summer and winter conditions make comparisons between antiperspirant products difficult and a statement about correlation between the two test sites back and axilla impossible. A standardization of the application phase, comparable to the simulated summer conditions described here, could be a solution to reduce the high variation of results in the axilla. Consequently, testing on the back is not only a more cost-effective method to investigate the antiperspirant efficacy of more than one formulation, but a reproducible method more independent of climatic influences during test implementation than the axilla test method. It could, therefore, be regarded as the method of choice for discriminating antiperspirant efficacy between several products during development of new antiperspirant formulations.

Thermally induced reversible conformational changes in the host–guest adduct of meso-tetramethyltetrakis(ethyl)calix[4]pyrrole

The binding of methanol, ethanol, and N, N-dimethylformamide to meso-tetramethyltetrakis(ethyl)calix[4]pyrrole ( 1) was investigated in both solid and solution with the exhibition of multi-fashion hydrogen bonding as shown by X-ray crystallography. The thermodynamic stability of these host–guest inclusion complexes were determined by exploiting TGA and DTA. An unexpected conformational change in 1·2EtOH occurred by thermal induction.

Control and Regulation of KplE1 Prophage Site-specific Recombination

KplE1 is one of the 10 prophage regions of Escherichia coli K12, located at 2464 kb on the chromosome. KplE1 is defective for lysis, but it is fully competent for excisive recombination. In this study, we have mapped the binding sites of the recombination proteins, namely IntS, TorI, and IHF on attL and attR, and the organization of these sites suggests that the intasome is architecturally different from the lambda canonical form. We also measured the relative contribution of these proteins to both excisive and integrative recombination by using a quantitative in vitro assay. These experiments show a requirement of the TorI excisionase for excisive recombination and of the IntS integrase for both integration and excision. Moreover, we observed a strong influence of the supercoiled state of the substrates. The KplE1 recombination module, composed of the integrase and excisionase genes together with the attL and attR DNA regions, is highly similar to that of several phages infecting various E. coli strains as well as Shigella flexneri and Shigella sonnei. The in vitro recombination data reveal that HK620 and KplE1 att sequences are exchangeable. This study thus defines a new site-specific recombination module, and implications for the mechanism and regulation of recombination are discussed.

An Internal Crack Subjected to a Thermal Flow in Magnetoelectroelastic Solids: Exact Fundamental Solution

The analysis of intensity factors for cracks under thermal, mechanical, electrical and magnetic boundary conditions has become a very important topic in fracture mechanics. In this paper, an exact and complete fundamental solution is derived for the problem of a penny-shaped crack in magneto-electro-thermo-elastic material under prescribed thermal flux on the crack faces. The problem is analyzed within the framework of the theory of linear magneto-electro-thermo-elasticity. Electro-magneto-thermo-elasticity includes the effective elastic, piezoelectric, piezomagnetic, dielectric permittivity, magnetic permeability and electromagnetic coupling moduli, as well as the effective thermal expansion coefficients and the associated pyroelectric and pyromagnetic constants. The coupling features of transversely isotropic magneto-electro-thermo-elastic solids are governed by a system of partial differential equations with respect to the elastic displacements, the electric potential and the magnetic potential and temperature field. The heat conduction equation and equilibrium equations for an infinite magneto-electro-thermo-elastic media are solved by means of Hankel integral transform. The intensity factors of thermal stress, electric displacement and magnetic induction are derived explicitly for impermeable and permeable cracks. Due to its explicitness, the solution is remarkable and should be of great interest in the magneto-electro-thermo-elastic material analysis and design.

Pentacene Growth on Organic-Inorganic Hybrid Type SiOC Film

Pentacene channel for organic thin film transistor was deposited on the SiOC film by thermal evaporation. The growth of pentacene is related with the Diels-Alder reaction and the nucleophilic reaction by the thermal induction. The surface is an important factor to control the recursive Diels-Alder reaction for growing of pentacene on SiOC film. The terminal C=C double bond of pentacene molecule was broken easily as a result of attack of the nucleophilic reagents on the surface of SiOC film. The nucleophilic reaction can be accelerated by increasing temperature on surface, and it making pentacene to grow hardly on the SiOC film with a flow rate ratio of O2/(BTMSM+O2)=0.5 due to its inorganic property. The nucleophlic reaction mechanism is SN2 (bimolecular nucleophilic substitution) type.

Bats avoid radar installations: could electromagnetic fields deter bats from colliding with wind turbines?

Large numbers of bats are killed by collisions with wind turbines, and there is at present no direct method of reducing or preventing this mortality. We therefore determine whether the electromagnetic radiation associated with radar installations can elicit an aversive behavioural response in foraging bats. Four civil air traffic control (ATC) radar stations, three military ATC radars and three weather radars were selected, each surrounded by heterogeneous habitat. Three sampling points matched for habitat type and structure, dominant vegetation species, altitude and surrounding land class were located at increasing distances from each station. A portable electromagnetic field meter measured the field strength of the radar at three distances from the source: in close proximity (<200 m) with a high electromagnetic field (EMF) strength >2 volts/metre, an intermediate point within line of sight of the radar (200–400 m) and with an EMF strength <2 v/m, and a control site out of sight of the radar (>400 m) and registering an EMF of zero v/m. At each radar station bat activity was recorded three times with three independent sampling points monitored on each occasion, resulting in a total of 90 samples, 30 of which were obtained within each field strength category. At these sampling points, bat activity was recorded using an automatic bat recording station, operated from sunset to sunrise. Bat activity was significantly reduced in habitats exposed to an EMF strength of greater than 2 v/m when compared to matched sites registering EMF levels of zero. The reduction in bat activity was not significantly different at lower levels of EMF strength within 400 m of the radar. We predict that the reduction in bat activity within habitats exposed to electromagnetic radiation may be a result of thermal induction and an increased risk of hyperthermia.

Nanotherapeutics for enhancing thermal therapy of cancer

Purpose: The current work describes the synergistic enhancement of hyperthermic cancer therapy by selective thermal sensitization and induction of vascular injury at the tumor site. The specificity of this response was mediated by CYT-6091: a pegylated colloidal gold-based nanotherapeutic designed to selectively deliver an inflammatory cytokine, tumor necrosis factor alpha (TNF), to solid tumors.Materials and methods: FSaII murine fibrosarcoma-bearing C3H mice received an intravenous injection of either soluble TNF or CYT-6091 (50–250 µg/kg TNF). Four hours later the tumors were exposed to localized heating (42.5 or 43.5°C, 60 min). Tumor responses were assessed by growth delay and/or perfusion.Results: Both soluble TNF and CYT-6091 reduced tumor perfusion by 80% of control (no treatment), 4 hours post administration. However, soluble TNF was toxic to the tumor burdened mice and resulted in 40% mortality alone and 100% mortality when combined with hyperthermia. Conversely, no toxicities were noted with CYT-6091 alone or when combined with hyperthermia. Additionally, CYT-6091 combined with heat yielded significant tumor regression in vivo as compared to heat or CYT-6091 alone as demonstrated by tumor growth delay. Pretreatment with soluble TNF or CYT-6091 followed by heating reduced in vitro tumor and endothelial cell survival by 40–50% (TNF) and 70–75% (CYT-6091) of the control cell (i.e. tumor and endothelial) values, respectively.Conclusions: CYT-6091, by selectively delivering TNF to solid tumors, improves the safety of TNF treatment. In addition, the targeted delivery of TNF augments cancer thermal therapy efficacy possibly by inducing a tumor-localized inflammatory response.

Heat shock protein 70 is translocated to lipid droplets in rat adipocytes upon heat stimulation

In mammalian cells, lipid storage droplets contain a triacylglycerol and cholesterol ester core surrounded by a phospholipid monolayer into which a number of proteins are imbedded. These proteins are thought to be involved in modulating the formation and metabolic functions of the lipid droplet. In this study, we show that heat stress upregulates several heat shock proteins (Hsps), including Hsp27, Hsp60, Hsp70, Hsp90, and Grp78, in primary and differentiated adipocytes. Immunostaining and immunoblotting data indicate that among the Hsps examined, only Hsp70 is induced to redirect to the lipid droplet surface in heat-stressed adipocytes. The thermal induction of Hsp70 translocation to lipid droplet does not typically happen in a temperature- or time-dependent manner and occurs abruptly at 30–40 min and rapidly achieves a steady state within 60 min after 40 °C stress of adipocytes. Though Hsp70 is co-localized with perilipin on the lipid droplets in stressed adipocytes, immunoprecipitation experiments suggest that Hsp70 does not directly interact with perilipin. Alkaline treatments indicate that Hsp70 associates with the droplet surface through non-hydrophobic interactions. We speculate that Hsp70 might noncovalently associate with monolayer microdomains of the lipid droplet in a manner similar to its interaction with lipid bilayer moieties composed of specific fatty acids. As an acute and specific cellular response to the heat stimulation, accumulation of Hsp70 on adipocytes lipid droplets might be involved in stabilizing the droplet monolayer, transferring nascent proteins to the lipid droplets, or chaperoning denatured proteins on the droplet for subsequent refolding.

Fever-range thermal stress promotes lymphocyte trafficking across high endothelial venules via an interleukin 6 trans-signaling mechanism

Fever is an evolutionarily conserved response during acute inflammation, although its physiological benefit is poorly understood. Here we show thermal stress in the range of fever temperatures increased the intravascular display of two 'gatekeeper' homing molecules, intercellular adhesion molecule 1 (ICAM-1) and CCL21 chemokine, exclusively in high endothelial venules (HEVs) that are chief portals for the entry of blood-borne lymphocytes into lymphoid organs. Enhanced endothelial expression of ICAM-1 and CCL21 was linked to increased lymphocyte trafficking across HEVs. A bifurcation in the mechanisms controlling HEV adhesion was demonstrated by evidence that the thermal induction of ICAM-1 but not of CCL21 involved an interleukin 6 trans-signaling pathway. Our findings identify the 'HEV axis' as a thermally sensitive alert system that heightens immune surveillance during inflammation by amplifying lymphocyte trafficking to lymphoid organs.

A magneto-electro-elastic material with a penny-shaped crack subjected to temperature loading

The analysis of intensity factors for a penny-shaped crack under thermal, mechanical, electrical and magnetic boundary conditions becomes a very important topic in fracture mechanics. An exact solution is derived for the problem of a penny-shaped crack in a magneto-electro-thermo-elastic material in a temperature field. The problem is analyzed within the framework of the theory of linear magneto-electro-thermo-elasticity. The coupling features of transversely isotropic magneto-electro-thermo-elastic solids are governed by a system of partial differential equations with respect to the elastic displacements, the electric potential, the magnetic potential and the temperature field. The heat conduction equation and equilibrium equations for an infinite magneto-electro-thermo-elastic media are solved by means of the Hankel integral transform. The mathematical formulations for the crack conditions are derived as a set of dual integral equations, which, in turn, are reduced to Abel's integral equation. Solution of Abel's integral equation is applied to derive the elastic, electric and magnetic fields as well as field intensity factors. The intensity factors of thermal stress, electric displacement and magnetic induction are derived explicitly for approximate (impermeable or permeable) and exact (a notch of finite thickness crack) conditions. Due to its explicitness, the solution is remarkable and should be of great interest in the magneto-electro-thermo-elastic material analysis and design.

Potent Induction of Arabidopsis thaliana Flowering by Elevated Growth Temperature

The transition to flowering is an important event in the plant life cycle and is modulated by several environmental factors including photoperiod, light quality, vernalization, and growth temperature, as well as biotic and abiotic stresses. In contrast to light and vernalization, little is known about the pathways that mediate the responses to other environmental variables. A mild increase in growth temperature, from 23 °C to 27 °C, is equally efficient in inducing flowering of Arabidopsis plants grown in 8-h short days as is transfer to 16-h long days. There is extensive natural variation in this response, and we identify strains with contrasting thermal reaction norms. Exploiting this natural variation, we show that FLOWERING LOCUS C potently suppresses thermal induction, and that the closely related floral repressor FLOWERING LOCUS M is a major-effect quantitative trait locus modulating thermosensitivity. Thermal induction does not require the photoperiod effector CONSTANS, acts upstream of the floral integrator FLOWERING LOCUS T, and depends on the hormone gibberellin. Analysis of mutants defective in salicylic acid biosynthesis suggests that thermal induction is independent of previously identified stress-signaling pathways. Microarray analyses confirm that the genomic responses to floral induction by photoperiod and temperature differ. Furthermore, we report that gene products that participate in RNA splicing are specifically affected by thermal induction. Above a critical threshold, even small changes in temperature can act as cues for the induction of flowering. This response has a genetic basis that is distinct from the known genetic pathways of floral transition, and appears to correlate with changes in RNA processing.