Project description:This study examined differentially expressed (DE) gene transcripts and regulated pathways of two geographically distinct channel catfish (Ictalurus punctatus) strains and one hybrid catfish (I. punctatus x [blue catfish] I. furcatus) strain to test whether one particular catfish type handled thermal stress better. Following a six-week growth experiment, where fish were subjected to daily cycling temperatures of either 27-31°C or 32-36°C, mimicking pond fluctuations. We sequenced 18 cDNA libraries of liver samples to obtain 61 million reads per library. There were 5,443 DE transcripts and 41,689 regulated pathways. Northern channel catfish had the highest amount of DE transcripts (48.6%), 5 times that of southern channel catfish, and the greatest amount of transcripts with fold changes ≥ 2. The overall amount of temperature-induced DE transcripts between southern hybrid and southern channel catfish was fairly comparable in relation to that of northern channel catfish, however, there were more transcripts up- or downregulated with ≥ 2 fold changes in channel catfish strains compared to the southern hybrid catfish. Results from this study strongly suggest genetic differences between geographic catfish types affect physiological responses to thermal stress. Furthermore, a number of genes were linked to thermal stress tolerance, which may be beneficial for understanding geographic differences in thermal stress tolerance in ectotherms and for strain development of catfish. Hepatic mRNA profiles of three fingerling catfish types following a six week growth experiment of daily cycling temperatures of either 27-31°C or 32-36°C, mimicking pond fluctuations.
Project description:Although rising ocean temperatures threaten scleractinian corals and the reefs they construct, certain reef corals can acclimate to elevated temperatures to which they are rarely exposed in situ. Specimens of the model Indo-Pacific reef coral Pocillopora damicornis collected from upwelling reefs of Southern Taiwan were previously found to have survived a 36-week exposure to 30°C, a temperature they encounter infrequently and one that can elicit the breakdown of the coral-dinoflagellate (genus Symbiodinium) endosymbiosis in many corals of the Pacific Ocean. To gain insight into the subcellular pathways utilized by both the coral hosts and their mutualistic Symbiodinium populations to acclimate to this temperature, mRNAs from both control (27°C) and high (30°C)-temperature samples were sequenced on an Illumina platform and assembled into a 236 435-contig transcriptome. These P. damicornis specimens were found to be ~60% anthozoan and 40% microbe (Symbiodinium, other eukaryotic microbes, and bacteria), from an mRNA-perspective. Furthermore, a significantly higher proportion of genes from the Symbiodinium compartment were differentially expressed after two weeks of exposure. Specifically, at elevated temperatures, Symbiodinium populations residing within the coral gastrodermal tissues were more likely to up-regulate the expression of genes encoding proteins involved in metabolism than their coral hosts. Collectively, these transcriptome-scale data suggest that the two members of this endosymbiosis have distinct strategies for acclimating to elevated temperatures that are expected to characterize many of Earth's coral reefs in the coming decades.
Project description:This paper presents the mechanical and microstructural characteristics of a lightweight aggregate geopolymer concrete (LWAGC) synthesized by the alkali-activation of a fly ash source (FA) before and after being exposed to elevated temperatures, ranging from 100 to 800 °C. The results show that the LWAGC unexposed to the elevated temperatures possesses a good strength-to-weight ratio compared with other LWAGCs available in the published literature. The unexposed LWAGC also shows an excellent strength development versus aging times, up to 365 days. For the exposed LWAGC to the elevated temperatures of 100 to 800 °C, the results illustrate that the concretes gain compressive strength after being exposed to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC started to deteriorate and decrease after being exposed to elevated temperatures of 400 °C, and up to 800 °C. Based on the mechanical strength results of the exposed LWAGCs to elevated temperatures of 100 °C to 800 °C, the relationship between the exposure temperature and the obtained residual compressive strength is statistically analyzed and achieved. In addition, the microstructure investigation of the unexposed LWAGC shows a good bonding between aggregate and mortar at the interface transition zone (ITZ). However, this bonding is subjected to deterioration as the LWAGC is exposed to elevated temperatures of 400, 600 and 800 °C by increasing the microcrack content and swelling of the unreacted silicates.
Project description:Bacterial wilt, caused by members of the heterogenous Ralstonia solanacearum species complex, is an economically important vascular disease affecting many crops. Human activity has widely disseminated R. solanacearum strains, increasing their global agricultural impact. However, tropical highland race 3 biovar 2 (R3bv2) strains do not cause disease in tropical lowlands, even though they are virulent at warm temperatures. We tested the hypothesis that differences in temperature adaptation and competitive fitness explain the uneven geographic distribution of R. solanacearum strains. Using three phylogenetically and ecologically distinct strains, we measured competitive fitness at two temperatures following paired-strain inoculations of their shared host, tomato. Lowland tropical strain GMI1000 was only weakly virulent on tomato under temperate conditions (24°C for day and 19°C for night [24/19°C]), but highland tropical R3bv2 strain UW551 and U.S. warm temperate strain K60 were highly virulent at both 24/19°C and 28°C. Strain K60 was significantly more competitive than both GMI1000 and UW551 in tomato rhizospheres and stems at 28°C, and GMI1000 also outcompeted UW551 at 28°C. The results were reversed at cooler temperatures, at which highland strain UW551 generally outcompeted GMI1000 and K60 in planta. The superior competitive index of UW551 at 24/19°C suggests that adaptation to cool temperatures could explain why only R3bv2 strains threaten highland agriculture. Strains K60 and GMI1000 each produced different bacteriocins that inhibited growth of UW551 in culture. Such interstrain inhibition could explain why R3bv2 strains do not cause disease in tropical lowlands.
Project description:The continuing spread of the Asian tiger mosquito Aedes albopictus, a vector of many arboviruses and some dirofilarial worms, in Europe calls for advanced investigations on its ecological ability to establish and overwinter in temperate, more northern geographic regions. To meet this purpose, eggs of Ae. albopictus laboratory strains of tropical, subtropical and temperate origin were exposed to field conditions during one or two winter seasons in northeastern Germany. After 1 to 16 weeks of outdoor exposure, eggs were flooded in the laboratory, and the hatching rates were determined. During the winter season 2015/2016, when temperatures reached -10°C, the subtropical strain showed hatching after all time periods while the tropical strain displayed hatching only until two weeks of cold exposure. In the winter season 2016/2017, with temperatures as low as ?6°C, all three strains produced hatching larvae after all time periods. Both the hatching rates and the hatching behaviour differed between the strains. Larvae of the subtropical and temperate strains hatched in installments over a period of four weeks while the larvae of the tropical strain hatched within a short time period, often one week. The results of the study demonstrate that Ae. albopictus strains of different, even tropical, origin might be able to survive a central European winter, although this is likely to depend on the specific course of the temperatures. Further studies with different temperature regimes and different mosquito strains are needed to specify these findings.
Project description:At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10-30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0-2.5 °C, during daily fluctuations that often exceeded 15°-20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on 'habitat-level' measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature.
Project description:Worldwide, shrub cover is increasing across alpine and tundra landscapes in response to warming ambient temperatures and declines in snowpack. With a changing climate, shrub encroachment may rely on recruitment from seed occurring outside of the optimum temperature range. We used a temperature gradient plate in order to determine the germination niche of 14 alpine shrub species. We then related the range in laboratory germination temperatures of each species to long-term average temperature conditions at: (1) the location of the seed accession site and (2) across each species geographic distribution. Seven of the species failed to germinate sufficiently to be included in the analyses. For the other species, the germination niche was broad, spanning a range in temperatures of up to 17 °C, despite very low germination rates in some species. Temperatures associated with the highest germination percentages were all above the range of temperatures present at each specific seed accession site. Optimum germination temperatures were consistently within or higher than the range of maximum temperatures modelled across the species' geographic distribution. Our results indicate that while some shrub species germinate well at high temperatures, others are apparently constrained by an inherent seed dormancy. Shrub encroachment in alpine areas will likely depend on conditions that affect seed germination at the microsite-scale, despite overall conditions becoming more suitable for shrubs at high elevations.
Project description:Temperature determines the rates of all biochemical and biophysical processes, and is also believed to be a key driver of macroevolutionary patterns. It is suggested that physiological constraints at low temperatures may diminish the fitness advantages of otherwise beneficial mutations; by contrast, relatively high, benign, temperatures allow beneficial mutations to efficiently show their phenotypic effects. To experimentally test this "mutational effects" mechanism, we examined the fitness effects of mutations across a temperature gradient using bacterial genotypes from the early stage of a mutation accumulation experiment with Escherichia coli. While the incidence of beneficial mutations did not significantly change across environmental temperatures, the number of mutations that conferred strong beneficial fitness effects was greater at higher temperatures. The results therefore support the hypothesis that warmer temperatures increase the chance and magnitude of positive selection, with implications for explaining the geographic patterns in evolutionary rates and understanding contemporary evolution under global warming.
Project description:Fire and high summer soil temperatures can break physical seed dormancy in Mediterranean fire-prone ecosystems. Their independent effect is somewhat recognized but both factors may act together with a synergistic effect yet unknown. This study aims to determine the isolated and combined effects of fire and summer temperatures on the release of physical seed dormancy in Cistaceae species. Fire and summer temperature treatments were applied in a factorial experiment to seeds of 12 species of Cistaceae. Seeds previously exposed or not to a heat shock (fire simulation) were kept for 1 or 2 months at constant or alternating temperatures (summer temperatures simulation). Additionally, I compared the effect of exposing the seeds to a heat shock before or after they had been subjected to the summer temperatures. Heat shock increased germination of all species, but summer temperatures produced different results. When seeds were exposed to summer temperatures after heat shock, germination decreased. This negative effect disappeared when heat shock was simulated at the end of the summer temperatures. Fire and summer temperatures modulate timing of germination in Cistaceae with a joint control on post-fire regeneration. Cycling of sensitivity to physical dormancy release may be the mechanism to explain this fine-tuning, which would ensure germination when environmental conditions are suitable for growth. These results contribute to our understanding of vegetation dynamics and postfire regeneration in Mediterranean ecosystems.
Project description:Rock substrates beneath active volcanoes are frequently subjected to temperature changes caused by the input of new magma from the depth and/or the intrusion of magma bodies of variable thickness within the subvolcanic rocks. The primary effect of the influx of hot magma is the heating of surrounding host rocks with the consequent modification of their physical and chemical properties. To assess mobilization in subvolcanic thermal regimes, we have performed radon (220Rn) thermal experiments on a phonolitic lava exposed to temperatures in the range of 100-900°C. Results from these experiments indicate that transient Rn signals are not unequivocally related to substrate deformation caused by tectonic stresses, but rather to the temperature-dependent diffusion of radionuclides through the structural discontinuities of rocks which serve as preferential pathways for gas release. Intense heating/cooling cycles are accompanied by rapid expansion and contraction of minerals. Rapid thermal cycling produced both inter- and intra-crystal microfracturing, as well as the formation of macroscopic faults. The increased number of diffusion paths dramatically intensified Rn migration, leading to much higher emissions than temperature-dependent transient changes. This geochemical behaviour is analogous to positive anomalies recorded on active volcanoes where dyke injections produce thermal stress and deformation in the host rocks. An increased Rn signal far away from the location of a magmatic intrusion is also consistent with microfracturing of subsurface rocks over long distances via thermal stress propagation and the opening of new pathways.