Extreme Temperature Tolerance Research Articles

Mussel‐Inspired Adhesive and Conductive Hydrogel with Long‐Lasting Moisture and Extreme Temperature Tolerance

AbstractConductive hydrogels are a promising class of materials to design bioelectronics for new technological interfaces with human body, which are required to work for a long‐term or under extreme environment. Traditional hydrogels are limited in short‐term usage under room temperature, as it is difficult to retain water under cold or hot environment. Inspired by the antifreezing/antiheating behaviors from nature, and based on mussel chemistry, an adhesive and conductive hydrogel is developed with long‐lasting moisture lock‐in capability and extreme temperature tolerance, which is formed in a binary‐solvent system composed of water and glycerol. Polydopamine (PDA)‐decorated carbon nanotubes (CNTs) are incorporated into the hydrogel, which assign conductivity to the hydrogel and serve as nanoreinforcements to enhance the mechanical properties of the hydrogel. The catechol groups on PDA and viscous glycerol endow the hydrogel with high tissue adhesiveness. Particularly, the hydrogel is thermal tolerant to maintain all the properties under extreme wide tempreature spectrum (−20 or 60 °C) or stored for a long term. In summary, this mussel‐inspired hydrogel is a promising material for self‐adhesive bioelectronics to detect biosignals in cold or hot environments, and also as a dressing to protect skin from injuries related to frostbites or burns.

Grafting as a Method to Increase the Tolerance Response of Bell Pepper to Extreme Temperatures

Core Ideas Shoot and root interactions under extreme temperatures contributed to tolerance. Impact of root dynamics on soil pore water EC and Cl uptake increased under extreme temperatures. Tolerance of extreme temperatures increased assimilation and allocation of C and N to organ growth. Fluctuations of winter and summer and day and night temperatures strongly influence shoot and root growth, as well as the whole plant tolerance to extreme soil temperatures. We compared the response of a commercial pepper (Capsicum annuum L.) hybrid (Romance, Rijk Zwaan) to a range of soil temperatures when grafted to a new rootstock hybrid (S101, Syngenta), self‐grafted, or ungrafted. The new rootstock hybrid was bred for enhancing abiotic stress tolerance. Plants were grown during winter and summer seasons in a plastic greenhouse with natural ventilation. Minirhizotron cameras and in‐growth cores were used to investigate grafted bell pepper root dynamics and root and shoot interactions in response to extreme (low and high air and soil) temperatures. Soil and air temperatures were measured throughout the experiment. The variations of the grafted peppers and the ungrafted aboveground biomass exposed to low and high temperatures during winter and summer were higher in the Romance grafted on the S101 rootstock than in the self‐grafted and ungrafted Romance. The plot of rootstock S101 accumulated Cl, and the rootstock efficiently allocated C into the leaves, stems, and roots and N into the leaves, stems, and fruits. These traits of rootstock S101 can be used to improve the tolerance of other pepper cultivars to low and high soil temperatures, which could lengthen the pepper growing season, as well as provide highly interesting information to plant breeders.

Cold tolerance of subtropical Porites lutea from the northern South China Sea

Marginal scleractinian corals growing at their latitudinal limits should be quite sensitive to variations in winter sea surface temperatures (SSTs). An extreme cold event occurring in early 2008 offered a unique opportunity to examine the effect of cold-water anomalies on Porites lutea corals and their physiological tolerance and acclimation in the subtropical northern South China Sea (NSCS). Besides in-situ observation, a subsequent aquarium-based experiment was designed for reproducing the chilling process and a 50-year-long Sr/Ca ratio profile from two P. lutea skeletal slabs was analyzed for reconstructed the historical annual minimum SSTs which ceased Porites calcification. The 2008 low-temperature anomaly caused the minimum daily mean SSTs dropped below 13°C in the Daya Bay. The stress symptoms displayed by local P. lutea colonies included polyp retraction, reduced coloration and pale, but none showed tissue sloughing. The ability of P. lutea to survive implied its tolerance of extreme low temperatures. Here we suggest a model on the tolerance of high-latitude Porites under low-temperature stresses, which is when SSTs drop below 18°C, Porites corals contract their tentacles (losing heterotrophic capability), then cease calcification (reducing energy consumption), and meanwhile maintain relatively high levels of zooxanthellae density (sustaining host’s life via photosynthetic capacity of symbiotic zooxanthellae). This study revealed remarkable acclimatization of P. lutea corals to low temperature extremes. This acclimatization is beneficial for Porites corals in the NSCS to expand their living ranges towards the higher-latitude areas and have the potential to be the incipient reef former.

Deciphering endophyte behaviour: the link between endophyte biology and efficacious biological control agents.

Endophytes associate with the majority of plant species found in natural and managed ecosystems. They are regarded as extremely important plant partners that provide improved stress tolerance to the host compared with plants that lack this symbiosis. Fossil records of endophytes date back more than 400 million years, implicating these microorganisms in host plant adaptation to habitat transitions. However, it is only recently that endophytes, and their bioactive products, have received meaningful attention from the scientific community. The benefits some endophytes can confer on their hosts include plant growth promotion and survival through the inhibition of pathogenic microorganisms and invertebrate pests, the removal of soil contaminants, improved tolerance of low fertility soils, and increased tolerance of extreme temperatures and low water availability. Endophytes are extremely diverse and can exhibit many different biological behaviours. Not all endophyte technologies have been successfully commercialised. Of interest in the development of the next generation of plant protection products is how much of this is due to the biology of the particular endophytic microorganism. In this review, we highlight selected case studies of endophytes and discuss their lifestyles and behavioural traits, and discuss how these factors contribute towards their effectiveness as biological control agents.

Drought and extreme temperature tolerance for Tillandsia dasyliriifolia , an epiphytic bromeliad from the northern coastal dune scrubland in Yucatan, Mexico

The ecophysiological investigations about epiphytic plants have focused on the establishment of mechanistic explanations of how plants respond to changes in their environment. The main objective of this work was to assess the drought and extreme temperature tolerance of Tillandsia dasyliriifolia individuals growing in two coastal dune scrub sites with different precipitation patterns and microhabitat distribution. This study was focused on the effect of plant size on tolerance parameters. Drought and extreme temperature tolerance were evaluated in small (S1, 9 cm) and large individuals (S2, 35 cm). Tolerance between sites was not different but varied between size classes. Tillandsia dasyliriifolia shows moderate tolerance to drought in comparison to more succulent plants. The 50% of the leaves in small plants died after 40 days of drought and after 60 days for large plants. T. dasyliriifolia also exhibits moderate tolerance to extreme temperatures tolerance, small plants tolerate a temperature range from 11 ºC to 40 ºC and the range for large plants is a little broader (9 °C to 43 °C).

Extreme low temperature tolerance in woody plants.

Woody plants in boreal to arctic environments and high mountains survive prolonged exposure to temperatures below -40°C and minimum temperatures below -60°C, and laboratory tests show that many of these species can also survive immersion in liquid nitrogen at -196°C. Studies of biochemical changes that occur during acclimation, including recent proteomic and metabolomic studies, have identified changes in carbohydrate and compatible solute concentrations, membrane lipid composition, and proteins, notably dehydrins, that may have important roles in survival at extreme low temperature (ELT). Consideration of the biophysical mechanisms of membrane stress and strain lead to the following hypotheses for cellular and molecular mechanisms of survival at ELT: (1) Changes in lipid composition stabilize membranes at temperatures above the lipid phase transition temperature (-20 to -30°C), preventing phase changes that result in irreversible injury. (2) High concentrations of oligosaccharides promote vitrification or high viscosity in the cytoplasm in freeze-dehydrated cells, which would prevent deleterious interactions between membranes. (3) Dehydrins bind membranes and further promote vitrification or act stearically to prevent membrane–membrane interactions.

QTL analyses for anther length and dehiscence at flowering as traits for the tolerance of extreme temperatures in rice (Oryza sativa L.)

Quantitative trait loci (QTLs) for anther length (AL), length of the dehiscence that forms at the apex of the anther [apical dehiscence length (ADL)] and at the base of the anther [basal dehiscence length (BDL)], and the percentage of longitudinal dehiscence (LD) in rice (Oryza sativa L.) were analyzed using data from two consecutive years (2009 and 2010). Backcross inbred lines (BILs) derived from backcrossing of the rice cultivars (Nipponbare × Kasalath) × Nipponbare (95 lines) were used in both years for the detection of the QTLs. Each phenotype was significantly correlated between the 2 years, though its heritability was low. The anther dehiscence is strongly under control from both the environmental and genetic factors. Four major QTLs (α < 0.05) were detected for AL, three for ADL, four for BDL, and one for LD, using composite interval mapping. These QTLs explained 47–42, 32–25 and 36–28 % of the phenotypic variation in total for AL, ADL and BDL in BILs in 2009–2010, respectively, and for LD, 25 % in 2010. The phenotypic effects of the QTLs were examined using 54 chromosome segment substitution lines (CSSLs) derived from Nipponbare × Kasalath. Four of the detected QTLs had significant effects in CSSLs with Kasalath-type segments at marker positions linked with the QTLs, and the CSSLs can, therefore, be donors for breeding rice with high-temperature tolerance.

Boiled, tumbled, burned, and heated: seed scarification techniques for Munro's globemallow appropriate for large-scale application

Physically dormant seeds of Munro’s globemallow ( Sphaeralcea munroana (Douglas) Spach [Malvaceae]) were scarified by boiling, tumbling, burning, dry-heating, and burning + heating treatments in an attempt to find an effective, operational, largescale treatment for nurseries and restoration activities. Results indicate that out of the tested treatments, seed germination was highest following boiling water scarification (49%). All other treatments did not achieve significant improvements in germination compared to the control. Findings should improve the use of this cool-season peren nial for restoration in the Great Basin, where its effectiveness in soil stabilization; its tolerance of disturbance, drought, and extreme temperatures; and its importance as a food source for animals make it a suitable candidate. In addition, the tested treat ments should serve as a foundation for further method refinement.

The protective mechanisms of CaHSP26 in transgenic tobacco to alleviate photoinhibition of PSII during chilling stress

A known sweet pepper cDNA clone, CaHSP26 encoding the chloroplast-localized small heat shock protein (CPsHSP), was isolated and introduced into tobacco plants. It has been reported that CaHSP26 is a member of the CPsHSP gene family related to extreme temperature tolerance in plants. In the present work, the transcripts were detected in the transgenic tobacco lines. The actual quantum yield of photosynthesis (ΦPSII), non-photochemical quenching, and stomatal conductance (gs) in the transgenic lines overexpressing CaHSP26 were higher than those in the wild-type plants under a range of photosynthetic photon flux density during chilling stress. Electron microscopic analysis showed that the transgenic line (L1) had larger size of stomata to lessen stomatal limitation. The activities of ascorbate peroxidase (APX), peroxidase (POD) and catalase (CAT) were also higher in the transgenic lines than those in wild-type plants. Additionally, a significant increase in cis-unsaturated fatty acid contents was observed in transgenic lines due to lower temperatures. These results suggested that CaHSP26 protein plays an important role in protection of PSII by maintaining the antioxidative enzyme activities to avoid or mitigate photooxidation and increasing the fluidity of the thylakoid membrane during chilling stress under low irradiance. Key message CaHSP26 protein protects PSII by maintaining the antioxidative enzyme activities to avoid or mitigate photooxidation and increases the fluidity of the thylakoid membrane during chilling stress under low irradiance.

Thermal tolerance of Frankliniella occidentalis: Effects of temperature, exposure time, and gender

Western flower thrips (WFT), Frankliniella occidentalis, is an invasive worldwide pest that causes great economic loss. Temperature plays an important role in shaping insect distributions. In this study, we report the survival rates of 3-day-old WFT exposed to rapid changes in extreme high and low temperatures. Temperature, exposure time, and gender all significantly affected the survival of adult WFT, with the lowest survival associated with more extreme temperatures and/or longer exposures. The temperature required to kill 50% of exposed WFT individuals (LT 50) decreased with extended exposure time, but females were more tolerant to extreme temperature than males. Investigation of rapid cold or heat hardening suggested that a short prior exposure to a sub-lethal low or high temperature increased WFT survival during a subsequent exposure to a lethal temperature. Tolerance of extreme temperatures and an ability to undergo rapid hardening are of great ecological relevance in determining the geographic distribution of WFT, allowing it to survive better in temporary bouts of extreme temperature stress. Our findings provide useful information on the environmental limits on the distribution of WFT, which have implications for control of this pest.

Fatty acid composition and extreme temperature tolerance following exposure to fluctuating temperatures in a soil arthropod

Ectotherms commonly adjust their lipid composition to ambient temperature to counteract detrimental thermal effects on lipid fluidity. However, the extent of lipid remodeling and the associated fitness consequences under continuous temperature fluctuations are not well-described. The objective of this study was to investigate the effect of repeated temperature fluctuations on fatty acid composition and thermal tolerance. We exposed the springtail Orchesella cincta to two constant temperatures of 5 and 20°C, and a continuously fluctuating treatment between 5 and 20°C every 2 days. Fatty acid composition differed significantly between constant low and high temperatures. As expected, animals were most cold tolerant in the low temperature treatment, while heat tolerance was highest under high temperature. Under fluctuating temperatures, fatty acid composition changed with temperature initially, but later in the experiment fatty acid composition stabilized and closely resembled that found under constant warm temperatures. Consistent with this, heat tolerance in the fluctuating temperature treatment was comparable to the constant warm treatment. Cold tolerance in the fluctuating temperature treatment was intermediate compared to animals acclimated to constant cold or warmth, despite the fact that fatty acid composition was adjusted to warm conditions. This unexpected finding suggests that in animals acclimated to fluctuating temperatures an additional underlying mechanism is involved in the cold shock response. Other aspects of homeoviscous adaptation may protect animals during extreme cold. This paper forms a next step to fully understand the functioning of ectotherms in more thermally variable environments.

Climate change in south-west Australia and north-west China: challenges and opportunities for crop production

Predictions from climate simulation models suggest that by 2050 mean temperatures on the Loess Plateau of China will increase by 2.5 to 3.75°C, while those in the cropping region of south-west Australia will increase by 1.25 to 1.75°C. By 2050, rainfall is not expected to change on the Loess Plateau of China, while in south-west Australia rainfall is predicted to decrease by 20 to 60 mm. The frequency of heat waves and dry spells is predicted to increase in both regions. The implications of rising temperatures are an acceleration of crop phenology and a reduction in crop yields, greater risk of reproductive failure from extreme temperatures, and greater risk of crop failure. The reduction in yield from increased phenological development can be countered by selecting longer-season cultivars and taking advantage of warmer minimum temperatures and reduced frost risk to plant earlier than with current temperatures. Breeding for tolerance of extreme temperatures will be necessary to counter the increased frequency of extreme temperatures, while a greater emphasis on breeding for increased drought resistance and precipitation-use efficiency will lessen the impact of reduced rainfall. Management options likely to be adopted in south-west Australia include the introduction of drought-tolerant perennial fodder species and shifting cropping to higher-rainfall areas. On the Loess Plateau of China, food security is paramount so that an increased area of heat-tolerant and high-yielding maize, mulching with residues and plastic film, better weed and pest control and strategic use of supplemental irrigation to improve rainfall-use efficiency are likely to be adopted.

Effects of methoprene on extreme temperature tolerance and reproduction of Tribolium castaneum (Coleoptera: Tenebrionidae)

The juvenile hormone analogue methoprene is a reduced-risk insecticide. It disrupts insect development of immature stages preventing the emergence of adults. Several studies have shown that lower concentrations that permit the emergence of adults also have sub-lethal effects. Exposure to methoprene (Diacon II) at 3.33 ppm reduced the heat tolerance of Tribolium castaneum (Herbst) adults. However, it did not affect the heat tolerance of larvae at 0.07 ppm. Higher concentrations of methoprene were lethal to larvae without heat treatment. Methoprene (67 ppm) had no effect on the cold tolerance of adults. Furthermore, methoprene (0.03 ppm) did not alter cold tolerance of larvae. Exposure to 15°C for 2 weeks increased the cold tolerance of adults from 4 d to 7 d, and larvae 3 d to 5 d; however, methoprene concentrations had no effect on cold tolerance. Tribolium castaneum larvae exposed to methoprene (0.001 ppm) had lower fecundity as adults. Males were more affected than females in reducing the offspring when paired with untreated mates. These results show the potential of methoprene as an emerging insecticide and a viable alternative to currently used synthetic insecticides. The data on the effect of methoprene on extreme temperature tolerance of T. castaneum have been submitted to the Journal of Stored Products Research. Keywords : Methoprene, Extreme temperature tolerance, Reproduction, Larvae, Adults

Molecular characterization and expression of a heat shock protein gene (HSP90) from the carmine spider mite, Tetranychus cinnabarinus (Boisduval).

In this study, the cDNA of Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae) HSP90 (designated TcHSP90) was cloned using a combination of the homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of TcHSP90 is 2595 bp, including a 5′-untranslated region (UTR) of 177 bp, 3′-UTR of 249 bp, and an open reading frame (ORF) of 2169 bp. The ORF encodes a polypeptide of 722 amino acids with a predicted molecular weight of 83.45 kDa and a theoretical isoelectric point of 4.81. There is an mRNA polyadenylation signal of ATTAAA at the positions 2558–2564. In addition, the expression pattern of TcHSP90 mRNA relative to that of β-actin gene in the three stains of T. cinnabarinus (AbR, abamectin-resistant strain; HR, heat-resistant strain; SS, the susceptible strain) were examined by using fluorescent real time quantitative PCR after the impact of abamectin, high and low temperature, respectively. The results showed that under the normal condition, the mRNA level of TcHSP90 was 1.64 and 1.29-fold higher in the AbR and HR than in SS, respectively. After 8 h treatment with abamectin, the TcHSP90 mRNA levels of SS, AbR, and HR were 1.25, 1.87, and 2.05-fold higher than those of their untreated controls, respectively. The TcHSP90 mRNA levels of SS, AbR, and HR were also significantly increased after being induced at 40° C for 1 h, and they were 3.76, 3.42, and 3.79-fold higher than those of their untreated controls, respectively. The mRNA level of TcHSP90 was also significantly increased after being induced at 4° C for 1 h. These results suggest that TcHSP90 might be involved in the abamectin and extreme temperature resistance or tolerance.

Supercapacitors using n and p-Type Conductive Polymers Exhibiting Metallic Conductivity

Energy storage devices such as supercapacitors require a superior, safe and reliable functioning over a broad range of temperature combined with high energy and high power densities. Development of improved high performance supercapacitors is important for fulfilling the energy and power needs of hybrid electric vehicles, portable electronics, and specialized pulse-power systems required by the military. To meet this need, Crosslink has developed supercapacitor electrodes based on inherently conductive polymers (ICPs). These electrodes combine both the beneficial pseudocapacitive behavior of the ICP coating and a low equivalent series resistance. In this developmental effort, highly-conductive (> 1000 S/cm) polyaniline (PANI) electrodes are used to fabricate high performance supercapacitors to obtain enhanced charge transfer and redox activity. We find that the high electrical conductivity of PANI leads to an enhancement in electrochemical properties such as energy and power densities. In addition, new n-type conductive polymer systems under development exhibit stable electrochemistry and high faradaic capacitance and are being used with the PANI system to build asymmetric supercapacitors. The conductive polymers may be employed as flexible free standing films or substrate coated electrodes. The conductive polymer-based supercapacitor assembly is designed to function with high energy and power densities, cycle life, and extreme temperature tolerance while keeping production costs low.

Influence of arbuscular mycorrhiza on lipid peroxidation and antioxidant enzyme activity of maize plants under temperature stress

The influence of the arbuscular mycorrhizal (AM) fungus, Glomus etunicatum, on characteristics of growth, membrane lipid peroxidation, osmotic adjustment, and activity of antioxidant enzymes in leaves and roots of maize (Zea mays L.) plants was studied in pot culture under temperature stress. The maize plants were placed in a sand and soil mixture under normal temperature for 6 weeks and then exposed to five different temperature treatments (5 degrees C, 15 degrees C, 25 degrees C, 35 degrees C, and 40 degrees C) for 1 week. AM symbiosis decreased membrane relative permeability and malondialdehyde content in leaves and roots. The contents of soluble sugar content and proline in roots were higher, but leaf proline content was lower in mycorrhizal than nonmycorrhizal plants. AM colonization increased the activities of superoxide dismutase, catalase, and peroxidase in leaves and roots. The results indicate that the AM fungus is capable of alleviating the damage caused by temperature stress on maize plants by reducing membrane lipid peroxidation and membrane permeability and increasing the accumulation of osmotic adjustment compounds and antioxidant enzyme activity. Consequently, arbuscular mycorrhiza formation highly enhanced the extreme temperature tolerance of maize plant, which increased host biomass and promoted plant growth.

Seed germination and seedling survival traits of invasive and non-invasive congeneric Ruellia species (Acanthaceae) in Yucatan, Mexico

We compared requirements for seed germination and seedling establishment for Ruellia nudiflora, an invasive species in Yucatan, Mexico with those of the congeneric non-invasive R. pereducta. Germination and seedling survival rates were higher for R. nudiflora than for R. pereducta under high light. Additionally, the ranges of temperature and water potential that allow germination for R. nudiflora were much broader than those of R. pereducta. Seedlings of R. nudiflora exhibited higher survival to drought by shedding their leaves during drought, an important strategy in environments under extreme drought. Seedlings of R. nudiflora also exhibited higher extreme temperature tolerance than R. pereducta seedlings. Overall, traits exhibited by R. nudiflora such as ability to germinate under a wide range of conditions, adaptation to environmental stress and high tolerance to environmental heterogeneity during the seedling stage, have been repeatedly recognized as determinants of colonization success of invasive species in open disturbed areas.

Abiotic stress and ABA-inducible Group 4 LEA from Brassica napus plays a key role in salt and drought tolerance

Late-embryogenesis abundant (LEA) proteins are a family of hydrophilic proteins that form an integral part of desiccation tolerance of seeds. LEA proteins have been also postulated to play a protective role under different abiotic stresses. Their role in abiotic stress tolerance has been well documented for Group 1, 2 and 3 LEAs among the nine different groups. The present study evaluates the functional role of a Group 4 LEA protein, LEA4-1 from Brassica napus. Expression analysis revealed that abscisic acid, salt, cold and osmotic stresses induce expression of LEA4-1 gene in leaf tissues in Brassica species. Conversely, reproductive tissues such as flowers and developing seeds showed constitutive expression of LEA4, which was up-regulated in flowers under salt stress. For functional evaluation of LEA4-1 with regard to stress tolerance, LEA4-1 cDNA was cloned from B. napus, and overexpressed in both Escherichia coli and transgenic Arabidopsis plants. Overexpression of BnLEA4-1 cDNA in E. coli conferred salt and extreme temperature tolerance to the transformed cells. Furthermore, transgenic Arabidopsis plants overexpressing BnLEA4-1 either under constitutive CaMV35S or abiotic stress inducible RD29A promoter showed enhanced tolerance to salt and drought stresses. These results demonstrate that LEA4-1 plays a crucial role in abiotic stress tolerance during vegetative stage of plant development.

Extreme Temperature Tolerance of a Hyperthermophilic Protein Coupled to Residual Structure in the Unfolded State

Understanding the mechanisms that dictate protein stability is of large relevance, for instance, to enable design of temperature-tolerant enzymes with high enzymatic activity over a broad temperature interval. In an effort to identify such mechanisms, we have performed a detailed comparative study of the folding thermodynamics and kinetics of the ribosomal protein S16 isolated from a mesophilic (S16 meso) and hyperthermophilic (S16 thermo) bacterium by using a variety of biophysical methods. As basis for the study, the 2.0 Å X-ray structure of S16 thermo was solved using single wavelength anomalous dispersion phasing. Thermal unfolding experiments yielded midpoints of 59 and 111 °C with associated changes in heat capacity upon unfolding (Δ C p 0) of 6.4 and 3.3 kJ mol − 1 K − 1 , respectively. A strong linear correlation between Δ C p 0 and melting temperature ( T m) was observed for the wild-type proteins and mutated variants, suggesting that these variables are intimately connected. Stopped-flow fluorescence spectroscopy shows that S16 meso folds through an apparent two-state model, whereas S16 thermo folds through a more complex mechanism with a marked curvature in the refolding limb indicating the presence of a folding intermediate. Time-resolved energy transfer between Trp and N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl iodoacetamide of proteins mutated at selected positions shows that the denatured state ensemble of S16 thermo is more compact relative to S16 meso. Taken together, our results suggest the presence of residual structure in the denatured state ensemble of S16 thermo that appears to account for the large difference in quantified Δ C p 0 values and, in turn, parts of the observed extreme thermal stability of S16 thermo. These observations may be of general importance in the design of robust enzymes that are highly active over a wide temperature span.

Extreme thermo-tolerance in seeds of desert succulents is related to maximum annual temperature

We tested the effect of high temperature treatment (103 °C for 17 h) on seed survival for 26, 6 and 5 species in the Aizoaceae, Crassulaceae and Cactaceae, respectively. For both the Aizoaceae and Cactaceae species there was a significant positive correlation between the proportion of seeds surviving and the absolute maximum annual air temperature at the collection site. These results suggest that tolerance of extreme temperatures may have evolved as a mechanism to enable persistence in the soil in these predominantly desert species. Furthermore, these species may provide a useful model system for investigating the mechanism(s) of both desiccation- and thermo-tolerance in seeds.