Differences In Heat Tolerance Research Articles

Continent-wide parallel urban evolution of increased heat tolerance in a common moth.

Urbanization and its urban-heat-island effect (UHI) have expanding footprints worldwide. The UHI means that urban habitats experience a higher mean and more frequent extreme high temperatures than rural habitats, impacting the ontogeny and resilience of urban biodiversity. However, many organisms occupy different microhabitats during different life stages and thus may experience the UHI differently across their development. While evolutionary changes in heat tolerance in line with the UHI have been demonstrated, it is unknown whether such evolutionary responses can vary across development. Here, using common-garden-reared Chiasmia clathrata moths from urban and rural populations from three European countries, we tested for urban evolution of heat shock tolerance in two life stages: larvae and adults. Our results indicate widespread urban evolution of increased heat tolerance in the adult stage only, suggesting that the UHI may be a stronger selective agent in adults. We also found that the difference in heat tolerance between urban and rural populations was similar to the difference between Mid- and North-European regions, suggesting similarity between adaptation to the UHI and natural, latitudinal temperature variation. Our observations incentivize further research to quantify the impact of these UHI adaptations on fitness during urbanization and climate change, and to check whether life-stage-specific adaptations in heat tolerance are typical of other ectothermic species that manage to survive in urbanized settings.

Intraspecific variation of heat tolerance in a model ectotherm: The role of oxygen, cell size and body size

Abstract Virtually all aspects of the biology of ectotherms are size‐and temperature‐dependent. Aerobic metabolism is often proposed to explain such relationships, with oxygen limitation setting limits to heat tolerance and constraining growth. However, experimental tests of the role of oxygen in heat tolerance have yielded mixed results, suggesting that oxygen limitation may be important only in certain contexts and on certain time scales but not others. Here, using thermal death time curves, which incorporate the intensity and duration of heat stress, we quantify the ability to survive heat stress in multiple inbred lines of Drosophila melanogaster, under normal and low oxygen conditions. The lines were selected to differ markedly in body size and cell size, as these traits have been hypothesised to shape thermal tolerance via their effects on oxygen supply and demand. Low oxygen condition markedly reduced survival time across inbred lines, especially when flies were exposed to prolonged, mild heat stress. Variations in heat tolerance among lines were partly related to cell size and body size differences, especially under chronic exposure to high temperatures, under hypoxia and in flies that exhibit larger cell size, supporting the idea that differences in cell size affect the oxygen supply and demand via differences in surface area to volume ratio. Because differences in heat tolerance were manifested at different timescales, our results underscore the need to close the gap between responses to acute timescales, typically employed in laboratory studies, and chronic timescales, which are ecologically more relevant. Read the free Plain Language Summary for this article on the Journal blog.

Variance in heat tolerance in bumble bees correlates with species geographic range and is associated with several environmental and biological factors.

Globally, insects have been impacted by climate change, with bumble bees in particular showing range shifts and declining species diversity with global warming. This suggests heat tolerance is a likely factor limiting the distribution and success of these bees. Studies have shown high intraspecific variance in bumble bee thermal tolerance, suggesting biological and environmental factors may be impacting heat resilience. Understanding these factors is important for assessing vulnerability and finding environmental solutions to mitigate effects of climate change. In this study, we assess whether geographic range variation in bumble bees in the eastern United States is associated with heat tolerance and further dissect which other biological and environmental factors explain variation in heat sensitivity in these bees. We examine heat tolerance by caste, sex, and rearing condition (wild/lab) across six eastern US bumble bee species, and assess the role of age, reproductive status, body size, and interactive effects of humidity and temperature on thermal tolerance in Bombus impatiens. We found marked differences in heat tolerance by species that correlate with each species' latitudinal range, habitat, and climatic niche, and we found significant variation in thermal sensitivity by caste and sex. Queens had considerably lower heat tolerance than workers and males, with greater tolerance when queens would first be leaving their natal nest, and lower tolerance after ovary activation. Wild bees tended to have higher heat tolerance than lab reared bees, and body size was associated with heat tolerance only in wild-caught foragers. Humidity showed a strong interaction with heat effects, pointing to the need to regulate relative humidity in thermal assays and consider its role in nature. Altogether, we found most tested biological conditions impact thermal tolerance and highlight the stages of these bees that will be most sensitive to future climate change.

Assessing the contribution of bacteria to the heat tolerance of experimentally evolved coral photosymbionts.

Coral reefs are extremely vulnerable to ocean warming, which triggers coral bleaching-the loss of endosymbiotic microalgae (Symbiodiniaceae) from coral tissues, often leading to death. To enhance coral climate resilience, the symbiont, Cladocopium proliferum was experimentally evolved for >10 years under elevated temperatures resulting in increased heat tolerance. Bacterial 16S rRNA gene metabarcoding showed the composition of intra- and extracellular bacterial communities of heat-evolved strains was significantly different from that of wild-type strains, suggesting bacteria responded to elevated temperatures, and may even play a role in C. proliferum thermal tolerance. To assess whether microbiome transplantation could enhance heat tolerance of the sensitive wild-type C. proliferum, we transplanted bacterial communities from heat-evolved to the wild-type strain and subjected it to acute heat stress. Microbiome transplantation resulted in the incorporation of only 30 low-abundance strains into the microbiome of wild-type cultures, while the relative abundance of 14 pre-existing strains doubled in inoculated versus uninoculated samples. Inoculation with either wild-type or heat-evolved bacterial communities boosted C. proliferum growth, although no difference in heat tolerance was observed between the two inoculation treatments. This study provides evidence that Symbiodiniaceae-associated bacterial communities respond to heat selection and may contribute to coral adaptation to climate change.

Genes and pathways correlated with heat stress responses and heat tolerance in maize kernels.

Global warming leads to frequent extreme weather, especially the extreme heat events, which threating the safety of maize production. Here we selected a pair of maize inbred lines, PF5411-1 and LH150, with significant differences in heat tolerance at kernel development stage. The two maize inbred lines were treated with heat stress at kernel development stage. Compared with the control groups, transcriptomic analysis identified 770 common up- and down-regulated genes between PF5411-1 and LH150 under heat stress conditions, and 41 putative TFs were predicted. Based on the interaction term of the two-factorial design, we also identified 6,744 differentially regulated genes between LH150 and PF5411-1, 111 common up-regulated and 141 common down-regulated genes were overlapped with the differentially regulated genes, respectively. Combined with proteins and metabolites data, several key pathways including seven differentially regulated genes were highly correlated with the heat tolerance of maize kernels. The first is the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway ko04141: protein processing in endoplasmic reticulum, four small heat shock protein (sHSP) genes were enriched in this pathway, participating with the process of ER-associated degradation (ERAD). The second one is the myricetin biosynthesis pathway, a differentially regulated protein, flavonoid 3',5'-hydroxylase [EC:1.14.14.81], catalyzed the synthesis of myricetin. The third one is the raffinose metabolic pathway, one differentially regulated gene encoded the raffinose synthase controlled the synthesis of raffinose, high level of raffinose enhances the heat tolerance of maize kernels. And the last one is the ethylene signaling pathway. Taken together, our work identifies many genes responded to heat stress in maize kernels, and finds out seven genes and four pathways highly correlated with heat tolerance of maize kernels.

Oxidative stress effects are not correlated with differences in heat tolerance among congeners of Mytilus.

The physiological mechanisms that limit thermal tolerance are broadly relevant to comparative biology and global change. Species differences in macromolecular stability play important roles in evolved patterns of heat tolerance, but other mechanisms such as oxidative stress have also been hypothesized to contribute. For example, mussels in the genus Mytilus exhibit evolved physiological differences at several levels of organization that have been linked with interspecific differences in whole-organism heat tolerance. Both omics and behavioral studies suggested that variation in resistance to oxidative stress plays a role in these differences. Functional data are needed to test this hypothesis. Here, we compared three Mytilus congeners to examine whether susceptibility to oxidative stress contributes to acute heat tolerance. We assayed the activity of two antioxidant enzymes (catalase, superoxide dismutase), as well as levels of oxidative damage to lipids, DNA and individual proteins (using gel-based proteomics methods). In addition, we assessed these oxidative stress responses after repeated episodes of heat stress experienced in air or while immersed in seawater, given that survival and competitive outcomes between Mytilus congeners differ in these two contexts. The results are generally inconsistent with patterns that would be expected if oxidative stress contributes to thermal sensitivity. Rather, the more heat-tolerant congeners suffer comparable or even elevated levels of oxidative damage. As predicted, different treatment contexts led to distinct changes in proteome-wide abundance patterns and, to a lesser extent, protein carbonylation profiles. Overall, the results question the relevance of oxidative damage as a mediator of heat tolerance in this genus.

Host species differences in the thermal mismatch of host-parasitoid interactions.

Extreme high temperatures associated with climate change can affect species directly, and indirectly through temperature-mediated species interactions. In most host-parasitoid systems, parasitization inevitably kills the host, but differences in heat tolerance between host and parasitoid, and between different hosts, may alter their interactions. Here, we explore the effects of extreme high temperatures on the ecological outcomes - including, in some rare cases, escape from the developmental disruption of parasitism - of the parasitoid wasp, Cotesia congregata, and two co-occurring congeneric larval hosts, Manduca sexta and M. quinquemaculata. Both host species had higher thermal tolerance than C. congregata, resulting in a thermal mismatch characterized by parasitoid (but not host) mortality under extreme high temperatures. Despite parasitoid death at high temperatures, hosts typically remain developmentally disrupted from parasitism. However, high temperatures resulted in a partial developmental recovery from parasitism (reaching the wandering stage at the end of host larval development) in some host individuals, with a significantly higher frequency of this partial developmental recovery in M. quinquemaculata than M. sexta. Hosts species also differed in their growth and development in the absence of parasitoids, with M. quinquemaculata developing faster and larger at high temperatures relative to M. sexta. Our results demonstrate that co-occurring congeneric species, despite shared environments and phylogenetic histories, can vary in their responses to temperature, parasitism, and their interaction, resulting in altered ecological outcomes.

Northern copepod mitochondria can't beat the heat

How hot is too hot and why is it too hot? Unravelling the physiology of how animals cope with warming environments can tell us a lot about their evolutionary history as well as their current (and future) habitats. One possible mechanism by which an animal's physiology could limit its heat tolerance is if high temperatures interfered with routine but important metabolic processes such as making energy, ATP, by the mitochondria. Copepods, which often live in splash pools above the high tide line, adapt to the peculiarities of their particular pools. The copepod Tigriopus californicus has made its home in rock pools from balmy Mexico to chilly northern California, and has adapted its mitochondria to the vastly differing climes. With beakers of these copepods, descended from various populations, available in the lab, Tim Healy and Ron Burton from the Scripps Institution of Oceanography, USA, compared how quickly the mitochondria from different populations of copepods made ATP when in warm water and how that related to each populations’ natural habitat to find out whether their mitochondria influenced what temperatures they tolerated and, in doing so, their natural habitat ranges.For each population, the researchers isolated mitochondria from several individuals and provided them with all the materials they needed to make ATP. The team then compared how quickly the mitochondria did this at a range of temperatures from 20°C to a scorching 36°C, and found that the mitochondria from copepods from cold climates generally made ATP faster than those from warm climates, especially at temperatures below 25°C; although that was not surprising, because some animals such as copepods can counteract the natural slowing effect of cold temperatures on their metabolism. However, the northern population's mitochondria were also much more sensitive to high temperatures, as their ability to make ATP declined sharply when the temperature was above the mid-30s. Meanwhile, the mitochondria from southern copepods resisted the heat and happily made ATP at temperatures hot enough to hinder making ATP in the northern populations. Taken together, this suggested that the mitochondria of each population are best adjusted to make ATP at the temperatures that they would naturally encounter in the wild. Healy and Burton then turned their attention to figuring out whether the differences in mitochondrial physiology uncovered in the lab contributed to differences in heat tolerance in the wild.The duo compared the temperature at which each population of copepods made ATP half as fast as normal with the temperature at which they stopped swimming, a sign that it was too hot for them, and discovered that the southern populations, whose mitochondria could churn out decent amounts of ATP at relatively high temperatures, also tended to keep swimming at hotter temperatures, supporting the idea that copepods hit their upper temperature limit when their mitochondria stop performing well. This suggested that having ‘southern style’ or ‘northern style’ mitochondria not only impacted which temperatures the copepods could make the most ATP, but also which temperatures they could survive in the wild.Taken together, it is clear that northern populations of copepods like the cold, while southern populations like the heat, and how fast mitochondria can make ATP at these temperatures underlies at least some of this variation. But how copepod mitochondria react to heat does more than distinguish different populations – it also seems to set the maximum temperature where different populations can survive. As animals scramble to respond to the looming threat of climate change, understanding what sets the temperatures an animal can tolerate will be key to understanding why animals live where they do in the present and where they might live in the future.

Does A Velamen Radicum Effectively Protect Epiphyte Roots against Excessive Infrared Radiation?

Velamen radicum, a dead tissue at maturity, characterizes the roots of many epiphytes. Apart from a role in water and nutrient uptake, protection against excessive radiation in the upper forest canopy has also been suggested, but this function has never been critically assessed. To test this notion, we studied the roots of 18 species of Orchidaceae and Araceae. We defined thermal insulation traits of velamina by monitoring the temperature on the velamen surface and just below the velamen while exposing it to infrared radiation. We investigated velamen's functionality-correlating morphological and thermal insulation traits. In addition, we investigated the viability of the living root tissue after heat exposure. The maximal surface temperatures ranged from 37-51 °C, while the temperature difference between the upper and lower velamen surface (i.e., ∆Tmax) ranged from 0.6-3.2 °C. We found a relationship of velamen thickness with ∆Tmax. Tissue viability was strongly affected by temperatures >42 °C, and no significant recovery after heat exposure was found. Thus, there is only limited support for an insulating function of velamen, but the data suggest considerable species-specific differences in heat tolerance. The latter could be a crucial determinant of the vertical distribution of epiphytes.

Effect of soil warming on growth and physiology of aspen seedlings from Alberta, Canada

Boreal tree species are migrating northwards due to rising temperatures, and differences in heat tolerance can impact the range limits of boreal species. Soil warming may benefit tree growth by promoting root development, or harm growth by creating a high-stress environment, increasing root respiration rates. We assessed the impact of soil warming on the growth of 2-year-old trembling aspen seedlings from 10 families. These families originated from Peace River, in central Alberta, and Camrose, near the southern boreal fringe in Alberta, Canada. We correlated growth traits with climatic data from each region and analyzed the effect of soil warming on the gas exchange of seedlings from Camrose. Families from Peace River exhibited greater growth overall, regardless of warming treatment, while families from Camrose showed a positive growth response under soil warming. Camrose families exposed to soil warming showed greater total leaf area and total leaf biomass compared to those without warming. A Principal Component Analysis (PCA) showed that, regardless of region, some families displayed stronger positive responses and appeared better adapted to soil warming than others. The overall positive response of the Camrose families to soil warming suggests that they have the capacity to take advantage of warmer environmental conditions. Our results indicate regional growth differences in aspen families in Alberta and variation in performance between families within a region, indicating there is differential capacity within local populations to acclimate under rapid climate change.

Differences in heat tolerance, water use efficiency and growth among Douglas-fir families and varieties evidenced by GWAS and common garden studies.

Severe and frequent heat and drought events challenge the survival and development of long-generation trees. In this study, we investigated the genomic basis of heat tolerance, water use efficiency and growth by performing genome-wide association studies in coastal Douglas-fir (Pseudotsuga menziesii) and intervarietal (menziesii × glauca) hybrid seedlings. GWAS results identified 32 candidate genes involved in primary and secondary metabolism, abiotic stress and signaling, among other functions. Water use efficiency (inferred from carbon isotope discrimination), photosynthetic capacity (inferred from %N), height and heat tolerance (inferred from electrolyte leakage in a heat stress experiment) were significantly different among Douglas-fir families and varieties. High-elevation seed sources had increased water use efficiency, which could be a result of higher photosynthetic capacity. Similarly, families with greater heat tolerance also had higher water use efficiency and slower growth, suggesting a conservative growth strategy. Intervarietal hybrids showed increased heat tolerance (lower electrolyte leakage at 50 and 55 °C) and higher water use efficiency compared with coastal families, suggesting that hybridization might be a source of pre-adapted alleles to warming climates and should be considered for large-scale reforestation projects under increasingly arid conditions.

Export of ice-nucleating particles from watersheds: results from the Amazon and Tocantins river plumes.

We examined ice-nucleating particles (INPs) in the plumes of the Tocantins and Amazon rivers, which drain watersheds with different proportions of degraded land. The concentration of INPs active at -15°C (INP-15) was an order of magnitude lower in the Tocantins (mean = 13.2 ml-1; s.d. = 7.8 ml-1), draining the more degraded watershed, compared with the Amazon (mean = 175.8 ml-1; s.d. = 11.2 ml-1), where the concentration was also significantly higher than in Atlantic surface waters (mean = 3.2 ml-1; s.d. = 2.3 ml-1). Differences in heat tolerance suggest that INPs emitted by the Amazon rainforest to the atmosphere or washed into the river might originate from contrasting sources on top of and below the rainforest canopy, respectively. For the Amazon River, we estimate a daily discharge of 1018 INP-15 to Atlantic waters. Rivers in cooler climate zones tend to have much higher concentrations of INPs and could, despite a smaller water volume discharged, transfer even larger absolute numbers of INP-15 to shelf waters than does the Amazon. To what extent these terrestrial INPs become aerosolized by breaking waves and bubble-bursting remains an open question.

Physiological and gene expression changes of Cryptomeria fortunei Hooibrenk families under heat stress.

Heat stress is one of the major abiotic stresses affecting plant growth and productivity. Cryptomeria fortunei (Chinese cedar) is an excellent timber and landscaping tree species in southern China thanks to its beautiful appearance, straight texture and ability to purify the air and improve the environment. In this study, we first screened 8 excellent C. fortunei families (#12, #21, #37, #38, #45, #46, #48, #54) in a second generation seed orchard. We then analyzed the electrolyte leakage (EL) and lethal temperature at 50% (LT50) values under heat stress, to identify the families with the best heat resistance (#48) and the lowest heat resistance (#45) and determine the physiological and morphological response of different threshold-resistance of C. fortune to heat stress. The relative conductivity of the C. fortunei families showed an increasing trend with increasing temperature, following an "S" curve, and the half-lethal temperature ranges between 39°C and 43.2°C. The activities of SOD and POD fluctuated in the early stage of stress but decreased after 37°C. We observed the changes in the cell ultrastructure at 43°C, and the mesophyll cell structure of #48 was less damaged than that of #45. Eight heat resistance gene, including CfAPX1, CfAPX2, CfHSP11, CfHSP21, CfHSP70, CfHSFA1a, CfHSFB2a and CfHSFB4, were all up-regulated in #45 and #48, and there were significant differences between #45 and #48 under different heat stress treatments. We found a significant difference in heat tolerance between #45 and #48, such that #48 shows higher heat tolerance capability and could be exploited in breeding programs. We conclude that the strongly heat-resistant family had a more stable physiological state and a wider range of heat stress adaptations.

The microbiome buffers tadpole hosts from heat stress: a hologenomic approach to understand host-microbe interactions under warming.

Phenotypic plasticity is an important strategy that animals employ to respond and adjust to changes in their environment. Plasticity may occur via changes in host gene expression or through functional changes in their microbiomes, which contribute substantially to host physiology. Specifically, the presence and function of host-associated microbes can impact how animals respond to heat stress. We previously demonstrated that 'depleted' tadpoles, with artificially disrupted microbiomes, are less tolerant to heat than 'colonized' tadpoles, with more natural microbiomes. However, the mechanisms behind these effects are unclear. Here, we compared gene expression profiles of the tadpole gut transcriptome, and tadpole gut microbial metagenome, between colonized and depleted tadpoles under cool or warm conditions. Our goal was to identify differences in host and microbial responses to heat between colonized and depleted tadpoles that might explain their observed differences in heat tolerance. We found that depleted tadpoles exhibited a much stronger degree of host gene expression plasticity in response to heat, while the microbiome of colonized tadpoles was significantly more heat sensitive. These patterns indicate that functional changes in the microbiome in response to heat may allow for a dampened host response, ultimately buffering hosts from the deleterious effects of heat stress. We also identified several specific host and microbial pathways that could be contributing to increased thermal tolerance in colonized tadpoles including amino acid metabolism, vitamin biosynthesis and ROS scavenging pathways. Our results demonstrate that the microbiome influences host plasticity and the response of hosts to environmental stressors.

Transient receptor potential (TRP) channels in the Manila clam (Ruditapes philippinarum): Characterization and expression patterns of the TRP gene family under heat stress in Manila clams based on genome-wide identification

In this study, we identified a total of 40 transient receptor potential genes (RpTRP) in Manila clam by genome-wide identification and classified them into four categories (TRPV, TRPA, TRPM, TRPC) based on gene structure and subfamily relationships. The protein length of RpTRP genes ranges from 281 amino acids to 1601 amino acids. Molecular weight and theoretical PI values range from 182.82 kDa to 32.43 kDa, respectively, with PI values between 5.17 and 9.25. By comparing the expression profiles of TRP genes during heat stress in Manila clams at different latitudes, we found that most genes in the TRP gene family were up-regulated in expression during heat challenge. Therefore, we determined that TRP genes have an important role in the heat stress of Manila clams. This work provides a basis for further studies on the molecular mechanisms of TRP-mediated heat tolerance in Manila clam and for explaining differences in heat tolerance in Manila clam at different latitudes through key differential TRP genes at the molecular level.

Photosynthetic and physiological responses of different peony cultivars to high temperature.

In order to investigate the causes of the differences in heat tolerance ('Lu He Hong' and 'Zhi Hong'), we studied the physiological changes, photosynthetic properties and regulatory mechanism of the two peony cultivars at high temperature. The results showed that the physiological changed of different peony cultivars varied significantly under high temperature stress. With the extension of high temperature stress time, MDA content of 'Lu He Hong' increased,while 'Zhi Hong' rised first and then decreased, SOD activity of 'Lu He Hong' rised first and then decreased, that of 'Zhi Hong' kept rising, POD activity of 'Lu He Hong' kept decreasing, while 'Zhi Hong' rised. The photosynthetic instrument records the change of peony photosynthesis parameters at high temperature; the chlorophyll A (Chla) fluorescence transient is recorded using the plant efficiency analyzer (PEA), analyzed according to the JIP test (O-J-I-P fluorescence transient analysis), and several parameters were derived to explain the photosynthetic efficiency difference between different peony cultivars. The tested cultivars responded differently to the survey conditions, and the PCA analysis showed that the 'Zhi Hong' was more well tolerated and showed better thermal stability of the PSII. The reduced efficiency of the 'Lu He Hong' PSII antenna leads to higher heat dissipation values to increase the light energy absorbed by unit reaction center (ABS/RC), the energy captured by unit reaction center (TR0/RC), and the energy dissipated by unit reaction center (DI0/RC), which significantly leads to its lower total photosynthetic performance (PItotal). The light capture complex of the variety 'Zhi Hong' has high connectivity with its reaction center, less damage to OEC activity, and better stability of the PSII system. The results show that 'Zhi Hong' improves heat resistance by stabilizing the cell membrane, a strong antioxidant system, as well as a more stable photosynthetic system. The results of this study provide a theoretical basis for the screening of heat-resistant peonies suitable for cultivation in Jiangnan area and for the selection and breeding of heat-resistant cultivars.

Evolutionary history constrains heat tolerance of native and exotic tropical Zingiberales

AbstractTropical wet forest plants experience relatively stable temperatures throughout the year. However, tropical forests represent a mosaic of habitats characterized by different temperatures. Heat tolerances are expected to be adapted to temperatures specific to their habitats. Although heat tolerance of species sharing similar environments is expected to be similar, it is also possible that heat tolerance is constrained by evolutionary history because closely related species usually display similar physiologies. When exotic species are introduced to novel communities, colonization may be facilitated by their previous adaptation to high temperatures and other physiological, genetic and demographic traits, which may grant them some competitive advantage. Increasing temperatures may represent a strong environmental filter affecting community assembly, and higher heat tolerances could facilitate the persistence of exotic species in novel environments.Using a community of 32 native and 7 exotic Zingiberales species from different tropical habitats in Costa Rica, Central America, we aim to answer the following questions: (a) does evolutionary history constrain heat tolerance? (b) do plants in the same habitat display similar heat tolerances? (c) do the heat tolerances of exotic species differ from those of native species?We measured temperature‐dependent changes in photosynthetic fluorescence to determine the temperature at which the first sign of damage to photosystem II is observed (T15), and the temperature at which the fluorescence of photosystem II is reduced by 50% (T50). Using a community phylogeny, we tested for phylogenetic signal inT15andT50. In addition, we tested for differences in heat tolerance among Zingiberales from old growth, secondary forests and open areas, as well as between native and exotic species.Our results support (a) a significant phylogenetic signal (Pagel'sλ) for bothT15andT50, (b) communities from open areas displayed similar photosynthetic heat tolerance compared to species from old growth and secondary forests, and (c) exotic Zingiberales are marginally tolerant to high temperatures than native species, but only forT15. Our results suggest that evolutionary history constraints heat responses of native and exotic Zingiberales in a warming world.Read the freePlain Language Summaryfor this article on the Journal blog.

Comparison of Gene Expression Changes in Three Wheat Varieties with Different Susceptibilities to Heat Stress Using RNA-Seq Analysis.

Wheat is highly susceptible to heat stress, which significantly reduces grain yield. In this study, we used RNA-seq technology to analyze the transcript expression at three different time-points after heat treatment in three cultivars differing in their susceptibility to heat stress: Jopum, Keumkang, and Olgeuru. A total of 11,751, 8850, and 14,711; 10,959, 7946, and 14,205; and 22,895, 13,060, and 19,408 differentially-expressed genes (log2 fold-change > 1 and FDR (padj) < 0.05) were identified in Jopum, Keumkang, and Olgeuru in the control vs. 6-h, in the control vs. 12-h, and in the 6-h vs. 12-h heat treatment, respectively. Functional enrichment analysis showed that the biological processes for DEGs, such as the cellular response to heat and oxidative stress—and including the removal of superoxide radicals and the positive regulation of superoxide dismutase activity—were significantly enriched among the three comparisons in all three cultivars. Furthermore, we investigated the differential expression patterns of reactive oxygen species (ROS)-scavenging enzymes, heat shock proteins, and heat-stress transcription factors using qRT-PCR to confirm the differences in gene expression among the three varieties under heat stress. This study contributes to a better understanding of the wheat heat-stress response at the early growth stage and the varietal differences in heat tolerance.

Heat tolerance during uncompensable heat stress in men and women wearing firefighter personal protective equipment

Firefighters run a risk of heat strain during occupational tasks. The number of female firefighters has been increasing, but research relevant to this group is still scarce. We aimed to investigate whether there are any sex differences in heat tolerance or physiological responses during uncompensable heat stress while wearing firefighter personal protective equipment. Twelve female (28 ± 7 years, 66 ± 5 kg, 51.7 ± 4.7 mL kg−1 min−1) and 12 male (27 ± 7 years, 83 ± 8 kg, 58.8 ± 7.5 mL kg−1 min−1) participants performed walking (maximum of 60 min) at 6W·kg−1, 40 °C, and 14% relative humidity. No differences were observed between groups in heat tolerance, rectal temperature, heart rate, percent body mass loss, thermal sensation, and rate of perceived exertion. Thus, when personnel are selected using gender-neutral physical employment standards, sex is not an independent factor influencing heat tolerance when wearing firefighter personal protective equipment during uncompensable heat stress.

Microclimate and Leaf Hydration Status Determine Differences in Heat Tolerance of the Photosynthetic Apparatus in Coffea Arabica and C. Canephora

Microclimate and Leaf Hydration Status Determine Differences in Heat Tolerance of the Photosynthetic Apparatus in Coffea Arabica and C. Canephora