Heat Adaptation Research Articles

Response and regulatory mechanisms of heat resistance in pathogenic fungi.

Both the increasing environmental temperature in nature and the defensive body temperature response to pathogenic fungi during mammalian infection cause heat stress during the fungal existence, reproduction, and pathogenic infection. To adapt and respond to the changing environment, fungi initiate a series of actions through a perfect thermal response system, conservative signaling pathways, corresponding transcriptional regulatory system, corresponding physiological and biochemical processes, and phenotypic changes. However, until now, accurate response and regulatory mechanisms have remained a challenge. Additionally, at present, the latest research progress on the heat resistance mechanism of pathogenic fungi has not been summarized. In this review, recent research investigating temperature sensing, transcriptional regulation, and physiological, biochemical, and morphological responses of fungi in response to heat stress is discussed. Moreover, the specificity thermal adaptation mechanism of pathogenic fungi in vivo is highlighted. These data will provide valuable knowledge to further understand the fungal heat adaptation and response mechanism, especially in pathogenic heat-resistant fungi.Key points • Mechanisms of fungal perception of heat pressure are reviewed. • The regulatory mechanism of fungal resistance to heat stress is discussed. • The thermal adaptation mechanism of pathogenic fungi in the human body is highlighted.

Analysis of heatwave characteristics under climate change over three highly populated cities of South India: a CMIP6-based assessment.

Climate change is arguably the most alarming global concern of the twenty-first century, particularly due to the increased frequency of meteorological extremes, e.g., heatwaves, droughts, and floods. Heatwaves are considered a potential health risk and urge further study, robust preparedness, and policy framing. This study presents an analysis of heatwave characteristics for historical (1980-2014), near-future (2021-2055), and far-future (2056-2090) scenarios over three highly populated cities of South India, i.e., Bangalore, Chennai, and Hyderabad. Two different approaches, i.e., the India Meteorological Department (IMD) criterion and the percentile-based criterion, are considered for defining the threshold of a heatwave day. Nine general circulation models (GCMs) from the Coupled Model Inter-comparison Project phase 6 (CMIP6) experiment are selected, evaluated after bias correction, and the best performer was utilized to obtain the temperature projections corresponding to two shared socioeconomic pathways (SSP 2-4.5 and 5-8.5) for the future periods. The results reveal a high frequency of heatwave days over the cities in recent years from both approaches, which may further exacerbate in the future, thereby putting a large population at risk. The number of heatwave days is much higher for SSP5-8.5 than that for SSP2-4.5, depicting the direct effects of anthropogenic activities on the frequency of heatwaves. The detailed analysis of heatwave projections will help develop equitable heat resilient mitigation and adaptation strategies for the future, thereby alleviating their pernicious impacts.

Green building: A comprehensive solution to urban heat

Many cities are facing urban heat problems, the combined effect of heatwaves under global climate change, and local warming associated with urbanization, resulting in severe environmental, economic, social, and health impacts. It is urgent to address urban heat problems. Buildings are an important cause of urban heat, while buildings are favorable spaces to deal with urban heat problems through built environment decarbonization and the implementation of cooling strategies. Green building (GB) which has been recognized as an innovative philosophy and practice in the building sector, is proposed to address urban heat challenges. However, existing studies have offered a limited understanding of GB-based urban heat mitigation and adaptation (UHMA). Therefore, this study aims to examine how GBs can contribute to UHMA. In particular, this study analyses the contribution of buildings to urban heat problems in aspects of carbon emissions and the extensive modifications towards artificial landscapes, and discusses the possible impacts caused by urban heat problems. Afterwards, this study develops the framework of GB’s responses to urban heat in global warming mitigation, local warming mitigation, and urban heat adaptation. Based on this, such responses are analyzed in aspects of site planning, outdoor environments, transportation, building design, energy efficiency, water efficiency, material efficiency, indoor environmental quality, operation management, construction, and maintenance following the whole life cycle perspective. This paper helps understand how GB techniques contribute to UHMA and provides a reference to the revision of the GB assessment system for addressing urban heat problems.

Research results on the use of frozen yak sperm

Mongolians have specific, historical traditions of nomadic ways for pastoral animal breeding. Since ancient times they are bred the five kinds of livestock with unique capabilities, adapted to four seasons grazing under harsh natural and climatic conditions of Central Asian mountainous and used their benefits. Unique biological quality of Mongolian livestock that helps the animal withstand the cold and feed shortage seasons in despite of feeding pasture plants only for all year round is an evidence of its pasture usability. Better growth of hair and wool of hardy Mongolian livestock, which are able to grow under severe natural and climatic conditions, during summer and autumn, and fibers appeared around the hair base during cold season make the animals resistant to cold. Mongolian livestock are the animals, which withstand very well the fluctuations of both heat and cold, have better maintenance of body heat and ecological adaptation, stronger body conformation, resist various diseases, and have alive behavior, better sociability and genetic capacity. Livestock in Mongolia are considered to be part of the nation’s wealth and are subject to state protection under the country’s constitution. Agriculture, particularly animal husbandry is one of the basic economic sectors of Mongolia and the sector comprises 84.2% of the country’s Gross Agricultural Product and is the only source of income for 18.5% of total households (Mongolian Statistical Yearbook, 2016). In addition, livestock and livestock-derived processed exports account for about 8.7% of foreign exchange earnings. In 2020, Mongolia has recorded the highest number of livestock at 67.1 million, of which 4.1 million are horses, 4.7 million are cattle, 0.47 million are camels, 30.0 million are sheep and 27.7 million are goats. The action plan of the Mongolian government, set a goal “In addition to increasing the number of high-yielding livestock, implementing a policy to support rural development by creating an appropriate herd structure, improving productivity and quality, and developing intensive animal husbandry, and raising highly productive livestock and milk, to protect the gene found of good beef cattle and to expand the breeding and selection of nuclear herds”. Therefore, important to protect the high-productive yak's gene found are to take semen from yak bull. The yak is bred in Mongolia, Tibet, Nepal, Kyrgyzstan, the Gorno-Altai region of the Russian Federation, the Himalayas, the Altai, and the Pamirs, and in the surrounding mountainous areas at an altitude of about 2,000 meters above sea level.

Towards a web tool for assessing the impact of climate change adaptation measures on heat stress at urban site level

In view of the increased frequency of heat events and their negative effects, principally in cities, many scholars and practitioners are focusing on ways of adapting to climate change. The urban population and, especially, vulnerable groups, are now being affected to such a degree that adaptation measures are deemed necessary. Clearly, the planning and implementation of such measures are dependent on municipal resources. Tools can greatly assist in the planning of such measures at urban site level. This article provides a systematic review of the tools currently available for planning and implementing climate change adaptation measures in cities. The results offer a comprehensive overview of existing planning tools, which can also serve as a handy look-up document for urban planners searching for such tools. We find that many of these tools require considerable improvement and optimisation. For example, our findings demonstrate that outputs may be overly generalised, often there is no way of entering site-specific information while additional co-benefits (e.g. ecosystem services) are ignored. By analysing selected tools, we pinpoint and discuss requirements for future planning tools. In particular, we present a concept for a tool currently under development which is designed to assist in the planning and implementation of heat adaptation measures at diverse (small) spatial scales. The advantages of this tool are that it can assess the indoor thermal situation in addition to outdoor conditions, thereby providing comprehensive information on the suitability of adaptation measures. Furthermore, decision-making processes could benefit from some estimation of the likely co-benefits (here, ecosystem services) if proposed adaptation measures were implemented.

Heat Adaptation and Nutrition Practices: Athlete and Practitioner Knowledge and Use.

To survey elite athletes and practitioners to identify (1)knowledge and application of heat acclimation/acclimatization (HA) interventions, (2)barriers to HA application, and (3)nutritional practices supporting HA. Elite athletes (n = 55) and practitioners (n = 99) completed an online survey. Mann-Whitney U tests (effect size [ES; r]) assessed differences between ROLE (athletes vs practitioners) and CLIMATE (hot vs temperate). Logistic regression and Pearson chi-square (ES Phi [ϕ]) assessed relationships. Practitioners were more likely to report measuring athletes' core temperature (training: practitioners 40% [athletes 15%]; P = .001, odds ratio = 4.0, 95% CI, 2%-9%; competition: practitioners 25% [athletes 9%]; P = .020, odds ratio = 3.4, 95% CI, 1%-10%). Practitioners (55% [15% athletes]) were more likely to perceive rectal as the gold standard core temperature measurement site (P = .013, ϕ = .49, medium ES). Temperate (57% [22% hot]) CLIMATE dwellers ranked active HA effectiveness higher (P < .001, r = .30, medium ES). Practitioners commonly identified athletes' preference (48%), accessibility, and cost (both 47%) as barriers to HA. Increasing carbohydrate intake when training in the heat was more likely recommended by practitioners (49%) than adopted by athletes (26%; P = .006, 95% CI, 0.1%-1%). Practitioners (56% [28% athletes]) were more likely to plan athletes' daily fluid strategies, adopting a preplanned approach (P = .001; 95% CI, 0.1%-1%). Practitioners, and to a greater extent athletes, lacked self-reported key HA knowledge (eg,core temperature assessment/monitoring methods) yet demonstrated comparatively more appropriate nutritional practices (eg,hydration).

Water AND Heat: Intervening in Adaptation Hazard Bias

After centuries of adapting to coastal living, increases in stormwater and tidal flooding events, along with projected sea level rise, led Charleston, South Carolina, USA to define flooding as an existential threat to the city. With billions of planned flood management projects underway, and additional billions of federal disaster flood recovery funds allocated to the State of South Carolina, the Governor's office established a South Carolina Office of Resilience in September 2020, with a focus on water management. The City of Charleston developed its own Flooding and Sea Level Rise Strategy. Simultaneously, the fourth National Climate Assessment pointed to heat health risks and projected costs of lost labor productivity concentrated in the Southeast, yet local recognition of heat as an equivalent threat to flooding was not apparent. Although Charleston's All Hazards Vulnerability Assessment included extreme heat as a significant hazard, without a group focused on heat, ongoing work in the city continued to prioritize water management as annual flood events rapidly escalated. This narrow adaptation framing was further solidified as funding focused on flood recovery and adaptation and technical experts worked within water-related boundaries. These interacting forces led to Hazard Bias, an inherent organizational process of reinforcing focus on a single hazard in the context of compound, complex hazard risks. To adapt to increasing heat, Charleston will need to raise compound risk awareness and adjust its capital investments in resilience to be inclusive of heat mitigation and adaptation as well as water. Yet in 2020 Charleston lacked basic urban heat data, technical expertise, and a strong source of motivation to develop a prioritization approach for recognizing multiple risks and complementary adaptation opportunities in those investments. Recognizing the inherent bias, a new coalition of heat researchers, practitioners, and health experts launched a tripartite heat-health research program and spurred the development of a new heat network in Charleston. The network reduced hazard bias by raising heat-health risk awareness and by intervening in adaptation planning to broaden water-only considerations to be inclusive of water AND heat. This paper provides a detailed case study how the intersections of multiple networks, messengers, and messages contributed to broadening the local resilience agenda from a “hazard bias” and how the lessons learned during this transformative process further reveal health inequities.

Socio-ecological inequality in heat: The role of green infrastructure in a subtropical city context

Urban green infrastructure is central to integrated climate responses linking ecosystem services and social equity within urban planning for extreme heat in cities. This study examines the extent to which temperature regulating services from green infrastructure influence electricity consumption along with socio-economic gradient across urban neighbourhoods of Taipei Basin, Taiwan. Socio-ecological inequality was found to follow a complicated pattern, whereby green polarisation was revealed - both privileged and deprived neighbourhoods had greener and cooler environments. Yet, household salary was a more important factor for determining the increase of electricity consumption in summer than environmental attributes of greenspace proportion, distance to waters and temperature. Indigenous populations were socio-economically more disadvantaged, but they tended to receive greater cooling services from semi-natural areas and increased electricity usage less in summer. Neighbourhoods with a higher female proportion of population were less green, but socio-economically more privileged. In line with this spatial pattern, this study draws attention to the need to take various kinds of green infrastructure into account in a heat adaptation plan, and prioritise greening initiatives in areas which are subject to joint disparity in natural cooling services and economic capacity for house cooling.

The Role of Cooling Centers in Protecting Vulnerable Individuals from Extreme Heat.

The Role of Cooling Centers in Protecting Vulnerable Individuals from Extreme Heat.

Human temperature regulation under heat stress in health, disease, and injury.

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Erratum. Heat Adaptation and Nutrition Practices: Athlete and Practitioner Knowledge and Use.

TO OUR READERS: An error appeared in the ahead-of-print version of the following article: Alabdulwahed S, Galán-López N, Hill T, et al. Heat adaptation and nutrition practices: athlete and practitioner knowledge and use [published online March 24, 2022]. Int J Sports Physiol Perform. https://doi.org/10.1123/ijspp.2021-0462. The wrong versions of Figures 1–4 were placed in the article, and in Supplementary Material S3 posted online with the article, the figure captions did not match up correctly with the figures. The article was corrected April 20, 2022. We apologize for this error.

Challenges of sperm cryopreservation in transferring heat adaptation of corals across ocean basins.

Reef-building corals live very close to their upper thermal limits and their persistence is imperiled by a rapidly warming climate. Human interventions may be used to increase the thermal limits of sensitive corals by cross-breeding with heat-adapted populations. However, the scope of breeding interventions is constrained by regional variation in the annual reproductive cycle of corals. Here we use cryopreservation technology to overcome this barrier and cross-breed conspecific coral populations across ocean basins for the first time. During regional spawning events, sperm samples were cryopreserved from populations of the widespread Indo-Pacific coral, Platygyra daedalea, from the southern Persian Gulf (maximum daily sea surface temperature of 36 °C), the Oman Sea (33 °C), and the central Great Barrier Reef (30 °C). These sperm samples were thawed during a later spawning event to test their ability to fertilize freshly spawned eggs of P. daedalea colonies from the central Great Barrier Reef. Average fertilization success for the Persian Gulf (9%) and Oman Sea (6%) sperm were 1.4–2.5 times lower than those for the native cryopreserved sperm from Great Barrier Reef (13–15%), potentially due to lower sperm quality of the Middle Eastern sperm and/or reproductive incompatibility between these distant populations. Overall, fertilization success with cryopreserved sperm was low compared with fresh sperm (>80%), likely due to the low motility of thawed sperm (≤5%, reduced from 50% to >90% in fresh sperm). To evaluate whether cross-bred offspring had enhanced thermal tolerance, the survival of larvae sired by Persian Gulf cryopreserved sperm, Great Barrier Reef cryopreserved sperm, and Great Barrier Reef fresh sperm was monitored for six days at ambient (27 °C) and elevated (33 °C) temperature. Against expectations of thermal tolerance enhancement, survival of larvae sired by Persian Gulf cryopreserved sperm was 2.6 times lower than larvae sired by Great Barrier Reef fresh sperm at 33 °C (27% versus 71%), but did not differ at 27 °C (77% versus 84%). This lack of enhanced thermal tolerance was unlikely due to outbreeding depression as survival was equally poor in larvae sired by Great Barrier Reef cryopreserved sperm. Rather, follow-up tests showed that cryoprotectant exposure during fertilization (0.1% DMSO) has a negative effect on the survival of P. daedalea larvae which is exacerbated at elevated temperature. Collectively, our findings highlight challenges of breeding corals for enhanced thermal tolerance using cryopreserved sperm, which may be overcome by methodological advances in the collection and preservation of high-quality motile sperm and minimizing the exposure time of eggs to cryoprotectants.

A potential wearable solution for preventing heat strain in workplaces: The cooling effect and the total evaporative resistance of a ventilation jacket

The increase in average seasonal temperatures has an impact in the occupational field, especially for those sectors whose work activities are performed outdoors (agricultural, road and construction sectors). Among the adaptation measures and solutions developed to counteract occupational heat strain, personal cooling garments represent a wearable technology designed to remove heat from the human body, enhancing human performance. This study aims to investigate the effectiveness and the cooling power of a specific cooling garment, i.e. a ventilation jacket, by quantifying the evaporative heat losses and the total evaporative resistance both when worn alone and in combination with a work ensemble, at three adjustments of air ventilation speed.Standardised “wet” tests in a climatic chamber were performed on a sweating manikin in isothermal conditions considering three clothing ensembles (single jacket, work ensemble and a combination of both) and three adjustments of fan velocity.Results showed a significant increase (p < 0.001) in evaporative heat loss values when the fan velocity increased, particularly within the trunk zones for all the considered clothing ensembles, showing that fans enhanced the dissipation by evaporation. The cooling power, quantified in terms of percent changes of evaporative heat loss, showed values exceeding 100% when fans were on, in respect to the condition of fans-off, for the trunk zones except for the Chest. A significant (p < 0.01) decrease (up to 42.3%) in the total evaporative resistance values of the jacket, coupled with the work ensemble, was found compared to the fans-off condition.Results confirmed and quantified the cooling effect of the ventilation jacket which enhanced the evaporative heat losses of the trunk zones, helping the body to dissipate heat and showing the potential for a heat adaptation measure to be developed.

A prenatal acoustic signal of heat affects thermoregulation capacities at adulthood in an arid-adapted bird

Understanding animal physiological adaptations for tolerating heat, and the causes of inter-individual variation, is key for predicting climate change impacts on biodiversity. Recently, a novel mechanism for transgenerational heat adaptation was identified in a desert-adapted bird, where parents acoustically signal hot conditions to embryos. Prenatal exposure to “heat-calls” adaptively alters zebra finch development and their thermal preferences in adulthood, suggesting a long-term shift towards a heat-adapted phenotype. However, whether such acoustic experience improves long-term thermoregulatory capacities is unknown. We measured metabolic rate (MR), evaporative water loss (EWL) and body temperature in adults exposed to a stepped profile of progressively higher air temperatures (Ta) between 27 and 44 °C. Remarkably, prenatal acoustic experience affected heat tolerance at adulthood, with heat-call exposed individuals more likely to reach the highest Ta in morning trials. This was despite MR and EWL reaching higher levels at the highest Ta in heat-call individuals, partly driven by a stronger metabolic effect of moderate activity. At lower Ta, however, heat-call exposed individuals had greater relative water economy, as expected. They also better recovered mass lost during morning trials. We therefore provide the first evidence that prenatal acoustic signals have long-term consequences for heat tolerance and physiological adaptation to heat.

Perception, physiological and psychological impacts, adaptive awareness and knowledge, and climate justice under urban heat: A study in extremely hot-humid Chongqing, China

Urban heat, the combined effect of heatwaves and urban heat islands (UHIs), is a severe challenge for many cities around the world. While there have been numerous studies on urban heat, society's understanding of it is still insufficient, hindering its mitigation and adaptation. This paper aims to investigate people's vulnerability to, and perception, awareness and knowledge of, urban heat. A questionnaire survey was conducted with 562 respondents in the hot and humid city of Chongqing, China in the summer of 2020. Data were analysed using descriptive statistics, Mann-Whitney U test, Kruskal-Wallis H test and logistic regression. Results indicated that urban heat is generally understood as having a moderate severity, while there is limited knowledge of heat-related risks. The perceived heat-related psychological impacts are more severe than physiological impacts. There is limited awareness and knowledge of heat-impact reduction methods. Nevertheless, people's awareness, perception and knowledge of urban heat increase once they suffer heat-induced impacts, indicating exposure/experience-driven awareness and knowledge. Moreover, climate injustice among different groups (e.g. gender, age, education, income, health) of people related to heat challenges was identified. People's perception, vulnerability, awareness and knowledge increased with age, but interestingly decreased with increasing education level and improved health conditions. Economic factor was not critical to heat-related responses. Men could be more vulnerable to physiological symptoms and daily functioning than women. The results of this study provide an understanding of urban heat perception and adaptive knowledge, enabling practitioners and policy makers to formulate effective urban heat mitigation and adaptation policies and regulations.

Genome-Wide Detection of Copy Number Variants in Chinese Indigenous Horse Breeds and Verification of CNV-Overlapped Genes Related to Heat Adaptation of the Jinjiang Horse.

In the present study, genome-wide CNVs were detected in a total of 301 samples from 10 Chinese indigenous horse breeds using the Illumina Equine SNP70 Bead Array, and the candidate genes related to adaptability to high temperature and humidity in Jinjiang horses were identified and validated. We determined a total of 577 CNVs ranging in size from 1.06 Kb to 2023.07 Kb on the 31 pairs of autosomes. By aggregating the overlapping CNVs for each breed, a total of 495 CNVRs were detected in the 10 Chinese horse breeds. As many as 211 breed-specific CNVRs were determined, of which 64 were found in the Jinjiang horse population. By removing repetitive CNV regions between breeds, a total of 239 CNVRs were identified in the Chinese indigenous horse breeds including 102 losses, 133 gains and 4 of both events (losses and gains in the same region), in which 131 CNVRs were novel and only detected in the present study compared with previous studies. The total detected CNVR length was 41.74 Mb, accounting for 1.83% of the total length of equine autosomal chromosomes. The coverage of CNVRs on each chromosome varied from 0.47% to 15.68%, with the highest coverage on ECA 12, but the highest number of CNVRs was detected on ECA1 and ECA24. A total of 229 genes overlapping with CNVRs were detected in the Jinjiang horse population, which is an indigenous horse breed unique to the southeastern coast of China exhibiting adaptability to high temperature and humidity. The functional annotation of these genes showed significant relation to cellular heat acclimation and immunity. The expression levels of the candidate genes were validated by heat shock treatment of various durations on fibroblasts of horses. The results show that the expression levels of HSPA1A were significantly increased among the different heat shock durations. The expression level of NFKBIA and SOCS4 declined from the beginning of heat shock to 2 h after heat shock and then showed a gradual increase until it reached the highest value at 6 h and 10 h of heat shock, respectively. Breed-specific CNVRs of Chinese indigenous horse breeds were revealed in the present study, and the results facilitate mapping CNVs on the whole genome and also provide valuable insights into the molecular mechanisms of adaptation to high temperature and humidity in the Jinjiang horse.

Post-exercise, passive heat acclimation with sauna or hot-water immersion provide comparable adaptations to performance in the heat in a military context

To mitigate the effects of heat during operations in hot environments, military personnel will likely benefit from heat acclimation (HA) conducted prior to deployment. Using post-exercise, passive heating, 25 participants completed a 5 d HA regime in sauna (70 °C, 18% RH) or hot-water immersion (HWI) (40 °C) for ≤40 min, preceded and followed by a heat stress test (1-h walking at 5 km.h−1 in 33 °C, 77% RH in military uniform (20 kg) before an incremental ramp to exhaustion). Fifteen completed both regimes in a randomised, cross-over manner. While performance did not significantly improve (+14%, [-1, 29], p = .079), beneficial adaptations were observed for mean exercising core temperature (-0.2 °C, [-0.2, −0.2], p <.001), skin temperature (-0.2 °C, [-0.2, −0.2], p = 035) and heart rate (-8 bpm, [-6, −10], p<.001) in both conditions. Post-exercise, passive HA of either modality may benefit military units operating in the heat. Practitioner summary: Strategies are required to prevent health and performance impairments during military operations upon arrival in hot environments. Using a randomised, cross-over design, participants completed five-day passive, post-exercise heat acclimation using sauna or hot-water immersion. Both regimes elicited beneficial albeit modest heat adaptations. Abbreviations: HA: heat acclimation; HST: heat stress test; HWI: hot-water immersion; RH: relative humidity

Combined Analysis of the Metabolome and Transcriptome to Explore Heat Stress Responses and Adaptation Mechanisms in Celery (Apium graveolens L.).

Celery is an important leafy vegetable that can grow during the cool season and does not tolerate high temperatures. Heat stress is widely acknowledged as one of the main abiotic stresses affecting the growth and yield of celery. The morphological and physiological indices of celery were investigated in the present study to explore the physiological mechanisms in response to high temperatures. Results showed that the antioxidant enzyme activity, proline, relative conductivity, and malondialdehyde were increased, while chlorophyll and the water content of leaves decreased under high-temperature conditions. Short-term heat treatment increased the stomatal conductance to cool off the leaves by transpiration; however, long-term heat treatment led to stomatal closure to prevent leaf dehydration. In addition, high temperature caused a disordered arrangement of palisade tissue and a loose arrangement of spongy tissue in celery leaves. Combined metabolomic and transcriptomic analyses were further used to reveal the regulatory mechanisms in response to heat stress at the molecular level in celery. A total of 1003 differential metabolites were identified and significantly enriched in amino acid metabolism and the tricarboxilic acid (TCA) cycle. Transcriptome sequencing detected 24,264 different genes, including multiple transcription factor families such as HSF, WRKY, MYB, AP2, bZIP, and bHLH family members that were significantly upregulated in response to heat stress, suggesting that these genes were involved in the response to heat stress. In addition, transcriptional and metabolic pathway analyses showed that heat stress inhibited the glycolysis pathway and delayed the TCA cycle but increased the expression of most amino acid synthesis pathways such as proline, arginine, and serine, consistent with the results of physiological indicators. qRT-PCR further showed that the expression pattern was similar to the expression abundance in the transcriptome. The important metabolites and genes in celery that significantly contributed to the response to high temperatures were identified in the present study, which provided the theoretical basis for breeding heat-resistant celery.

A crossover control study of three methods of heat acclimation on the magnitude and kinetics of adaptation.

What is the central question to the study? Are primary indices of heat adaptation (e.g., expansion of plasma volume and reduction in resting core temperature) differentially affected by the three major modes of short-term heat acclimation, that is, exercise in the heat, hot water immersion and sauna? What it the main finding and its importance? The three modes elicited typical adaptations expected with short-term heat acclimation, but these were not significantly different between modes. This comparison has not previously been made and highlights that individuals can expect similar adaptation to heat regardless of the mode used. Heat acclimation (HA) can improve heat tolerance and cardiovascular health. The mode of HA potentially impacts the magnitude and time course of adaptations, but almost no comparative data exist. We therefore investigated adaptive responses to three common modes of HA, particularly with respect to plasma volume. Within a crossover repeated-measures design, 13 physically active participants (five female) undertook four, 5-day HA regimes (60min/day) in randomised order, separated by ≥4weeks. Rectal temperature (Tre ) was clamped at neutrality via 36.6°C (thermoneutral) water immersion (TWI; i.e., control condition), or raised by 1.5°C via heat stress in 40°C water, sauna (55°C, 52% relative humidity), or exercise in humid heat (40°C, 52% relative humidity; ExH). Adaptation magnitude was assessed as the pooled response across days 4-6, while kinetics was assessed via the 6-day time series. Plasma volume expansion was similar in all heated conditions but only higher than TWI in exercise in the heat (ExH) (by 4%, P=0.036). Approximately two-thirds of the expansion was attained within the initial 24h and was moderately related to that present on day 6, regardless of HA mode (r=0.560-0.887). Expansion was mediated by conservation of both sodium and albumin content, with little evidence for these having differential roles between modes (P=0.706 and 0.320, respectively). Resting Tre decreased by 0.1-0.3°C in all heated conditions, and systolic blood pressure decreased by 4mmHg, but not differentially between conditions (P≥0.137). In conclusion, HA mode did not substantially affect the magnitude or rate of adaptation in key resting markers of short-term HA.

Genome-wide scan for selection signatures and genes related to heat tolerance in domestic chickens in the tropical and temperate regions in Asia

Heat stress is one of the major environmental stressors challenging the global poultry industry. Identifying the genes responsible for heat tolerance is fundamentally important for direct breeding programs. To uncover the genetic basis underlying the ambient temperature adaptation of chickens, we analyzed a total of 59 whole genomes from indigenous chickens that inhabit South Asian tropical regions and temperate regions from Northern China. We applied FST and π-ratio to scan selective sweeps and identified 34 genes with a signature of positive selection in chickens from tropical regions. Several of these genes are functionally implicated in metabolism (FABP2, RAMP3, SUGCT, and TSHR) and vascular smooth muscle contractility (CAMK2), and they may be associated with adaptation to tropical regions. In particular, we found a missense mutation in thyroid-stimulating hormone receptor (41020238:G>A) that shows significant differences in allele frequency between the chicken populations of the two regions. To evaluate whether the missense mutation in TSHR could enhance the heat tolerance of chickens, we constructed segregated chicken populations and conducted heat stress experiments using homozygous mutations (AA) and wild-type (GG) chickens. We found that GG chickens exhibited significantly higher concentrations of alanine aminotransferase, lactate dehydrogenase, and creatine kinase than AA chickens under heat stress (35 ± 1°C) conditions (P < 0.05). These results suggest that TSHR (41020238:G>A) can facilitate heat tolerance and adaptation to higher ambient temperature conditions in tropical climates. Overall, our results provide potential candidate genes for molecular breeding of heat-tolerant chickens.