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The rate of heat-related fatalities in crop production workers is almost 20 times that of other industries. Heat stress was investigated in migrant tomato workers in July, 2012, using measurements of body temperature, heart rates, body weight loss, evaluation of the thermal environment, and survey data. Using occupational safety criteria, these workers were found to work in an environment that should require protective measures to prevent heat strain. Increases in body temperature, heart rate, and physiological strain correlated with heat exposure. One third of workers had body weight percentage losses that indicated dehydration. However, working in hot environments appears to elicit a low magnitude of strain in well acclimated workers who self-pace. Key findings suggest the need for worker and employer safety training regarding acclimation and hydration. Survey data showed that less than 30% have had any heat-related safety training.

Ocean warming is leading to increased occurrence of coral mass bleaching events, threatening the persistence of these ecosystems and the communities that rely on them. While reef recovery is possible, conservation approaches based purely on transplantation/coral-gardening will not suffice to maintain these ecosystems over the projected environmental changes. Assisted evolution approaches aim to boost acclimatization and adaptation processes. A potential approach could be to harness the naturally occurring mechanism of environmental memory that has been observed in corals and other organisms, where an organism remembers a priming stress event to allow a faster/stronger response when the stress re-occurs. In this thesis I aimed to investigate whether this mechanism exists and how it is regulated on a molecular level in the sea anemone Aiptasia. Aiptasia were primed to heat stress by exposing them to 32 °C water for several years, or for one week. After a recovery period of one week at 25 °C, a naïve and the primed treatments were exposed to lethal thermal stress at 34 °C for three days. Primed treatments performed better than the naïve treatment in survival, photosynthetic efficiency and symbiont density for two days, after which the priming advantage was lost. The difference between the primed treatments indicated that the priming dose may affect priming success. There were clear indications of an epigenetic transcriptional memory mechanism on a transcriptional level. I observed a pronounced difference between control and heat-stressed treatments, indicating that transcription returned to near baseline expression after cessation of the priming exposure. The functional categories of differentially expressed genes in heat stress relative to control were similar between naïve and primed treatments, with the main difference observed in a stronger up- and downregulation of stress response genes in the long-term primed treatment. I optimized a chromatin immunoprecipitation protocol for use with Aiptasia by adjusting fixation, sonication and immunoprecipitation conditions. The enrichment of H3K4me2/me3 and poised RNA Pol II in the promoters of stress response genes will be investigated next to elucidate the mechanism of the observed epigenetic transcriptional memory in Aiptasia, and to ultimately inform conservation strategies for coral reefs globally.

BACKGROUND: Age-related declines in endothelial function have been well documented with larger declines observed in middle-aged. Passive heat exposure has been shown to be a promising method to improve vascular endothelial health, with sauna specifically being linked to reduced risk of cardiovascular disease. Increases in blood flow and shear rates associated with heat exposure are often considered to have a major influence on the observed improved endothelial function following heat exposure. The magnitude of these changes in response to sauna have not yet been defined. Therefore, the purpose of this study is to quantify and compare the vascular response to an acute bout of sauna heating in young and middle-aged individuals. METHODS: 10 young (24.9 ± 4.2 years, 6 males and 4 females) and 8 middle-aged adults (55.6 ± 3.9 years 4 males and 4 females) underwent 40 min of sauna exposure at 80 oC. Esophageal and intramuscular temperatures were recorded throughout the duration of the experiment. Brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. RESULTS: Core and muscle temperatures significantly increased by 1.5 ± 0.53 and 1.95 ± 0.70 °C, respectively (P < 0.05) and the magnitude of increase did not differ between young and middle-aged participants (P0.867 and 0.488, respectively). Shear rate increased by 170– 200% (P < 0.001), while blood flow increased by 180–390% (P < 0.001) in the superficial femoral and brachial artery, respectively, in both groups. Importantly, the changes in shear and flow did not significantly differ between young and middle-aged subjects for either artery (P = 0.190–0.899.) Systolic blood pressure (SBP) was significantly reduced from 135.25 ± 17.50 to 122.38 ± 19.7 mmHg (P = 0.017) only in middle-aged participants and a decrease in diastolic blood pressure was observed from 81.6 ± 13.0 mmHg at baseline to 69.8 ± 8.4 mmHg (P < .001). Heat-induced dilation was strongly correlated to baseline endothelial function in the young (R = 0.86, P = 0.006), but not the old (R = 0.22, P = 0.631). CONCLUSIONS: These results indicate that young and middle-aged adults have similar shear-rate and blood flow responses to acute sauna heating, which significantly reduces blood pressure in middle-aged, but not young individuals. Future heat therapy studies may elicit meaningful cardiovascular benefits from lower magnitudes of chronic passive heat stress.

<p> As the effects of climate change become more evident, the development of effective strategies for improving livestock climatic adaptation and the long-term sustainability of animal food production have become key priorities around the world, including in the US. Together with nutrition, infrastructure, and management practices, genetically improving animals is an effective and lasting alternative to simultaneously improve productive efficiency and climatic adaptation of animals. Genetic improvement requires basic understanding of the genomic architecture of the indicator traits of interest and the availability of large-scale datasets. Understanding the role of evolution and selection (both natural and artificial) on shaping animal genomes is of paramount importance for the optimization of breeding programs and conservation of genetic resources. In addition, properly quantifying environmental stress and individual animal responses to thermal stress are still important challenges in breeding programs. Thus, the identification of optimal statistical methods and traits that better capture key biological mechanisms involved in the heat stress response has the potential to enable more accurate selection for thermal tolerant individuals. Therefore, this thesis aimed to investigate complementary topics related to thermal tolerance in livestock species based on genomic information. A total of 946 genotypes from 34 cattle breeds, as well as Datong yak (<em>Bos grunniens</em>) and Bali (<em>Bos javanicus</em>) populations, adapted to divergent climatic conditions, were used to investigate the genetic diversity and unravel genomic regions potentially under selection for thermal tolerance, with a focus on Chinese local cattle breeds and yak. Different signature of selection analyses and a comprehensive description of genetic diversity in 32 worldwide cattle and Datong yak populations was presented. Moderate genetic diversity was observed within each Chinese cattle population. However, these results highlighted the need to adopt strategies to avoid further reduction in the genetic diversity of these populations. Several candidate genes were identified as potentially under selection for thermal tolerance, and important biological pathways, molecular functions, and cellular components were identified, which contribute to our understanding of the genetic background of thermal tolerance in <em>Bos</em> species. Secondly, 8,992 genotyped individuals were used to provide a comprehensive description of genotype-by-environment interaction effects, defining optimal environmental variables based on public weather station data, and critical periods to evaluate heat tolerance for various reproduction, growth, and body composition traits in US Large White pigs. The period of 30 days before the measurement date was suggested to analyze genotype-by-environment interaction for off-test weight, muscle depth, and backfat thickness. While for number of piglets weaned and weaning weight, the suggested period ranged from the last trimester of gestation until weaning. This same population was used to access the genomic predictive ability of heat tolerance based on routinely-measured traits and explore candidate regions involved in the biological mechanisms that underlie heat stress response in pigs. Genotype-by-environment interaction was identified for most of the traits evaluated, and moderate (>0.36 ± 0.05) breeding values prediction accuracy were achieved using genomic information. Lastly, various behavioral, anatomical, and physiological indicators of heat stress were measured in a population of 1,645 multiparous Large White x Landrace lactating sows. This dataset was used to identify the best statistical models and estimate genomic-based genetic parameters for 23 indicators of heat stress, including automatically-measured vaginal temperature, skin surface temperatures, respiration efficiency, respiration rate, panting score, body condition scores, hair density, body size, and ear measurements. All the traits evaluated are heritable, with heritability estimates ranging from 0.04 ± 0.01 to 0.40 ± 0.09. The genetic correlations among these traits ranged from -0.49 (between repeated records of vaginal temperature measured at 0800 hours and caliper body condition score) to 1.0 (between repeated records of vaginal temperature measured at 0800 hours and single record of vaginal temperature measured at 0800 hours; and between repeated records of vaginal temperature measured at 1200 hours and single record of vaginal temperature measured at 1200 hours). These findings indicate that genetic progress for thermotolerance in pigs can be achieved through direct indicators of heat stress in selection schemes. However, special attention is needed due to complex relationship between these traits as evidenced by their genetic correlations. In conclusion, this thesis provides important information to be used when designing breeding strategies for improving thermal tolerance in cattle and pigs, important genomic regions and metabolic pathways that are important for understanding the biological mechanism regulating thermal tolerance, as well as future directions for investigations in the area of livestock climatic adaptation.</p>

As part of the Southeast Quality Milk Initiative, this investigation analyzes relationships between several heat abatement management, housing and feeding practices that may influence cow thermal comfort with milk quality. Farms producing high quality milk have low bulk tank somatic cell (BTSCC) and bacteria or standard plate counts (BTSPC). Dairy farms in Kentucky (n = 96), Mississippi (n = 7), Tennessee (n = 84) and Virginia (n = 96) were surveyed. Management of heat abatement programs were associated with smaller BTSCC and BTSPC. Farms that used pasture as their primary housing system had greater BTSCS and BTSPC than farms that confined cows to barns year-round. The practice of making fresh feed available to cows upon returning from the milking parlor was also associated with better milk quality. Management of heat abatement programs, housing and feeding practices show promise as a means to improve milk quality on Southeastern dairy farms.

Cells exposed to heat stress experience an increase in the amount of misfolded and aggregated proteins. Cells respond to this threat through coordinated and finely tuned ad- justments in gene expression. When the ambient temperature increases, cells activate the heat stress response (HSR), a process in which the transcription of mRNAs encoding heat shock proteins (Hsps) is upregulated. During severe heat stress, cells also downregulate the synthesis of misfolding-prone housekeeping proteins while the synthesis of Hsps takes precedence. Consequently, the amount of misfolded and aggregated proteins is reduced by Hsps. While the transcriptional HSR has been studied in depth over the last 50 years, our understanding of protein translation regulation during heat stress remains limited. Biomolecular condensates have been proposed as a new way to regulate cellular functions. In budding yeast exposed to severe heat stress, the repression in the synthesis of housekeep- ing proteins coincides with the formation of condensates called heat stress granules (HSGs). HSGs are enriched for translation factors and translationally-repressed mRNAs and they have been implicated in translation regulation. However, if and how HSGs regulate translation during severe heat stress has remained elusive. Using in vitro reconstitution assays, I demonstrate that the heat-induced condensation of translation factors together with mRNA is an adaptive mechanism to regulate protein synthesis during severe heat stress. My thesis work focused on the translation initiation factor complex eIF4F from Saccharomyces cerevisiae. eIF4F was previously shown to promote global translation of capped mRNAs. One subunit of eIF4F is eIF4G, an RNA-binding and scaffold protein that interacts with numerous translation initiation factors. Two other subunits of eIF4F are the RNA helicase eIF4A and the mRNA cap-binding protein eIF4E. eIF4G also interacts with the poly(A) binding protein (Pab1p) and the RNA helicase Ded1p, which like eIF4F, are crucial in translation initiation. Importantly, eIF4G, eIF4E, Pab1p and Ded1p condense into HSGs in yeast upon severe heat stress, while eIF4A remains soluble in the cytosol. To investigate the function of these translation factors in regulating translation, I purified eIF4F, Pab1p and Ded1p. Using purified eIF4F, nanoluciferase-encoding reporter mRNAsand an in vitro translation assay, I showed that eIF4F enhances general protein synthesis. Together with Pab1p and Ded1p, eIF4F enhances the translation of reporter mRNAs with 5’ UTRs of housekeeping transcripts to a greater extent than reporter mRNAs with 5’ UTRs of Hsp-encoding genes. These findings suggest important differences in translation regulation at physiological temperatures and that efficient translation of housekeeping mRNAs requires synergy between eIF4F, Pab1p and Ded1p. Next, I reconstituted eIF4G condensates in vitro using biochemical approaches. I found that eIF4G forms condensates with mRNA. The condensation of eIF4G-mRNA is promoted by heat-induced structural rearrangements and interaction valences between eIF4G RNAbinding domains (RBDs). eIF4G has three RBDs, where the removal of either RBDs did not affect the RNA binding affinity but repressed condensation. Thus, eIF4G-mRNA condensation requires cooperativity between the three RBDs. Critically, I found that the mechanism of heat-induced condensation is conserved and adapted in eIF4G orthologues from yeast species that thrive in colder or warmer temperatures. Using multi-component in vitro assays, I found that heated eIF4G-mRNA condensates recruit eIF4E and Pab1p. In agreement with the fact that eIF4A does not assemble into HSGs in cells, eIF4A did not partition into eIF4G-mRNA condensates, which is likely due to a heat-induced weakening of interactions with eIF4G. I next characterized eIF4G variants with targeted mutations in the eIF4E- and Pab1-binding sites of eIF4G. This allowed me to demonstrate that the recruitment of eIF4E into eIF4G-mRNA condensates is driven by protein-mediated interactions. Furthermore, I found that heterotypic interactions between eIF4G, Pab1 and the poly(A) tail of mRNA promote the solidification of heated condensates. This is consistent with previous observations reporting solid-like properties of HSGs. Finally, I investigated the translation activity of heated translation factor condensates in yeast cell-free extracts. Solid-like eIF4F-mRNA condensates with Pab1p or Ded1p resulted in a pronounced repression of translation. This coincided with the recruitment of reporter mRNAs into condensates. Based on these findings, I thus propose that the repression in translation of housekeeping mRNAs during severe heat stress in yeast is a consequence of the formation of solid-like translation factor and mRNA condensates. Further analyses revealed that mRNA outside of condensates are translated in an eIF4A-dependent manner. This is because eIF4A is not recruited to the condensates and remains active upon heating. In summary, I propose that heat stress promotes the condensation of mRNA with eIF4G, eIF4E, Pab1p and Ded1p into solid-like condensates. In vitro assays suggest that translation factors inside of condensates are inactive while the mRNA is translationally repressed. This model highlights a mechanism for the downregulation in the synthesis of housekeeping proteins during severe heat stress in yeast. My findings also suggest that the preferential translation of mRNAs encoding Hsps occurs independently of the condensate-forming translation factors and may be mediated by eIF4A, which does not localise into HSGs. I thus conclude that translation regulation during severe heat stress is achieved by specific translation initiation factors that form inactive and solid-like condensates with mRNA.

Animal welfare, reproduction, and milk production can be negatively affected when dairy cattle experience heat stress. Dairy cows in southern latitudes spend nearly 4 to 6 months in a state of heat stress. Animal health professionals and dairy producers use changes in physiological responses and behavioral patterns of cows as a tool for identifying poor health and welfare in periods of heat stress. The objectives of this study were to monitor the effects of heat stress on grazing dairy cows provided with shade or sprinklers by comparing various physiological indices of heat stress, and to, design and utilize a heat stress scoring system to evaluate heat stress severity on grazing dairy cows with access to shade and sprinklers. Finally, the results were used to predict the accuracy of the scoring system with machine learning methods. The findings from this study provide a new tool to assess heat stress in dairy cows.

Woody ornamental plants are considered the key for well- designed landscapes; Callistemon citrinus is one of those plants. In arid and semiarid areas, Callistemon has been used in gardens and landscapes for its unique characteristics. This study was conducted to evaluate the performance of Callistemon in landscapes under different environmental stress conditions including water, and heat. Further, the potential of using 3D software SketchUp in landscape design was also investigated. Callistemon plants were grown under 100, 50 or 30% of field capacity with or without shredded hardwood mulch. When field capacity decreased, root: shoot ratio and water use efficiency were improved, but canopy temperature increased. The decreased water caused decreases in leaf greenness, chlorophyll a, shoot volume, root volume, leaf water potential, and transpiration rate. Mulch increased root volume and leaf water potential. Callistemon growth under shade structure angle and orientation was examined. Shade structures were installed at 90° and 70° to the ground and three orientations, south, east, and west. Transpiration rate was reduced under the shade. The plant’s response to heat was also examined. Plant were exposed to 45/35, 35/25, or 25/15 °C, d/n. The plant’s physiological response was tested after two weeks. Highest temperatures decreased Chl b content and SOD activity compared to control. In contrast, carotenoid content and H2O2 level increased under the highest temperature treatment. Catalase activity was increased at moderate but decreased under the highest temperatures. Designing a 3D model using SketchUp software was examined. The program function was evaluated, and the designed experiment was tested. Planning a site with shadows predicted was achieved. The work was done with greater precision and less effort. The program was effective in reducing time and cost. SketchUp can be successfully used in landscape work.

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