Lily LlHSFC2 coordinates with HSFAs to balance heat stress response and improve thermotolerance

Heat stress transcription factors (HSFs) are core regulators of plant heat stress response. Much research has focused on class A and B HSFs, leaving those of class C relatively understudied. Here, we reported a lily (Lilium longiflorum) heat-inducible HSFC2 homology involved in thermotolerance. LlHSFC2 was located in the nucleus and cytoplasm and exhibited a repression ability by binding heat stress element. Overexpression of LlHSFC2 in Arabidopsis, tobacco (Nicotiana benthamiana), and lily, all increased the thermotolerance. Conversely, silencing of LlHSFC2 in lily reduced its thermotolerance. LlHSFC2 could interact with itself, or interact with LlHSFA1, LlHSFA2, LlHSFA3A, and LlHSFA3B of lily, AtHSFA1e and AtHSFA2 of Arabidopsis, and NbHSFA2 of tobacco. LlHSFC2 interacted with HSFAs to accelerate their transactivation ability and act as a transcriptional coactivator. Notably, compared with the separate LlHSFA3A overexpression, co-overexpression of LlHSFC2/LlHSFA3A further enhanced thermotolerance of transgenic plants. In addition, after suffering HS, the homologous interaction of LlHSFC2 was repressed, but its heterologous interaction with the heat-inducible HSFAs was promoted, enabling it to exert its co-activation effect for thermotolerance establishment and maintenance. Taken together, we identified that LlHSFC2 plays an active role in the general balance and maintenance of heat stress response by cooperating with HSFAs, and provided an important candidate for the enhanced thermotolerance breeding of crops and horticulture plants.

Dietary supplementation of vitamin D3 and calcium partially recover the compromised time budget and circadian rhythm of lying behavior in lactating cows under heat stress

Heat stress (HS) impedes cattle behavior and performance and is an animal comfort and welfare issue. The objective of this study was to characterize the time budget and circadian rhythm of lying behavior in dairy cows during HS and to assess the effect of dietary supplementation of vitamin D3 and Ca. Twelve multiparous Holstein cows (42.2 ± 5.6 kg milk/d; 83 ± 27 d in milk) housed in tiestalls were used in a split-plot design with the concentration of dietary vitamin E and Se as main plots (LESe: 11.1 IU/kg and 0.55 mg/kg, and HESe: 223 IU/kg and 1.8 mg/kg, respectively). Within each plot cows were randomly assigned to (1) HS with low concentrations of vitamin D3 and Ca (HS, 1,012 IU/kg and 0.73%, respectively), (2) HS with high concentrations of vitamin D3 and Ca (HS+D3/Ca; 3,764 IU/kg and 0.97%, respectively), or (3) thermoneutral pair-fed (TNPF) with low concentrations of vitamin D3 and Ca (1,012 IU/kg and 0.73%, respectively) in a Latin square design with 14-d periods and 7-d washouts. Lying behavior was measured with HOBO Loggers in 15-min intervals. Overall, cows in HS spent less time lying per day relative to TNPF from d 7 to 14. Daily lying time was positively correlated with milk yield, energy-corrected milk yield, and feed efficiency, and was negatively correlated with rectal temperature, respiratory rate, fecal calprotectin, tumor necrosis factor-α, and C-reactive protein. A treatment by time interaction was observed for lying behavior: the time spent lying was lesser for cows in HS than in TNPF in the early morning (0000-0600 h) and in the night (1800-2400 h). The circadian rhythm of lying behavior was characterized by fitting a cosine function of time into linear mixed model. Daily rhythmicity of lying was detected for cows in TNPF and HS+D3/Ca, whereas only a tendency in HS cows was observed. Cows in TNPF had the highest mesor (the average level of diurnal fluctuations; 34.2 min/h) and amplitude (the distance between the peak and mesor; 17.9 min/h). Both the mesor and amplitude were higher in HS+D3/Ca relative to HS (26.6 vs. 25.2 min/h and 3.91 min/h vs. 2.18 min/h, respectively). The acrophase (time of the peak) of lying time in TNPF, HS, and HS+D3/Ca were 0028, 0152, and 0054 h, respectively. Lastly, a continuous increase in daily lying time in TNPF was observed during the first 4 d of the experimental period in which DMI was gradually restricted, suggesting that intake restrictions may shift feeding behavior and introduce biases in the behavior of animals. In conclusion, lying behavior was compromised in dairy cows under HS, characterizing reduced daily lying time and disrupted circadian rhythms, and the compromised lying behavior can be partially restored by supplementation of vitamin D3 and Ca. Further research may be required for a more suitable model to study behavior of cows under HS.

Effects of Ban Lian Zi Jin San on intestinal inflammation and barrier function of heat-stressed broilers

Heat stress (HS) in broilers can be an environmental stressor that leads to intestinal inflammation and intestinal barrier damage. In order to examine the effect of Ban Lian Zi Jin San (BLZJS) on intestinal inflammation and barrier function in heat-stressed broilers, a model of chronic cyclic HS in broilers was established. A total of 300 twenty-one-day-old broilers were divided into 5 treatments at random. Broilers in 3 BLZJS dosage groups were kept in an ecologically controlled room at 37℃ ± 2℃ for 6 wk, and fed basal diets supplemented with 0.5, 1, and 2% BLZJS. Broilers in HS group were housed in the same room, but fed the basal diets. The findings indicated that supplementation of BLZJS significantly declined serum HS indexes levels (HSP70, HSP90), and increased serum antioxidant capacity (SOD and T-AOC) in broilers (P < 0.05). Besides, supplementation of BLZJS significantly inhibited the expression of HS indexes (HSP70 and HSP90), genes related to TLR4 inflammatory signal pathway (TLR4, MyD88, TRIF, IRAK-4, and NF-κB), inflammatory factors (IL-6 and TNF-α), and upregulated anti-inflammatory cytokines (IL-10) and intestinal tight junction-related genes (Occludin, Claudin-1, and ZO-1) in broiler jejunum (P < 0.05). On the other hand, supplementation of BLZJS could significantly reduce the protein expression of NF-κB and HSP70 in chick jejunum (P < 0.05). In conclusion, BLZJS inhibited the activation of TLR4 signal pathway and reduced the production of inflammatory factors, restoring the level of intestinal tight junction protein and protecting jejunal intestinal barrier function in heat-stressed broilers.

l-Carnitine pretreatment ameliorates heat stress-induced acute kidney injury by restoring mitochondrial function of tubular cells

A major complication of heat-related illness is the development of acute kidney injury (AKI) and damage to kidney tubular cells. Because kidney tubular cells use fatty acids as a major energy source, impaired fatty acid oxidation (FAO) may be associated with kidney injury due to heat stress. Carnitine is essential in the transportation of fatty acid into mitochondria for FAO. To date, there has been little attention given to the role of carnitine in heat-related illness and AKI. To evaluate the relationship between carnitine inadequacy and heat-related illness severity or AKI, we examined serum carnitine levels in patients with heat-related illness. We also used heat-stressed mice to investigate the effect of l-carnitine pretreatment on various kidney functions such as mitochondrial activity, proinflammatory changes in kidney macrophages, and histological damage. We observed an elevation in serum acylcarnitine levels, indicating carnitine insufficiency in patients with severe heat-related illness and/or AKI. l-Carnitine pretreatment ameliorated ATP production in murine tubular cell mitochondria and prevented a change in the kidney macrophage population dynamics observed in AKI: a decrease in tissue-resident macrophages, influx of bone marrow-derived macrophages, and change toward proinflammatory M1 polarization. In conclusion, carnitine insufficiency may be closely associated with severe heat-related illness and related AKI. Enhancement of the FAO pathway by l-carnitine pretreatment may prevent heat stress-induced AKI by restoring mitochondrial function.NEW & NOTEWORTHY Enhancing fatty acid oxidation (FAO) after acute kidney injury (AKI) improves renal outcomes. This report shows that carnitine insufficiency, which could inhibit FAO, correlates to severe heat-related illness and AKI in a clinical study. We also demonstrate that administering l-carnitine to mice improves mitochondrial respiratory function and prevents deleterious changes in renal macrophage, resulting in improved renal outcomes of heat-induced AKI. l-Carnitine may be an effective preventive treatment for severe heat-related illness and related AKI.

Host starvation and in hospite degradation of algal symbionts shape the heat stress response of the Cassiopea-Symbiodiniaceae symbiosis

BACKGROUND

Global warming is causing large-scale disruption of cnidarian-Symbiodiniaceae symbioses fundamental to major marine ecosystems, such as coral reefs. However, the mechanisms by which heat stress perturbs these symbiotic partnerships remain poorly understood. In this context, the upside-down jellyfish Cassiopea has emerged as a powerful experimental model system.

RESULTS

We combined a controlled heat stress experiment with isotope labeling and correlative SEM-NanoSIMS imaging to show that host starvation is a central component in the chain of events that ultimately leads to the collapse of the Cassiopea holobiont. Heat stress caused an increase in catabolic activity and a depletion of carbon reserves in the unfed host, concurrent with a reduction in the supply of photosynthates from its algal symbionts. This state of host starvation was accompanied by pronounced in hospite degradation of algal symbionts, which may be a distinct feature of the heat stress response of Cassiopea. Interestingly, this loss of symbionts by degradation was concealed by body shrinkage of the starving animals, resulting in what could be referred to as "invisible" bleaching.

CONCLUSIONS

Overall, our study highlights the importance of the nutritional status in the heat stress response of the Cassiopea holobiont. Compared with other symbiotic cnidarians, the large mesoglea of Cassiopea, with its structural sugar and protein content, may constitute an energy reservoir capable of delaying starvation. It seems plausible that this anatomical feature at least partly contributes to the relatively high stress tolerance of these animals in rapidly warming oceans. Video Abstract.

HD-Zip I protein LlHOX6 antagonizes homeobox protein LlHB16 to attenuate basal thermotolerance in lily

Homeodomain-leucine zipper (HD-Zip) I transcription factors are crucial for plant responses to drought, salt, and cold stresses. However, how they are associated with thermotolerance remains mostly unknown. We previously demonstrated that lily (Lilium longiflorum) LlHB16 (HOMEOBOX PROTEIN 16) promotes thermotolerance, whereas the roles of other HD-Zip I members are still unclear. Here, we conducted a transcriptomic analysis and identified a heat-responsive HD-Zip I gene, LlHOX6 (HOMEOBOX 6). We showed that LlHOX6 represses the establishment of basal thermotolerance in lily. LlHOX6 expression was rapidly activated by high temperature, and its protein localized to the nucleus. Heterologous expression of LlHOX6 in Arabidopsis (Arabidopsis thaliana) and overexpression in lily reduced their basal thermotolerance. In contrast, silencing LlHOX6 in lily elevated basal thermotolerance. Cooverexpressing or cosilencing LlHOX6 and LlHB16 in vivo compromised their functions in modulating basal thermotolerance. LlHOX6 interacted with itself and with LlHB16, although heterologous interactions were stronger than homologous ones. Notably, LlHOX6 directly bounds DNA elements to repress the expression of the LlHB16 target genes LlHSFA2 (HEAT STRESS TRANSCRIPTION FACTOR A2) and LlMBF1c (MULTIPROTEIN BRIDGING FACTOR 1C). Moreover, LlHB16 activated itself to form a positive feedback loop, while LlHOX6 repressed LlHB16 expression. The LlHOX6-LlHB16 heterooligomers exhibited stronger DNA binding to compete for LlHB16 homooligomers, thus weakening the transactivation ability of LlHB16 for LlHSFA2 and LlMBF1c and reducing its autoactivation. Altogether, our findings demonstrate that LlHOX6 interacts with LlHB16 to limit its transactivation, thereby impairing heat stress responses in lily.

Enhancing drought, heat shock, and combined stress tolerance in Myrobalan 29C rootstocks with foliar application of potassium nitrate

BACKGROUND

Drought and heat stress are significant concerns to food security in arid and semi-arid regions, where global warming is predicted to increase both frequency and severity. To cope with these challenges, the use of drought-tolerant plants or technological interventions are essential. In this study, the effects of foliar potassium nitrate (KNO3) application on the stress tolerance and recovery of Myrobalan 29C rootstocks (Prunus cerasifera Ehrh.) were evaluated. These rootstocks are widely recognized for their adaptability and are extensively used in fruit production. To assess their response, the rootstocks were subjected to drought, heat shock, or a combination of both stressors. Additionally, they were treated with 1.0% KNO3 via foliar application. Throughout the stress and recovery periods, various morphological, physiological, and bio-chemical parameters were measured.

RESULTS

Based on our results, KNO3 treatment improved LRWC, Chl stability, SC, and key stress markers like proline, MDA, H2O2, along with antioxidant enzymes CAT, SOD, POD during both stress and recovery phases. Moreover, our results emphasized KNO3's critical role in hormone regulation under stress. KNO3 application significantly altered hormone levels, notably increasing ABA during drought and heat shock stress, essential for stress response and adaptation. In contrast, IAA, GA, and cytokinin's significantly increased during the recovery phase in KNO3-treated plants, indicating improved growth regulation and stress recovery. In addition, KNO3 application improved the recovery process of the rootstocks by restoring their physiological and biochemical functions.

CONCLUSION

This study suggests that the application of foliar KNO3 is an effective technique for enhancing the drought and heat tolerance as well as the recovery of Myrobalan 29C rootstocks. These results hold significant value for farmers, policymakers, and researchers, as they offer crucial insights into the development of drought-tolerant crops and the management of climate change's adverse effects on agriculture.

A proxitome-RNA-capture approach reveals that processing bodies repress coregulated hub genes

Cellular condensates are usually ribonucleoprotein assemblies with liquid- or solid-like properties. Because these subcellular structures lack a delineating membrane, determining their compositions is difficult. Here we describe a proximity-biotinylation approach for capturing the RNAs of the condensates known as processing bodies (PBs) in Arabidopsis (Arabidopsis thaliana). By combining this approach with RNA detection, in silico, and high-resolution imaging approaches, we studied PBs under normal conditions and heat stress. PBs showed a much more dynamic RNA composition than the total transcriptome. RNAs involved in cell wall development and regeneration, plant hormonal signaling, secondary metabolism/defense, and RNA metabolism were enriched in PBs. RNA-binding proteins and the liquidity of PBs modulated RNA recruitment, while RNAs were frequently recruited together with their encoded proteins. In PBs, RNAs follow distinct fates: in small liquid-like PBs, RNAs get degraded while in more solid-like larger ones, they are stored. PB properties can be regulated by the actin-polymerizing SCAR (suppressor of the cyclic AMP)-WAVE (WASP family verprolin homologous) complex. SCAR/WAVE modulates the shuttling of RNAs between PBs and the translational machinery, thereby adjusting ethylene signaling. In summary, we provide an approach to identify RNAs in condensates that allowed us to reveal a mechanism for regulating RNA fate.

Biochemical, histological and transcriptomic analyses for the immunological organs provide insights into heat stress-induced disease susceptibility in Largemouth Bass

Aquaculture of Largemouth Bass (LMB, Micropterus salmoides), an economically important species, is badly affected by the outbreak of bacterial diseases in summer. However, the mechanisms underlying heat-induced disease susceptibility remain largely unknown. In this study, after exposure to 34 °C for 1, 7 and 14 d, the head kidney, spleen and blood of LMB were sampled for biochemical and histological assays to explore the effects of heat exposure on the oxidative and immunological indices. Compared to the controls maintained at 28 °C, chronic heat exposure (34 °C for 14 d) induced oxidative stress, caused cell apoptosis and decreased expression of the immunological genes in the head kidney and spleen tissues; and attenuated the blood immunological indices. Consistent with the impaired immunological functions, chronic heat exposure predisposed LMB to Aeromonas hydrophila infection and significantly (p < 0.001) increased tissue bacterial load. Furthermore, the effects of chronic heat exposure (heat), A. hydrophila infection (infection) and heat exposure followed by A. hydrophila infection (heat + infection) on gene expression in the head kidney and spleen of LMB were characterized by RNA sequencing. The results indicated that chronic heat exposure facilitated the bacteria-elicited changes in expression of the genes involved in a couple of metabolic and signaling pathways in both tissues. Upon heat + infection, the pathways involved in energy production and nutrients biosynthesis were enhanced, whereas those associated with the host cell functions such as cell-cell interactions and cell signaling were depressed. Our data provide new insights into the mechanisms underlying heat-induced disease susceptibility in LMB.

Metabolomics analysis to interpret changes in physiological and metabolic responses to chronic heat stress in Pekin ducks

Heat stress (HS) is a major environmental threat that affects duck production in subtropical and tropical regions, especially in summer. This study aimed to evaluate the physiological and metabolic responses of Pekin ducks to chronic HS conditions via liquid chromatography-mass spectrometry (LC-MS) using a paired-fed (PF) experimental design. On the basis of equivalent feed intake (HS vs. PF), HS significantly reduced growth performance and the percentage of leg and breast muscles, however, markedly increased the percentage of abdominal fat and breast skin fat. Serum metabolomics results revealed that heat-stressed ducks showed enhanced glycolysis and pentose phosphate pathways, as demonstrated by higher glucose 6-phosphate and 6-phogluconic acid levels in the PF vs. HS comparison. HS decreased hepatic mRNA levels of mitochondrial fatty acid β-oxidation-related genes (MCAD and SCAD) compared to the PF group, resulting in acetylcarnitine accumulation in serum. Moreover, HS elevated the concentrations of serum amino acids and mRNA levels of ubiquitination-related genes (MuRF1 and MAFbx) in the skeletal muscle and amino acid transporter-related genes (SLC1A1 and SLC7A1) and gluconeogenesis-related genes (PCK1 and PCase) in the liver compared to the PF group. When compared to the normal control group (NC), HS further decreased growth performance, but it elevated the abdominal fat rate. However, increased mRNA levels of ubiquitination-related genes and serum amino acid accumulation were not observed in the HS group compared to the NC group, implying that reduced feed intake masked the effect of HS on skeletal muscle breakdown and is a form of protection for the organism. These results suggest that chronic HS induces protein degradation in the skeletal muscle to provide amino acids for hepatic gluconeogenesis to provide sufficient energy, as Pekin ducks under HS conditions failed to efficiently oxidise fatty acids and ketones in the mitochondria, leading to poor growth performance and slaughter characteristics.

Deciphering temporal gene expression dynamics in multiple coral species exposed to heat stress: Implications for predicting resilience

Coral reefs are facing unprecedented threats due to global climate change, particularly elevated sea surface temperatures causing coral bleaching. Understanding coral responses at the molecular level is crucial for predicting their resilience and developing effective conservation strategies. In this study, we conducted a comprehensive gene expression analysis of four coral species to investigate their long-term molecular response to heat stress. We identified distinct gene expression patterns among the coral species, with laminar corals exhibiting a stronger response compared to branching corals. Heat shock proteins (HSPs) showed an overall decreasing expression trend, indicating the high energy cost associated with sustaining elevated HSP levels during prolonged heat stress. Peroxidases and oxidoreductases involved in oxidative stress response demonstrated significant upregulation, highlighting their role in maintaining cellular redox balance. Differential expression of genes related to calcium homeostasis and bioluminescence suggested distinct mechanisms for coping with heat stress among the coral species. Furthermore, the impact of heat stress on coral biomineralization varied, with downregulation of carbonic anhydrase and skeletal organic matrix proteins indicating reduced capacity for biomineralization in the later stages of heat stress. Our findings provide insights into the molecular mechanisms underlying coral responses to heat stress and highlight the importance of considering species-specific responses in assessing coral resilience. The identified biomarkers may serve as indicators of heat stress and contribute to early detection of coral bleaching events. These findings contribute to our understanding of coral resilience and provide a basis for future research aimed at enhancing coral survival in the face of climate change.

Comparative physiology reveals heat stress disrupts acid-base homeostasis independent of symbiotic state in the model cnidarian Exaiptasia diaphana

Climate change threatens the survival of symbiotic cnidarians by causing photosymbiosis breakdown in a process known as bleaching. Direct effects of temperature on cnidarian host physiology remain difficult to describe because heatwaves depress symbiont performance, leading to host stress and starvation. The symbiotic sea anemone Exaiptasia diaphana provides an opportune system to disentangle direct versus indirect heat effects on the host, as it can survive indefinitely without symbionts. We tested the hypothesis that heat directly impairs cnidarian physiology by comparing symbiotic and aposymbiotic individuals of two laboratory subpopulations of a commonly used clonal strain of E. diaphana, CC7. We exposed anemones to a range of temperatures (ambient, +2°C, +4°C and +6°C) for 15-18 days, then measured their symbiont population densities, autotrophic carbon assimilation and translocation, photosynthesis, respiration and host intracellular pH (pHi). Symbiotic anemones from the two subpopulations differed in size and symbiont density and exhibited distinct heat stress responses, highlighting the importance of acclimation to different laboratory conditions. Specifically, the cohort with higher initial symbiont densities experienced dose-dependent symbiont loss with increasing temperature and a corresponding decline in host photosynthate accumulation. In contrast, the cohort with lower initial symbiont densities did not lose symbionts or assimilate less photosynthate when heated, similar to the response of aposymbiotic anemones. However, anemone pHi decreased at higher temperatures regardless of cohort, symbiont presence or photosynthate translocation, indicating that heat consistently disrupts cnidarian acid-base homeostasis independent of symbiotic status or mutualism breakdown. Thus, pH regulation may be a critical vulnerability for cnidarians in a changing climate.

Protein thermal sensing regulates physiological amyloid aggregation

To survive, cells must respond to changing environmental conditions. One way that eukaryotic cells react to harsh stimuli is by forming physiological, RNA-seeded subnuclear condensates, termed amyloid bodies (A-bodies). The molecular constituents of A-bodies induced by different stressors vary significantly, suggesting this pathway can tailor the cellular response by selectively aggregating a subset of proteins under a given condition. Here, we identify critical structural elements that regulate heat shock-specific amyloid aggregation. Our data demonstrates that manipulating structural pockets in constituent proteins can either induce or restrict their A-body targeting at elevated temperatures. We propose a model where selective aggregation within A-bodies is mediated by the thermal stability of a protein, with temperature-sensitive structural regions acting as an intrinsic form of post-translational regulation. This system would provide cells with a rapid and stress-specific response mechanism, to tightly control physiological amyloid aggregation or other cellular stress response pathways.

Genetic diversity of SNPs associated with candidate genes for heat stress in Coreño Creole cattle in Mexico

Mexican Coreño Creole cattle are an important genetic resource adapted to local environmental conditions, so the study of their genetic diversity is essential to know their status and implement conservation programs and their use for crossbreeding. This study evaluated the genetic diversity of heat stress tolerance characteristics of Coreño Creole cattle, and a gene ontology enrichment was performed to know the biological processes in which candidate genes are involved. A total of 48 samples from three localities of Nayarit were genotyped using 777 K Illumina BovineHD BeadChip and 34 single nucleotide polymorphisms associated with candidate genes were selected. Genetic diversity was analyzed using allelic frequencies, expected heterozygosity (He), and Wright's fixation index (FST) using PLINK v1.9 software. Candidate genes were uploaded to the open-source GOnet for pathway analysis and linkage to biological processes. Coreño Creole cattle showed low genetic diversity (He = 0.35), the average FST obtained was 0.044, and only eight markers had allele frequencies higher than 0.80 in the three locations. We found that the genes GOT1 and NCAD are related in the biological processes of stress response, cell differentiation, and homeostatic process. The results revealed that Coreño Creole cattle have low genetic diversity; this could be due to the isolation of these populations.

Transcriptome and photosynthetic analyses provide new insight into the molecular mechanisms underlying heat stress tolerance in Rhododendron × pulchrum Sweet

Rhododendron species provide excellent ornamental use worldwide, yet heat stress (HS) is one of the major threats to their cultivation. However, the intricate mechanisms underlying the photochemical and transcriptional regulations associated with the heat stress response in Rhododendron remain relatively unexplored. In this study, the analyses of morphological characteristics and chlorophyll fluorescence (ChlF) kinetics showed that HS (40 °C/35 °C) had a notable impact on both the donor's and acceptor's sides of photosystem II (PSII), resulting in reduced PSII activity and electron transfer capacity. The gradual recovery of plants observed following a 5-day period of culture under normal conditions indicates the reversible nature of the HS impact on Rhododendron × pulchrum. Analysis of transcriptome data unveiled noteworthy trends: four genes associated with photosynthesis-antenna protein synthesis (LHCb1, LHCb2 and LHCb3) and the antioxidant system (glutamate-cysteine ligase) experienced significant down-regulation in the leaves of R. × pulchrum during HS. Conversely, aseorbate peroxidase and glutathione S-transferase TAU 8 demonstrated an up-regulated pattern. Furthermore, six down-regulated genes (phos-phoenolpyruvate carboxylase 4, sedoheptulose-bisphosphatase, ribose-5-phosphate isomerase 2, high cyclic electron flow 1, beta glucosidase 32 and starch synthase 2) and two up-regulated genes (beta glucosidase 2 and UDP-glucose pyrophosphorylase 2) implicated in photosynthetic carbon fixation and starch/sucrose metabolism were identified during the recovery process. To augment these insights, a weighted gene co-expression network analysis yielded a co-expression network, pinpointing the hub genes correlated with ChlF dynamics' variation trends. The cumulative results showed that HS inhibited the synthesis of photosynthesis-antenna proteins in R. × pulchrum leaves. This disruption subsequently led to diminished photochemical activities in both PSII and PSI, albeit with PSI exhibiting heightened thermostability. Depending on the regulation of the reactive oxygen species scavenging system and heat dissipation, photoprotection sustained the recoverability of R. × pulchrum to HS.

Heat shock response during the resolution of inflammation and its progressive suppression in chronic-degenerative inflammatory diseases

The heat shock response (HSR) is a crucial biochemical pathway that orchestrates the resolution of inflammation, primarily under proteotoxic stress conditions. This process hinges on the upregulation of heat shock proteins (HSPs) and other chaperones, notably the 70 kDa family of heat shock proteins, under the command of the heat shock transcription factor-1. However, in the context of chronic degenerative disorders characterized by persistent low-grade inflammation (such as insulin resistance, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases) a gradual suppression of the HSR does occur. This work delves into the mechanisms behind this phenomenon. It explores how the Western diet and sedentary lifestyle, culminating in the endoplasmic reticulum stress within adipose tissue cells, trigger a cascade of events. This cascade includes the unfolded protein response and activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome, leading to the emergence of the senescence-associated secretory phenotype and the propagation of inflammation throughout the body. Notably, the activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome not only fuels inflammation but also sabotages the HSR by degrading human antigen R, a crucial mRNA-binding protein responsible for maintaining heat shock transcription factor-1 mRNA expression and stability on heat shock gene promoters. This paper underscores the imperative need to comprehend how chronic inflammation stifles the HSR and the clinical significance of evaluating the HSR using cost-effective and accessible tools. Such understanding is pivotal in the development of innovative strategies aimed at the prevention and treatment of these chronic inflammatory ailments, which continue to take a heavy toll on global health and well-being.

Modeling the impact of heat stress on the toxicokinetics of toluene and acetone

Many workers can be exposed simultaneously to heat and volatile chemicals. In a controlled human exposure study, it was observed that an increase in ambient temperature was associated with increased blood concentrations for acetone and toluene. Based on the expected changes in physiological parameters that occur with an increase in ambient temperature, we aimed to develop a PBPK model for acetone and toluene that could account for the impact of temperature on the kinetics of these solvents. Changes in temperature-dependent physiological parameters (i.e. blood flows, cardiac output, alveolar ventilation) based on recent measurements in volunteers were introduced in the PBPK models to simulate observed blood concentrations for different temperature exposure conditions. Because initial simulations did not adequately predict solvent kinetics at any temperature, the most sensitive parameter (alveolar ventilation; Qp) was, therefore, optimized on experimental acetone blood concentrations to obtain a relationship with temperature. The new temperature-dependent Qp relationship gave Qp values consistent with the literature and estimated a mean increase of 19% at 30 °C (wet bulb globe temperature) compared to 21 °C. The integration of a new temperature-dependent Qp relationship in the PBPK toluene model yielded adequate simulations of the experimental data for toluene in blood, exhaled air and urine. With further validation with other solvents, the temperature-dependant PBPK model could be a useful tool to better assess the risks of simultaneous exposure to volatile chemicals and heat stress and interpret biomonitoring data in workers as well as in the general population. TRN: NCT02659410, Registration date: January 15, 2016.

The autumn low milk yield syndrome in Brown Swiss cows in continental climates: hypotheses and facts

Extensive research has been conducted globally on the impact of heat stress (HS) on animal health and milk production in dairy cows. In this article, we examine the possible reasons for the decrease in milk production in Brown Swiss (BS) cows during the autumn season, known as the autumn low milk yield syndrome (ALMYS). This condition has been extensively studied in high-yielding Holstein Friesian (HF) cattle and has also been observed in BS cows with a daily milk yield of around 30 kg. Our hypothesis is that the drop in milk yield and the increased prevalence of mastitis in autumn, as found in our recent studies, may be a long-term consequence of summer HS. We re-evaluate our previous findings in light of the possible manifestation of an HS-related form of ALMYS in BS cows. As milk yield, mastitis spread, and reproductive function of cows are interrelated and have seasonal dependence, we examine the consistency of our hypothesis with existing data. The significant drop in milk yield in BS cows in autumn (by 2.0-3.2 kg), as well as the threshold of milk yield decrease (temperature-humidity index of 70.7), may point in favour of the manifestation of ALMYS in BS cows, similar to HF cows. Only the percentage effect of seasonal factor (59.4%; p < 0.05) on milk yield of BS cows was significant. HS-related ALMYS provides a robust conceptual framework for diverse sets of productive and animal health data in BS cows, similar to observations in high-yielding HF cattle. However, the limitations associated with the lack of additional data (e.g. immunological indicators) suggest the need for further research to confirm ALMYS in BS breed.

Protective influence of supplementary betaine against heat stress by regulating intestinal oxidative status and microbiota composition in broiler chickens

To assess the impact of supplementing betaine (BT) under heat stress (HS) conditions on broiler performance and intestinal health from 21 to 42 days of age, a total of 150 male Ross 308 broilers were indiscriminately allotted to 3 treatments with 10 replications of 5 birds each. The control (CON) group was given a basal ration and accommodated at a thermoneutral condition (22 ± 1 °C), whereas the HS and HS + BT groups were raised under cyclic HS (33 ± 1 °C for 8 h and 22 ± 1 °C for 16 h per day) and received the basal ration without or with 1000 mg/kg BT, respectively. The HS reduced average daily gain (ADG); average daily feed intake; villus height (VH); VH to crypt depth (CD) ratio (VCR); activities of trypsin, lipase, glutathione peroxidase (GPX), and catalase; and enumeration of Lactobacillus and Bifidobacterium (P < 0.05) and augmented feed conversion ratio (FCR), CD, malondialdehyde (MDA) accumulation, and enumeration of Escherichia coli, Clostridium, and coliforms (P < 0.05). Conversely, BT supplementation heightened ADG, VH, VCR, trypsin activity, GPX activity, and populations of Lactobacillus and Bifidobacterium (P < 0.05) and lowered FCR, MDA accumulation, and Clostridium population (P < 0.05). Furthermore, the FCR value, trypsin and GPX activities, MDA content, and Bifidobacterium and Clostridium populations in the HS + BT group were nearly equivalent to those in the CON group. To conclude, feeding BT under HS conditions could improve broiler performance through improving intestinal health by specifically mitigating oxidative damage and enhancing the colonization of beneficial bacteria.

Physiological and transcriptional analyses reveal the resistance mechanisms of kiwifruit (Actinidia chinensis) mutant with enhanced heat tolerance

High temperature is an environmental stressor that severely threatens plant growth, development, and yield. In this study, we obtained a kiwifruit mutant (MT) of 'Hongyang' (WT) through 60Co-γ irradiation. The MT possessed different leaf morphology and displayed prominently elevated heat tolerance compared to the WT genotype. When exposure to heat stress, the MT plants exhibited stabler photosynthetic capacity and accumulated less reactive oxygen species, along with enhanced antioxidant capacity and higher expression levels of related genes in comparison with the WT plants. Moreover, global transcriptome profiling indicated that an induction in genes related to stress-responsive, phytohormone signaling, and transcriptional regulatory pathways, which might contribute to the upgrade of thermotolerance in the MT genotype. Collectively, the significantly enhanced thermotolerance of MT might be mainly attributed to profitable leaf structure variations, improved photosynthetic and antioxidant capacities, as well as extensive transcriptome reprogram. These findings would be insightful in elucidating the sophisticated mechanisms of kiwifruit response to heat stress, and suggest the MT holds great potential for future kiwifruit improvement with enhanced heat tolerance.

Yield compensation among plant regions improves soybean adaptation to short-term high-temperature stress during the reproductive period

Extreme heat events prolong the reproductive period and threaten soybean yield, whereas the specific stage at which individual fruits growth is delayed, and yield/yield components at the node, region, and plant levels under short-term heat stress in the reproductive stage are elusive. In this study, heat treatments (40/30 °C) were applied at 0-6 days (HTF0-6), 6-12 days (HTF6-12), 12-18 days (HTF12-18), and 0-12 days (HTF0-12) after the plant's first flower opened, and a control treatment (32/22 °C) was performed. The influences of heat stress on fruit development and yield/yield components at the node, region, and plant levels were investigated. As a result, the growth of individual fruits at nodes was delayed by HTF0-6 and HTF0-12, which was primarily caused by the prolongation of flowering to pods with a length of 2 cm. Interestingly, there were no significant differences in yield between the control treatment and the various high-temperature stress treatments at the plant level. Further analysis of the regional yield of soybean showed that the yield in the bottom and top regions of plants played significant roles in compensating for yield loss in the middle region after HTF0-12. Moreover, the delayed growth of individual fruits in the middle region was negatively correlated with yield. Our results indicate that the prolongation of fruit development induced by HTF0-6 and HTF0-12 may adversely affect soybean yield. However, the spatial compensation of plants could help maintain soybean yield under various short-term high temperature stress treatments during the reproductive period, which should be considered when breeding for and selecting heat-tolerant varieties.

Antioxidative response of parthenocarpic tomato, iaa9-3 and iaa9-5, under heat stress condition

It has previously been shown that parthenocarpic tomato mutants, iaa9-3 and iaa9-5, can adapt, grow, and produce fruit under heat-stress conditions. However, the physiological processes in those two mutants especially for the enzymatic system that works to neutralize ROS are not clear. The objective of this research was to determine how the scavenging enzyme system responds to the heat stress in those mutants. The iaa9-3, iaa9-5, and WT-MT as a control were cultivated under two environmental conditions; normal and heat stress conditions. Vegetative and reproductive growth were observed during cultivation period. The activities of catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) were investigated in both wild-type and parthenocarpic tomato mutants under normal and heat stress conditions. The results showed that under heat stress condition, the mutants, iaa9-3 and iaa9-5, and WT-MT resulted in reduction of the vegetative growth, but those mutants showed better growth than WT-MT. Higher chlorophyll content in iaa9-3 and iaa9-5 was observed under normal or heat stress condition. Despite their growth reduction under heat stress conditions, iaa9-3 and iaa9-5 resulted in the significant higher CAT, APX and SOD activity than WT-MT. The results suggest that higher chlorophyll content and enhanced CAT, APX and SOD activity in the iaa9-3 and iaa9-5 mutants are adaptive strategies to survive in heat stress conditions.

Heat stress-associated changes in the intestinal barrier, inflammatory signals, and microbiome communities in dairy calves

Recent studies indicate that heat stress pathophysiology is associated with intestinal barrier dysfunction, local and systemic inflammation, and gut dysbiosis. However, inconclusive results and a poor description of tissue-specific changes must be addressed to identify potential intervention targets against heat stress illness in growing calves. Therefore, the objective of this study was to evaluate components of the intestinal barrier, pro- and anti-inflammatory signals, and microbiota community composition in Holstein bull calves exposed to heat stress. Animals (mean age = 12 wk old; mean body weight = 122 kg) penned individually in temperature-controlled rooms were assigned to (1) thermoneutral conditions (constant room temperature at 19.5°C) and restricted offer of feed (TNR, n = 8), or (2) heat stress conditions (cycles of room temperatures ranging from 20 to 37.8°C) along with ad libitum offer of feed (HS, n = 8) for 7 d. Upon treatment completion, sections of the jejunum, ileum, and colon were collected and snap-frozen immediately to evaluate gene and protein expression, cytokine concentrations, and myeloperoxidase activity. Digesta aliquots of the ileum, colon, and rectum were collected to assess bacterial communities. Plasma was harvested on d 2, 5, and 7 to determine cytokine concentrations. Overall, results showed a section-specific effect of HS on intestinal integrity. Jejunal mRNA expression of TJP1 was decreased by 70.9% in HS relative to TNR calves. In agreement, jejunal expression of heat shock transcription factor-1 protein, a known tight junction protein expression regulator, decreased by 48% in HS calves. Jejunal analyses showed that HS decreased concentrations of IL-1α by 36.6% and tended to decrease the concentration of IL-17A. Conversely, HS elicited a 3.5-fold increase in jejunal concentration of anti-inflammatory IL-36 receptor antagonist. Plasma analysis of pro-inflammatory cytokines showed that IL-6 decreased by 51% in HS relative to TNR calves. Heat stress alteration of the large intestine bacterial communities was characterized by increased genus Butyrivibrio_3, a known butyrate-producing organism, and changes in bacteria metabolism of energy and AA. A strong positive correlation between the rectal temperature and pro-inflammatory Eggerthii spp. was detected in HS calves. In conclusion, this work indicates that HS impairs the intestinal barrier function of jejunum. The pro- and anti-inflammatory signal changes may be part of a broader response to restore intestinal homeostasis in jejunum. The changes in large intestine bacterial communities favoring butyrate-producing organisms (e.g., Butyrivibrio spp.) may be part of a successful response to maintain the integrity of the colonic mucosa of HS calves. The alteration of intestinal homeostasis should be the target for heat stress therapies to restore biological functions, and, thus highlights the relevance of this work.

The effect of Thai ginger (Kaempferia parviflora) extract orally administration on sperm production, semen preservation, and fertility in Thai native chickens under heat stress

Thai indigenous roosters are exposed to unsuitable temperatures and humidity, resulting in a lower reproductive potential. Kaempferia parviflora (KP) extract containing methoxyflavones was fed to roosters to improve their reproductive performance. Thirty-two Thai native roosters were orally administered KP extract at 300, 450, and 600 mg, calculated according to their average body weight, for at least 14 d before semen collection and continued supplementation until the end of the experiment. The nonsupplemented group served as the control. Fresh semen in terms of semen volume, sperm concentration, mass movement score, and sperm viability were evaluated. Semen preservation at 5°C and fertility test were examined for total motility (MOT), progressive motility (PMOT), sperm viability, and lipid peroxidation up to 48 h of storage. Testosterone concentrations and testicular function were also determined. The results showed that the highest sperm concentration and sperm motility of fresh semen were observed in KP extract at 600 mg (P < 0.001). KP extract at 600 mg resulted in higher sperm viability than the control and KP extract at 300 mg (P < 0.05), but was not different from KP at 450 mg (P > 0.05). The highest MOT, PMOT, and viability were found in the roosters that received 600 mg oral KP extract (P < 0.05), while those of the roosters that received oral KP extract 300 mg and the control were the lowest (P < 0.05) at all storage times. Lipid peroxidation was significantly lower in the KP extract up to 24 h (P < 0.05). The fertility and hatchability of the KP extract at 600 mg at T48 showed a minor decrease compared to the control at T0. These results might be inferred as a result of good spermatogenesis, as revealed by the results of histological examination and testosterone activity. In summary, oral administration of 600 mg KP extract improved sperm production and successfully preserved rooster semen for a long duration of up to 48 h of storage.

De novo transcriptome sequencing and annotation of the Antarctic polychaete Microspio moorei (Spionidae) with its characterization of the heat stress-related proteins (HSP, SOD & CAT)

We present a de novo transcriptome assembly for the non-model Antarctic polychaete worm Microspio moorei (Spionidae) collected during Antarctic field expedition in Fildes Bay, King George Island, Antarctic Peninsula, in 2017. Here, we report the first transcriptome reference array for Microspio spp. The gene sequences of the spionid worm were annotated from a wide range of functions (i.e., biological, and metabolic processes, catalytic processes, and catalytic activity). HSP70, HSP90 SOD and CAT families were compared to reported annelid transcriptomes and proteomes. The phylogenetic analysis using COI, 16S, and 18S markers effectively clusters the species within the family. However, it also casts uncertainty on the monophyletic nature of the Microspio genera, indicating the necessity for additional data and potentially requiring a reevaluation of its grouping. Within these protein families, 3D model software was used to create one representative of their protein structures. Structural predictions were compared with related reported annelids living at different temperatures and a human X-ray reference. We found structural differences (RMSE >1.8) between the human HSP proteins but no significant differences between the polychaete-predicted proteins (RMSE <1.2). These results encourage further research of heat stress-related proteins, the development of genetic markers for climate change-induced temperature stress, and the study of the underlying mechanisms of the heat response. Moreover, these results motivate the extension of these findings to congeneric species.