Short-term Heat Stress Research Articles

H3K4me2, H4K5ac and DNA methylation function in short- and long-term heat stress responses through affecting the expression of the stress-related genes in G. hirsutum

High temperature or heat stress (HS) is becoming a major threat to plant growth and crop production due to global warming. Plant adaptation to HS is markedly affected by epigenetic modifications like histone modifications and DNA methylation. However, the roles of the epigenetic modifications in modulating the responses to HS in cotton seedlings are largely unknown. In this study, the effects of short- and long-term HS on seedling growth, and the functions of histone modifications and DNA methylation in cotton responding to HS were investigated. The results showed that HS led to marked inhibition of growth, accompanied with changes in the transcript abundances of many HS-related genes and those in the contents of H3K4me2 and H4K5ac. Moreover, changes in H3K4me2 and H4K5ac levels were associated with those in the expression levels of multiple HS-responsive genes including GhHSFA1a (Heat shock factor A1a), GhHSFA2, GhHSP3 (Heat shock protein 3), GhRBCS (Small subunit of rubisco), GhERF1A (Ethylene response factor 1A) and GhHXK1 (Hexokinase 1) under high temperature stress. Also, alterations in DNA methylation levels were associated with those in the expression levels of GhHSFA1a upon HS. ChIP-qPCR results revealed that H3K4me2 levels elevated upon short-term HS, and H4K5ac levels raised during the whole HS process, particularly upon long-term HS. Virus-induced gene silencing (VIGS) experiments demonstrated that GhHSFA1a and GhHSFA2 positively, and GhERF1A and GhHXK1 negatively regulated HS tolerance in cotton. Collectively, these results suggest that H3K4me2, H4K5ac and DNA methylation modulate the expression of the HS-related genes, contributing to thermotolerant regulation in G. hirsutum.

Ectopic Expression of Os-miR408 Improves Thermo-Tolerance of Perennial Ryegrass

With global warming, high temperature stress has become a main threat to the growth of cool-season turfgrasses, including perennial ryegrass. As one of the conserved plant microRNA families, miR408s are known to play roles in various abiotic stresses, including cold, drought, salinity, and oxidative stress, but no report, thus far, was found for heat. Here, perennial ryegrass plants overexpressing rice Os-miR408 were used to investigate the role of miR408 in plant heat tolerance. Both wild type (WT) and miR408 transgenic perennial ryegrass plants (TG) were subjected to short-term heat stress at 38 °C for 72 h (experiment 1) or at 42 °C for 48 h (experiment 2), and then let recover for 7 days at optimum temperature. Morphological changes and physiological parameters, including antioxidative responses of TG and WT plants, were compared. The results showed that miR408 downregulated the expression of two putative target genes, PLASTOCYANIN and LAC3. Additionally, overexpression of Os-miR408 improved thermo-tolerance of perennial ryegrass, demonstrated by lower leaf lipid peroxidation and electrolyte leakage, and higher relative water content after both 38 and 42 °C heat stresses. In addition, the enhanced thermotolerance of TG plants could be associated with its morphological changes (e.g., narrower leaves, smaller tiller angles) and elevated antioxidative capacity. This study is the first that experimentally reported a positive role of miR408 in plant tolerance to heat stress, which provided useful information for further understanding the mechanism by which miR408 improved plant high-temperature tolerance, and offered a potential genetic resource for breeding heat-resistant cool-season turfgrass in the future.

Development of a gRNA-tRNA array of CRISPR/Cas9 in combination with grafting technique to improve gene-editing efficiency of sweet orange.

Here, we developed a reliable protocol for the fast and efficient gene-edited Anliu sweet orange plants production. The application of in vitro shoot grafting technology significantly reduced the growth cycle of transgenic seedlings, and the survival rate of cleft grafting was more than 90%. In addition, the mutation efficiency of the grafted geneedited sweet orange was significantly improved by short-term heat stress treatments. Thus, the combination strategy of grafting and heat stress treatments provided a reference for the fast and efficient multiplex gene editing of sweet orange.

Heat Stress at Early Reproductive Stage Differentially Alters Several Physiological and Biochemical Traits of Three Tomato Cultivars

Global warming is predicted to be increased in the upcoming years, resulting in frequent heatwaves or hot days worldwide, which can seriously affect crop growth and productivity. The responses of heat stress to several photophysiological and biochemical traits in three tomato cultivars were investigated in a pot experiment, and the heat tolerance capability of these cultivars was evaluated based on the investigated traits. The experiment was followed by a factorial completely randomized design, and the factors were (i) tomato cultivars (BARI Hybrid Tomato-5, BARI Tomato-14, and BARI Tomato-15) and (ii) heat stress (control and heat). The plants of three tomato cultivars were exposed to short-term heat stress (four days at 38/25 °C day/night temperature) at the flowering stage. The measured traits such as dry mass, leaf greenness (SPAD), maximum photochemical efficiency of photosystem II (Fv/Fm), photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), leaf chlorophyll, and carotenoid content were significantly declined, while the catalase and ascorbate peroxidase activities were increased by heat stress in all three tomato cultivars except BARI Tomato-15, which showed unaltered gs, E, and carotenoids. The percent reduction (over control) in SPAD, Fv/Fm, A, total chlorophyll, and total carotenoids was significantly lower (11, 06, 25, 34, and 19%, respectively), whereas the percent increase in catalase and ascorbate peroxidase activities was substantially higher (70 and 72%, respectively) in BARI Tomato-15 than in other cultivars. Based on the measured physiological and biochemical traits, the cultivar BARI Tomato-15 showed better heat tolerance than the other cultivars.

The transcription factor dFOXO controls the expression of insulin pathway genes and lipids content under heat stress in <i>Drosophila melanogaster</i>

The insulin/insulin-like growth factor signaling (IIS) pathway is one of the key elements in an organism’s response to unfavourable conditions. The deep homology of this pathway and its evolutionary conservative role in controlling the carbohydrate and lipid metabolism make it possible to use Drosophila melanogaster for studying its functioning. To identify the properties of interaction of two key IIS pathway components under heat stress in D. melanogaster (the forkhead box O transcription factor (dFOXO) and insulin-like peptide 6 (DILP6), which intermediates the dFOXO signal sent from the fat body to the insulin-producing cells of the brain where DILPs1–5 are synthesized), we analysed the expression of the genes dilp6, dfoxo and insulin-like receptor gene (dInR) in females of strains carrying the hypomorphic mutation dilp641 and hypofunctional mutation foxoBG01018. We found that neither mutation influenced dfoxo expression and its uprise under short-term heat stress, but both of them disrupted the stress response of the dilp6 and dInR genes. To reveal the role of identified disruptions in metabolism control and feeding behaviour, we analysed the effect of the dilp641 and foxoBG01018 mutations on total lipids content and capillary feeding intensity in imago under normal conditions and under short-term heat stress. Both mutations caused an increase in these parameters under normal conditions and prevented decrease in total lipids content following heat stress observed in the control strain. In mutants, feeding intensity was increased under normal conditions; and decreased following short-term heat stress in all studied strains for the first 24 h of observation, and in dilp641 strain, for 48 h. Thus, we may conclude that dFOXO takes part in regulating the IIS pathway response to heat stress as well as the changes in lipids content caused by heat stress, and this regulation is mediated by DILP6. At the same time, the feeding behaviour of imago might be controlled by dFOXO and DILP6 under normal conditions, but not under heat stress.

The transcription factor dfoxo controls the expression of insulin pathway genes and lipids content under heat stress in Drosophila melanogaster.

The insulin/insulin-like growth factor signaling (IIS) pathway is one of the key elements in an organism’s response to unfavourable conditions. The deep homology of this pathway and its evolutionary conservative role in controlling the carbohydrate and lipid metabolism make it possible to use Drosophila melanogaster for studying its functioning. To identify the properties of interaction of two key IIS pathway components under heat stress in D. melanogaster (the forkhead box O transcription factor (dfoxo) and insulin-like peptide 6 (dilp6), which intermediates the dfoxo signal sent from the fat body to the insulin-producing cells of the brain where DILPs1–5 are synthesized), we analysed the expression of the genes dilp6, dfoxo and insulin-like receptor gene (dInR) in females of strains carrying the hypomorphic mutation dilp641and hypofunctional mutation foxoBG01018. We found that neither mutation inf luenced dfoxo expression and its uprise under short-term heat stress, but both of them disrupted the stress response of the dilp6 and dInR genes. To reveal the role of identif ied disruptions in metabolism control and feeding behaviour, we analysed the effect of the dilp641 and foxoBG01018 mutations on total lipids content and capillary feeding intensity in imago under normal conditions and under short-term heat stress. Both mutations caused an increase in these parameters under normal conditions and prevented decrease in total lipids content following heat stress observed in the control strain. In mutants, feeding intensity was increased under normal conditions; and decreased following short-term heat stress in all studied strains for the f irst 24 h of observation, and in dilp641 strain, for 48 h. Thus, we may conclude that dfoxo takes part in regulating the IIS pathway response to heat stress as well as the changes in lipids content caused by heat stress, and this regulation is mediated by dilp6. At the same time, the feeding behaviour of imago might be controlled by dfoxo and dilp6 under normal conditions, but not under heat stress.

Dill seed germ development after short-term temperature stress.

NNew data on germ growth processes of dill seeds formed at the first and second branching orders after exposure to short-term heat stress (40 °C) are presented. Morphometric method and analysis of dill seed embryo growth in dynamics were used. The studies were carried out in 20152017 at the All-Russian Research Institute of Vegetable Growing, a branch of FSBSI FSCVG. Seeds of dill (Anethum graveolens L.) of the variety Centaurus from the first and second branching orders were the object of research. First, seeds were germinated in a thermostat. Then, swollen roots were exposed to a temperature of 40 °C according to the experiment scheme: 0 (control); 1; 2; 3; 4 and 5 days. After incubation, the seeds were transferred to standard conditions (temperature 20 °C) and germinated in Petri dishes on filter paper without light for 21 days. Germ size was measured using image analysis software. Critical embryo length and degree of underdevelopment were determined, and the ratio of embryo length to endosperm length (I Z/E) was calculated. Logistic regression with four parameters: b, c, d, e., was used to construct a germ growth curve. The relationship between the parameters was assessed using Pearson correlation analysis. The differences were considered statistically significant at P≤0.05. The duration of temperature action, which has an inhibitory effect on embryo growth, germination rate, the number of germinated seeds, were revealed. It was found that the embryos of seeds obtained from different branching orders have different sizes and have different intensity of growth under stress and standard conditions. It was shown that the effect of brief temperature (40 °C) on embryo growth depends on branching order and that embryos of seeds of the second branching order are more sensitive to high temperature. Morphometric parameters of the source were shown to play a critical role in the ability of dill seeds to resist the effect of temperature stressor during germination.

Multiomics analysis of kernel development in response to short-term heat stress at the grain formation stage in waxy maize.

Understanding the adaptive changes in maize kernels under high-temperature stress during grain formation stage is critical for developing strategies to alleviate the negative effects on yield and quality. In this study, we subjected waxy maize (Zea mays L. sinensis Kulesh) to four different temperature regimes from 1-15 d after pollination (DAP), namely normal day/normal night (control), hot day/normal night, normal day/hot night, and hot day/hot night. Compared to the control, the three high-temperature treatments inhibited kernel development and starch deposition. To understand how the kernels responded to high-temperature stress, their transcriptomes, proteomes, and metabolomes were studied at 10 DAP and 25 DAP. This showed that genes and proteins related to kernel development and starch deposition were up- and down-regulated, respectively, at 10 DAP, but this pattern was reversed at 25 DAP. Metabolome profiling under high-temperature stress showed that the accumulation patterns of metabolites at 10 DAP and 25 DAP were inversely related. Our multiomics analyses indicated that the response to high-temperature stress of signaling pathways mediated by auxin, abscisic acid, and salicylic acid was more active at 10 DAP than at 25 DAP. These results confirmed that high-temperature stress during early kernel development has a carry-over effect on later development. Taken together, our multiomics profiles of developing kernels under high-temperature stress provide insights into the processes that underlie maize yield and quality under high-temperature conditions.

Loss of obligate crossovers, defective cytokinesis and male sterility in barley caused by short-term heat stress.

Short-term heat stress during male meiosis causes defects in crossover formation, meiotic progression and cell wall formation in the monocot barley, ultimately leading to pollen abortion. High temperature conditions cause a reduction of fertility due to alterations in meiotic processes and gametogenesis. The male gametophyte development has been shown to be particularly sensitive to heat stress, and even short-term and modest temperature shifts cause alterations in crossover formation. In line with previous reports, we observed that male meiosis in the monocot barley exposed for 24-45h to heat stress (32-42°C) partially or completely eliminates obligate crossover formation and causes unbalanced chromosome segregation and meiotic abortion. Depending on the severity of heat stress, the structure and organization of the chromosomes were altered. In addition to alterations in chromosome structure and dynamics, heat treatment abolished or reduced the formation of a callose wall surrounding the meiocytes and interrupted the cell cycle progression leading to cytokinesis defects and microspore cell death.

Heat Stress Pre-Exposure May Differentially Modulate Plant Defense to Powdery Mildew in a Resistant and Susceptible Barley Genotype.

Heat stress negatively affects barley production and under elevated temperatures defense responses to powdery mildew (Blumeria graminis f. sp. hordei, Bgh) are altered. Previous research has analyzed the effects of short-term (30 s to 2 h) heat stress, however, few data are available on the influence of long-term exposure to heat on powdery mildew infections. We simultaneously assessed the effects of short and long term heat pre-exposure on resistance/susceptibility of barley to Bgh, evaluating powdery mildew infection by analyzing symptoms and Bgh biomass with RT-qPCR in barley plants pre-exposed to high temperatures (28 and 35 °C from 30 s to 5 days). Plant defense gene expression after heat stress pre-exposure and inoculation was also monitored. Our results show that prolonged heat stress (24, 48 and 120 h) further enhanced Bgh susceptibility in a susceptible barley line (MvHV118-17), while a resistant line (MvHV07-17) retained its pathogen resistance. Furthermore, prolonged heat stress significantly repressed the expression of several defense-related genes (BAX inhibitor-1, Pathogenesis related-1b and Respiratory burst oxidase homologue F2) in both resistant and susceptible barley lines. Remarkably, heat-suppressed defense gene expression returned to normal levels only in MvHV07-17, a possible reason why this barley line retains Bgh resistance even at high temperatures.

Towards enhancing coral heat tolerance: a \u201cmicrobiome transplantation\u201d treatment using inoculations of homogenized coral tissues

BackgroundMicrobiome manipulation could enhance heat tolerance and help corals survive the pressures of ocean warming. We conducted coral microbiome transplantation (CMT) experiments using the reef-building corals, Pocillopora and Porites, and investigated whether this technique can benefit coral heat resistance while modifying the bacterial microbiome. Initially, heat-tolerant donors were identified in the wild. We then used fresh homogenates made from coral donor tissues to inoculate conspecific, heat-susceptible recipients and documented their bleaching responses and microbiomes by 16S rRNA gene metabarcoding.ResultsRecipients of both coral species bleached at lower rates compared to the control group when exposed to short-term heat stress (34 °C). One hundred twelve (Pocillopora sp.) and sixteen (Porites sp.) donor-specific bacterial species were identified in the microbiomes of recipients indicating transmission of bacteria. The amplicon sequence variants of the majority of these transmitted bacteria belonged to known, putatively symbiotic bacterial taxa of corals and were linked to the observed beneficial effect on the coral stress response. Microbiome dynamics in our experiments support the notion that microbiome community evenness and dominance of one or few bacterial species, rather than host-species identity, were drivers for microbiome stability in a holobiont context.ConclusionsOur results suggest that coral recipients likely favor the uptake of putative bacterial symbionts, recommending to include these taxonomic groups in future coral probiotics screening efforts. Our study suggests a scenario where these donor-specific bacterial symbionts might have been more efficient in supporting the recipients to resist heat stress compared to the native symbionts present in the control group. These findings urgently call for further experimental investigation of the mechanisms of action underlying the beneficial effect of CMT and for field-based long-term studies testing the persistence of the effect.AsHw_a2eZumNFLCqTFt1FJVideo abstract

Effects of recovery from short-term heat stress exposure on feed intake, plasma amino acid profiles, and metabolites in growing pigs.

Heat stress (HS) damages health and decreases performance variables in pigs, and if severe enough, causes mortality. However, metabolic changes under HS and recovery following HS are poorly understood. Therefore, this study was aimed to expose the essential mechanisms by which growing pigs respond to HS and the temporal pattern of plasma concentrations (PC) of amino acids (AAs) and metabolites. Crossbred male growing pigs were penned separately and allowed to adapt to thermal-neutral (TN) conditions (20°C and 80% relative humidity; TN[-1D]). On the first day, all pigs were exposed to HS for 24 h (36°C and 60% relative humidity), then to TN conditions for 5 days (TN[2D] to TN[5D]). All pigs had ad libitum access to water and 3 kg feed twice daily. Rectal temperature (RT) and feed intake (FI) were determined daily. HS pigs had higher RT (40.72°C) and lower (50%) FI than TN(-1D) pigs (p < 0.01). The PC of indispensable (threonine, valine, and methionine) and dispensable (cysteine and tyrosine) AAs were higher (p < 0.05) in HS than TN(-1D) pigs and remained increased during recovery time. Nonprotein α-aminobutyric acid and β-alanine concentrations were higher (p < 0.05) in HS than TN(-1D) pigs. The metabolite concentration of creatinine was higher (p < 0.01) under HS treatment than other treatments, but that of alanine and leucine remained increased (p < 0.05) through 5 d of recovery. In summary, some major differences were found in plasma AA profiles and metabolites between HS- and TN-condition pigs. This indicates that the HS pigs were forced to alter their metabolism, and these results provide information about mechanisms of acute HS responses relative to the recovery time.

High Temperature Alters Secondary Metabolites and Photosynthetic Efficiency in Heracleum sosnowskyi.

Due to global warming, invasive species have spread across the world. We therefore studied the impact of short-term (1 day or 2 days) and longer (7 days) heat stress on photosynthesis and secondary metabolites in Heracleum sosnowskyi, one of the important invasive species in the European Union. H. sosnowskyi leaves exposed to short-term heat stress (35 °C/1 d) showed a decrease in chlorophyll and maximum potential quantum efficiency of photosystem II (Fv/Fm) compared to control, 35 °C/2 d, or 30 °C/7 d treatments. In turn, the high level of lipid peroxidation and increased H2O2 accumulation indicated that the 30 °C/7 d stress induced oxidative damage. The contents of xanthotoxin and bergapten were elevated in the 2 d and 7 d treatments, while isopimpinellin was detected only in the heat-stressed plants. Additionally, the levels of free proline and anthocyanins significantly increased in response to high temperature, with a substantially higher increase in the 7 d (30 °C) treatment. The results indicate that the accumulation of proline, anthocyanins, and furanocoumarins, but not of phenolic acids or flavonols, contributes to protection of H. sosnowskyi plants against heat stress. Further studies could focus on the suppression of these metabolites to suppress the spread of this invasive species.

The Effect of Foliar Putrescine Application, Ammonium Exposure, and Heat Stress on Antioxidant Compounds in Cauliflower Waste.

This work has been focused on the study of how we can affect the short heat stress on the bioactive compounds content. Some recent investigations have observed that management of nitrogen fertilization can alleviate short-term heat effects on plants. Additionally, the short-term heat stress can be also ameliorated by using putrescine, a polyamine, due to its crucial role in the adaptation of plants to heat stress Therefore, different NO3−/NH4+ ratios and a foliar putrescine treatment have been used in order to increase tolerance to thermal stress in order to take advantage of the more frequent and intense heat waves and make this crop more sustainable. So, other objective of this work is to make the cauliflower waste more attractive for nutraceutical and pharmaceutical preparations. Thus, the effect of a thermal stress combined with a 50:50 NO3−/NH4+ ratio in the nutrient solution, and the foliar application of 2.5 mM putrescine increased in the content of various sugars (inositol, glucose, and fructose), total phenolic compounds and polyamines, as well as in the antioxidant activity. The greatest accumulation of these compounds was observed in young leaves. Our results show from a physiological and agronomic point of view, that the foliar application of putrescine and the 50:50 NO3−/NH4+ treatment managed to alleviate the negative effects of the abiotic stress suffered at high temperature, yielding plants with higher antioxidant compounds content.

Factors affecting the rapid changes of protein under short-term heat stress

BackgroundProtein content determines the state of cells. The variation in protein abundance is crucial when organisms are in the early stages of heat stress, but the reasons affecting their changes are largely unknown.ResultsWe quantified 47,535 mRNAs and 3742 proteins in the filling grains of wheat in two different thermal environments. The impact of mRNA abundance and sequence features involved in protein translation and degradation on protein expression was evaluated by regression analysis. Transcription, codon usage and amino acid frequency were the main drivers of changes in protein expression under heat stress, and their combined contribution explains 58.2 and 66.4% of the protein variation at 30 and 40 °C (20 °C as control), respectively. Transcription contributes more to alterations in protein content at 40 °C (31%) than at 30 °C (6%). Furthermore, the usage of codon AAG may be closely related to the rapid alteration of proteins under heat stress. The contributions of AAG were 24 and 13% at 30 and 40 °C, respectively.ConclusionIn this study, we analyzed the factors affecting the changes in protein expression in the early stage of heat stress and evaluated their influence.

&lt;p class="Body"&gt;&lt;strong&gt;Effects of short-term heat stress on the development and reproduction of predatory mite &lt;em&gt;Neoseiulus barkeri&lt;/em&gt; (Acari, Phytoseiidae)&lt;/strong&gt;&lt;/p&gt;

The predatory mite Neoseiulus barkeri (Acari: Phytoseiidae), which is one of the best natural enemies, has been used as a biological control agent against multiple insect pests, such as spider mite, Tetranychus urticae and thrips. Its growth and development were affected by the environmental temperature changes. This study was conducted to evaluate the hatching rate of the eggs and the immature developmental times of N. barkeri after incubation of the eggs under heat stress at 38, 40 and 42℃, 85% ± 5% RH and a 16h:8h light: dark (L:D) photoperiod for 2, 4 and 6h. After adult females emerged, they were treated under the same conditions again, and the parameters such as oviposition period, fecundity and female longevity were observed. The results showed that with the increase of the temperature and the extension of the duration of the heat stress, the hatching rate was lower. The eggs treated at 42℃ for 2h or more could not hatch, and the developmental duration of each immature stage showed a trend of decreasing at first and then increasing. The fastest development was observed after incubation of eggs at 40℃ for 2h, and the shortest developmental duration was 4.60d. Under the condition of 38℃, the oviposition period and life span of adult females were shortened with the extension of treatment time, and the fecundity decreased at first and then increased. At 40℃, the fecundity, oviposition period and longevity of adult females showed a trend of gradual increase with the extension of treatment time. The shortest oviposition period, the lowest fecundity and the shortest life span of adult females were 12.14d, 18.92 eggs and 16.65d, respectively after incubation of eggs at 40℃, for 2h. Therefore, the short-term heat stress had a significant effect on the hatching rate and the duration of the immature stage, and also had a negative effect on the fecundity, oviposition period and longevity of adult females. In rearing and field release, heat stress should be avoided as much as possible to achieve the best predation and control effect of N. barkeri.

Characterization of Short-Term Heat Stress in Holstein Dairy Cows Using Altered Indicators of Metabolomics, Blood Parameters, Milk MicroRNA-216 and Characteristics

Simple SummaryIn this study, we characterize the influence of short-term (4 days) heat stress on Holstein cows during early lactation. The use of indicators, such as production performance, physiological variables, blood parameters, micro-RNA expression, and metabolomes, in heat-stressed cows during early lactation—which is a high-stress phase—may provide insights into how to deal with the level of damage to dairy cows, through appropriate nutritional and management strategies. We identify that short-term heat stress has a negative effect, to some extent, on feed and water intake, rectal temperature, heart rate, blood hematology and metabolites, milk characteristics, miRNA expression in milk, and metabolomics in blood.This study aims to characterize the influence of short-term heat stress (HS; 4 day) in early lactating Holstein dairy cows, in terms of triggering blood metabolomics and parameters, milk yield and composition, and milk microRNA expression. Eight cows (milk yield = 30 ± 1.5 kg/day, parity = 1.09 ± 0.05) were homogeneously housed in environmentally controlled chambers, assigned into two groups with respect to the temperature humidity index (THI) at two distinct levels: approximately ~71 (low-temperature, low-humidity; LTLH) and ~86 (high-temperature, high-humidity; HTHH). Average feed intake (FI) dropped about 10 kg in the HTHH group, compared with the LTLH group (p = 0.001), whereas water intake was only numerically higher (p = 0.183) in the HTHH group than in the LTLH group. Physiological parameters, including rectal temperature (p = 0.001) and heart rate (p = 0.038), were significantly higher in the HTHH group than in the LTLH group. Plasma cortisol and haptoglobin were higher (p < 0.05) in the HTHH group, compared to the LTLH group. Milk yield, milk fat yield, 3.5% fat-corrected milk (FCM), and energy-corrected milk (ECM) were lower (p < 0.05) in the HTHH group than in the LTLH group. Higher relative expression of milk miRNA-216 was observed in the HTHH group (p < 0.05). Valine, isoleucine, methionine, phenylalanine, tyrosine, tryptophan, lactic acid, 3-phenylpropionic acid, 1,5-anhydro-D-sorbitol, myo-inositol, and urea were decreased (p < 0.05). These results suggest that early lactating cows are more vulnerable to short-term (4 day) high THI levels—that is, HTHH conditions—compared with LTLH, considering the enormous negative effects observed in measured blood metabolomics and parameters, milk yield and compositions, and milk miRNA-216 expression.

Scrotal thermoregulation and sequential sperm abnormalities in buffalo bulls (Bubalus bubalis) under short-term heat stress.

Heat stress reduces the reproductive capacity of bulls raised in tropical climate. However, the reestablishment of scrotal thermoregulation and the dynamics of sperm defects emergence after stress are not completely known in buffaloes. Thus, the study aimed to evaluate the effect of short-term heat stress over scrotal thermoregulation and sperm attributes, relating them to spermatogenesis stages. Five buffalo bulls went through scrotal insulation during 48h (from day 0 to day 2). Semen samples were collected every 7 days (from day -7 to day 49) and analyzed about the progressive motility, viability, and sperm morphology. Heat stress significantly destabilized scrotal thermoregulation (P<0.001). Scrotal temperature was from 4.2 to 6.3°C lower than the core body temperature, except on insulation days (P<0.001), and returned to the basal condition five days after the removal of the stressing stimulus. More significant deleterious effects were observed in sperm morphology than in cell concentration, motility, and viability. The chronology of morphologic defects expression demonstrated tail defects (days 7-14), cytoplasmic droplets (days 14-28), and head defects (day 28), returning to pre-insulation condition 35 days after the thermal challenge. Thus, hyperthermia harmed more intensely spermatozoa in epididymal transit, elongated spermatids, and secondary spermatocytes. It is concluded that water buffalo bulls present a peculiar manifestation of sperm morphology after short-term stress, indicating an important difference related to the bovine species. Therefore, during the andrological evaluation of buffalo bulls, it is necessary to avoid the allometric extrapolation between these species.

RNA-Seq Highlights Molecular Events Associated With Impaired Pollen-Pistil Interactions Following Short-Term Heat Stress in Brassica napus.

The global climate change is leading to increased frequency of heatwaves with crops getting exposed to extreme temperature events. Such temperature spikes during the reproductive stage of plant development can harm crop fertility and productivity. Here we report the response of short-term heat stress events on the pollen and pistil tissues in a commercially grown cultivar of Brassica napus. Our data reveals that short-term temperature spikes not only affect pollen fitness but also impair the ability of the pistil to support pollen germination and pollen tube growth and that the heat stress sensitivity of pistil can have severe consequences for seed set and yield. Comparative transcriptome profiling of non-stressed and heat-stressed (40°C for 30 min) pollen and pistil (stigma + style) highlighted the underlying cellular mechanisms involved in heat stress response in these reproductive tissues. In pollen, cell wall organization and cellular transport-related genes possibly regulate pollen fitness under heat stress while the heat stress-induced repression of transcription factor encoding transcripts is a feature of the pistil response. Overall, high temperature altered the expression of genes involved in protein processing, regulation of transcription, pollen-pistil interactions, and misregulation of cellular organization, transport, and metabolism. Our results show that short episodes of high-temperature exposure in B. napus modulate key regulatory pathways disrupted reproductive processes, ultimately translating to yield loss. Further investigations on the genes and networks identified in the present study pave a way toward genetic improvement of the thermotolerance and reproductive performance of B. napus varieties.

Early life thermal stress modulates hepatic expression of thermotolerance related genes and physiological responses in two rabbit breeds

There are few data about early thermal conditioning (TC) and its effect on later life in rabbits. Therefore, the present study aimed to investigate the impact of exposing two rabbit breeds to early age short-term heat stress (EA-STHS) on physiological parameters and hepatic expression levels of some genes. Rabbits from New Zealand White (NZW) and Baladi Black (BB) rabbit breeds were reared in a controlled environmental chamber (28 ± 2 °C and 40 ± 2% RH). At 42 days of age, rabbits from both breeds were equally divided into two groups; control (untreated) and heat exposed groups (kept at 36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, rabbits of all groups were re-exposed to acute heat stress (36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, plasma CORT, plasma MDA, and hepatic MDA had significantly lower levels in the rabbits from the two breeds subjected to EA-STHS than untreated control groups. plasma TAC and the relative hepatic expression of all the studied genes like Hsp70, HspA9, Hsp90α and UCP2 had significantly higher levels in EA-STHS treated NZW and BB rabbits compared with the control groups. In conclusion, the results suggest that EA-STHS has a long-lasting effect on the later life response to acute heat stress in NZW and BB breeds, as indicated by the hepatic expression profile of several genes, corticosterone, and antioxidant parameters. Additionally, each breed had characteristic patterns for the tested parameters at each time point and treatment. HIGHLIGHTS Rabbits are susceptible to thermal stress, which is associated with adverse effects on production and reproduction traits. Early-age thermal conditioning is one of the suggested protective treatments to reduce the heat stress adverse effects. Early age short-term thermal stress may induce thermotolerance ability to later time heat exposure in both rabbit breeds.