Heat Stress Treatment Research Articles

Characterisation of the heat shock protein Tid and its involvement in stress response regulation in Apis cerana.

Objective: The impact of various environmental stresses on native Apis cerana cerana fitness has attracted intense attention in China. However, the defence responses of A. cerana cerana to different stressors are poorly understood. Here, we aimed to elucidate the regulatory mechanism mediated by the tumorous imaginal discs (Tid) protein of A. cerana cerana (AccTid) in response to stressors. Methods: We used some bioinformatics softwares to analyse the characterisation of Tid. Then, qRT-PCR, RNA interference and heat resistance detection assays were used to explore the function of Tid in stress response in A. cerana cerana. Results: AccTid is a homologous gene of human Tid1 and Drosophila Tid56, contains a conserved J domain and belongs to the heat shock protein DnaJA subfamily. The level of AccTid induced expression was increased under temperature increases from 40°C to 43°C and 46°C, and AccTid knockdown decreased the heat resistance of A. cerana cerana, indicating that the upregulation of AccTid plays an important role when A. cerana cerana is exposed to heat stress. Interestingly, contrary to the results of heat stress treatment, the transcriptional level of AccTid was inhibited by cold, H2O2 and some agrochemical stresses and showed no significant change under ultraviolet ray and sodium arsenite stress. These results suggested that the requirement of A. cerana cerana for Tid differs markedly under different stress conditions. In addition, knockdown of AccTid increased the mRNA levels of some Hsps and antioxidant genes. The upregulation of these Hsps and antioxidant genes may be a functional complement of AccTid knockdown. Conclusion: AccTid plays a crucial role in A. cerana cerana stress responses and may mediate oxidative damage caused by various stresses. Our findings will offer fundamental knowledge for further investigations of the defence mechanism of A. cerana cerana against environmental stresses.

Transcriptome Analysis in High Temperature Inhibiting Spermatogonial Stem Cell Differentiation In Vitro.

As one of the factors of male infertility, high temperature induces apoptosis of differentiated spermatogenic cells, sperm DNA oxidative damage, and changes in morphology and function of Sertoli cells. Spermatogonial stem cells (SSCs) are a type of germline stem cells that maintain spermatogenesis through self-renewal and differentiation. At present, however, the effect of high temperature on SSC differentiation remains unknown. In this study, an in vitro SSC differentiation model was used to investigate the effect of heat stress treatment on SSC differentiation, and RNA sequencing (RNA-seq) was used to enrich the key genes and pathways in high temperature inhibiting SSC differentiation. Results show that 2days of 37°C or 43°C (30min per day) heat stress treatment significantly inhibited SSC differentiation. The differentiation-related genes c-kit, stra8, Rec8, Sycp3, and Ovol1 were down-regulated after 2 and 4days of heat stress at 37°C. The transcriptome of SSCs was significantly differentially expressed on days 2 and 4 after heat stress treatment at 37°C. In total, 1660 and 7252 differentially expressed genes (DEGs) were identified by RNA-seq in SSCs treated with heat stress at 37°C for 2 and 4days, respectively. KEGG pathway analysis showed that p53, ribosome, and carbon metabolism signaling pathways promoting stem cell differentiation were significantly enriched after heat stress treatment at 37°C. In conclusion, 37°C significantly inhibited SSC differentiation, and p53, ribosome, and carbon metabolism signaling pathways were involved in this differentiation inhibition process. The results of this study provide a reference for further investigation into the mechanism by which high temperature inhibits SSC differentiation.

Effects of dietary antioxidant supplementation on metabolism and inflammatory biomarkers in heat-stressed dairy cows

Heat-stress-induced inflammation may be ameliorated by antioxidant supplementation due to the purported effects of increased production of reactive oxygen species or oxidative stress on the gastrointestinal tract barrier. Thus, study objectives were to evaluate whether antioxidant supplementation [AGRADO Plus 2.0 (AP); EW Nutrition] affects metabolism and inflammatory biomarkers in heat-stressed lactating dairy cows. Thirty-two mid-lactation multiparous Holstein cows were assigned to 1 of 4 dietary-environmental treatments: (1) thermoneutral (TN) conditions and fed a control diet (TN-CON; n = 8), (2) TN and fed a diet with AP (10 g antioxidant; n = 8), (3) heat stress (HS) and fed a control diet (HS-CON; n = 8), or (4) HS and fed a diet with AP (HS-AP; n = 8). The trial consisted of a 23-d prefeeding phase and 2 experimental periods (P). Respective dietary treatments were top-dressed starting on d 1 of the prefeeding period and continued daily throughout the duration of the experiment. During P1 (4 d), baseline data were collected. During P2 (7 d), HS was artificially induced using an electric heat blanket (Thermotex Therapy Systems Ltd.). During P2, the effects of treatment, day, and treatment-by-day interaction were assessed using PROC MIXED of SAS (SAS Institute Inc.). Heat stress (treatments 3 and 4) increased rectal, vaginal, and skin temperatures (1.2°C, 1.1°C, and 2.0°C, respectively) and respiration rate (33 breaths per minute) relative to TN cows. As expected, HS decreased dry matter intake, milk yield, and energy-corrected milk yield (32%, 28%, and 28% from d 4 to 7, respectively) relative to TN. There were no effects of AP on body temperature indices or production. Milk fat, protein, and lactose concentrations remained unaltered by HS or AP; however, milk urea nitrogen was increased during HS regardless of AP supplementation (26% relative to TN). Circulating glucose remained unchanged by HS, AP, or time. Additionally, HS decreased circulating glucagon (29% from d 3 to 7 relative to TN), but there was no additional effect of AP. There was a tendency for nonesterified fatty acid concentrations to be increased in HS-AP cows throughout P2 (60% relative to TN-CON), whereas it remained similar in all other treatments. Blood urea nitrogen increased for both HS treatments from d 1 to 3 before steadily decreasing from d 5 to 7, with the overall increase being most pronounced in HS-CON cows (27% relative to TN-CON). Further, supplementing AP decreased blood urea nitrogen in HS-AP on d 3 relative to HS-CON (15%). Circulating serum amyloid A tended to be and lipopolysaccharide binding protein was increased by HS, but neither acute-phase protein was affected by AP. Overall, AP supplementation appeared to marginally alter metabolism but did not meaningfully alter inflammation during HS.

Beneficial Effect of Exogenously Applied Calcium Chloride on the Anatomy and Fast Chlorophyll Fluorescence in Rhododendron × pulchrum Leaves Following Short-Term Heat Stress Treatment

The heat tolerance of plants can be improved by using exogenous calcium chloride (CaCl2) to cope with temperature fluctuations. Since global climates continue to warm, it is important to further explore the way in which plants respond to heat stress with the use of CaCl2. We aimed to explore the effect of exogenous CaCl2 on the leaf microstructure, leaf epidermal ultrastructure, and chlorophyll a fluorescence of Rhododendron × pulchrum (R. × pulchrum) under heat stress. In the leaves of R. × pulchrum treated with exogenous CaCl2, compared to the control, the thickness of the epidermis, spongy tissues, and stomatal aperture increased, whereas the stomata density and ratio of closed/open stomata decreased. In the leaves of R. × pulchrum under heat stress conditions, compared to the control, the values of the maximal photochemical efficiency of photosystem II (Fv/Fm), the performance index on an absorption basis (PIABS), the quantum yield for the reduction of terminal electron acceptors on the acceptor side of PSI (φRo), and the energy absorbed per unit cross-section of a photosynthesizing object at the moment of achieving the fluorescence maximum (ABS/CSM) all decreased, whereas the quantum yield of the energy dissipation (φDo) increased significantly. However, these differences disappeared when R. × pulchrum was treated with exogenous CaCl2. This suggests that exogenous CaCl2 can improve the heat tolerance in R. × pulchrum by regulating the leaf anatomical structure and the behavior of epidermal cells and stomata in leaves, protecting the stability of photosystems I and II and improving the electron transfer from QA to QB. Our study could provide a theoretical basis for the breeding, further research, and utilization of Rhododendron in the context of global warming.

Negative effects of heat stress on ovarian tissue in female rabbit.

Numerous studies have highlighted the role of miRNA in the deformation and necrosis of cells of ovarian tissue caused by heat stress (HS), which ultimately affects ovarian function. Although the role of small RNAs has been investigated in alterations in ovarian tissue functioning in response to HS, the expression profile of ovarian miRNA has been explored to a lesser extent. In this study, female rabbits were subject to HS treatment by using electrical heater. The current work demonstrated that HS could significantly change physiological performance of female rabbits including body weight, rectal temperature and relative ovary weight, and significantly reduce serum IL-2, IL-8, CAT, and GSH-Px concentrations by enzyme-linked immunosorbent assay (ELISA) technique. As a result, an increase in apoptosis in ovarian cells, as well as unhealthy follicles, were observed by Hematoxylin-eosin (HE) and TUNEL staining. Additionally, small RNA-seq revealed changes in the miRNA expression profile of rabbit ovaries under HS. Five hundred fourteen miRNAs were obtained including known miRNAs 442 and novel miRNAs 72. Among these miRNAs, 23 miRNAs were significantly expressed under HS. Eleven differentially expressed miRNAs (DE miRNAs) and 9 their predicted targets were confirmed by qPCR, which were expected miRNA-mRNA negative regulation pattern. Among the DE miRNAs and targets, miR-141-39 may target COQ6, miR-449a-5p and miR-34c-5p may control RFC5 and RTN2 together, miR-449a-5p may target ACADVL, miR-34c-5p potentially targets Bcl-2 and miR-196b-5p potentially regulates CASK and HOXB6. Thus, the current work suggested the negative effects of HS on the ovarian tissue of female rabbits, and in conclusion these changes could be caused by decreased serum IL-2, IL-8, CAT and GSH-Px levels, increased ovarian apoptosis, and changed the expression of miRNAs.

Global 3′-UTRome of porcine immature Sertoli cells altered by acute heat stress

Alternative polyadenylation (APA) affects the composition of cis-elements in 3′-untranslated region (3′-UTR), to regulate gene expression and localization, and subsequently the downstream biological processes. Acute heat stress could change rapidly the cellular transcriptome, however the underlying molecular changes are less explored. Here, we systematically catalogued the global 3′-UTRome dynamics, by analyzing our previously reported transcriptome sequencing data of porcine immature Sertoli (iST) cells before (Control group), acute heat stress treatment at 43 °C for 0.5h (HS0.5 group), and 36h recovery culture (HS0.5-R36h group) after acute heat stress treatment. After three group comparisons (HS0.5 vs. Control, HS0.5-R36 vs. HS0.5, and HS0.5-R36 vs. Control), DaPars (dynamic analysis of alternative polyadenylation) identified 639, 464 and 290 mRNAs, and APAtrap (a tool to identify APA sites and detect changes of APA site usage) identified 713, 518 and 321 mRNAs, with significantly different 3′-UTRs (Padj.≤0.05), respectively. These genes with different 3′-UTR patterns were mainly enriched in P53, glycolysis/gluconeogenesis, HIF-1, apoptosis, PI3K-Akt and AMPK signaling pathways. Further analysis identified that average 3′-UTR lengths of Acss2, Inpp1 and Nr1h4 were more than 140 nt longer (HS0.5-R36 vs. HS0.5), and contained different cis-elements (PAS, CPE and microRNA binding sites). Moreover, Hsp70.2, Inhbb and Dhrs were identified to have extremely different 3′-UTR abundances. Further 3′RACE assays validated several 3′-UTRs of Nr1h4, and RT-qPCR confirmed the abundance changes of different 3′-UTR isoforms for Nr1h4 and Hsp70.2. Our findings provide useful information and resources to further uncover the molecular role of 3′-UTR, in regulating the response of porcine iST cells to acute heat stress.

Transcriptome and metabolome analyses reveal the regulatory effects of compound probiotics on cecal metabolism in heat-stressed broilers

The effect of compound probiotics on the caecum of broilers under heat stress was assessed in this study. A total of 400 twenty-eight-day-old AA male broilers were randomly divided into 4 treatment groups, where each group had 5 replicates of 20 broilers. The 4 treatment groups were a heat stress control group (broilers receiving a normal diet) and groups HP I, HP II, and HP Ⅲ, consisting of broilers receiving 1, 5, and 10 g of compound probiotics added to each kilogram of feed, respectively. Compound probiotics (L. casei, L. acidophilus, and B. lactis at a ratio of 1:1:2) were used to formulate a compound probiotic powder, with 1×1010 CFU/g of effective viable bacteria. Heat stress treatment was performed at 32 ± 1°C from 9:00 to 17:00 every day from 28 d to 42 d. In d 28 to 42, compared with the HC group, the ADG of broilers in the HP II and III groups was significantly increased (P < 0.05); the ADFI difference between groups was not significant (P > 0.05); the FCR of HP II and III broilers was significantly decreased (P < 0.05); and the FCR of the HP I group increased, but the difference was not significant (P > 0.05). Transcriptome results demonstrate that 665 differential genes were screened (DEGs; upregulated: 366, downregulated: 299). The DEGs were enriched in the B cell receptor signaling pathway, the intestinal immune network for IgA synthesis, the Fc epsilon RI signaling pathway, and other signaling pathways, according to KEGG enrichment analysis. Metabolome analysis identified 92 differential metabolites (DAMs; upregulated: 48, downregulated: 44). KEGG enrichment analysis indicated significant enrichment of Pantothenate and CoA biosynthesis and beta-Alanine metabolism. The combined transcriptome and metabolome analysis revealed that the DAMs and DEGs were mostly involved in beta-alanine metabolism, arginine biosynthesis, amino sugar and nucleotide sugar, and alanine, aspartate, and glutamate metabolism. The results of this study suggest that the addition of compound probiotics has a positive effect on intestinal metabolites, improving the growth performance and contributing to the overall health of broilers under heat stress.

Effect of Heat Stress on Some Physiological and Anatomical Characteristics of Rice (Oryza sativa L.) cv. KDML105 Callus and Seedling.

Global warming is a serious problem, with significant negative impacts on agricultural productivity. To better understand plant anatomical adaptation mechanisms as responses to heat stress, improved basic knowledge is required. This research studied the physiological and anatomical responses of Khao Dawk Mali 105 (KDML105) to artificial heat stress. Dehusked seeds were sterilized and cultured on Murashige and Skoog (MS) medium, supplemented with 3 mg/L 2,4-Dichlorophenoxyacetic acid (2,4-D) for callus induction. The cultures were maintained at 25 °C and 35 °C for 4 weeks, while the other culture was treated with heat shock at 42 °C for 1 week before further incubation at 25 °C for 3 weeks. Results revealed that elevated temperatures (35 °C and 42 °C) adversely impacted seedling growth. Plant height, root length, leaf number per plant, fresh and dry weight, chlorophyll a, chlorophyll b and total chlorophyll content decreased after heat stress treatment, while malondialdehyde (MDA) and electrolyte leakage percentage significantly increased, compared to the control. Heat stress induced ROS accumulation, leading to lipid peroxidation and membrane instability. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) results also confirmed negative correlations between MDA, electrolyte leakage and other parameters. MDA content and electrolyte leakage are effective indicators of heat stress in rice. Surface anatomical responses of rice seedlings to heat stress were studied but significant alterations were not observed, and heat stress had no significant negative effects on KDML105 calli. Size and mass of calli increased because heat stress stimulated gene expression that induced thermotolerance. Our results provide useful information for rice breeding and heat stress tolerance programs to benefit long-term global food security.

Alleviation effects of niacin supplementation on beef cattle subjected to heat stress: A metagenomic insight.

The objective of this study was to investigate the alleviation effects of niacin supplementation on beef cattle subjected to heat stress and to provide a theoretical basis for exploring the alleviation methods of heat stress environmental factors on the rumen of beef cattle. In the experiment, 36 Jinjiang bull cattle with a body weight of about 400 ± 20.0 kg were randomly divided into three treatments, each treatment contains four replicates, with three cattle in each replicate. Treatments included thermoneutral treatment (TN; temperature: 24–25°C, humidity: 45–55%), heat stress treatment, exposure to environmental temperature (HS; average THI: 82.74), and heat stress supplemented with niacin treatment (HN; high temperature + 800 mg/kg NA). Measured indicators were body temperature, respiratory rate, production performances, rumen fermentations, and microbial diversity. Results showed that adding niacin reduced the body temperature and respiratory rate (P < 0.05) but had no significant effect on the production performances compared with heat-stressed beef cattle. HS treatment significantly increased body temperature and respiratory rate (P < 0.01), while decreasing the content of acetic acid, butyric acid, and total volatile fatty acids (P < 0.05) compared with the TN treatment. Supplement of niacin did not affect ruminal fermentation parameters (P > 0.05) but had a decreased tendency on A/P (P < 0.1). Microbial diversity results showed that, at the phylum level, the relative abundance of Desulfobacterota in the HS treatment was increased compared with TN and HN treatment (P < 0.05). At the genus level, the relative abundance of Succiniclasticum and Family_XIII_AD3011 group in the HN treatment significantly proliferated compared with the HS treatment (P < 0.05). In conclusion, niacin supplementation may alleviate heat stress by proliferating those bacteria belonging to the phylum Succiniclasticum, which may further contribute to the digestion of cellulose and the improvement of the metabolic function of Jinjiang cattle under heat-stress conditions.

Pepper autophagy related gene CaATG8e differentially regulates plant tolerance to heat and salt stress

As a conserved protein degradation system, autophagy plays important roles in removing or degrading misfolded and denatured proteins to maintain the homeostasis in cells. As a core member of autophagy, the involvement of ATG8 in plant tolerance to abiotic stress is paid more attention. In this study, by the SMART online tool, the Atg8 conserved domain was detected in CaATG8e, and by the MEGA11 software, CaATG8e displayed closer phylogenetic relationship to the homologs from other Solanaceae species rather than another 4 CaATG8s members. The expression of CaATG8e was decreased after heat and salt stress treatments. When the expression of CaATG8e was silenced by virus induced gene silencing (VIGS) technique, the pepper seedlings presented improved tolerance to heat stress. Compared to those in control of TRV2:00, the accumulations of autophagosome punctate, H2O2, and dead cells, the increment of relative electrolyte leakage, and the decrement of chlorophyll content were reduced in TRV2:CaATG8e, while the enhancement of transcript level of CaHsfA2, CaHSP70.1, and CaHSP16.1 were strengthened. On the contrary, when CaATG8e was overexpressed by the method of floral dip, Arabidopsis displayed compromised tolerance to heat stress with the decreasing of the rate of green cotyledons and the chlorophyll content. However, CaATG8e had no obvious effects in the regulation of tolerance to salt stress in both pepper and Arabidopsis. These results suggest that CaATG8e negatively regulates the heat tolerance of pepper via increasing the H2O2 accumulations and suppressing the expression of HSR (heat shock response) related genes.

Effects of brown seaweed products on growth performance, plasma biochemistry, immune response, and antioxidant capacity of broiler chickens challenged with heat stress

Brown seaweed (Ascophyllum nodosum) is an exceptional bioactive substance known for its excellent antioxidant ability. Given the potential benefits of brown seaweed, the current study was conducted to determine its efficacy on growth performance, blood biochemistry, immunoglobulins (IgG and IgM), and the antioxidant capacity of broiler chickens challenged with heat stress (HS). A total of 336 mixed-sex Ross 308 broiler chicks (one-day-old) were randomly assigned into two groups; The thermoneutral group (TN, broilers were raised at 24 ± 1°C); and the heat stress group (HS; broilers were exposed to 32°C to 34°C, 8 h/d from day 21 to 27; the temperature in the remaining time was same as TN group). All birds in each group were randomly allotted to 4 dietary treatments—Negative control (NC) (without seaweed), NC + 1 mL seaweed extract (SWE) in drinking water, NC + 2 mL SWE in drinking water, and NC + 2% seaweed meal (SWM) in feed. Each treatment was assigned to six replicates with 7 broilers/replicate. Average body weight gain (ABWG), average feed intake (AFI), average water intake (AWI), feed conversion ratio (FCR), and mortality were determined weekly. On day 28, two male birds/cage were euthanized to collect blood and immune organs for subsequent biochemical, antioxidant, and immune status analysis. Data were analyzed as a 4 × 2 factorial analysis of variance using the GLM procedure of Minitab software. Overall, 2% SWM inclusion significantly increased (P < 0.05) the AFI, ABWG, and AWI of broiler chickens irrespective of HS. HS significantly reduced (P < 0.05) AFI and increased (P < 0.05) the bird's rectal temperature, plasma concentrations of sodium, chloride, glucose, amylase, and uric acid compared to TN birds. HS increased (P < 0.05) serum IgM and IgG and decreased plasma glutathione reductase and glutathione peroxidase compared to TN birds, while the activity of superoxide dismutase was not affected by HS and dietary treatments. 1 mL SWE in water and 2% SWM in feed significantly reduced (P < 0.05) the plasma activity of alanine aminotransferase and gamma-glutamyl transferase of heat-stressed broilers, respectively compared to other treatments. Conclusively, dietary supplementation of brown seaweed improved the growth performance of birds irrespective of HS and may help to reduce the negative effects of HS by improving the plasma enzyme activities of heat-stressed birds.

ZmNAC074, a maize stress-responsive NAC transcription factor, confers heat stress tolerance in transgenic Arabidopsis.

The harsh environment such as high temperature greatly limits the growth, development and production of crops worldwide. NAC (NAM, ATAF1/2, and CUC2) transcription factors (TFs) play key regulatory roles in abiotic stress responses of plants. However, the functional roles of NAC TFs in heat stress response of maize remain elusive. In our present study, we identified and isolated a stress-responsive NAC transcription factor gene in maize, designated as ZmNAC074 and orthologous with rice OsNTL3. Further studies revealed that ZmNAC074 may encode a membrane-bound transcription factor (MTF) of NAC family in maize, which is comprised of 517 amino acid residues with a transmembrane domain at the C-terminus. Moreover, ZmNAC074 was highly expressed and induced by various abiotic stresses in maize seedlings, especially in leaf tissues under heat stress. Through generating ZmNAC074 transgenic plants, phenotypic and physiological analyses further displayed that overexpression of ZmNAC074 in transgenic Arabidopsis confers enhanced heat stress tolerance significantly through modulating the accumulation of a variety of stress metabolites, including reactive oxygen species (ROS), antioxidants, malondialdehyde (MDA), proline, soluble protein, chlorophyll and carotenoid. Further, quantitative real-time PCR analysis showed that the expression levels of most ROS scavenging and HSR- and UPR-associated genes in transgenic Arabidopsis were significantly up-regulated under heat stress treatments, suggesting that ZmNAC074 may encode a positive regulator that activates the expression of ROS-scavenging genes and HSR- and UPR-associated genes to enhance plant thermotolerance under heat stress conditions. Overall, our present study suggests that ZmNAC074 may play a crucial role in conferring heat stress tolerance in plants, providing a key candidate regulatory gene for heat stress tolerance regulation and genetic improvement in maize as well as in other crops.

Impact of waterlogging and heat stress on rice rhizosphere microbiome assembly and potential function in carbon and nitrogen transformation

ABSTRACT The impacts of rhizosphere microorganisms on the turnover of nutrients are affected by many environmental factors. In this study, rice plants were subjected to deep flooding and heat stress for one week at the jointing stage. Rhizospheric soil was sampled for the analysis of rice rhizosphere bacterial assembly and functional groups responsible for carbon and nitrogen transformation. Compared with the control, both deep flooding and heat stress increased bacterial alpha diversity. Moreover, heat stress and the interactions of heat stress and deep flooding improved the bacterial cooperation. Heat stress reduced the relative abundance of Actinobacteria and Firmicutes, which are responsible for organic carbon decomposition. The relative abundance of the gene encoding lignin-degrading catalases under deep flooding and heat stress treatments reduced by 6% and 8%, respectively. The interaction of heat stress and deep flooding increased the relative abundance of the nifD gene by 5%, may slowed down nitrate reduction to nitrite. Our results highlight the effects of heat and flooding stress on the bacteria-mediated mechanisms responsible for regulating organic carbon sequestration and nitrogen cycling in rhizosphere of paddy fields.

Effects of cytokinin and abscisic acid on heat resistance of Vetiveria zizanioides

Vetiveria zizanioides is ideal in maintaining soil and water, and is widely used for remediation of soil contaminated by heavy metals. However, it is affected by high-temperature stress. In this study, Vetiveria zizanioides plants were sprayed with 6-BA and ABA in a growth chamber 1 d before heat stress treatment, then the plants were subjected to high-temperature conditions. Relative water content, relative electrical conductivity, contents of ascorbic acid (AsA) and reduced glutathione (GSH) as the antioxidative substances, and content of malondiadehyde (MDA) were determined. Also, the antioxidative enzyme activities and the osmoprotectants levels were detected. Diaminobenzidine (DAB) staining of leaves and roots in Vetiveria zizanioides was observed for determination of hydrogen peroxide accumulation. The results showed that relative water content was decreased, relative electrical conductivity and MDA content were increased by the heat stress treatment. Under high-temperature conditions, relative water content was increased and relative electrical conductivity was decreased by 6-BA and ABA treatments. At the middle and the late stages of the heat stress treatment, activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and the contents of ASA and GSH in leaves of the 6-BA-treated and ABA-treated plants were significantly higher, whereas the MDA content was significantly lower than those in the high-temperature controls. Hydrogen peroxide accumulation levels in the 6-BA-treated and ABA-treated leaves and roots were lower than in the high-temperature controls. Contents of soluble sugar, sucrose, and glucose in the 6-BA-treated and ABA-treated leaves were significantly higher than those in the high-temperature controls. Proline content in the 6-BA-treated and ABA-treated leaves was stable. The results suggested that the enhancement of the heat resistance by 6-BA and ABA treatments was correlated with the activation of the antioxidant system, as well as the sugar-based osmoprotectant.

Prenatal thermal stress affects acute-phase proteins, heat shock protein 70, and circulating corticosterone in developing broiler embryos and neonates

Higher or lower incubation temperature may impose some degree of stress on developing poultry embryos. This study was designed to delineate the effects of prenatal thermal stress on serum levels of acute-phase proteins (APPs), namely ceruloplasmin (CPN) and alpha-1-acid glycoprotein (AGP), the regulation of brain mRNA levels of heat shock protein (Hsp) 70, and serum levels of corticosterone (CORT) in embryos and neonatal chicks. Hatching eggs were subjected to three thermal treatments; (i) standard optimum temperature throughout (SS: 37.8 °C and 56 % RH), (ii) heat stress for 12 h daily (HS: 40.0 °C and 56 % RH), and (iii) cold stress for 12 h daily 18 (CS: 30.2 °C and 56 % RH). The heat and cold stress treatments were imposed from the 10th to the 18th day of incubation (ED). Results showed that thermal stress had a negligible effect on hatchability rate and body temperatures of neonatal chicks. The CS treatment was detrimental to embryonic growth. The HS treatment elevated AGP (ED 16, ED 18, and post-hatch day 1), CPN (on post-hatch day 1), and CORT (ED 14). On the contrary, the CS embryos had reduced AGP (ED14, ED16, ED18, and post-hatch day 1), CPN (ED 16), and CORT (ED 14, ED 16, ED 18). The brain mRNA levels of Hsp70 were upregulated throughout the experimental period in both the HS and CS embryos and chicks. Based on these modifications, AGP, together with Hsp70 mRNA expression, could be considered effective biomarkers useful to evaluate the magnitude and the time response of embryos and neonatal chicks to prenatal thermal stress. It is concluded that developing chicken embryos have the ability to evoke APPs, Hsp70 and CORT reactions which are important to cope with thermal stress.

Transcriptomic and alternative splicing analyses provide insights into the roles of exogenous salicylic acid ameliorating waxy maize seedling growth under heat stress

BackgroundSalicylic acid (SA) is a phytohormone which works to regulate the abiotic stress response of plants. However, the molecular mechanism by which SA mediates heat tolerance in waxy maize (Zea mays L. sinsensis Kulesh) remains unknown.ResultsTwo varieties of waxy maize seedlings, heat-tolerant ‘Yunuo7’ (Y7) and heat-sensitive ‘Suyunuo5’ (S5), were pretreated with SA prior to heat stress (HTS). After treatment, physiological and transcriptomic changes were analyzed. Compared with HTS, the exogenous application of SA enhanced the shoot dry weight, the activities of antioxidant enzymes (e.g., SOD, POD, CAT and APX), and the concentration of endogenous phytohormones (e.g., SA, ABA, IAA, GA3), while decreased the MDA content. Transcriptome analysis showed that the number of differentially expressed genes (DEGs) identified in the control (CK) vs HTS and HTS vs HTS + SA comparisons were more in S5 than in Y7. HTS induced the downregulation of genes involved in photosynthesis and the upregulation of genes encoding heat shock transcription factors (HSFs) and heat shock proteins (HSPs). Compared with HTS, SA pretreatment reversed the expression of 5 photosynthesis-related genes, 26 phytohormone-related genes, and all genes encoding HSFs and HSPs in S5. Furthermore, the number of alternative splicing (AS) events increased under HTS treatment for both varieties, while decreased under SA pretreatment of S5. Differentially spliced genes (DSGs) showed little overlap with DEGs, and DEGs and DSGs differed significantly in functional enrichment.ConclusionsPhysiological and transcriptional together indicated that HTS and SA pretreatment had a greater effect on S5 than Y7. Additionally, it appears that transcriptional regulation and AS work synergistically to enhance thermotolerance in heat-sensitive waxy maize. Our study revealed the regulatory effects and underlying molecular mechanisms of SA on waxy maize seedling under HTS.

Genome-wide identification and functional analyses of heat shock transcription factors involved in heat and drought stresses in ryegrass

Italian ryegrass ( Lolium multiflorum ) is one of the most important and widely cultivated cool-season forage and turfgrass around the world. Heat and drought are two key factors limiting its growth and distribution. Heat shock transcription factors ( Hsfs ) are important regulators involved in various abiotic stresses; however, how the Hsf family responds to heat and drought stresses and the roles of LmHsfs in heat and drought tolerance remain to be determined in Italian ryegrass . In the present study, 16 putative Hsf genes were identified by whole-genome bioinformatics analysis, including eight HsfAs , five HsfBs , and three HsfCs . The subcellular localization, physiological and biochemical characteristics, conserved domains, gene structure, and phylogenetic relationship of the Hsf family were systematically analyzed in silico. Gene expression profiling analyses revealed that all Hsfs were responsive to heat and drought stresses. Most Hsfs , including LmHsfA2 , LmHsfA3 , LmHsfA4 , LmHsfA5 , LmHsfA6 , LmHsfA7 , LmHsfA8 , LmHsfB1 , and LmHsfB2 , were induced to the highest expression levels at 1 h of heat stress treatment, while the majority of LmHsfs were up-regulated with a peak at 10 d of drought stress treatment. Subsequently, the biological function of LmHsfA5 which was induced by both heat and drought stresses was analyzed. Heterologous overexpression of LmHsfA5 improved heat and drought tolerance in transgenic Arabidopsis . The qRT-PCR analysis showed that the expression of APX2 and HSP18.2 were significantly induced in LmHsfA5- overexpressing lines under both normal and heat stress conditions. What’s more, yeast one-hybrid, dual-luciferase assay, and electrophoretic mobility shift assay exhibited that LmHsfA5 could bind to the promoters of LmHSP18.2 and LmAPX2 and induce their expression, indicating that LmHsfA5 may positively regulate heat and drought tolerance via directly activating the expression of LmHSP18.2 and LmAPX2 in ryegrass. This study provides a basis for further research on LmHsfs functions in abiotic stress. • 16 LpHsfs were identified by whole-genome bioinformatics analysis. • All LmHsfs were responsive to heat and drought stresses. • Heterologous expression of LmHsfA5 improved heat and drought tolerance in Arabidopsis. • LmHsfA5 directly activates the expression of LmHSP18.2 and LmAPX2 .

Effect of Dietary 4-Phenylbuthyric Acid Supplementation on Acute Heat-Stress-Induced Hyperthermia in Broiler Chickens.

Simple SummaryHeat stress (HS) induces endoplasmic reticulum (ER) stress and disrupts the ER and cellular homeostasis. A recent study showed that ER stress was induced in broiler chickens under severe and acute HS; however, it was unclear how the alleviation of ER stress affects the physiological state of broiler chickens. Therefore, this study aimed to investigate the ameliorative effects of an ER stress alleviator, 4-phenylbutyric acid (4-PBA), which is a chemical chaperone that reduces ER stress, on the body temperature response, energy metabolic state, and cellular ER stress in HS-exposed birds. 4-PBA supplementation did not negatively affect the growth rate. In addition, 4-PBA suppressed the HS-induced ER stress response in skeletal muscle. Surprisingly, 4-PBA significantly decreased body temperature elevation in HS birds. The present study showed that the ER stress, alleviated by 4-PBA, might contribute to the induction of heat tolerance in broiler chickens.Hot, humid weather causes heat stress (HS) in broiler chickens, which can lead to high mortality. A recent study found that HS causes endoplasmic reticulum (ER) stress. However, the possible involvement of ER stress in HS-induced physiological alterations in broiler chickens is unclear. This study aimed to evaluate the effect of the dietary supplementation of 4-phenylbutyric acid (4-PBA), an alleviator of ER stress, in acute HS-exposed young broiler chickens. Twenty-eight 14-day-old male broiler chickens (ROSS 308) were divided into two groups and fed either a control diet or a diet containing 4-PBA (5.25 g per kg of diet feed) for 10 days. At 24 days old, each group of chickens was kept in thermoneutral (24 ± 0.5 °C) or acute HS (36 ± 0.5 °C) conditions for 2 h. The results showed that thermoneutral birds supplemented with 4-PBA exhibited no negative effects in terms of broiler body weight gain and tissue weight compared to non-supplemental birds. HS increased body temperature in both the control and 4-PBA groups, but the elevation was significantly lower in the 4-PBA group than in the control group. The plasma non-esterified fatty acid concentration was significantly increased by HS treatment in non-supplemental groups, while the increase was partially attenuated in the 4-PBA group. Moreover, 4-PBA prevented HS-induced gene elevation of the ER stress markers GRP78 and GRP94 in the skeletal muscle. These findings suggest that the 4-PBA effect may be specific to the skeletal muscle in HS-exposed birds and that 4-PBA supplementation attenuated HS-induced muscle ER stress, which could be associated with a supplementation of the body temperature elevation and lipolysis.

Heat stress and evisceration caused lipid metabolism and neural transduction changes in sea cucumber: Evidence from metabolomics

When encountering adverse environmental conditions, some holothurians can eject their internal organs in a process called evisceration. As global warming intensified, eviscerated and intact sea cucumbers both experience heat stress, but how they performed was uncertain. We constructed 24 metabolomics profiles to reveal the metabolite changes of eviscerated and intact sea cucumbers under normal and high temperature conditions, respectively. Carboxylic acids and fatty acyls were the most abundant metabolic categories in evisceration and heat stress treatments, respectively. Neural transduction was involved in sea cucumber evisceration and stress response, and the commonly enriched pathway was “neuroactive ligand-receptor interaction”. Lipid metabolism in eviscerated sea cucumbers differed from those of intact individuals and was more seriously affected by heat stress. Choline is a key metabolite for revealing the evisceration mechanism. Our results contribute to understanding the mechanisms of evisceration in sea cucumbers, and how sea cucumbers might respond to increasingly warming ocean conditions.

Genome-Wide Identification and Functional Analysis of Polyamine Oxidase Genes in Maize Reveal Essential Roles in Abiotic Stress Tolerance.

Polyamines (PAs) play a critical role in growth and developmental processes and stress responses in plants. Polyamine oxidase (PAO) is a flavin adenine dinucleotide (FAD)-dependent enzyme that plays a major role in PA catabolism. Here, for the first time, PAO genes in maize were screened for the whole genome-wide and nine ZmPAO genes were identified in this study, named as ZmPAO1-9. Based on structural characteristics and a comparison of phylogenetic relationships of PAO gene families from seven representative species, all nine PAO proteins in maize were categorized into three distinct subfamilies. Further, chromosome location and schematic structure revealed an unevenly distribution on chromosomes and evolutionarily conserved structure features of ZmPAO genes in maize, respectively. Furthermore, transcriptome analysis demonstrated that ZmPAO genes showed differential expression patterns at diverse developmental stages of maize, suggesting that these genes may play functional developmental roles in multiple tissues. Further, through qRT-PCR validation, these genes were confirmed to be responsive to heat, drought and salinity stress treatments in three various tissues, indicating their potential roles in abiotic stress responses. Eventually, to verify the biological function of ZmPAO genes, the transgenic Arabidopsis plants overexpressing ZmPAO6 gene were constructed as a typical representative to explore functional roles in plants. The results demonstrated that overexpression of ZmPAO6 can confer enhanced heat tolerance through mediating polyamine catabolism in transgenic Arabidopsis, which might result in reduced H2O2 and MDA accumulation and alleviated chlorophyll degradation under heat stress treatment, indicating that ZmPAO6 may play a crucial role in enhancing heat tolerance of transgenic Arabidopsis through the involvement in various physiological processes. Further, the expression analysis of related genes of antioxidant enzymes including glutathione peroxidase (GPX) and ascorbate peroxidase (APX) demonstrated that ZmPAO6 can enhance heat resistance in transgenic Arabidopsis through modulating heat-induced H2O2 accumulation in polyamine catabolism. Taken together, our results are the first to report the ZmPAO6 gene response to heat stress in plants and will serve to present an important theoretical basis for further unraveling the function and regulatory mechanism of ZmPAO genes in growth, development and adaptation to abiotic stresses in maize.