Heat Shock Transcription Factor Research Articles

Heat Shock Transcription Factor GhHSFB2a Is Crucial for Cotton Resistance to Verticillium dahliae.

Heat shock transcription factors (HSFs) play a critical regulatory role in many plant disease resistance pathways. However, the molecular mechanisms of cotton HSFs involved in resistance to the soil-borne fungus Verticillium dahliae are limited. In our previous study, we identified numerous differentially expressed genes (DEGs) in the transcriptome and metabolome of V. dahliae-inoculated Arabidopsis thaliana. In this study, we identified and functionally characterized GhHSFB2a, which is a DEG belonging to HSFs and related to cotton immunity to V. dahliae. Subsequently, the phylogenetic tree of the type two of the HSFB subfamily in different species was divided into two subgroups: A. thaliana and strawberry, which have the closest evolutionary relationship to cotton. We performed promoter cis-element analysis and showed that the defense-reaction-associated cis-acting element-FC-rich motif may be involved in the plant response to V. dahliae in cotton. The expression pattern analysis of GhHSFB2a displayed that it is transcriptional in roots, stems, and leaves and significantly higher at 12 h post-inoculation (hpi). Subcellular localization of GhHSFB2a was observed, and the results showed localization to the nucleus. Virus-induced gene silencing (VIGS) analysis exhibited that GhHSFB2a silencing increased the disease index and fungal biomass and attenuated resistance against V. dahliae. Transcriptome sequencing of wild-type and GhHSFB2a-silenced plants, followed by Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, protein-protein interaction, and validation of marker genes revealed that ABA, ethylene, linoleic acid, and phenylpropanoid pathways are involved in GhHSFB2a-mediated plant disease resistance. Ectopic overexpression of the GhHSFB2a gene in Arabidopsis showed a significant increase in the disease resistance. Cumulatively, our results suggest that GhHSFB2a is required for the cotton immune response against V. dahliae-mediated ABA, ethylene, linoleic acid, and phenylpropanoid pathways, indicating its potential role in the molecular design breeding of plants.

NTR1 is involved in heat stress tolerance through mediating expression regulation and alternative splicing of heat stress genes in Arabidopsis.

As a common adverse environmental factor, heat stress (HS) not only drastically changes the plant transcriptome at the transcription level but also increases alternative splicing (AS), especially intron retention (IR) events. However, the exact mechanisms are not yet well understood. Here, we reported that NTC-related protein 1 (NTR1), which acts as an accessory component for spliceosome disassembly, is necessary for this process. The mutants of NTR1, both the T-DNA insertion and the point mutation identified through ethyl methanesulfonate (EMS) mutagenesis screening, are vulnerable to HS, indicating that NTR1 is essential for plant HS tolerance. At the molecular level, genes of response to heat and response to temperature stimulus are highly enriched among those of heat-induced but less-expressed ntr1 mutants. Moreover, a large portion of HS response (HSR) genes such as heat shock transcription factors (HSFs) and heat shock proteins (HSPs) are less induced by heat treatment, and more AS events, especially IR events, were found in heat-treated ntr1 mutants. Furthermore, HS suppressed the expression of NTR1 and NTR1-associated complex components. Thus, it is very likely that upon HS, the plant reduces the expression of the NTR1-associated complex to fulfill the fast demands for transcription of HSR genes such as HSFs and HSPs, which in turn results in the accumulation of improperly spliced especially IR products and eventually causes harm to plants.

Hypoxia-inducible factor-1α is involved in the response to heat stress in lactating dairy cows

Hypoxia-inducible factor-1α (HIF-1α) is important in maintaining cellular oxygen homeostasis and cellular heat tolerance. To explore the role of HIF-1α in the response to heat stress (HS) in dairy cows, 16 Chinese Holstein cows (milk yield: 32 ± 4 kg/d, days in milk: 272 ± 7 d, parity: 2–3) were used to collect coccygeal vein blood and milk samples when cows were under mild (temperature-humidity index = 77) and moderate HS (temperature-humidity index = 84), respectively. Compared to cows under mild HS, the respiratory rate (P < 0.01), rectal temperature (P < 0.01), and blood concentrations of heat shock protein (HSP)70 (P < 0.01) and HSP27 (P < 0.01) were higher, but oxygen saturation (P = 0.02) and hemoglobin (P < 0.01) were lower in cows under moderate HS. Blood HIF-1α concentration was greater (P < 0.01) during moderate HS, indicating that HIF-1α is involved in lactating cows' response to HS. To confirm these findings, we collected coccygeal vein blood and milk samples from 59 dairy cows under moderate HS. The HIF-1α levels were correlated with the levels of heat shock transcription factor (HSF) (r = 0.7857, P < 0.01), HSP70 (r = 0.4543, P < 0.01) and HSP27 (r = 0.8782, P < 0.01). A comparison of 15 cows with higher HIF-1α (>482 ng/L) and 15 cows with lower HIF-1α levels (<439 ng/L) showed that reactive oxidative species were higher (P = 0.02), but superoxide dismutase (P < 0.01), total antioxidation capacity (P = 0.02) and glutathione peroxidase (P < 0.01) were lower in higher HIF-1α cows. These results suggested that HIF-1α may be indicative of the risk of oxidative stress in heat-stressed cows and may participate in the response of cows to HS by synergistically activating the expression of the HSP family with HSF.

Alternative Splicing of TaHsfA2-7 Is Involved in the Improvement of Thermotolerance in Wheat.

High temperature has severely affected plant growth and development, resulting in reduced production of crops worldwide, especially wheat. Alternative splicing (AS), a crucial post-transcriptional regulatory mechanism, is involved in the growth and development of eukaryotes and the adaptation to environmental changes. Previous transcriptome data suggested that heat shock transcription factor (Hsf) TaHsfA2-7 may form different transcripts by AS. However, it remains unclear whether this post-transcriptional regulatory mechanism of TaHsfA2-7 is related to thermotolerance in wheat (Triticum aestivum). Here, we identified a novel splice variant, TaHsfA2-7-AS, which was induced by high temperature and played a positive role in thermotolerance regulation in wheat. Moreover, TaHsfA2-7-AS is predicted to encode a small truncated TaHsfA2-7 isoform, retaining only part of the DNA-binding domain (DBD). TaHsfA2-7-AS is constitutively expressed in various tissues of wheat. Notably, the expression level of TaHsfA2-7-AS is significantly up-regulated by heat shock (HS) during flowering and grain-filling stages in wheat. Further studies showed that TaHsfA2-7-AS was localized in the nucleus but lacked transcriptional activation activity. Ectopic expression of TaHsfA2-7-AS in yeast exhibited improved thermotolerance. Compared to non-transgenic plants, overexpression of TaHsfA2-7-AS in Arabidopsis results in enhanced tolerance to heat stress. Simultaneously, we also found that TaHsfA1 is directly involved in the transcriptional regulation of TaHsfA2-7 and TaHsfA2-7-AS. In summary, our findings demonstrate the function of TaHsfA2-7-AS splicing variant in response to heat stress and establish a link between regulatory mechanisms of AS and the improvement of thermotolerance in wheat.

HSF1 promotes CD69+ Treg differentiation to inhibit colitis progression.

Regulatory T cells (Tregs) are critical for generating and maintaining peripheral tolerance. Treg-based immunotherapy is valuable for the clinical management of diseases resulting from dysregulation of immune tolerance. However, the lack of potency is a potential limitation of Treg therapy. In addition, CD69 positive-Treg (CD69+ Treg) represent a newly identified subset of Tregs with potent immune suppressive capability. Methods: Foxp3 YFP-Cre CD69 fl/fl and CD4 Cre CD69 fl/fl mice were generated to determine the relevance of CD69 to Treg. Chromatin Immunoprecipitation Assay (ChIP) and luciferase Assay were performed to detect the regulation of CD69 transcription by heat shock transcription factor 1(HSF1). Gene expression was measured by western blotting and qRT-PCR. The differentiation of naive T cells to CD69+Foxp3+ iTregs was determined by flow cytometry. The immunosuppressive ability of Tregs was analyzed by ELISA and flow cytometry. Colon inflammation in mice was reflected by changes in body weight and colon length, the disease activity index (DAI), and H&E staining of colon tissues. Results: Induced Tregs (iTregs) from CD4 Cre CD69 fl/fl mice failed to alleviate colitis. The transcription factor HSF1 interacted with the promoter of the CD69 gene to prompt its transcription during Treg differentiation. Genetic and chemical inhibition of HSF1 impaired CD69+ Treg differentiation and promoted the pathogenesis of colitis in mice. In contrast, HSF1 protein stabilized by inhibiting its proteasomal degradation promoted CD69+ Treg differentiation and alleviated colitis in mice. Moreover, adoptive transfer of iTregs with HSF1 stabilization by proteasome inhibitor (PSI) dramatically prevented the development of colitis in mice and was accompanied by decreased production of pro-inflammatory cytokines and reduced accumulation of pro-inflammatory lymphocytes in colitis tissue, whereas Tregs induced in the absence of PSI were less stable and ineffective in suppressing colitis. Conclusions: HSF1 promotes CD69+ Tregs differentiation by activating the CD69 transcription, which is critical for the immunosuppressive function of Tregs. Stabilization of HSF1 by PSIs results in the efficient generation of Tregs with high potency to treat colitis and probably other autoimmune diseases involving Tregs deficiency.

Growth Cessation and Dormancy Induction in Micropropagated Plantlets of Rheum rhaponticum ‘Raspberry’ Influenced by Photoperiod and Temperature

Dormancy development in micropropagated plantlets at the acclimatization stage and early growth ex vitro is undesirable as it lowers their survival rate and restricts the efficient year-round production of planting material. Thus far, little is known about the factors and mechanisms involved in the dormancy development of micropropagated herbaceous perennials, including rhubarb. This study determined physiological and molecular changes in the Rheum rhaponticum (culinary rhubarb) 'Raspberry' planting material in response to photoperiod and temperature. We found that the rhubarb plantlets that were grown under a 16-h photoperiod (LD) and a temperature within the normal growth range (17-23 °C) showed active growth of leaves and rhizomes and did not develop dormancy. Rapid growth cessation and dormancy development were observed in response to a 10-h photoperiod (SD) or elevated temperature under LD. These morphological changes were accompanied by enhanced abscisic acid (ABA) and starch levels and also the upregulation of various genes involved in carbohydrate synthesis and transport (SUS3, AMY3, BMY3, BGLU17) and ABA synthesis and signaling (ZEP and ABF2). We also found enhanced expression levels of heat shock transcription factors (HSFA2 and HSFA6B), heat shock proteins (HSP22, HSP70.1, HSP90.2 and HSP101) and antioxidant enzymes (PRX12, APX2 and GPX). This may suggest that dormancy induction in micropropagated rhubarb plantlets is a stress response to light deficiency and high temperatures and is endogenously coordinated by the ABA, carbohydrate and ROS pathways.

Overexpression of PvBiP2 improved biomass yield and cadmium tolerance in switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.), the prime bioenergy feedstock crop, is one ideal candidate for phytoremediation of cadmium (Cd). The absorption of Cd imposes severe endoplasmic reticulum (ER)-stress in plants. ER chaperone binding proteins (BiPs) are important modulators in ER-stress responses. The objective of this study was to characterize one Cd-responsive BiP gene, PvBiP2, in switchgrass for its roles in Cd tolerance and plant growth. PvBiP2 was up-regulated by Cd and the ER-stress inducer, dithiothreitol (DTT) and could be trans-activated by one Cd-responsive heat shock transcription factor PvHsfA4. Overexpression of PvBiP2 in switchgrass significantly increased its plant growth with higher height, stem diameter, leaf width, internode length, and tiller numbers than those of the wildtype (WT) plants under non-stress conditions. After 30 days of Cd treatment, the PvBiP2 over-expression transgenic lines showed 40–45% higher dry biomass accumulation with net photosynthesis rate (Pn), but lower electrolyte leakage (EL), malondialdehyde (MDA), and glutathione (GSH) levels than WT. Moreover, over-expressing PvBiP2 led to ∼90–140% Cd accumulation in plants but 46–57% lower Cd translocation rates to shoots. Together, the PvHSFA4-PvBiP2 module acted as positive regulators in plant Cd tolerance, and over-expressing PvBiP2 promoted plant vegetative growth as well as Cd tolerance making it an ideal molecular target for genetic improvement in switchgrass in the future.

Regulatory Mechanisms of Heat Stress Response and Thermomorphogenesis in Plants.

As worldwide warming intensifies, the average temperature of the earth continues to increase. Temperature is a key factor for the growth and development of all organisms and governs the distribution and seasonal behavior of plants. High temperatures lead to various biochemical, physiological, and morphological changes in plants and threaten plant productivity. As sessile organisms, plants are subjected to various hostile environmental factors and forced to change their cellular state and morphological architecture to successfully deal with the damage they suffer. Therefore, plants have evolved multiple strategies to cope with an abnormal rise in temperature. There are two main mechanisms by which plants respond to elevated environmental temperatures. One is the heat stress response, which is activated under extremely high temperatures; the other is the thermomorphogenesis response, which is activated under moderately elevated temperatures, below the heat-stress range. In this review, we summarize recent progress in the study of these two important heat-responsive molecular regulatory pathways mediated, respectively, by the Heat Shock Transcription Factor (HSF)-Heat Shock Protein (HSP) pathway and PHYTOCHROME INTER-ACTING FACTOR 4 (PIF4) pathways in plants and elucidate the regulatory mechanisms of the genes involved in these pathways to provide comprehensive data for researchers studying the heat response. We also discuss future perspectives in this field.

Identification, classification, and expression profile analysis of heat shock transcription factor gene family in Salvia miltiorrhiza.

In response to abiotic stresses, transcription factors are essential. Heat shock transcription factors (HSFs), which control gene expression, serve as essential regulators of plant growth, development, and stress response. As a model medicinal plant, Salvia miltiorrhiza is a crucial component in the treatment of cardiovascular illnesses. But throughout its growth cycle, S.miltiorrhiza is exposed to a series of abiotic challenges, including heat and drought. In this study, 35 HSF genes were identified based on genome sequencing of Salvia miltiorrhiza utilizing bioinformatics techniques. Additionally, 35 genes were classified into three groups by phylogeny and gene structural analysis, comprising 22 HSFA, 11 HSFB, and two HSFC. The distribution and sequence analysis of motif showed that SmHSFs were relatively conservative. In SmHSF genes, analysis of the promoter region revealed the presence of many cis-acting elements linked to stress, hormones, and growth and development, suggesting that these factors have regulatory roles. The majority of SmHSFs were expressed in response to heat and drought stress, according to combined transcriptome and real-time quantitative PCR (qRT-PCR) analyses. In conclusion, this study looked at the SmHSF gene family using genome-wide identification, evolutionary analysis, sequence characterization, and expression analysis. This research serves as a foundation for further investigations into the role of HSF genes and their molecular mechanisms in plant stress responses.

Targeting small heat shock proteins to degrade aggregates as a potential strategy in neurodegenerative diseases.

Neurodegenerative diseases (NDs) are aging-related diseases that involve the death of neurons in the brain. Dysregulation of protein homeostasis leads to the production of toxic proteins or the formation of aggregates, which is the pathological basis of NDs. Small heat shock proteins (HSPB) is involved in the establishment of a protein quality control (PQC) system to maintain cellular homeostasis. HSPB can be secreted into the extracellular space and delivered by various routes, especially extracellular vehicles (EVs). HSPB plays an important role in influencing the aggregation phase of toxic proteins involved in heat shock transcription factor (HSF) regulation, oxidative stress, autophagy and apoptosis pathways. HSPB conferred neuroprotective effects by resisting toxic protein aggregation, reducing autophagy and reducing neuronal apoptosis. The HSPB treatment strategies, including targeted PQC system therapy and delivery of EVs-HSPB, can improve disease manifestations for NDs. This review aims to provide a comprehensive insight into the impact of HSPB in NDs and the feasibility of new technology to enhance HSPB expression and EVs-HSPB delivery for neurodegenerative disease.

Arbuscular mycorrhiza induces low oxidative burst in drought-stressed walnut through activating antioxidant defense systems and heat shock transcription factor expression.

Arbuscular mycorrhizal fungi (AMF) have important roles in enhancing drought tolerance of host plants, but it is not clear whether and how AMF increase drought tolerance in walnut (Juglans regia). We hypothesized that AMF could activate antioxidant defense systems and heat shock transcription factors (Hsfs) transcription levels to alleviate oxidative damage caused by drought. The walnut variety 'Liaohe No. 1' was inoculated with Diversispora spurca and exposed to well-watered (WW, 75% of the maximum soil water capacity) and drought stress (DS, 50% of the maximum soil water capacity) for 6 weeks. Plant growth, antioxidant defense systems, and expressions of five JrHsfs in leaves were studied. Such drought treatment inhibited root mycorrhizal colonization, while plant growth performance was still improved by AMF inoculation. Mycorrhizal fungal inoculation triggered the increase in soluble protein, glutathione (GSH), ascorbic acid (ASC), and total ASC contents and ascorbic peroxidase and glutathione reductase activities, along with lower hydrogen peroxide (H2O2), superoxide anion radical (O2 •-), and malondialdehyde (MDA) levels, compared with non-inoculation under drought. Mycorrhizal plants also recorded higher peroxidase, catalase, and superoxide dismutase activities than non-mycorrhizal plants under drought. The expression of JrHsf03, JrHsf05, JrHsf20, JrHsf22, and JrHsf24 was up-regulated under WW by AMF, while the expression of JrHsf03, JrHsf22, and JrHsf24 were up-regulated only under drought by AMF. It is concluded that D. spurca induced low oxidative burst in drought-stressed walnut through activating antioxidant defense systems and part Hsfs expressions.

Ultraviolet-B Irradiation Induces Resistance against Powdery Mildew in Cucumber (Cucumis sativus L.) through a Different Mechanism Than That of Heat Shock-Induced Resistance

Heat shock treatment (HST) and UV-B irradiation can reduce pathogen infection in crops. However, information on the mechanism of UV-B action is limited. Here, we investigated the mechanism of UV-B-induced resistance against powdery mildew in cucumber and compared it to that of heat-shock-induced resistance. We measured the percentage of leaf area showing disease symptoms and examined the expression levels of defense- and heat-shock-related genes across treatment groups. UV-B irradiation (intensity, 5 µW/cm2) for 4 h/d followed by pathogen inoculation reduced the appearance of powdery mildew by 21.17% compared with the control group. Unlike HST—which induces systemic resistance—UV-B irradiation induced local resistance in cucumber, as indicated by local changes in gene expression (Chi2 and ETR2). UV-B-treated plants inoculated with powdery mildew showed higher expression levels of Chi2, ETR2, and LOX6 than plants that were either treated with UV-B or inoculated. UV-B had no major effects on systemic acquired resistance or heat shock transcription factors, which are known to be affected by HST. Combined HST and UV-B had a strong synergistic effect in reducing powdery mildew in cucumber. Our results indicate that UV-B treatment likely operates through a different mechanism than HST in triggering cucumber resistance against powdery mildew infection.

Signaling pathways in cancer-associated fibroblasts: recent advances and future perspectives.

As a critical component of the tumor microenvironment (TME), cancer-associated fibroblasts (CAFs) play important roles in cancer initiation and progression. Well-known signaling pathways, including the transforming growth factor-β (TGF-β), Hedgehog (Hh), Notch, Wnt, Hippo, nuclear factor kappa-B (NF-κB), Janus kinase (JAK)/signal transducer and activator of transcription (STAT), mitogen-activated protein kinase (MAPK), and phosphoinositide 3-kinase (PI3K)/AKT pathways, as well as transcription factors, including hypoxia-inducible factor (HIF), heat shock transcription factor 1 (HSF1), P53, Snail, and Twist, constitute complex regulatory networks in the TME to modulate the formation, activation, heterogeneity, metabolic characteristics and malignant phenotype of CAFs. Activated CAFs remodel the TME and influence the malignant biological processes of cancer cells by altering the transcriptional and secretory characteristics, and this modulation partially depends on the regulation of signaling cascades. The results of preclinical and clinical trials indicated that therapies targeting signaling pathways in CAFs demonstrated promising efficacy but were also accompanied by some failures (e.g., NCT01130142 and NCT01064622). Hence, a comprehensive understanding of the signaling cascades in CAFs might help us better understand the roles of CAFs and the TME in cancer progression and may facilitate the development of more efficient and safer stroma-targeted cancer therapies. Here, we review recent advances in studies of signaling pathways in CAFs and briefly discuss some future perspectives on CAF research.

Heat Shock Transcription Factor 2 Is Significantly Involved in Neurodegenerative Diseases, Inflammatory Bowel Disease, Cancer, Male Infertility, and Fetal Alcohol Spectrum Disorder: The Novel Mechanisms of Several Severe Diseases.

HSF (heat shock transcription factor or heat shock factor) was discovered as a transcription factor indispensable for heat shock response. Although four classical HSFs were discovered in mammals and two major HSFs, HSF1 and HSF2, were cloned in the same year of 1991, only HSF1 was intensively studied because HSF1 can give rise to heat shock response through the induction of various HSPs' expression. On the other hand, HSF2 was not well studied for some time, which was probably due to an underestimate of HSF2 itself. Since the beginning of the 21st century, HSF2 research has progressed and many biologically significant functions of HSF2 have been revealed. For example, the roles of HSF2 in nervous system protection, inflammation, maintenance of mitosis and meiosis, and cancer cell survival and death have been gradually unveiled. However, we feel that the fact HSF2 has a relationship with various factors is not yet widely recognized; therefore, the biological significance of HSF2 has been underestimated. We strongly hope to widely communicate the significance of HSF2 to researchers and readers in broad research fields through this review. In addition, we also hope that many readers will have great interest in the molecular mechanism in which HSF2 acts as an active transcription factor and gene bookmarking mechanism of HSF2 during cell cycle progression, as is summarized in this review.

HEAT-RESPONSIVE PROTEIN regulates heat stress via fine-tuning ethylene/auxin signaling pathways in cotton.

Plants sense and respond to fluctuating temperature and light conditions during the circadian cycle; however, the molecular mechanism underlying plant adaptability during daytime warm conditions remains poorly understood. In this study, we reveal that the ectopic regulation of a HEAT RESPONSIVE PROTEIN (GhHRP) controls the adaptation and survival of cotton (Gossypium hirsutum) plants in response to warm conditions via modulating phytohormone signaling. Increased ambient temperature promptly enhanced the binding of the phytochrome interacting factor 4 (GhPIF4)/ethylene-insensitive 3 (GhEIN3) complex to the GhHRP promoter to increase its mRNA level. The ectopic expression of GhHRP promoted the temperature-dependent accumulation of GhPIF4 transcripts and hypocotyl elongation by triggering thermoresponsive growth-related genes. Notably, the upregulation of the GhHRP/GhPIF4 complex improved plant growth via modulating the abundance of Arabidopsis thaliana auxin biosynthetic gene YUCCA8 (AtYUC8)/1-aminocyclopropane-1-carboxylate synthase 8 (AtACS8) for fine-tuning the auxin/ethylene interplay, ultimately resulting in decreased ethylene biosynthesis. GhHRP thus protects chloroplasts from photo-oxidative bursts via repressing AtACS8 and AtACS7 and upregulating AtYUC8 and the heat shock transcription factors (HSFA2), heat shock proteins (HSP70 and HSP20). Strikingly, the Δhrp disruption mutant exhibited compromised production of HSP/YUC8 that resulted in an opposite phenotype with the loss of the ability to respond to warm conditions. Our results show that GhHRP is a heat-responsive signaling component that assists plants in confronting the dark phase and modulates auxin signaling to rescue growth under temperature fluctuations.

Protective effect of heat shock transcription factor 1 on acute lung injury in septic rats by regulating NOD-like receptor protein 3 inflammasome activation

To determine whether heat shock transcription factor 1 (HSF1) ameliorates sepsis induced acute lung injury (ALI) by regulating NOD-like receptor protein 3 (NLRP3) inflammasome activity in rat alveolar macrophages (AM). Twenty-four SPF Sprague-Dawley (SD) rats were divided into control group, lipopolysaccharide (LPS) group, overexpression empty vector+LPS group, and overexpression HSF1+LPS group by random number table method, with 6 rats in each group. The rat model of sepsis-induced ALI was reproduced by intraperitoneal injection of LPS (5 mg/kg); the rats in the control group were given the same volume of normal saline. The rats in the overexpression empty vector+LPS group and the overexpression HSF1+LPS group were instilled with 100 μL of overexpressed empty vector adenovirus or overexpressed HSF1 adenovirus through the trachea, respectively; the rats in the control group and LPS group were instilled with an equal volume of normal saline at the same time. At 6 hours after the model was reproduced, carotid blood was collected to determine the oxygenation index (PaO2/FiO2); lung tissue was obtained, and hematoxylin-eosin (HE) staining was performed to observe the pathological changes of lung tissue under a light microscope. Lung tissue wet/dry ratio (W/D) was determined. Immunohistochemistry was used to detect the positive expression of macrophage-specific marker antibody CD68. Western blotting was used to detect the protein expressions of HSF1 and NLRP3. Bronchoalveolar lavage fluid (BALF) was collected, and the levels of interleukins (IL-1β, IL-18) were detected by enzyme-linked immunosorbent assay (ELISA). In addition, BALF of normal rats was collected, and primary AM was isolated, cultured and divided into four groups. The AM in the blank control group was cultured normally without any treatment; the LPS group was treated with 1 mg/L LPS for 24 hours to reproduced the LPS stimulation model; AM in the overexpression empty vector+LPS group and the overexpression HSF1+LPS group were transfected with empty vector plasmid or overexpressed HSF1 plasmid, respectively, for 48 hours, and then the AM was treated with 1 mg/L LPS. The cell viability was detected by cell counting kit-8 (CCK-8). The protein expressions of HSF1 and NLRP3 in AM were detected by Western blotting. The levels of IL-1β and IL-18 in AM culture medium were determined by ELISA. Compared with the control group, the rat lung structure in the LPS group was severely injured, the alveolar cavity and pulmonary interstitium were congested and edema, the alveolar walls were significantly thickened and ruptured, accompanied by a large number of inflammatory cells infiltration. The lung W/D ratio increased, the infiltration degree of macrophages increased, PaO2/FiO2 decreased, HSF1 protein expression decreased and NLRP3 protein expression increased in lung tissue and AM, and IL-1β and IL-18 levels in BALF and AM culture medium increased. Compared with the LPS group, the degree of lung injury in the overexpression HSF1+LPS group was significantly improved, the lung W/D ratio was significantly reduced (4.76±0.16 vs. 6.93±0.33, P < 0.05), the macrophage infiltration was reduced, PaO2/FiO2 increased significantly [mmHg (1 mmHg ≈ 0.133 kPa): 397.62±19.46 vs. 280.12±37.42, P < 0.05], HSF1 protein expression was significantly up-regulated in lung tissue and AM (HSF1/GAPDH: 0.90±0.04 vs. 0.61±0.04 in lung tissue, 1.10±0.10 vs. 0.57±0.08 in AM, both P < 0.05), NLRP3 protein expression was significantly down-regulated (NLRP3/GAPDH: 0.75±0.14 vs. 1.05±0.11 in lung tissue, 0.81±0.09 vs. 1.14±0.17 in AM, both P < 0.05), and the contents of IL-1β and IL-18 in BALF and AM medium were significantly decreased [IL-1β (ng/L): 7.82±0.45 vs. 14.09±0.58 in BALF, 11.11±0.46 vs. 16.66±0.96 in AM; IL-18 (ng/L): 50.44±3.30 vs. 66.31±5.67 in BALF, 43.95±0.88 vs. 73.52±1.23 in AM, all P < 0.05]. There was no significant difference in the detection indicators between the overexpression empty vector+LPS group and the LPS group. HSF1 attenuates LPS-induced ALI in rats, and the mechanism may be related to the inhibition of NLRP3 inflammasome activation in AM.

Genome-wide identification of heat shock transcription factor families in perennial ryegrass highlights the role of LpHSFC2b in heat stress response.

Perennial ryegrass (Lolium perenne) is a cool-season turf and forage grass. Heat shock transcription factors (HSFs) play an important role in regulating plant abiotic stress. However, HSFs in perennial ryegrass have rarely been characterized. Here, 25 LpHSFs were identified from the perennial ryegrass genome. Phylogenetic analysis showed that the LpHSFs could be classified into 12 subclasses. Gene structure analysis showed that 22 LpHSFs have only one intron. Cis-acting elements analysis revealed that the promoter of 15 LpHSFs contained hormone-responsive and abiotic stress-responsive elements. Expression profile analysis indicated that 24 LpHSFs were differentially expressed under submerge, drought, heat, and cold stresses. In addition, a subclass C2 gene, LpHSFC2b, was significantly induced by abiotic stresses. The LpHSFC2b protein is localized to the nucleus, and heterologous expression of LpHSFC2b in Arabidopsis improves plant thermotolerance. This study provides insights useful for the breeding of stress tolerance in perennial ryegrass.

Integrative analysis of high temperature-induced transcriptome and metabolome alterations in the leaves of five raspberry (Rubus ideaus L.) cultivars

Raspberry has been widely accepted as a healthy fruit, but its planting in northwest China is restricted due to its heat sensitivity. To make the best use of raspberry and compare the potential for their cultivation in northwest China, five important raspberry cultivars ('Autumn Britten', 'Autumn Bliss', 'Red Autumn', 'Korean Black', 'Heritage') were collected and evaluated for their responses under high temperature stress (HTS, 32.8 ℃, compared to ambient temperature 20.4 ℃). The transcriptome and metabolome profiles are dramatically affected and show different response patterns of different cultivars to HTS. While ‘Korean Black’ and ‘Hertitage’ exhibited distinctive responses to HTS when comparing transcriptome and metabolome profiles. After enrichment analysis, we found that HTS mainly affected the amino acids and saccharide metabolism, accumulation of antioxidant metabolites and plant hormone-related MAPK signaling pathways, and alteration of α-linolenic acid metabolism in all five cultivars. Transcription factors were also analyzed and HSF (Heat Shock Transcription Factor) was identified as promising regulatory candidate for heat stress responsive gene expression in raspberry cultivars. Integrative analysis shows that the α-linolenic acid metabolism pathway is greatly altered in ‘Korean Black’ at both metabolite accumulation and gene expression levels under HTS. Especially for linolenic acid 13(S)-HPOT and jasmonic acid, as well as for genes such as PLA2-ALPHA（Ro04-snap-gene-272.47）, DAD1（Ro02-snap-gene-93.71）, LOX3（Ro03-snap-gene-410.98）, JMT（Ro04-snap-gene-23.45) are critical in HTS responses when comparing ‘Hertitage’ and ‘Korean Black’. Our work provides potential metabolic mechanisms for raspberry stress responses and suggests master genes and transcription factors responsible for stress resistance as potential targets for molecular breeding. • Five important raspberry cultivars were collected and evaluated for their responses under high temperature stress. • There are different response patterns of different cultivars to HTS. • The α-linolenic acid metabolism pathway is greatly altered under HTS.

Inducible transcriptional condensates drive 3D genome reorganization in the heat shock response

Mammalian developmental and disease-associated genes concentrate large quantities of the transcriptional machinery by forming membrane-less compartments known as transcriptional condensates. However, it is unknown whether these structures are evolutionarily conserved or involved in 3D genome reorganization. Here, we identify inducible transcriptional condensates in the yeast heat shock response (HSR). HSR condensates are biophysically dynamic spatiotemporal clusters of the sequence-specific transcription factor heat shock factor 1 (Hsf1) with Mediator and RNA Pol II. Uniquely, HSR condensates drive the coalescence of multiple Hsf1 target genes, even those located on different chromosomes. Binding of the chaperone Hsp70 to a site on Hsf1 represses clustering, whereas an intrinsically disordered region on Hsf1 promotes condensate formation and intergenic interactions. Mutation of both Hsf1 determinants reprograms HSR condensates to become constitutively active without intergenic coalescence, which comes at a fitness cost. These results suggest that transcriptional condensates are ancient and flexible compartments of eukaryotic gene control.

Exploiting Virus Infection to Protect Plants from Abiotic Stresses: Tomato Protection by a Begomovirus.

Tomato cultivation is threatened by environmental stresses (e.g., heat, drought) and by viral infection (mainly viruses belonging to the tomato yellow leaf curl virus family-TYLCVs). Unlike many RNA viruses, TYLCV infection does not induce a hypersensitive response and cell death in tomato plants. To ensure a successful infection, TYLCV preserves a suitable cellular environment where it can reproduce. Infected plants experience a mild stress, undergo adaptation and become partially "ready" to exposure to other environmental stresses. Plant wilting and cessation of growth caused by heat and drought is suppressed by TYLCV infection, mainly by down-regulating the heat shock transcription factors, HSFA1, HSFA2, HSFB1 and consequently, the expression of HSF-regulated stress genes. In particular, TYLCV captures HSFA2 by inducing protein complexes and aggregates, thus attenuating an acute stress response, which otherwise causes plant death. Viral infection mitigates the increase in stress-induced metabolites, such as carbohydrates and amino acids, and leads to their reallocation from shoots to roots. Under high temperatures and water deficit, TYLCV induces plant cellular homeostasis, promoting host survival. Thus, this virus-plant interaction is beneficial for both partners.