Heat Shock Transcription Factor Research Articles

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.

A long noncoding RNA HILinc1 enhances pear thermotolerance by stabilizing PbHILT1 transcripts through complementary base pairing

As global warming intensifies, heat stress has become a major environmental constraint threatening crop production and quality worldwide. Here, we characterize Heat-induced long intergenic noncoding RNA 1 (HILinc1), a cytoplasm-enriched lincRNA that plays a key role in thermotolerance regulation of pear (Pyrus spp.). HILinc1 Target 1 (PbHILT1) which is the target transcript of HILinc1, was stabilized via complementary base pairing to upregulate its expression. PbHILT1 could bind to Heat shock transcription factor A1b (PbHSFA1b) to enhance its transcriptional activity, leading to the upregulation of a major downstream transcriptional regulator, Multiprotein bridging factor 1c (PbMBF1c), during heat response. Transient overexpressing of either HILinc1 or PbHILT1 increases thermotolerance in pear, while transient silencing of HILinc1 or PbHILT1 makes pear plants more heat sensitive. These findings provide evidences for a new regulatory mechanism by which HILinc1 facilitates PbHSFA1b activity and enhances pear thermotolerance through stabilizing PbHILT1 transcripts.

A Heat Shock Transcription Factor TrHSFB2a of White Clover Negatively Regulates Drought, Heat and Salt Stress Tolerance in Transgenic Arabidopsis

Heat shock transcription factors (HSF) are divided into classes A, B and C. Class A transcription factors are generally recognized as transcriptional activators, while functional characterization of class B and C heat shock transcription factors have not been fully developed in most plant species. We isolated and characterized a novel HSF transcription factor gene, TrHSFB2a (a class B HSF) gene, from the drought stress-sensitive forage crop species, white clover (Trifolium repens). TrHSFB2a was highly homologous to MtHSFB2b, CarHSFB2a, AtHSFB2b and AtHSFB2a. The expression of TrHSFB2a was strongly induced by drought (PEG6000 15% w/v), high temperature (35 °C) and salt stresses (200 mM L-1 NaCl) in white clover, while subcellular localization analysis showed that it is a nuclear protein. Overexpression of the white clover gene TrHSFB2a in Arabidopsis significantly reduced fresh and dry weight, relative water contents (RWC), maximum photosynthesis efficiency (Fv/Fm) and performance index on the absorption basis (PIABS), while it promoted leaf senescence, relative electrical conductivity (REC) and the contents of malondialdehyde (MDA) compared to a wild type under drought, heat and salt stress conditions of Arabidopsis plants. The silencing of its native homolog (AtHSFB2a) by RNA interference in Arabidopsis thaliana showed opposite trends by significantly increasing fresh and dry weights, RWC, maximum photosynthesis efficiency (Fv/Fm) and performance index on the absorption basis (PIABS) and reducing REC and MDA contents under drought, heat and salt stress conditions compared to wild type Arabidopsis plants. These phenotypic and physiological indicators suggested that the TrHSFB2a of white clover functions as a negative regulator of heat, salt and drought tolerance. The bioinformatics analysis showed that TrHSFB2a contained the core B3 repression domain (BRD) that has been reported as a repressor activator domain in other plant species that might repress the activation of the heat shock-inducible genes required in the stress tolerance process in plants. The present study explores one of the potential causes of drought and heat sensitivity in white clover that can be overcome to some extent by silencing the TrHSFB2a gene in white clover.

Genome-Wide Identification and Expression Analysis of HSF Transcription Factors in Alfalfa (Medicago sativa) under Abiotic Stress.

Alfalfa (Medicago sativa) is one of the most important legume forage species in the world. It is often affected by several abiotic stressors that result in reduced yields and poor growth. Therefore, it is crucial to study the resistance of M. sativa to abiotic stresses. Heat shock transcription factors (HSF) are key players in a number of transcriptional regulatory pathways. These pathways play an essential role in controlling how plants react to different abiotic stressors. Studies on the HSF gene family have been reported in many species but have not yet undergone a thorough analysis in M. sativa. Therefore, in order to identify a more comprehensive set of HSF genes, from the genomic data, we identified 16 members of the MsHSF gene, which were unevenly distributed over six chromosomes. We also looked at their gene architectures and protein motifs, and phylogenetic analysis allowed us to divide them into 3 groups with a total of 15 subgroups. Along with these aspects, we then examined the physicochemical properties, subcellular localization, synteny analysis, GO annotation and enrichment, and protein interaction networks of amino acids. Finally, the analysis of 16 MsHSF genes’ expression levels across all tissues and under four abiotic stresses using publicly available RNA-Seq data revealed that these genes had significant tissue-specific expression. Moreover, the expression of most MsHSF genes increased dramatically under abiotic stress, further validating the critical function played by the MsHSF gene family in abiotic stress. These results provided basic information about MsHSF gene family and laid a foundation for further study on the biological role of MsHSF gene in response to stress in M. sativa.

HSF1 is a driver of leukemia stem cell self-renewal in acute myeloid leukemia

Acute myeloid leukemia (AML) is maintained by self-renewing leukemic stem cells (LSCs). A fundamental problem in treating AML is that conventional therapy fails to eliminate LSCs, which can reinitiate leukemia. Heat shock transcription factor 1 (HSF1), a central regulator of the stress response, has emerged as an important target in cancer therapy. Using genetic Hsf1 deletion and a direct HSF1 small molecule inhibitor, we show that HSF1 is specifically required for the maintenance of AML, while sparing steady-state and stressed hematopoiesis. Mechanistically, deletion of Hsf1 dysregulates multifaceted genes involved in LSC stemness and suppresses mitochondrial oxidative phosphorylation through downregulation of succinate dehydrogenase C (SDHC), a direct HSF1 target. Forced expression of SDHC largely restores the Hsf1 ablation-induced AML developmental defect. Importantly, the growth and engraftment of human AML cells are suppressed by HSF1 inhibition. Our data provide a rationale for developing efficacious small molecules to specifically target HSF1 in AML.

Functional Characterization of Heat Shock Factor (CrHsf) Families Provide Comprehensive Insight into the Adaptive Mechanisms of Canavalia rosea (Sw.) DC. to Tropical Coral Islands.

Heat shock transcription factors (Hsfs) are key regulators in plant heat stress response, and therefore, they play vital roles in signal transduction pathways in response to environmental stresses, as well as in plant growth and development. Canavalia rosea (Sw.) DC. is an extremophile halophyte with good adaptability to high temperature and salt-drought tolerance, and it can be used as a pioneer species for ecological reconstruction on tropical coral islands. To date, very little is known regarding the functions of Hsfs in the adaptation mechanisms of plant species with specialized habitats, especially in tropical leguminous halophytes. In this study, a genome-wide analysis was performed to identify all the Hsfs in C. rosea based on whole-genome sequencing information. The chromosomal location, protein domain or motif organization, and phylogenetic relationships of 28 CrHsfs were analyzed. Promoter analyses indicated that the expression levels of different CrHsfs were precisely regulated. The expression patterns also revealed clear transcriptional changes among different C. rosea tissues, indicating that the regulation of CrHsf expression varied among organs in a developmental or tissue-specific manner. Furthermore, the expression levels of most CrHsfs in response to environmental conditions or abiotic stresses also implied a possible positive regulatory role of this gene family under abiotic stresses, and suggested roles in adaptation to specialized habitats such as tropical coral islands. In addition, some CrHsfAs were cloned and their possible roles in abiotic stress tolerance were functionally characterized using a yeast expression system. The CrHsfAs significantly enhanced yeast survival under thermal and oxidative stress challenges. Our results contribute to a better understanding of the plant Hsf gene family and provide a basis for further study of CrHsf functions in environmental thermotolerance. Our results also provide valuable information on the evolutionary relationships among CrHsf genes and the functional characteristics of the gene family. These findings are beneficial for further research on the natural ecological adaptability of C. rosea to tropical environments.

Ovarian tumorB1-mediated heat shock transcription factor 1 deubiquitination is critical for glycolysis and development of endometriosis

Endometriosis is a common chronic condition characterized by abnormal growth of the endometrium outside the uterus. Heat shock transcription factor 1 (HSF1) is a significant regulator of the proteotoxic stress response and plays an essential role in developing endometriosis. However, the mechanisms regulating HSF1 protein stability in endometriosis remain unclear. Here, we demonstrate that OTUB1 interacts with HSF1 and promotes HSF1 protein stability through deubiquitination. In addition, OTUB1 enhances glycolysis and epithelial-mesenchymal transition of endometriosis cells, leading to promote proliferation, migration, and invasion of endometriosis cells. The progression of endometriosis is inhibited in an OTUB1-knockout mouse model. In summary, OTUB1 promotes the development of endometriosis by up-regulating HSF1. OTUB1/HSF1 axis may become a new therapeutic target for endometriosis.

Heat shock transcriptional factors (HSFs) are expressed in response to hydrogen peroxide production in grapevines inoculated with Colletotrichum Species

Heat shock transcriptional factors (HSFs) are expressed in plants due to external stress, high temperatures, or pathogenic infections. This study was undertaken to analyze the expression of HSF genes in grapevines inoculated with pathogens. Spores of Colletotrichum acutatum and C. gloeosporioides were inoculated on the leaves, and on immature and mature fruits of ‘Campbell Early’ and creeping grapevine (Vitis flexuosa). The real-time PCR of RNA isolated from infected leaves and fruits showed specific upregulation of HSF11, HSF12, HSF14, and HSF15 subsequent to both high temperature and pathogen infections. However, HSF16 and HSF17 were up-regulated specifically by pathogenic infections only and showed different expression patterns in response to wounding. Among the hydrogen peroxide-related genes, the expression of catalase (CAT) and superoxide dismutase (SOD) was up-regulated by pathogen infections. Concurrently, expression of six HSFs (HSF11, HSF12, HSF14, HSF15, HSF16, and HSF17) dose-dependently increased with accumulation of hydrogen peroxide in the leaves and fruits of grapevines. The expression of selected HSF genes was up-regulated differentially as a defense reaction in ‘Campbell Early’ and V. flexuosa grapevine in response to external stress (such as wounding) and pathogen inoculation. This indicates that expression of some HSFs is regulated through the hydrogen peroxide-mediated pathways in response to pathogens. Further studies determining the mechanism of HSF gene expression induced by external stress are required.

Knockdown of heat shock transcription factor 1 decreases temperature stress tolerance in Bemisia tabaci MED.

The primary function of heat shock transcription factor (HSF) in the heat shock response is to activate the transcription of genes encoding heat shock proteins (HSPs). The phloem-feeding insect Bemisia tabaci (Gennadius) is an important pest of cotton, vegetables and ornamentals that transmits several plant viruses and causes enormous agricultural losses. In this study, the gene encoding HSF (Bthsf1) was characterized in MED B. tabaci. The full-length cDNA encoded a protein of 652 amino acids with an isoelectric point of 5.55. The BtHSF1 deduced amino acid sequence showed strong similarity to HSF in other insects. Expression analyses using quantitative real-time PCR indicated that Bthsf1 was significantly up-regulated in B. tabaci adults and pupae during thermal stress. Although Bthsf1 was induced by both hot and cold stress, the amplitude of expression was greater in the former. Bthsf1 had distinct, significant differences in expression pattern during different duration of high but not low temperature stress. Oral ingestion of dsBthsf1 repressed the expression of Bthsf1 and four heat shock proteins (Bthsp90, Bthsp70-3, Bthsp20 and Bthsp19.5) in MED B. tabaci during hot and cold stress. In conclusion, our results show that Bthsf1 is differentially expressed during high and low temperature stress and regulates the transcription of multiple hsps in MED B. tabaci.

Potential G‐quadruplexes within the Promoter Nuclease Hypersensitive Sites of the Heat‐Responsive Genes in Rice

G-quadruplexes (G4s) have been shown to be involved in the regulation of multiple cellular processes. Exploring putative G4-forming sequences (PQSs) in heat-responsive genes of rice and their folding structures under different conditions will help to understand the mechanism in response to heat stress. In this work, we discovered a prevalence of PQSs in nuclease hypersensitive sites within the promoters of heat-responsive genes. Moreover, 50 % of the searched G3 PQSs ((G3+ L1-7 )3+ G3+ ) locate in heat shock transcription factors. Circular dichroism spectroscopy, thermal difference spectroscopy, and UV melting analysis demonstrated the representative PQSs could adopt stable G4s at physiological temperature and potassium concentration. These PQSs were able to stall Klenow fragment (KF) DNA polymerase by the formation of G4s. However, the G4s with Tm values around 50-60 °C could be increasingly unwound by KF with the increase of temperatures from 25 to 50 °C, implying that these G4s could sense the changes in temperature by structural switch. This work offers fresh clues to understanding the potential of G4-involved functions of PQSs and the molecular events in plants in response to heat 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.

Hydrocortisone alleviates sepsis-induced acute kidney injury through HSF-1-mediated transcriptional suppression of XPO1

BackgroundHydrocortisone (HYD) has been suggested as a drug for anti-sepsis treatment, but its clinical efficacy remains controversial. This study aims to evaluate the function of HYD in sepsis-induced acute kidney injury (AKI) and the molecules involved. MethodsA mouse model of sepsis was induced by cecal ligation and puncture (CLP) and treated with HYD. The kidney injury biomarkers and inflammatory cytokines in serum samples were determined. The pathological changes in mouse kidney tissues were examined by histological staining. Differentially expressed genes after HYD treatment were screened by microarray analysis. Expression of heat shock transcription factor 1 (HSF1) in the serum samples of septic patients and mouse kidney tissues after HYD treatment was determined. The downstream targets of HSF1 were bioinformatically predicted. Gain- and loss-of-function assays of HSF1 and exportin 1 (XPO1) were performed to validate their functions in AKI. ResultsCLP increased the levels of blood urea nitrogen and serum creatinine and the serum levels of pro-inflammatory cytokines. The levels of these biomarkers and the pathological changes and symptoms in mice induced by CLP were significantly alleviated by HYD treatment. HYD elevated the expression of HSF1, which was initially suppressed by CLP in mice. HSF1 bound to XPO1 promoter to suppress its transcription. Downregulation of HSF1 blocked the protective effects of HYD, but further suppression of XPO1 restored the function of HYD and ameliorated the kidney injury in mice. ConclusionThis study demonstrates that HYD alleviates sepsis-induced acute kidney injury through HSF1-mediated transcriptional suppression of XPO1.

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 .

The in vivo performance of a heat shock transcription factor from Populus euphratica, PeHSFA2, promises a prospective strategy to alleviate heat stress damage in poplar

Heat stress driven by global warming has affected forest yields and survival at a larger scale in recent decades, hence breeding heat-tolerant tree species has become imperative. We here investigated the role of PeHSFA2, a crucial gene in plant heat shock response from Populus euphratica, in regulating plant heat stress protection. PeHSFA2 is localized to the cytoplasm and nucleus and can be transported from the cytoplasm into the nucleus under detrimental high-temperature conditions. Poplar plants with overexpressed PeHSFA2 outperformed the control group when subjected to severe heat stress, for they had higher leaf water content, lower leaf relative electrolyte leakage, and better photosynthetic activity after heat treatment. The results of qRT-PCR analyses revealed that PeHSFA2 regulates the transcription of a group of heat-protective genes including small heat shock protein, GALACTINOL SYNTHASE 2.2, and ASCORBATE PEROXIDASE 2 in white poplar. Transactivation assays confirmed that PeHSFA2 activated the expression of PtoHSP19.9, PtoHSP21.3, PtoHSP21.8, PtoHSP22.0, PtoGOLS2.2, and PtoAPX2 via binding to the promoter regions of these genes. These results emphasize the point that PeHSFA2 can vehemently reinforce plant thermotolerance via regulating the transcription of a set of heat shock response genes, and PeHSFA2 possesses enormous potential in breeding poplar plants with substantially enhanced thermotolerance.

A heat shock transcription factor gene (HaHSFA1) from a desert shrub, Haloxylon ammodendron, elevates salt tolerance in Arabidopsis thaliana

Haloxylon ammodendron is a typical desert xerophyte with worthy genetic resources, therefore, it is necessary to explore the resistance genes of H. ammodendron , and to improve the stress tolerance of other plant species through genetic engineering. In this study, a heat shock transcription factor gene, HaHSFA1 , was firstly cloned from H. ammodendron and overexpressed in Arabidopsis thaliana . The sensitivity of transgenic plants to exogenous ABA, osmotic stress and salt stress were analyzed; the effects of overexpression of HaHSFA1 in Arabidopsis on salt tolerance were deeply investigated. The results indicated that overexpression of HaHSFA1 increased chlorophyll content in Arabidopsis, and the growth of plants was promoted. The leaf soluble sugar and proline contents in OE lines were significantly increased compared with those in WT. OE lines maintained lower osmotic potential and higher shoot water content. Overexpression of HaHSFA1 in Arabidopsis also enhanced antioxidant activity, which may be important for protecting plasma membrane integrity in cells. Overexpression of HaHSFA1 in Arabidopsis improved root activity and increased selective absorption and transport capacity for K + over Na + , which was of great significance to reduce the toxic effect of Na + . This study indicated that overexpression of HaHSFA1 from H. ammodendron significantly elevates the salt tolerance of Arabidopsis, and HaHSFA1 has potential application values in improving abiotic stress tolerance in crops by genetic engineering. • HaHSFA1 was firstly cloned from a desert shrub, Haloxylon ammodendron . • Overexpression of HaHSFA1 enhanced osmotic adjustment and ROS scavenging ability in Arabidopsis. • Overexpression of HaHSFA1 maintained higher selectivity of absorption and transport for K + over Na + in Arabidopsis.

Brassinosteroids promote thermotolerance through releasing BIN2-mediated phosphorylation and suppression of HsfA1 transcription factors in Arabidopsis

High temperature adversely affects plant growth and development. The steroid phytohormones brassinosteroids (BRs) are recognized to play important roles in plant heat stress responses and thermotolerance, but the underlying mechanisms remain obscure. Here, we demonstrate that the glycogen synthase kinase 3 (GSK3)-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2), a negative component in the BR signaling pathway, interacts with the master heat-responsive transcription factors CLASS A1 HEAT SHOCK TRANSCRIPTION FACTORS (HsfA1s). Furthermore, BIN2 phosphorylates HsfA1d on T263 and S56 to suppress its nuclear localization and inhibit its DNA-binding ability, respectively. BR signaling promotes plant thermotolerance by releasing the BIN2 suppression of HsfA1d to facilitate its nuclear localization and DNA binding. Our study provides insights into the molecular mechanisms by which BRs promote plant thermotolerance by strongly regulating HsfA1d through BIN2 and suggests potential ways to improve crop yield under extreme high temperatures.

Biological characteristics of heat shock transcription factors and their roles in abiotic stress adaptation of higher plant

Heat shock transcription factors (HSFs) are involved in the regulation of plant growth and development. Furthermore, HSFs regulate the expression of a series of genes related to various abiotic stress adaptations. HSFs usually form homotrimers to activate their transcriptional activity and function. Here, we review the basic structure, subcellular localization, transcriptional regulation, functional diversity of HSFs, and their roles in plant adaptation to abiotic stresses, such as extreme temperature, salinity, drought, strong light and oxidative stress, etc. HSFs are high-quality candidate genes for improving the resistance of higher plants to multiple stresses. Studies of HSFs have important application value. In the future, using HSFs to improve the resistance of various crops through genetic engineering would be prospects of development.