Heat stress proteins and transcription factors

High and Low Temperatures Differentially Affect Survival, Reproduction, and Gene Transcription in Male and Female Moths of Spodoptera frugiperda

In this study, we found that both heat and cold stresses significantly affected the survival and reproduction of both sexes in Spodoptera frugiperda adults, with larvae showing relatively higher extreme temperature tolerance. Further transcriptomic analysis in adults found remarkable differences and similarities between sexes in terms of temperature stress responses. Metabolism-related processes were suppressed in heat stressed females, which did not occur to the same extend in males. Moreover, both heat and cold stress reduced immune activities in both sexes. Heat stress induced the upregulation of many heat shock proteins in both sexes, whereas the response to cold stress was insignificant. More cold tolerance-related genes, such as cuticle proteins, UDP-glucuronosyltransferase, and facilitated trehalose transporter Tret1, were found upregulated in males, whereas most of these genes were downregulated in females. Moreover, a large number of fatty acid-related genes, such as fatty acid synthases and desaturases, were differentially expressed under heat and cold stresses in both sexes. Heat stress in females induced the upregulation of a large number of zinc finger proteins and reproduction-related genes; whereas cold stress induced downregulation in genes linked to reproduction. In addition, TRPA1-like encoding genes (which have functions involved in detecting temperature changes) and sex peptide receptor-like genes were found to be differentially expressed in stressed moths. These results indicate sex-specific heat and cold stress responses and adaptive mechanisms and suggest sex-specific trade-offs between stress-resistant progresses and fundamental metabolic processes as well as between survival and reproduction.

A small heat shock protein GmHSP18.5a improves the male fertility restorability of cytoplasmic male sterility-based restorer line under high temperature stress in soybean

Small heat shock protein (sHSP) is involved in high temperature (HT) stress response. However, the function of sHSPs in regulating male fertility of soybean under HT stress remains largely unknown. Here, we identified a sHSP gene, GmHSP18.5a, which was responded to HT stress during flowering in cytoplasmic male sterility (CMS)-based restorer line of soybean. Moreover, GmHSFA6b turned out to directly activated the expression of GmHSP18.5a by binding to the heat shock cis-element in its promoter. Overexpression of GmHSP18.5a increased male fertility in transgenic Arabidopsis, soybean CMS-based restorer line and its hybrid F1 with CMS line under HT stress. Reactive oxygen species (ROS) content detection revealed that GmHSP18.5a promoted the ROS scavenging ability of Arabidopsis inflorescence and soybean flower bud under HT stress. Enzyme activity assay and gene expression analysis indicated that GmHS18.5a mainly increased the activity of antioxidant enzymes and the expression level of ROS metabolism-related genes under HT stress. Our results indicated that GmHSP18.5a improved the male fertility restorability of CMS-based restorer line in soybean by regulating ROS metabolic pathway and reducing ROS accumulation. Our findings not only revealed the molecular mechanism of sHSP regulating the male fertility of soybean under HT stress, but also provided a theoretical basis for creating strong restorer line with thermotolerance.

Integrated Analysis of the Transcriptome and Metabolome of Brassica rapa Revealed Regulatory Mechanism under Heat Stress

Affected by global warming; heat stress is the main limiting factor for crop growth and development. Brassica rapa prefers cool weather, and heat stress has a significant negative impact on its growth, development, and metabolism. Understanding the regulatory patterns of heat-resistant and heat-sensitive varieties under heat stress can help deepen understanding of plant heat tolerance mechanisms. In this study, an integrative analysis of transcriptome and metabolome was performed on the heat-tolerant ('WYM') and heat-sensitive ('AJH') lines of Brassica rapa to reveal the regulatory networks correlated to heat tolerance and to identify key regulatory genes. Heat stress was applied to two Brassica rapa cultivars, and the leaves were analyzed at the transcriptional and metabolic levels. The results suggest that the heat shock protein (HSP) family, plant hormone transduction, chlorophyll degradation, photosynthetic pathway, and reactive oxygen species (ROS) metabolism play an outstanding role in the adaptation mechanism of plant heat tolerance. Our discovery lays the foundation for future breeding of horticultural crops for heat resistance.

Alternative splicing of TaHSFA6e modulates heat shock protein-mediated translational regulation in response to heat stress in wheat

Heat stress greatly threatens crop production. Plants have evolved multiple adaptive mechanisms, including alternative splicing, that allow them to withstand this stress. However, how alternative splicing contributes to heat stress responses in wheat (Triticum aestivum) is unclear. We reveal that the heat shock transcription factor gene TaHSFA6e is alternatively spliced in response to heat stress. TaHSFA6e generates two major functional transcripts: TaHSFA6e-II and TaHSFA6e-III. TaHSFA6e-III enhances the transcriptional activity of three downstream heat shock protein 70 (TaHSP70) genes to a greater extent than does TaHSFA6e-II. Further investigation reveals that the enhanced transcriptional activity of TaHSFA6e-III is due to a 14-amino acid peptide at its C-terminus, which arises from alternative splicing and is predicted to form an amphipathic helix. Results show that knockout of TaHSFA6e or TaHSP70s increases heat sensitivity in wheat. Moreover, TaHSP70s are localized in stress granule following exposure to heat stress and are involved in regulating stress granule disassembly and translation re-initiation upon stress relief. Polysome profiling analysis confirms that the translational efficiency of stress granule stored mRNAs is lower at the recovery stage in Tahsp70s mutants than in the wild types. Our finding provides insight into the molecular mechanisms by which alternative splicing improves the thermotolerance in wheat.

Molecular and biochemical biomarkers in the American oyster Crassostrea virginica exposed to herbicide Roundup® at high temperature

Aquatic organisms are frequently exposed to various environmental stressors. Thus, the effects of high temperatures and herbicides on aquatic organisms are a major subject of interest. In this study, we studied the effects of short-term exposure (1 week) to Roundup®, a glyphosate-based herbicide (concentrations: 0.5 and 5 µg/L), on the morphology of gills, digestive glands, and connective tissues, and the expression of heat shock protein-70 (HSP70, a chaperone protein), cytochrome P450 (CYP450, a biomarker of environmental contaminants), dinitrophenyl protein (DNP, a biomarker of protein oxidation), nitrotyrosine protein (NTP, a biomarker of protein nitration), antioxidant enzymes such as superoxidase dismutase (SOD) and catalase (CAT) in tissues of American oyster, Crassostrea virginica (Gmelin, 1791) maintained at high temperature (30 °C). Histological analyses showed an increase in mucous production in the gills and digestive glands, and in hemocyte aggregation in the connective tissues as well as a structural change of lumen in the digestive glands of oysters exposed to Roundup. Immunohistochemical and quantitative RT-PCR analyses showed significant (P < 0.05) increases in HSP70, CYP450, DNP, NTP, CAT, and SOD mRNA and protein expressions in the tissues of oysters exposed to Roundup. Taken together, these results suggest that exposure to Roundup at high temperature induces overproduction of reactive oxygen species/reactive nitrogen species which in turn leads to altered prooxidant-antioxidant activity in oyster tissues. Moreover, our results provide new information on protein oxidation/nitration and antioxidant-dependent mechanisms for HSP70 and CYP450 regulations in oysters exposed to Roundup at high temperature.

Overexpression of AHL proteins enhances root hair production by altering the transcription of RHD6-downstream genes

AT-HOOK MOTIF NUCLEAR LOCALIZED (AHL) proteins occur in all sequenced plant species. They bind to the AT-rich DNA sequences in chromosomes and regulate gene transcription related to diverse biological processes. However, the molecular mechanism underlying how AHL proteins regulate gene transcription is poorly understood. In this research, we used root hair production as a readout to study the function of two Arabidopsis AHL proteins, AHL17, and its closest homolog AHL28. Overexpression of AHL17 or AHL28 greatly enhanced root hair production by increasing the transcription of an array of genes downstream of RHD6. RHD6 is a key transcription factor that regulates root hair development. Mutation of RHD6 completely suppressed the overproduction of root hairs by blocking the transcription of AHL17-activated genes. The overexpression of AHL17 or AHL28, however, neither affected the transcription of RHD6 nor the accumulation of RHD6 protein. These two AHL proteins also did not directly interact with RHD6. Furthermore, we found that three members of the Heat Shock Protein70 family, which have been annotated as the subunits of the plant Mediator complex, could form a complex with both AHL17 and RHD6. Our research might reveal a previously unrecognized mechanism of how AHL proteins regulate gene transcription.

Exogenous Methyl Jasmonate Mediated MiRNA-mRNA Network Improves Heat Tolerance of Perennial Ryegrass

Heat stress can hinder the growth of perennial ryegrass (Lolium perenne L.). Methyl jasmonate (MeJA) applied exogenously can increase heat stress tolerance in plants; however, the regulatory mechanisms involved in heat tolerance mediated by MeJA are poorly understood in perennial ryegrass. Here, the microRNA (miRNA) expression profiles of perennial ryegrass were assessed to elucidate the regulatory pathways associated with heat tolerance induced by MeJA. Plants were subjected to four treatments, namely, control (CK), MeJA pre-treatment (T), heat stress treatment (H), and MeJA pre-treatment + heat stress (TH). According to the results, 102 miRNAs were up-regulated in all treatments, with 20, 27, and 33 miRNAs being up-regulated in the T, H, and TH treatment groups, respectively. The co-expression network analysis between the deferentially expressed miRNAs and their corresponding target genes showed that 20 miRNAs modulated 51 potential target genes. Notably, the miRNAs that targeted genes related to with regards to heat tolerance were driven by MeJA, and they were involved in four pathways: novel-m0258-5p mediated signal transduction, novel-m0350-5p mediated protein homeostasis, miR397-z, miR5658-z, and novel-m0008-5p involved in cell wall component, and miR1144-z and miR5185-z dominated chlorophyll degradation. Overall, the findings of this research paved the way for more research into the heat tolerance mechanism in perennial ryegrass and provided a theoretical foundation for developing cultivars with enhanced heat tolerance.

Involvement of microRNA164 in responses to heat stress in Arabidopsis

MicroRNAs (miRNAs) are considered to be integral parts of plant stress regulatory networks. Under long-term heat stress, miR164 is induced. Conversely, its targets are repressed. Transgenic overexpressors (164OE) and mutants of MIR164 (mir164) were used to study miR164's functions during heat responses. Target gene expression decreased in 164OE transgenic plants and increased in mir164a-4 and mir164b mutants. Under heat stress, the mir164 mutants presented heat-sensitive phenotypes, while 164OE transgenic plants showed better thermotolerance than wild-type (WT) plants. Overexpression of miR164 decreased heat-inhibition of hypocotyl lengths. Under heat stress, miR164 target genes modulated the expression of chlorophyll b reductase and chlorophyll catabolic genes, reducing the chlorophyll a/b ratio. More H₂O₂ accumulated in the mir164 mutants under heat stress, which may have caused oxidative damage. In addition, expression of HSPs was altered in the experimental plants compared to that of the WT. Overall, miR164 influenced target gene expression, altering development, chlorophyll a/b ratio, H₂O₂-caused damage, and HSPs expression under long-term heat stress. These phenomena, in turn, likely influence the thermotolerance of plants.

Transcriptomic Analysis of Heat Stress Response in Brassica rapa L. ssp. pekinensis with Improved Thermotolerance through Exogenous Glycine Betaine

Chinese cabbage (Brassica rapa L. ssp. pekinensis) is sensitive to high temperature, which will cause the B. rapa to remain in a semi-dormancy state. Foliar spray of GB prior to heat stress was proven to enhance B. rapa thermotolerance. In order to understand the molecular mechanisms of GB-primed resistance or adaptation towards heat stress, we investigated the transcriptomes of GB-primed and non-primed heat-sensitive B. rapa ‘Beijing No. 3’ variety by RNA-Seq analysis. A total of 582 differentially expressed genes (DEGs) were identified from GB-primed plants exposed to heat stress relative to non-primed plants under heat stress and were assigned to 350 gene ontology (GO) pathways and 69 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. The analysis of the KEGG enrichment pathways revealed that the most abundantly up-regulated pathways were protein processing in endoplasmic reticulum (14 genes), followed by plant hormone signal transduction (12 genes), ribosome (8 genes), MAPK signaling pathway (8 genes), homologous recombination (7 genes), nucleotide excision repair metabolism (5 genes), glutathione metabolism (4 genes), and ascorbate and aldarate metabolism (4 genes). The most abundantly down-regulated pathways were plant-pathogen interaction (14 genes), followed by phenylpropanoid biosynthesis (7 genes); arginine and proline metabolism (6 genes); cutin, suberine, and wax biosynthesis (4 genes); and tryptophan metabolism (4 genes). Several calcium sensing/transducing proteins, as well as transcription factors associated with abscisic acid (ABA), salicylic acid (SA), auxin, and cytokinin hormones were either up- or down-regulated in GB-primed B. rapa plants under heat stress. In particular, expression of the genes for antioxidant defense, heat shock response, and DNA damage repair systems were highly increased by GB priming. On the other hand, many of the genes involved in the calcium sensors and cell surface receptors involved in plant innate immunity and the biosynthesis of secondary metabolites were down-regulated in the absence of pathogen elicitors in GB-primed B. rapa seedlings. Overall GB priming activated ABA and SA signaling pathways but deactivated auxin and cytokinin signaling pathways while suppressing the innate immunity in B. rapa seedlings exposed to heat stress. The present study provides a preliminary understanding of the thermotolerance mechanisms in GB-primed plants and is of great importance in developing thermotolerant B. rapa cultivars by using the identified DEGs through genetic modification.

bZIP17 regulates heat stress tolerance at reproductive stage in Arabidopsis

High temperature elicits a well-conserved response called the unfolded protein response (UPR) to bring protein homeostasis in the endoplasmic reticulum (ER). Two key UPR regulators bZIP28 and bZIP60 have been shown to be essential for maintaining fertility under heat stress conditions in Arabidopsis, however, the function of transcriptional activator bZIP17, a paralog of bZIP28, in heat stress response at reproductive stage is not reported. Here we found that bzip17 mutant plants were sensitive to heat stress in terms of silique length and fertility comparing to that of wildtype (WT) Arabidopsis plants, and transcriptomic analysis showed that 1380 genes were specifically up-regulated and 493 genes were specifically down-regulated by heat stress in the flowers of WT plants comparing to that in bzip17 mutant plants. These bZIP17-dependent up-regulated genes were enriched in responses to abiotic stresses such as water deprivation and salt stress. Further chromatin immuno-precipitation coupled with high-throughput sequencing (ChIP-Seq) uncovered 1645 genes that were direct targets of bZIP17 in MYC-bZIP17 expressing seedlings subjected to heat stress. Among these 1645 genes, ERSE-II cis-element was enriched in the binding peaks of their promoters, and the up-regulation of 113 genes by heat stress in flowers was dependent on bZIP17. Our results revealed direct targets of bZIP17 in flowers during heat stress responses and demonstrated the important role of bZIP17 in maintaining fertility upon heat stress in plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42994-021-00062-1.

Relative expression of the developmentally important candidate genes in immature oocytes and in vitro-produced embryos of buffalo (Bubalus bubalis)

The study was undertaken to examine the relative abundance (RA) of the major developmental important candidate genes in different grades of immature oocytes (A-grade, B-grade, C-grade and D-grade) and various stages of in vitro-produced embryos (2-cell, 4-cell, 8–16-cell, morula, and blastocyst) of buffalo using RT-qPCR. Results showed that the RA of GLUT1, CX43, HSP70.1 and GDF9 was significantly higher (P < 0.05) in the A-grade of oocytes than the C-grade and D-grade but did not differ significantly from the B-grade of oocytes. Similarly, RA of BMP15 and Survivin were significantly higher (P < 0.05) in A-grade than the other grades of oocytes, however, poly(A) polymerase expression was not significantly different (P > 0.05) among the immature oocytes. The expression of GLUT1 was significantly higher (P < 0.05) in the blastocysts, but the expression of CX43 (P < 0.05; P > 0.05), HSP70.1 (P < 0.05; P > 0.05) and GDF9 (P > 0.05) was higher at the 2-cell stage than the other stages of embryos. Interestingly, the expression levels of poly(A) polymerase (P < 0.05), BMP15 (P < 0.05; P > 0.05) and Survivin (P > 0.05) were higher at the 8–16-cell stage than the other stages of embryos. It is concluded that A-grade of immature oocytes has shown more mRNA abundance for the major developmental important genes; therefore A-grade oocytes may be considered as the most developmentally competent and suitable for handmade cloning research in buffalo.

Analyzing the regulatory role of heat shock transcription factors in plant heat stress tolerance: a brief appraisal

An increase in ambient temperature throughout the twenty-first century has been described as a "worldwide threat" for crop production. Due to their sessile lifestyles, plants have evolved highly sophisticated and complex heat stress response (HSR) mechanisms to respond to higher temperatures. The HSR allows plants to minimize the damages caused by heat stress (HS), thus enabling cellular protection. HSR is crucial for their lifecycle and yield, particularly for plants grown in the field. At the cellular level, HSR involves the production of heat shock proteins (HSPs) and other stress-responsive proteins to counter the negative effects of HS. The expression of most HSPs is transcriptionally regulated by heat shock transcription factors (HSFs). HSFs are a group of evolutionary conserved regulatory proteins present in all eukaryotes and regulate various stress responses and biological processes in plants. In recent years, significant progress has been made in deciphering the complex regulatory network of HSFs, and several HSFs not only from model plants but also from major crops have been functionally characterized. Therefore, this review explores the progress made in this fascinating research area and debates the further potential to breed thermotolerant crop cultivars through the modulation of HSF networks. Furthermore, we discussed the role of HSFs in plant HS tolerance in a class-specific manner and shed light on their functional diversity, which is evident from their mode of action. Additionally, some research gaps have been highlighted concerning class-specific manners.

Morphological, Gene, and Hormonal Changes in Gonads and In-Creased Micrococcal Nuclease Accessibility of Sperm Chromatin Induced by Mercury

Mercury is one of the most dangerous environmental pollutants. In this work, we analysed the effects of exposure of Mytilus galloprovincialis to 1, 10 and 100 pM HgCl2 for 24 h on the gonadal morphology and on the expression level of three stress genes: mt10, hsp70 and πgst. In this tissue we also evaluated the level of steroidogenic enzymes 3β-HSD and 17β-HSD and the expression of PL protein genes. Finally, we determined difference in sperm chromatin accessibility to micrococcal nuclease. We found alterations in gonadal morphology especially after exposure to 10 and 100 pM HgCl2 and hypo-expression of the three stress genes, particularly for hsp70. Furthermore, decreased labelling with both 3β-HSD and 17β-HSD antibodies was observed following exposure to 1 and 10 pM HgCl2 and complete absence at 100 pM HgCl2 exposure. Gonads of mussels exposed to all HgCl2 doses showed decreased expression of PL protein genes especially for PLIII. Finally, micrococcal nuclease digestions showed that all doses of HgCl2 exposure resulted in increased sperm chromatin accessibility to this enzyme, indicative of improper sperm chromatin structure. All of these changes provide preliminary data of the potential toxicity of mercury on the reproductive health of this mussel.

A small RNA of miR2119b from soybean CMS line acts as a negative regulator of male fertility in transgenic Arabidopsis

The miR2119 is involved in the growth, development and abiotic stress response of some legumes, including Medicago truncatula, Phaseolus vulgaris and soybean (Glycine max (L.) Merr.). Our previous small RNA sequencing analysis showed that miR2119b was up-regulated in the flower buds of soybean cytoplasmic male sterile (CMS) line compared with its maintainer line, but the role and mechanism of miR2119b in the regulation of soybean male fertility are still unclear. In this study, the gma-miR2119b and its target gene alcohol dehydrogenase 1.3b (ADH1.3b) were characterized and found to be highly expressed in the flowers of soybean CMS line and its maintainer. Transgenic Arabidopsis plants overexpressing gma-miR2119b exhibit male fertility abnormalities, including pollen fertility and germination rate decreased. Enzyme activity detection found the ADH and catalase (CAT) enzyme activities in inflorescence of gma-miR2119b overexpressed plants were lower than those of wild-type. Bioinformatics and gene expression analysis showed that gma-miR2119b/GmADH1.3b module was responsive to high temperature (HT) stress during flowering. After HT stress, the gma-miR2119b overexpressed plants showed male sterility, including shorter filament, sterile pollen, indehiscent anther and non seed. Moreover, some key genes involved in HT response and reactive oxygen species (ROS) signal regulation pathway, including heat shock protein70, galactinol synthase 1 and CAT, showed down-regulated expression in transgenic plants under HT stress, suggesting that gma-miR2119b regulates male fertility via HT-ROS signaling pathway under HT stress. It was speculated that the gma-miR2119b acted as a negative regulator of male fertility in plants by regulating ADH1, HT-induced and ROS scavenging genes expression.

Expression of the developmental important candidate genes in oocytes, embryos, embryonic stem cells, cumulus cells, and fibroblast cells of buffalo (Bubalus bubalis)

The present study was undertaken to study the expression of the developmental important gene transcripts in immature oocytes, mature oocytes, different stages of IVF produced embryos, embryonic stem (ES), cumulus (BCC), fetal fibroblast (BFF), newborn fibroblast (NBF) and adult fibroblast (BAF) cells of buffalo by semi-quantitative RT-PCR. The expression of GLUT1, HSP70.1, POL A Polymerase, GDF9, BMP15, and SURVIVIN transcripts was found in immature oocytes, mature oocytes, 2-cell, 4-cell, 8-16 cell, morula, and the blastocyst. Interestingly, the CX43 expression was found in oocytes, embryos, and other cell types, but it was not detected in the blastocyst. However, the IFNT expression was found in the blastocyst only, but not in other cells. The buffalo ES cells showed the expression of intracellular and cell surface markers (NANOG, OCT4, SOX2, FOXD3, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81) and alkaline phosphatase activity. Two ES cell lines (S-line and M-line-II) were continued to survive up to 98th passages (~630 days) and 97th passages (~624 days), respectively. It was interesting to note that GLUT1, CX43, HSP70.1, POL A Polymerase, GDF9, BMP15, and SURVIVIN transcripts (except the IFNT) were expressed in buffalo ES, BCC, BFF, NBF and BAF cells. This is the first preliminary report that the buffalo ES, BCC, BFF, NBF, and BAF cells expressed the several developmental important candidate genes. It is concluded that the expression of the major developmental important genes was not only expressed in the oocytes and embryos but also expressed in the ES, BCC, BFF, NBF, and BAF cells of buffalo.

HSP70-3 Interacts with Phospholipase Dδ and Participates in Heat Stress Defense

Heat shock proteins (HSPs) function as molecular chaperones and are key components responsible for protein folding, assembly, translocation, and degradation under stress conditions. However, little is known about how HSPs stabilize proteins and membranes in response to different hormonal or environmental cues in plants. Here, we combined molecular, biochemical, and genetic approaches to elucidate the involvement of cytosolic HSP70-3 in plant stress responses and the interplay between HSP70-3 and plasma membrane (PM)-localized phospholipase Dδ (PLDδ) in Arabidopsis (Arabidopsis thaliana). Analysis using pull-down, coimmunoprecipitation, and bimolecular fluorescence complementation revealed that HSP70-3 specifically interacted with PLDδ. HSP70-3 bound to microtubules, such that it stabilized cortical microtubules upon heat stress. We also showed that heat shock induced recruitment of HSP70-3 to the PM, where HSP70-3 inhibited PLDδ activity to mediate microtubule reorganization, phospholipid metabolism, and plant thermotolerance, and this process depended on the HSP70-3-PLDδ interaction. Our results suggest a model whereby the interplay between HSP70-3 and PLDδ facilitates the re-establishment of cellular homeostasis during plant responses to external stresses and reveal a regulatory mechanism in regulating membrane lipid metabolism.

Transcriptomic analyses provide insights into the adaptive responses to heat stress in the ark shells, Scapharca subcrenata

The ark shell, Scapharca subcrenata, is susceptible to high temperature which may lead to mass mortality in hot summers. Herein, we conducted the transcriptomic analyses of haemocytes in ark shells under thermal stress, to reveal the underlying molecular mechanisms of heat resistance in these animals. The results showed that a total of 7773, 11,500 and 13,046 unigenes were expressed differentially at 12, 24 and 48 h post thermal stress, respectively. The expression levels of key DEGs as revealed by RNA-seq were confirmed by quantitative real-time PCR. GO and KEGG enrichment analyses showed that the DEGs were mainly associated with apoptosis, NF-kappa B signaling pathway, TNF signaling pathway and RIG-I-like receptor signaling pathway. Among the DEGs, 40 were candidate heat stress response-related genes and 169 were identified to be involved in antioxidant defense, cell detoxification, protein metabolism and endoplasmic reticulum stress responses. It seemed that ark shells may adapt to short term thermal stress through regulation of protein metabolism, DNA replication and anti-apoptotic system. However, if the stress sustains, it may cause irreparable injury gradually in the animals due to oxygen limitation and metabolic dysregulation. Noteworthily, the expression of DEGs involved in protein biosynthesis and proteolysis was significantly elevated in ark shells under heat stress. These findings may provide preliminary insights into the molecular response of ark shells to acute thermal stress and lay the groundwork for marker-assisted selection of heat-resistant strains in S. subcrenata.

MicroRNAs as Important Regulators of Heat Stress Responses in Plants

Heat stress is a major abiotic stress that significantly affects plant growth and productivity. Plants have, however, evolved complex adaptive mechanisms to cope with heat stress. MicroRNAs (miRNAs) are important molecules that regulate gene expression through the post-transcriptional degradation of target mRNA molecules or by repressing translation. Plant miRNAs play essential roles in development and a variety of stress responses. Recent advances in high-throughput sequencing technologies have enabled the identification and characterization of an increasing number of heat-responsive miRNAs in diverse plant species. Heat-regulated miRNAs combined with their target genes constitute large regulatory networks that control various metabolic pathways, including protein refolding, antioxidant defense, maintenance of photosynthetic systems, protection of reproductive tissues, regulation of flowering time, and miRNA biogenesis. In this review, we summarize the information acquired to date about the significance of plant miRNAs and their target genes in heat stress tolerance, thereby helping to identify the regulatory mechanisms that underlie heat stress responses in plants.

Transcriptomic signatures of cold adaptation and heat stress in the winter ant (Prenolepis imparis)

Climate change is a serious threat to biodiversity; it is therefore important to understand how animals will react to this stress. Ectotherms, such as ants, are especially sensitive to the climate as the environmental temperature influences myriad aspects of their biology, from optimal foraging time to developmental rate. In this study, we conducted an RNA-seq analysis to identify stress-induced genes in the winter ant (Prenolepis imparis). We quantified gene expression during heat and cold stress relative to a control temperature. From each of our conditions, we sequenced the transcriptome of three individuals. Our de novo assembly included 13,324 contigs that were annotated against the nr and SwissProt databases. We performed gene ontology and enrichment analyses to gain insight into the physiological processes involved in the stress response. We identified a total of 643 differentially expressed genes across both treatments. Of these, only seven genes were differentially expressed in the cold-stressed ants, which could indicate that the temperature we chose for trials did not induce a strong stress response, perhaps due to the cold adaptations of this species. Conversely, we found a strong response to heat: 426 upregulated genes and 210 downregulated genes. Of these, ten were expressed at a greater than ten-fold change relative to the control. The transcripts we could identify included those encoding for protein folding genes, heat shock proteins, histones, and Ca2+ ion transport. One of these transcripts, hsc70-4L was found to be under positive selection. We also characterized the functional categories of differentially expressed genes. These candidate genes may be functionally conserved and relevant for related species that will deal with rapid climate change.

NLRP3 Inflammasome-Mediated Inflammation in Acute Pancreatitis

The discovery of inflammasomes has enriched our knowledge in the pathogenesis of multiple inflammatory diseases. The NLR pyrin domain-containing protein 3 (NLRP3) has emerged as the most versatile and well-characterized inflammasome, consisting of an intracellular multi-protein complex that acts as a central driver of inflammation. Its activation depends on a tightly regulated two-step process, which includes a wide variety of unrelated stimuli. It is therefore not surprising that the specific regulatory mechanisms of NLRP3 inflammasome activation remain unclear. Inflammasome-mediated inflammation has become increasingly important in acute pancreatitis, an inflammatory disorder of the pancreas that is one of the fatal diseases of the gastrointestinal tract. This review presents an update on the progress of research into the contribution of the NLRP3 inflammasome to acute pancreatic injury, examining the mechanisms of NLRP3 activation by multiple signaling events, the downstream interleukin 1 family of cytokines involved and the current state of the literature on NLRP3 inflammasome-specific inhibitors.

Genome-wide identification and transcript profiles of walnut heat stress transcription factor involved in abiotic stress

BACKGROUND

Walnut (Juglans regia) is an important tree cultivated worldwide and is exposed to a series of both abiotic and biotic stress during their life-cycles. The heat stress transcription factors (HSFs) play a crucial role in plant response to various stresses by regulating the expression of stress-responsive genes. HSF genes are classified into 3 classes: HSFA, HSFB, and HSFC. HSFA gene has transcriptional activation function and is the main regulator of high temperature-induced gene expression. HSFB gene negatively regulates plant resistance to drought and NaCl. And HSFC gene may be involved in plant response to various stresses. There are some reports about the HSF family in herbaceous plants, however, there are no reports about the HSFs in walnut.

RESULT

In this study, based on the complete genome sequencing of walnut, the bioinformatics method was used and 29 HSF genes were identified. These HSFs covered 18 HSFA, 9 HSFB, and 2 HSFC genes. Phylogenetic analysis of these HSF proteins along with those from Arabidopsis thaliana showed that the HSFs in the two species are closely related to each other and have different evolutionary processes. The distribution of conserved motifs and the sequence analysis of HSF genes family indicated that the members of the walnut HSFs are highly conserved. Quantitative Real-Time PCR (qRT-PCR) analysis revealed that the most of walnut HSFs were expressed in the walnut varieties of 'Qingxiang' and 'Xiangling' under high temperature (HT), high salt and drought stress, and some JrHSFs expression pattern are different between the two varieties.

CONCLUSION

The complex HSF genes family from walnut was confirmed by genome-wide identification, evolutionary exploration, sequence characterization and expression analysis. This research provides useful information for future studies on the function of the HSF genes and molecular mechanism in plant stress response.

Widely Targeted Metabolomic and Transcriptomic Analyses of a Novel Albino Tea Mutant of “Rougui”

Albino tea mutants with specific shoot colors (white or yellow) have received increasing attention from researchers due to their unique phenotypes, beneficial metabolites, and special flavor. In this study, novel natural yellow leaf mutants of the same genetic background of “Rougui” were obtained, and the transcriptome and metabolite profiles of the yellow leaf mutant (YR) and original green cultivar (GR) were investigated. A total of 130 significantly changed metabolites (SCMs) and 55 differentially expressed genes (DEGs) were identified in YR compared to GR. The leaf coloration of YR was primarily affected by pigment metabolism including of chlorophyll, carotenoids, and flavonoids, and the co-expression of three heat shock proteins (HSPs) and four heat shock transcription factors (HSFs) may also regulate leaf coloration by affecting chloroplast biogenesis. Of the 130 SCMs, 103 showed clearly increased abundance in YR, especially nucleotides and amino acids and their derivatives and flavonoids, suggesting that YR may be an ideal albino tea germplasm for planting and breeding. Our results may help to characterize the leaf coloration and metabolic mechanism of albino tea germplasm.

A 28.6-kD small heat shock protein (MnHSP28.6) protects Macrobrachium nipponense against heavy metal toxicity and oxidative stress by virtue of its anti-aggregation activity

Small heat shock proteins (sHSPs) are ATP-independent chaperones and involved into various physiological and stress processes. In the present study, a 28.6-kD sHSP coding gene, MnHSP28.6, was cloned and characterized from the oriental river prawn Macrobrachium nipponense. Tissue distribution analysis via qPCR and western blot revealed that MnHSP28.6 predominantly expressed in muscle. The temporal transcription of MnHSP28.6 in muscle after bacterial challenge, heavy metal exposure and doxorubicin (DOX) injection was investigated by qPCR. The results showed that the expression of MnHSP28.6 were strongly enhanced by both Cd²⁺ and Cu²⁺ exposure, as well as DOX injection, but not by bacterial infection. Aggregation assays showed that recombinant MnHSP28.6 could effectively prevent temperature-induced aggregation of citrate synthase, and reduction-induced aggregation of insulin in vitro. MnHSP28.6 also could protect muscle extracts from heat-induced protein denaturation and superoxide dismutase (SOD) inactivation. Expressing MnHSP28.6 in E. coli conferred host cell impressive protection against H₂O₂ compared to control. These results suggest a protective role of MnHSP28.6 in maintaining protein homeostasis, preventing aggregation, promoting resistance to heavy metal and keeping redox balance.

Priming of Plant Resistance to Heat Stress and Tomato Yellow Leaf Curl Thailand Virus With Plant-Derived Materials

Plants are often simultaneously exposed to diverse environmental stresses, and can tune suitable responses to them through hormones. Salicylic acid (SA) and jasmonic acid (JA) signaling pathways are known to enhance resistance against heat stress and tomato yellow leaf curl Thailand virus (TYLCTHV) infection. However, there is limited information regarding alternative natural priming agents against heat stress and viruses. In this study, two plant-derived priming agents, eugenol and anise oil, were tested for their roles in conferring thermotolerance and virus resistance in tomato plants. Under heat stress, the survival rates and average fresh weight were higher in plants treated with eugenol or anise oil than in control plants. These two priming agents were further tested for antiviral activities. After TYLCTHV infection, the disease incidence and relative abundance of TYLCTHV were lower in anise oil- and eugenol-treated plants than in control plants. Further analyses revealed that a few SA, JA, and RNA silencing genes were enhanced in the former. Moreover, SA, JA, and H2O2 contents increased considerably after eugenol and anise oil treatments. Our findings imply that anise oil and eugenol initiated SA- and JA-mediated defenses to promote thermotolerance and antiviral responses of tomato plants.

Improving Potato Stress Tolerance and Tuber Yield Under a Climate Change Scenario - A Current Overview

Global climate change in the form of extreme heat and drought poses a major challenge to sustainable crop production by negatively affecting plant performance and crop yield. Such negative impact on crop yield is likely to be aggravated in future because continued greenhouse gas emissions will cause further rise in temperature leading to increased evapo-transpiration and drought severity, soil salinity as well as insect and disease threats. This has raised a major challenge for plant scientists on securing global food demand, which urges an immediate need to enhance the current yield of major food crops by two-fold to feed the increasing population. As a fourth major food crop, enhancing potato productivity is important for food security of an increasing population. However, potato plant is highly prone to high temperature, drought, soil salinity, as well as insect and diseases. In order to maintain a sustainable potato production, we must adapt our cultivation practices and develop stress tolerant potato cultivars that are appropriately engineered for changing environment. Yet the lack of data on the underlying mechanisms of potato plant resistance to abiotic and biotic stress and the ability to predict future outcomes constitutes a major knowledge gap. It is a challenge for plant scientists to pinpoint means of improving tuber yield under increasing CO2, high temperature and drought stress including the changing patterns of pest and pathogen infestations. Understanding stress-related physiological, biochemical and molecular processes is crucial to develop screening procedures for selecting crop cultivars that can better adapt to changing growth conditions. Elucidation of such mechanism may offer new insights into the identification of specific characteristics that may be useful in breeding new cultivars aimed at maintaining or even enhancing potato yield under changing climate. This paper discusses the recent progress on the mechanism by which potato plants initially sense the changes in their surrounding CO2, temperature, water status, soil salinity and consequently respond to these changes at the molecular, biochemical and physiological levels. We suggest that future research needs to be concentrated on the identification and characterization of signaling molecules and target genes regulating stress tolerance and crop yield potential.

New insight into foregut functions of xenobiotic detoxification in the cockroach Periplaneta americana

The physiological functions of insect foregut, especially in xenobiotic detoxification, are scarcely reported because of unimportance in appearance and insufficient molecular information. The cockroach Periplaneta americana, an entomological model organism, provides perfect material to study physiological functions of foregut tissue due to its architectural feature. Through Illumina sequencing of foregut tissue from P. americana individuals (control) or insects treated with cycloxaprid, as a novel neonicotinoid insecticide, 54 193 166 clean reads were obtained and further assembled into 53 853 unigenes with an average length of 366 bp. Furthermore, the number of unigenes involved in xenobiotic detoxification was analyzed, mainly including 70 cytochrome P450s, 12 glutathione S-transferases (GSTs), seven carboxylesterases (CarEs) and seven adenosine triphosphate-binding cassette (ABC) transporters. Compared to control, the expression of 22 xenobiotic detoxification unigenes was up-regulated after cycloxaprid application, mainly containing 18 P450s, one GST, two CarEs and one ABC adenosine triphosphate transporter, indicating that the oxidation-reduction was the major reactive process to cycloxaprid application. Through quantitative real-time polymerase chain reaction analysis, the expression of selected unigenes (six P450s, one GST and one CarE) was up-regulated at least two-fold following cycloxaprid treatment, and was generally in agreement with transcriptome data. Compared to the previous midgut transcriptome of P. americana, it looks like the expressive abundance of the xenobiotic detoxification unigenes might be important factors to the detoxifying functional differences between foregut and midgut. In conclusion, insect foregut would also play important roles in the physiological processes related to xenobiotic detoxification.

Candidate Genes for Yellow Leaf Color in Common Wheat (Triticum aestivum L.) and Major Related Metabolic Pathways according to Transcriptome Profiling

The photosynthetic capacity and efficiency of a crop depends on the biosynthesis of photosynthetic pigments and chloroplast development. However, little is known about the molecular mechanisms of chloroplast development and chlorophyll (Chl) biosynthesis in common wheat because of its huge and complex genome. Ygm, a spontaneous yellow-green leaf color mutant of winter wheat, exhibits reduced Chl contents and abnormal chloroplast development. Thus, we searched for candidate genes associated with this phenotype. Comparative transcriptome profiling was performed using leaves from the yellow leaf color type (Y) and normal green color type (G) of the Ygm mutant progeny. We identified 1227 differentially expressed genes (DEGs) in Y compared with G (i.e., 689 upregulated genes and 538 downregulated genes). Gene ontology and pathway enrichment analyses indicated that the DEGs were involved in Chl biosynthesis (i.e., magnesium chelatase subunit H (CHLH) and protochlorophyllide oxidoreductase (POR) genes), carotenoid biosynthesis (i.e., β-carotene hydroxylase (BCH) genes), photosynthesis, and carbon fixation in photosynthetic organisms. We also identified heat shock protein (HSP) genes (sHSP, HSP70, HSP90, and DnaJ) and heat shock transcription factor genes that might have vital roles in chloroplast development. Quantitative RT-PCR analysis of the relevant DEGs confirmed the RNA-Seq results. Moreover, measurements of seven intermediate products involved in Chl biosynthesis and five carotenoid compounds involved in carotenoid-xanthophyll biosynthesis confirmed that CHLH and BCH are vital enzymes for the unusual leaf color phenotype in Y type. These results provide insights into leaf color variation in wheat at the transcriptional level.

Korean ginseng extract ameliorates abnormal immune response through the regulation of inflammatory constituents in Sprague Dawley rat subjected to environmental heat stress

Background

Increases in the average global temperature cause heat stress–induced disorders by disrupting homeostasis. Excessive heat stress triggers an imbalance in the immune system; thus protection against heat stress is important to maintain immune homeostasis. Korean ginseng (Panax ginseng Meyer) has been used as a herbal medicine and displays beneficial biological properties.

Methods

We investigated the protective effects of Korean ginseng extracts (KGEs) against heat stress in a rat model. Following acclimatization for 1 week, rats were housed at room temperature for 2 weeks and then exposed to heat stress (40°C/2 h/day) for 4 weeks. Rats were treated with three KGEs from the beginning of the second week to the end of the experiment.

Results

Heat stress dramatically increased secretion of inflammatory factors, and this was significantly reduced in the KGE-treated groups. Levels of inflammatory factors such as heat shock protein 70, interleukin 6, inducible nitric oxide synthase, and tumor necrosis factor-alpha were increased in the spleen and muscle upon heat stress. KGEs inhibited these increases by down-regulating heat shock protein 70 and the associated nuclear factor-κB and mitogen-activated protein kinase signaling pathways. Consequently, KGEs suppressed activation of T-cells and B-cells.

Conclusion

KGEs suppress the immune response upon heat stress and decrease the production of inflammatory cytokines in muscle and spleen. We suggest that KGEs protect against heat stress by inhibiting inflammation and maintaining immune homeostasis.

MicroRNA160 Modulates Plant Development and Heat Shock Protein Gene Expression to Mediate Heat Tolerance in Arabidopsis

Global warming is causing a negative impact on plant growth and adversely impacts on crop yield. MicroRNAs (miRNAs) are critical in regulating the expression of genes involved in plant development as well as defense responses. The effects of miRNAs on heat-stressed Arabidopsis warrants further investigation. Heat stress increased the expression of miR160 and its precursors but considerably reduced that of its targets, ARF10, ARF16, and ARF17. To study the roles of miR160 during heat stress, transgenic Arabidopsis plants overexpressing miR160 precursor a (160OE) and artificial miR160 (MIM160), which mimics an inhibitor of miR160, were created. T-DNA insertion mutants of miR160 targets were also used to examine their tolerances to heat stress. Results presented that overexpressing miR160 improved seed germination and seedling survival under heat stress. The lengths of hypocotyl elongation and rachis were also longer in 160OE than the wild-type (WT) plants under heat stress. Interestingly, MIM160 plants showed worse adaption to heat. In addition, arf10, arf16, and arf17 mutants presented similar phenotypes to 160OE under heat stress to advance abilities of thermotolerance. Moreover, transcriptome and qRT-PCR analyses revealed that HSP17.6A, HSP17.6II, HSP21, and HSP70B expression levels were regulated by heat in 160OE, MIM160, arf10, arf16, and arf17 plants. Hence, miR160 altered the expression of the heat shock proteins and plant development to allow plants to survive heat stress.

The transcriptional response of the Pacific oyster Crassostrea gigas against acute heat stress

The Pacific oyster, Crassostrea gigas, has evolved sophisticated mechanisms to adapt the changing ambient conditions, and protect themselves from stress-induced injuries. In the present study, the expression profiles of mRNA transcripts in the haemocytes of oysters under heat stress were examined to reveal the possible mechanism of heat stress response. There were 23,315, 23,904, 23,123 and 23,672 transcripts identified in the haemocytes of oysters cultured at 25 °C for 0, 6, 12, and 24 h (designed as B, H6, H12, H24), respectively. And 22,330 differentially expressed transcripts (DTs) were yielded in the pairwise comparisons between the above four samples, which corresponded to 8074 genes. There were 9, 12 and 22 Gene Ontology (GO) terms identified in the DT pairwise comparison groups of H6_B, H12_H6 and H24_H12, respectively, and the richest GO terms in biological process category were cellular catabolic process, translational initiation and apoptotic process, respectively. There were 108, 102 and 102 KEGG pathways successfully retrieved from DTs comparison groups DTH6_B, DTH12_H6 and DTH24_H12, respectively, among which 93 pathways were shared by all three comparison groups, and most of them were related to metabolism of protein, carbohydrate and fat. The expression patterns of 12 representative heat stress response-relevant genes detected by quantitative real-time PCR (qRT-PCR) were similar to those obtained from transcriptome analysis. By flow cytometric analysis, the apoptosis rate of haemocytes increased significantly after oysters were treated at 25 °C for 24 h and recovered at 4 °C for 12 h (p < 0.05) and 36 h (p < 0.01), and it also increased significantly when the heat treatment lasted to 60 h (p < 0.01). The present results indicated that, when oysters encountered short term heat stress, the expression of genes related to energy metabolism, as well as unfolded protein response (UPR) and anti-apoptotic system, were firstly regulated to maintain basic life activities, and then a large number of genes involved in stabilizing protein conformation and facilitating further protein refolding were activated to repair the stress injury. However, the stress injury gradually became irreparable with the stress persisting, and apoptosis was activated when the heat treatment prolonged to 24 h. The information was useful to better understand the molecular mechanism of heat stress response and develop strategies for the improvement of oyster survival rate during summer high-temperature period.

Interaction of heat shock protein 60 (HSP60) with microRNA in Chinese mitten crab during Spiroplasma eriocheiris infection

Heat shock protein 60 from the Chinese mitten crab Eriocheir sinensis (EsHSP60) was previously identified in relation to Spiroplasma eriocheiris infection by isobaric tags for relative and absolute quantitation labelling followed by liquid chromatography-tandem mass spectrometry. In the present study, to validate the immune function of this protein, the cDNA of the EsHSP60 gene was cloned. Various crab tissues were assessed using real-time PCR, which showed that EsHSP60 transcription occurred in all tissues examined. The expression profiles of EsHSP60 in haemolymph at transcription and protein levels when infected with S. eriocheiris were investigated by real-time PCR and Western blot analysis, respectively. A significant increase of EsHSP60 transcription and protein expression appeared post-injection in response to S. eriocheiris infection when compared to the control group. The double-luciferase reporter gene assay showed that the microRNA PC-533-3p interacted with the 3'-untranslated region of EsHSP60 and inhibited the translation of EsHSP60. The expression profiles of PC-533-3p during S. eriocheiris infection were also investigated by real-time PCR. However, the change tendency of PC-533-3p was opposite to that of the EsHSP60 after S. eriocheiris challenge. These data indicate that the EsHSP60 proteins may play an important role in mediating the immune responses of E. sinensis to an S. eriocheiris challenge.

Thermotolerance, oxidative stress, apoptosis, heat-shock proteins and damages to reproductive cells of insecticide-susceptible and -resistant strains of the diamondback moth Plutella xylostella

In this study, we investigated thermotolerance, several physiological responses and damage to reproductive cells in chlorpyrifos-resistant (Rc) and -susceptible (Sm) strains of the diamondback moth, Plutella xylostella subjected to heat stress. The chlorpyrifos resistance of these strains was mediated by a modified acetylcholinesterase encoded by an allele, ace1R, of the ace1 gene. Adults of the Rc strain were less heat resistant than those of the Sm strain; they also had lower levels of enzymatic activity against oxidative damage, higher reactive oxygen species contents, weaker upregulation of two heat shock protein (hsp) genes (hsp69s and hsp20), and stronger upregulation of two apoptotic genes (caspase-7 and -9). The damage to sperm and ovary cells was greater in Rc adults than in Sm adults and was temperature sensitive. The lower fitness of the resistant strain, compared with the susceptible strain, is probably due to higher levels of oxidative stress and apoptosis, which also have deleterious effects on several life history traits. The greater injury observed in conditions of heat stress may be due to both the stronger upregulation of caspase genes and weaker upregulation of hsp genes in resistant than in susceptible individuals.

Bio-effect-monitoring of long-term thermal wastes on the oyster, Crassostrea gigas, using heat shock proteins

We bio-monitored the stress of oyster, Crassostrea gigas, for possible long term effects of thermal waste from a power plant. The expression level of its heat shock proteins (HSPs) was measured by real time-reverse transcript PCR along with their density and growth in the field. Oyster size varied in a distance dependent pattern. Physics modeling for evaluation of spreading of the thermal effluent revealed that station A is affected by the thermal effluents abundance, and the size of C. gigas showed a negative relationship with distance to the power plant. The abundance and size of C. gigas were smallest at station A, which was closest to the thermal effluent outlet. The kinetics of changes in the hsp70 and hsp90 mRNA levels in the mantle of C. gigas were also investigated. Regardless of the higher expression level of hsp70 mRNA than hsp90, both hsp70 and hsp90 mRNA levels were significantly higher at station A. The expression levels decreased inversely with distance from the thermal effluent outlet, with expression of hsp70 mRNA at station A being approximately 7-fold higher than at station B and 15-fold higher than at station C. Similarly, expression of hsp90 mRNA at station A was approximately 14-fold higher than at station B and 22-fold higher than at station C. The present findings provide new insights on biological correlation among the growth of individuals and population size and the molecular index in C. gigas following thermal effects.

Dissecting the proteome dynamics of the early heat stress response leading to plant survival or death in Arabidopsis

In many plant species, an exposure to a sublethal temperature triggers an adaptative response called acclimation. This response involves an extensive molecular reprogramming that allows the plant to further survive to an otherwise lethal increase of temperature. A related response is also launched under an abrupt and lethal heat stress that, in this case, is unable to successfully promote thermotolerance and therefore ends up in plant death. Although these molecular programmes are expected to have common players, the overlapping degree and the specific regulators of each process are currently unknown. We have carried out a high-throughput comparative proteomics analysis during acclimation and during the early stages of the plant response to a severe heat stress that lead Arabidopsis seedlings either to survival or death. This analysis dissects these responses, unravels the common players and identifies the specific proteins associated with these different fates. Thermotolerance assays of mutants in genes with an uncharacterized role in heat stress demonstrate the relevance of this study to uncover both positive and negative heat regulators and pinpoint a pivotal role of JR1 and BAG6 in heat tolerance.

The α-Crystallin Domain Containing Genes: Identification, Phylogeny and Expression Profiling in Abiotic Stress, Phytohormone Response and Development in Tomato (Solanum lycopersicum)

The α-crystallin domain (ACD) is an ancient domain conserved among all kingdoms. Plant ACD proteins have roles in abiotic stresses, transcriptional regulation, inhibiting virus movement, and DNA demethylation. An exhaustive in-silico analysis using Hidden Markov Model-based conserved motif search of the tomato proteome yielded a total of 50 ACD proteins that belonged to four groups, sub-divided further into 18 classes. One of these groups belongs to the small heat shock protein (sHSP) class of proteins, molecular chaperones implicated in heat tolerance. Both tandem and segmental duplication events appear to have shaped the expansion of this gene family with purifying selection being the primary driving force for evolution. The expression profiling of the Acd genes in two different heat stress regimes suggested that their transcripts are differentially regulated with roles in acclimation and adaptive response during recovery. The co-expression of various genes in response to different abiotic stresses (heat, low temperature, dehydration, salinity, and oxidative stress) and phytohormones (abscisic acid and salicylic acid) suggested possible cross-talk between various members to combat a myriad of stresses. Further, several genes were highly expressed in fruit, root, and flower tissues as compared to leaf signifying their importance in plant development too. Evaluation of the expression of this gene family in field grown tissues highlighted the prominent role they have in providing thermo-tolerance during daily temperature variations. The function of three putative sHSPs was established as holdase chaperones as evidenced by protection to malate-dehydrogenase against heat induced protein-aggregation. This study provides insights into the characterization of the Acd genes in tomato and forms the basis for further functional validation in-planta.

BmHSP20.8 is Localized in the Mitochondria and has a Molecular Chaperone Function In Vitro

Heat shock proteins (HSPs) are abundant and ubiquitous in almost all organisms from bacteria to mammals. BmHSP20.8 is a small (sHSP) in Bombyx mori that contains a 561 bp open reading frame that encodes a protein of 186 amino acid residues with a predicted molecular mass of 20.8 kDa. The subcellular localization prediction indicated that BmHSP20.8 is likely distributed in the mitochondria with a 51% probability. To identify the subcellular localization of BmHSP20.8, three recombinant vectors were constructed and used to transfect BmN cells. The cytoplasmic and mitochondrial proteins were extracted 72 h after transfection. The Western blot showed that recombinant BmHSP20.8 exists only in the mitochondria. To locate the mitochondrial localization signal domain of BmHSP20.8 more accurately, we cloned four truncated recombinant vectors. The Western blot analysis of the cytoplasmic and mitochondrial proteins showed that the mitochondrial localization signal domain of BmHSP20.8 is located between amino acids 143 to 186. We constructed the pETduet-HIS-SUMO-BmHSP20.8 vector and a soluble BmHSP20.8 was expressed. In a citrate synthase (CS) thermal aggregation experiment, we found that the recombinant BmHSP20.8 protein can protect CS from aggregating at 43 and 48 °C and thus exhibited molecular chaperone activity. Taken together, the results showed that BmHSP20.8 could be a mitochondrial protein and has a molecular chaperone activity, suggesting an important role in mitochondria.

Role of HSP70 in cytoplasm protection against thermal stress in rohu, Labeo rohita

To understand the function of HSP70 of Labeo rohita (LrHSP70) in cellular protection, LrHSP70 ORF cDNA was inserted into the plasmid of pET-32a(+) or pEGFP-L1. Then, the recombinant plasmids were transformed or transfected into Escherichia coli cells, mouse myeloma cells (MPC-11) or fish hepatoma cells (PLHC-1). Western blot results revealed that LrHSP70 was expressed in E. coli cells and molecular weight was estimated to be 70 kDa. In cells, LrHSP70 was over-expressed following thermal or cold stress. Results revealed that LrHSP70 protected prokaryotic cells against thermal or cold extremes as well as played the same role in MPC-11 and PLHC-1 cells. After heat treatment at 42 °C for 1 h, the viability of the cell was declined considerably. PLHC-1 cells with pEGFP-L1/LrHSP70 exhibited a higher survival rate (50%) than wild-type cells (18%) or cells with only pEGFP-L1 (21.2%). When the time lag extended to 2 h, the survival rates were 30%, 3.4% and 5.3% respectively. The present study revealed that LrHSP70 plays an important role in response to thermal and cold stress in fish.

Identification of differentially expressed genes in Chrysanthemum nankingense (Asteraceae) under heat stress by RNA Seq

The RNA-Seq platform was used to characterize the high-temperature stress response of Chrysanthemum nankingense. A set of 54,668 differentially expressed unigenes was identified. After a threshold of ratio change ≥ 2 and a q-value of <0.05 were applied, the number of differentially transcribed genes was reduced to 3955, of which 765 were up-regulated and 3190 were down-regulated in response to heat stress. The differentially transcribed genes were predicted to participate in 26 biological processes, 4 cellular components, and 13 molecular functions. Among the most differentially expressed genes between the two libraries were well-recognized high-temperature responsive protein families, such as heat shock factors and heat shock proteins, various transcription factor families, and a number of RNA metabolism-related genes. Overall, the RNA-Seq analyses revealed a high degree of transcriptional complexity in early heat stress response. Some of these high-temperature responsive C. nankingense genes may prove useful in efforts to improve thermotolerance of commercial chrysanthemum.

Genome duplication and gene loss affect the evolution of heat shock transcription factor genes in legumes

Whole-genome duplication events (polyploidy events) and gene loss events have played important roles in the evolution of legumes. Here we show that the vast majority of Hsf gene duplications resulted from whole genome duplication events rather than tandem duplication, and significant differences in gene retention exist between species. By searching for intraspecies gene colinearity (microsynteny) and dating the age distributions of duplicated genes, we found that genome duplications accounted for 42 of 46 Hsf-containing segments in Glycine max, while paired segments were rarely identified in Lotus japonicas, Medicago truncatula and Cajanus cajan. However, by comparing interspecies microsynteny, we determined that the great majority of Hsf-containing segments in Lotus japonicas, Medicago truncatula and Cajanus cajan show extensive conservation with the duplicated regions of Glycine max. These segments formed 17 groups of orthologous segments. These results suggest that these regions shared ancient genome duplication with Hsf genes in Glycine max, but more than half of the copies of these genes were lost. On the other hand, the Glycine max Hsf gene family retained approximately 75% and 84% of duplicated genes produced from the ancient genome duplication and recent Glycine-specific genome duplication, respectively. Continuous purifying selection has played a key role in the maintenance of Hsf genes in Glycine max. Expression analysis of the Hsf genes in Lotus japonicus revealed their putative involvement in multiple tissue-/developmental stages and responses to various abiotic stimuli. This study traces the evolution of Hsf genes in legume species and demonstrates that the rates of gene gain and loss are far from equilibrium in different species.

HEAT-INDUCED TAS1 TARGET1 Mediates Thermotolerance via HEAT STRESS TRANSCRIPTION FACTOR A1a-Directed Pathways in Arabidopsis

Many heat stress transcription factors (Hsfs) and heat shock proteins (Hsps) have been identified to play important roles in the heat tolerance of plants. However, many of the key factors mediating the heat response pathways remain unknown. Here, we report that two genes, which are targets of TAS1 (trans-acting siRNA precursor 1)-derived small interfering RNAs that we named HEAT-INDUCED TAS1 TARGET1 (HTT1) and HTT2, are involved in thermotolerance. Microarray analysis revealed that the HTT1 and HTT2 genes were highly upregulated in Arabidopsis thaliana seedlings in response to heat shock. Overexpression of TAS1a, whose trans-acting small interfering RNAs target the HTT genes, elevated accumulation of TAS1-siRNAs and reduced expression levels of the HTT genes, causing weaker thermotolerance. By contrast, overexpression of HTT1 and HTT2 upregulated several Hsf genes, leading to stronger thermotolerance. In heat-tolerant plants overexpressing HsfA1a, the HTT genes were upregulated, especially at high temperatures. Meanwhile, HsfA1a directly activated HTT1 and HTT2 through binding to their promoters. HTT1 interacted with the heat shock proteins Hsp70-14 and Hsp40 and NUCLEAR FACTOR Y, SUBUNIT C2. Taken together, these results suggest that HTT1 mediates thermotolerance pathways because it is targeted by TAS1a, mainly activated by HsfA1a, and acts as cofactor of Hsp70-14 complexes.

The heat shock factor family from Triticum aestivum in response to heat and other major abiotic stresses and their role in regulation of heat shock protein genes

Heat shock factors (Hsfs) play a central regulatory role in acquired thermotolerance. To understand the role of the major molecular players in wheat adaptation to heat stress, the Hsf family was investigated in Triticum aestivum. Bioinformatic and phylogenetic analyses identified 56 TaHsf members, which are classified into A, B, and C classes. Many TaHsfs were constitutively expressed. Subclass A6 members were predominantly expressed in the endosperm under non-stress conditions. Upon heat stress, the transcript levels of A2 and A6 members became the dominant Hsfs, suggesting an important regulatory role during heat stress. Many TaHsfA members as well as B1, C1, and C2 members were also up-regulated during drought and salt stresses. The heat-induced expression profiles of many heat shock protein (Hsp) genes were paralleled by those of A2 and A6 members. Transactivation analysis revealed that in addition to TaHsfA members (A2b and A4e), overexpression of TaHsfC2a activated expression of TaHsp promoter-driven reporter genes under non-stress conditions, while TaHsfB1b and TaHsfC1b did not. Functional heat shock elements (HSEs) interacting with TaHsfA2b were identified in four TaHsp promoters. Promoter mutagenesis analysis demonstrated that an atypical HSE (GAACATTTTGGAA) in the TaHsp17 promoter is functional for heat-inducible expression and transactivation by Hsf proteins. The transactivation of Hsp promoter-driven reporter genes by TaHsfC2a also relied on the presence of HSE. An activation motif in the C-terminal domain of TaHsfC2a was identified by amino residue substitution analysis. These data demonstrate the role of HsfA and HsfC2 in regulation of Hsp genes in wheat.

De novo characterization of the Dialeurodes citri transcriptome: mining genes involved in stress resistance and simple sequence repeats (SSRs) discovery

The citrus whitefly, Dialeurodes citri (Ashmead), is one of the three economically important whitefly species that infest citrus plants around the world; however, limited genetic research has been focused on D. citri, partly because of lack of genomic resources. In this study, we performed de novo assembly of a transcriptome using Illumina paired-end sequencing technology (Illumina Inc., San Diego, CA, USA). In total, 36,766 unigenes with a mean length of 497 bp were identified. Of these unigenes, we identified 17,788 matched known proteins in the National Center for Biotechnology Information database, as determined by Blast search, with 5731, 4850 and 14,441 unigenes assigned to clusters of orthologous groups (COG), gene ontology (GO), and SwissProt, respectively. In total, 7507 unigenes were assigned to 308 known pathways. In-depth analysis of the data showed that 117 unigenes were identified as potentially involved in the detoxification of xenobiotics and 67 heat shock protein (Hsp) genes were associated with environmental stress. In addition, these enzymes were searched against the GO and COG database, and the results showed that the three major detoxification enzymes and Hsps were classified into 18 and 3, 6, and 8 annotations, respectively. In addition, 149 simple sequence repeats were detected. The results facilitate the investigation of molecular resistance mechanisms to insecticides and environmental stress, and contribute to molecular marker development. The findings greatly improve our genetic understanding of D. citri, and lay the foundation for future functional genomics studies on this species.

Regulation of the heat stress response in Arabidopsis by MPK6-targeted phosphorylation of the heat stress factor HsfA2

So far little is known on the functional role of phosphorylation in the heat stress response of plants. Here we present evidence that heat stress activates the Arabidopsis mitogen-activated protein kinase MPK6. In vitro and in vivo evidence is provided that MPK6 specifically targets the major heat stress transcription factor HsfA2. Activation of MPK6 results in complex formation with HsfA2. MPK6 phosphorylates HsfA2 on T249 and changes its intracellular localisation. Protein kinase and phosphatase inhibitor studies indicate that HsfA2 protein stability is regulated in a phosphorylation-dependent manner, but this mechanism is independent of MPK6. Overall, our data show that heat stress-induced targeting of HsfA2 by MPK6 participates in the complex regulatory mechanism how plants respond to heat stress.

Controlled atmosphere and temperature treatment system to disinfest fruit moth, Carposina sasakii (Lepidoptera: Carposinidae) on apples

Carposina sasakii Matsumura (Lepidoptera: Carposinidae) is a serious pest of apples and peaches in Korea and Japan. Because of its limited distribution, C. sasakii has been identified as a quarantine pest in several countries. The Controlled Atmosphere/Temperature Treatment System (CATTS) was tested as an alternative to methyl bromide fumigation to control C. sasakii in apples. The fifth instar was the most tolerant immature stage to a heat treatment of 44 degrees C for 20 min. When the apples infested with different stages of C. sasakii were treated under CATTS conditions (heating rate of 16 degrees C/h, chamber temperature of 46 degrees C, final core temperature of 44 degrees C under 1% O2/15% CO2 atmosphere), young larvae (first-fourth instars) did not survive after 40 min exposure, but the fifth instars required an exposure of at least 60 min to attain 100% mortality. A partial heat shock protein 90 (hsp90) was cloned and showed inducible expression in response to heat shock at 44 degrees C. CATTS suppressed transcription of the hsp90 gene. Apples did not show any appreciable loss of quality in relation to fruit firmness, sweetness, and decay after a 60 min CATTS treatment. These results suggest that CATTS can be applicable to control C. sasakii in apples.

Molecular cloning of heat shock protein 60 (PtHSP60) from Portunus trituberculatus and its expression response to salinity stress

Heat shock protein 60 (HSP60) is a highly conserved and multi-functional molecular chaperone that plays an essential role in both cellular metabolism and stress response. Portunus trituberculatus is an important marine fishery and aquaculture species, and water salinity condition influenced its artificial propagations significantly. In order to investigate the function of P. trituberculatus HSP60 against osmotic stress, P. trituberculatus HSP60 gene was firstly cloned. The full-length cDNA of PtHSP60 contains 1,743 nucleotides encoding 577 amino acids with a calculated molecular weight of 61.25 kDa. Multiple alignments indicated that the deduced amino acid sequences of PtHSP60 shared a high level of identity with invertebrate and vertebrate HSP60 sequence including shrimp, fruit fly, zebrafish, and human. The expression profiles of PtHSP60 at mRNA and protein levels under salinity treatment were investigated by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. It was found that the mRNA transcripts of PtHSP60 gene varied among different tissues under normal salinity conditions, and the antennal gland showed the highest expression level among the tissues tested. As for low salinity challenge, the mRNA expression of PtHSP60 gene was higher in the gill and appendicular muscle compared with other tissues, and gill and hypodermis represented the higher gene expressions during the hyperosmotic stress, which indicated that those tissues were salinity-sensitive tissues. In addition, salinity challenges significantly altered the expression of PtHSP60 at mRNA and protein level in a salinity- and time-dependent manner in P. trituberculatus gill tissue. The results indicate that PtHSP60 played important roles in mediating the salinity stress in P. trituberculatus.

Molecular communications between plant heat shock responses and disease resistance

As sessile, plants are continuously exposed to potential dangers including various abiotic stresses and pathogen attack. Although most studies focus on plant responses under an ideal condition to a specific stimulus, plants in nature must cope with a variety of stimuli at the same time. This indicates that it is critical for plants to fine-control distinct signaling pathways temporally and spatially for simultaneous and effective responses to various stresses. Global warming is currently a big issue threatening the future of humans. Reponses to high temperature affect many physiological processes in plants including growth and disease resistance, resulting in decrease of crop yield. Although plant heat stress and defense responses share important mediators such as calcium ions and heat shock proteins, it is thought that high temperature generally suppresses plant immunity. We therefore specifically discuss on interactions between plant heat and defense responses in this review hopefully for an integrated understanding of these responses in plants.