Heat Shock Stress Research Articles

MicroRNA-mediated network redundancy is constrained by purifying selection and contributes to expression robustness in Drosophila melanogaster

MicroRNAs (miRNAs) are post-transcriptional, non-coding regulatory RNAs that function coordinately with transcription factors (TFs) in gene regulatory networks. TFs and their targets are often co-regulated by miRNAs, forming composite feedforward circuits (cFFCs) with varying degrees of redundancy, primarily mediated by miRNAs. However, the maintenance of miRNA-mediated regulatory redundancy and its impact on gene expression evolution remain elusive. By integrating ChIP-seq data from ENCODE and miRNA targeting from TargetScanFly, we quantified miRNA-mediated cFFC redundancy in Drosophila melanogaster embryos and larvae, revealing more than three quarters of miRNA targets are involved in redundant cFFCs. Higher cFFC redundancy, where more miRNAs target the same gene within a cFFC, is correlated with stronger purifying selection, reduced expression divergence between species, and increased expression stability under heat shock stress. Redundant cFFCs primarily regulate older or broadly expressed young genes. These findings highlight the role of miRNA-mediated cFFC redundancy in enhancing gene expression robustness through natural selection.

CLK2 Condensates Reorganize Nuclear Speckles and Induce Intron Retention.

Intron retention (IR) constitutes a less explored form of alternative splicing, wherein introns are retained within mature mRNA transcripts. This investigation demonstrates that the cell division cycle (CDC)-like kinase 2 (CLK2) undergoes liquid-liquid phase separation (LLPS) within nuclear speckles in response to heat shock (HS). The formation of CLK2 condensates depends on the intrinsically disordered region (IDR) located within the N-terminal amino acids 1-148. Phosphorylation at residue T343 sustains CLK2 kinase activity and promotes overall autophosphorylation, which inhibits the LLPS activity of the IDR. These CLK2 condensates initiate the reorganization of nuclear speckles, transforming them into larger, rounded structures. Moreover, these condensates facilitate the recruitment of splicing factors into these compartments, restricting their access to mRNA for intron splicing and promoting the IR. The retained introns lead to the sequestration of transcripts within the nucleus. These findings extend to the realm of glioma stem cells (GSCs), where a physiological state mirroring HS stress inhibits T343 autophosphorylation, thereby inducing the formation of CLK2 condensates and subsequent IR. Notably, expressing the CLK2 condensates hampers the maintenance of GSCs. In conclusion, this research unveils a mechanism by which IR is propelled by CLK2 condensates, shedding light on its role in coping with cellular stress.

Ribosomal protein L32 contributes to the growth, antibiotic resistance and virulence of Glaesserella parasuis.

Glaesserella parasuis is the pathogen that causes Glässer's disease in pigs, which is characterized by fibrinous polyserositis, arthritis and meningitis. Research on ribosomal protein L32 in microorganisms has mainly focused on regulating gene transcription and translation, but its effect on bacterial virulence is unclear. The role of L32 gene in G. parasuis is not clear, and in order to study the function of L32 gene, a suicide plasmid-mediated natural transformation method was used to construct a L32 gene deletion mutant. We found that although L32 was shown to be non-essential for cell proliferation, the growth curve of ΔL32 is clearly different compared with that of ZJ1208. ΔL32 produced more outer membrane vesicles (OMVs) with a variety of irregular shapes, but produced similar biofilm to the parental strain. ΔL32 is more sensitive to osmotic pressure, oxidation pressure and heat shock stress. Meanwhile, ΔL32 is significantly more susceptible to antimicrobials such as spectinomycin, apramycin, sulfafurazole, but not to other antibiotics used in this study. In the mouse challenge experiment, the mortality of mice infected with the mutant strain decreased by 40% compared to those infected with the wild-type strain, indicating that L32 is a virulence-associated factor which contributes to bacterial fitness in host environments. The above results show that L32 is important for the growth, stress resistance and virulence of G. parasuis, and this study also confirms for the first time that L32 plays an important role in antibiotic resistance against aminoglycosides and sulfonamides.

Calibrated ribosome profiling assesses the dynamics of ribosomal flux on transcripts

Ribosome profiling, which is based on deep sequencing of ribosome footprints, has served as a powerful tool for elucidating the regulatory mechanism of protein synthesis. However, the current method has substantial issues: contamination by rRNAs and the lack of appropriate methods to measure ribosome numbers in transcripts. Here, we overcome these hurdles through the development of “Ribo-FilterOut”, which is based on the separation of footprints from ribosome subunits by ultrafiltration, and “Ribo-Calibration”, which relies on external spike-ins of stoichiometrically defined mRNA-ribosome complexes. A combination of these approaches estimates the number of ribosomes on a transcript, the translation initiation rate, and the overall number of translation events before its decay, all in a genome-wide manner. Moreover, our method reveals the allocation of ribosomes under heat shock stress, during aging, and across cell types. Our strategy of modified ribosome profiling measures kinetic and stoichiometric parameters of cellular translation across the transcriptome.

Influence of α-lipoic acid on longevity and stress resistance in Drosophila melanogaster fed with a high-fat diet.

Consumption of a high-fat diet is accompanied by the risks of obesity and early onset of age-associated complications for which dietary interventions are imperative to combat. α-lipoic acid has been shown to hinder diet-induced obesity and induce lifespan-extending efficacy in model organisms. In this study, α-lipoic acid was investigated for its efficacy in improving lifespan and stress resistance in the Canton-S strain of Drosophila melanogaster fed with a high-fat diet. Furthermore, as mating status significantly impacts survival in fruit flies, flies were reared in two experimental groups-group one, in which males and females were bred together, and group two, in which males and females were bred separately. In group one, α-lipoic acid improved the mean lifespan, reduced the fecundity of females, and reduced the mean body weight of flies at a dose range of 2-2.5mM, respectively. In group two, α-lipoic acid improved the mean lifespan, reduced the fecundity of females, and reduced the mean body weight of flies at a dose range of 1-2.5mM, respectively. Improved climbing efficiency was observed with α-lipoic acid at the dose range of 1.5-2.5mM in flies of group one and 1-2.5mM in flies of group two, respectively. Administration of α-lipoic acid improved resistance to oxidative stress in only female flies of group one at 2.5mM, whereas in group two, both male and female flies exhibited enhanced resistance to oxidative stress with α-lipoic acid at a dose range of 2-2.5mM, respectively. Male and female flies of only group one showed improved resistance to heat shock stress with α-lipoic acid at a dose range of 2-2.5mM. Only female flies of group two exhibited a slight improvement in recovery time following cold shock with α-lipoic acid only at 2.5mM. No significant change in resistance to starvation stress was observed with any dose of α-lipoic acid in either group of flies. To summarize, data from this study suggested a probable dose and gender-dependent efficacy of α-lipoic acid in flies fed with a high-fat diet, which was significantly influenced by the mating status of flies due to varied rearing conditions.

Temperature acclimation and response to acute thermal stress in the adults of the snow crab Chionoecetes opilio Fabricius, 1788 (Decapoda: Brachyura: Oregoniidae)

ABSTRACT Ectothermic marine animals vary widely in their tolerance to temperature changes, and polar stenothermal species seem to have poor ability to compensate for a rise in water temperature. The sub-Arctic snow crab (Chionoecetes opilioFabricius, 1788) lives in the northwestern Atlantic Ocean and northern Pacific Ocean at temperatures ranging from about −1.5 °C to 4 °C. Since the metabolic costs overtake caloric intake above 7 °C, the snow crab appears to be energetically restricted to cold water. We investigated thermal stress responses in adult male crabs exposed to a sudden temperature increase to 9.5 °C for 24 hr after four weeks of acclimation at 2.5 °C or 5.5 °C. Heart-rate loggers implanted in a limited number of crabs showed 60% increase in cardiac activity during the thermal stress. Surplus oxygen supply in all crabs was inferred by the low hemolymph lactate and unchanged glucose levels, but only the crabs acclimated at 5.5 °C were still active at the elevated temperature. Low heat shock and oxidative stress responses were suggested by the missing upregulation of the genes encoding four heat shock proteins (Hsp70a, Hsc71, Hsp90a2, Hsp60) and the antioxidative enzymes superoxide dismutase and catalase. The trend towards inverse temperature-dependent on the expression of the hsp genes may be related to increased protein damage at low temperatures, or possible trade-offs between costs and benefits of producing heat shock proteins at elevated temperature. Although adult snow crabs seem to be able to cope with short-term heat stress, the tolerance to chronic elevated temperatures should be further examined using a larger number of individuals.

Functional analysis of OmpA and its contribution to pathogenesis of Edwardsiella tarda

Outer membrane protein A (OmpA), a major component of outer membrane proteins in gram-negative bacteria, is considered to be an important virulence factor in various pathogenic bacteria, but its underlying mechanisms involved in pathogenic process of Edwardsiella tarda has not yet been fully elucidated. E. tarda is an important facultative intracellular pathogen with a broad host range. This bacterium could survive and replicate in macrophages as an escape mechanism from the host defense. To address the functions of OmpA and its potential roles in the pathogenesis of E. tarda, ΔompA mutant strain and ΔompA-C complementary strain were constructed by the allelic exchange method in this study. Here, we demonstrate that the abilities of motility, biofilm formation and adherence to RAW264.7 cells of ΔompA were significantly impaired, although there was no difference in growth between wild-type (WT) strain and ΔompA. Moreover, inactivation of ompA rendered E. tarda more sensitive to oxidative, heat shock and osmotic stress, which simulate the in vivo conditions that E. tarda encounters within the intramacrophage environment. Consist with this observation, ΔompA was also found to be markedly attenuated for growth within macrophages. In addition, compared with the WT strain, ΔompA activated macrophages to release more inflammatory mediators, including tumor necrosis factor alpha (TNF-α), reactive oxygen species (ROS) and nitric oxide (NO). However, flow cytometry analysis revealed that ΔompA induced less apoptosis of RAW264.7 cells as compared with WT strain, characterized by decreased Annexin V binding and the activation of caspase-3. Overall, our findings suggest an importance of OmpA to E. tarda and provide the first comprehensive insight into its functions and potential roles in the pathogenesis of E. tarda, including its effect on interaction with macrophages.

Heat shock combined with salinity impairs photosynthesis but stimulates antioxidant defense in rice plants

The interactive mechanisms that occur between heat shock and salt stress and their reflexes on photosynthesis and redox metabolism in plants are little understood yet. We tested the hypothesis that heat shock negatively interacts with salt stress, affecting most intensely K+/Na+ homeostasis, stomatal closure, and CO2 assimilation, in comparison to PSII activity and oxidative stress in rice leaves. 31-day old rice plants were previously exposed to 0 and 100 mM NaCl for eight days at 27 °C and afterwards two groups were transferred to high temperature (42 °C, heat shock) for 10 hours (heat and heat + salt) whereas two other groups remained at 27 °C (control and single salt treatments). Heat-salinity interaction greatly stimulated Na+ accumulation in leaves causing intense decrease in K+/Na+ ratios, inducing significant osmotic and ionic alterations. Stomata were closed intensely causing drastic impairment in CO2 assimilation and decrease in water use efficiency. In contrast, the PSII activity was much lesser affected, corroborated by a low increase in the fraction of closed reaction centers of PSII and slight decrease in electron transport rates. Despite that unbalance in photosynthesis, combined stress partially favored oxidative protection as indicated by a reduction in the levels of H2O2 and lipid peroxidation associated with reduction in the contents of reduced forms of ascorbate and glutathione. These favorable antioxidant responses were accompanied by increases in the activities of ascorbate peroxidases, superoxide dismutases, glutathione peroxidases, and phenol peroxidases whereas catalases and glycolate oxidases decreased. These antioxidant responses were not enough to mitigate overall physiological damages caused by combined stress, as indicated by drastic increase in membrane damage and decrease in relative water content in leaves. Heat shock drastically aggravates the negative effects caused by salt stress on the photosynthetic efficiency, especially CO2 assimilation, despite the heat – salinity interaction has partially favored the antioxidant defense.

SUMOylated Golgin45 associates with PML-NB to transcriptionally regulate lipid metabolism genes during heat shock stress

Golgin tethers are known to mediate vesicular transport in the secretory pathway, whereas it is relatively unknown whether they may mediate cellular stress response within the cell. Here, we describe a cellular stress response during heat shock stress via SUMOylation of a Golgin tether, Golgin45. We found that Golgin45 is a SUMOylated Golgin via SUMO1 under steady state condition. Upon heat shock stress, the Golgin enters the nucleus by interacting with Importin-β2 and gets further modified by SUMO3. Importantly, SUMOylated Golgin45 appears to interact with PML and SUMO-deficient Golgin45 mutant functions as a dominant negative for PML-NB formation during heat shock stress, suppressing transcription of lipid metabolism genes. These results indicate that Golgin45 may play a role in heat stress response by transcriptional regulation of lipid metabolism genes in SUMOylation-dependent fashion.

Mono-methylated histones control PARP-1 in chromatin and transcription.

PARP-1 is central to transcriptional regulation under both normal and stress conditions, with the governing mechanisms yet to be fully understood. Our biochemical and ChIP-seq-based analyses showed that PARP-1 binds specifically to active histone marks, particularly H4K20me1. We found that H4K20me1 plays a critical role in facilitating PARP-1 binding and the regulation of PARP-1-dependent loci during both development and heat shock stress. Here, we report that the sole H4K20 mono-methylase, pr-set7, and parp-1 Drosophila mutants undergo developmental arrest. RNA-seq analysis showed an absolute correlation between PR-SET7- and PARP-1-dependent loci expression, confirming co-regulation during developmental phases. PARP-1 and PR-SET7 are both essential for activating hsp70 and other heat shock genes during heat stress, with a notable increase of H4K20me1 at their gene body. Mutating pr-set7 disrupts monomethylation of H4K20 along heat shock loci and abolish PARP-1 binding there. These data strongly suggest that H4 monomethylation is a key triggering point in PARP-1 dependent processes in chromatin.

Long noncoding RNAs heat shock RNA omega nucleates TBPH and promotes intestinal stem cell differentiation upon heat shock

In Drosophila, long noncoding RNA Hsrω rapidly assembles membraneless organelle omega speckles under heat shock with unknown biological function. Here, we identified the distribution of omega speckles in multiple tissues of adult Drosophila melanogaster and found that they were selectively distributed in differentiated enterocytes but not in the intestinal stem cells of the midgut. We mimicked the high expression level of Hsrω via overexpression or intense heat shock and demonstrated that the assembly of omega speckles nucleates TBPH for the induction of ISC differentiation. Additionally, we found that heat shock stress promoted cell differentiation, which is conserved in mammalian cells through paraspeckles, resulting in large puncta of TDP-43 (a homolog of TBPH) with less mobility and the differentiation of human induced pluripotent stem cells. Overall, our findings confirm the role of Hsrω and omega speckles in the development of intestinal cells and provide new prospects for the establishment of stem cell differentiation strategies.

Enhancing drought, heat shock, and combined stress tolerance inMyrobalan29C rootstocks with foliar application of potassium nitrate.

Drought and heat stress are significant concerns to food security in arid and semi-arid regions, where global warming is predicted to increase both frequency and severity. To cope with these challenges, the use of drought-tolerant plants or technological interventions are essential. In this study, the effects of foliar potassium nitrate (KNO3) application on the stress tolerance and recovery of Myrobalan 29C rootstocks (Prunus cerasifera Ehrh.) were evaluated. These rootstocks are widely recognized for their adaptability and are extensively used in fruit production. To assess their response, the rootstocks were subjected to drought, heat shock, or a combination of both stressors. Additionally, they were treated with 1.0% KNO3 via foliar application. Throughout the stress and recovery periods, various morphological, physiological, and bio-chemical parameters were measured. Based on our results, KNO3 treatment improved LRWC, Chl stability, SC, and key stress markers like proline, MDA, H2O2, along with antioxidant enzymes CAT, SOD, POD during both stress and recovery phases. Moreover, our results emphasized KNO3's critical role in hormone regulation under stress. KNO3 application significantly altered hormone levels, notably increasing ABA during drought and heat shock stress, essential for stress response and adaptation. In contrast, IAA, GA, and cytokinin's significantly increased during the recovery phase in KNO3-treated plants, indicating improved growth regulation and stress recovery. In addition, KNO3 application improved the recovery process of the rootstocks by restoring their physiological and biochemical functions. This study suggests that the application of foliar KNO3 is an effective technique for enhancing the drought and heat tolerance as well as the recovery of Myrobalan 29C rootstocks. These results hold significant value for farmers, policymakers, and researchers, as they offer crucial insights into the development of drought-tolerant crops and the management of climate change's adverse effects on agriculture.

Heat Treatments at Varying Ambient Temperatures and Durations Differentially Affect Plant Defense to Blumeria hordei in a Resistant and a Susceptible Hordeum vulgare Line.

Our previous research showed that a powdery mildew resistant barley line (MvHV07-17) maintains its resistance to Blumeria hordei (Bh) even if plants are exposed to a long-term high temperature of 35°C for 120 h before Bh inoculation, whereas such high temperature pretreatment further increases susceptibility to infection in the susceptible barley line MvHV118-17. In the present study, we extended this approach using short-term high-temperature water treatment (49°C for 30 s) to determine how it affects powdery mildew resistance in these barley lines. We found that this short-term heat shock (HS) impaired plant defense responses, as reflected by development of Bh colonies and visible necrotic spots on leaves of MvHV07-17, which does not develop visible symptoms upon Bh inoculation under optimal growth conditions. In contrast, both HS and long-term heat stress enhanced susceptibility to Bh in MvHV118-17 plants. These results were supported by the measurement of Bh biomass using a qPCR method. Furthermore, microscopic examinations showed that HS elevated the rate of successful Bh penetration events and the spread of cell death in the surrounding mesophyll area and allowed for colony formation and sporulation in resistant barley, whereas early and effective plant defense responses, such as papilla formation and single-cell epidermal hypersensitive response, were significantly reduced. Furthermore, we found that the accumulation of hydrogen peroxide in both resistant and susceptible barley was correlated with susceptibility induced by HS and long-term heat-stress. This study may contribute to a better understanding of plant defense responses to Bh in barley exposed to heat. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

SUMOylation modulates eIF5A activities in both yeast and pancreatic ductal adenocarcinoma cells

BackgroundThe eukaryotic translation initiation protein eIF5A is a highly conserved and essential factor that plays a critical role in different physiological and pathological processes including stress response and cancer. Different proteomic studies suggest that eIF5A may be a small ubiquitin-like modifier (SUMO) substrate, but whether eIF5A is indeed SUMOylated and how relevant is this modification for eIF5A activities are still unknown.MethodsSUMOylation was evaluated using in vitro SUMOylation assays, Histidine-tagged proteins purification from His6–SUMO2 transfected cells, and isolation of endogenously SUMOylated proteins using SUMO-binding entities (SUBES). Mutants were engineered by site-directed mutagenesis. Protein stability was measured by a cycloheximide chase assay. Protein localization was determined using immunofluorescence and cellular fractionation assays. The ability of eIF5A1 constructs to complement the growth of Saccharomyces cerevisiae strains harboring thermosensitive mutants of a yeast EIF5A homolog gene (HYP2) was analyzed. The polysome profile and the formation of stress granules in cells expressing Pab1–GFP (a stress granule marker) by immunofluorescence were determined in yeast cells subjected to heat shock. Cell growth and migration of pancreatic ductal adenocarcinoma PANC-1 cells overexpressing different eIF5A1 constructs were evaluated using crystal violet staining and transwell inserts, respectively. Statistical analysis was performed with GraphPad Software, using unpaired Student’s t-test, or one-way or two-way analysis of variance (ANOVA).ResultsWe found that eIF5A is modified by SUMO2 in vitro, in transfected cells and under endogenous conditions, revealing its physiological relevance. We identified several SUMO sites in eIF5A and found that SUMOylation modulates both the stability and the localization of eIF5A in mammalian cells. Interestingly, the SUMOylation of eIF5A responds to specific stresses, indicating that it is a regulated process. SUMOylation of eIF5A is conserved in yeast, the eIF5A SUMOylation mutants are unable to completely suppress the defects of HYP2 mutants, and SUMOylation of eIF5A is important for both stress granules formation and disassembly of polysomes induced by heat-shock. Moreover, mutation of the SUMOylation sites in eIF5A abolishes its promigratory and proproliferative activities in PANC-1 cells.ConclusionsSUMO2 conjugation to eIF5A is a stress-induced response implicated in the adaptation of yeast cells to heat-shock stress and required to promote the growth and migration of pancreatic ductal adenocarcinoma cells.Graphical

Effects of Extreme-Ambient Temperatures in Silver Barb (Barbonymus gonionotus): Metabolic, Hemato-Biochemical Responses, Enzymatic Activity and Gill Histomorphology

A global interest in Silver Barb (Barbonymus gonionotus) cultivation has arisen because of a combination of declining wild stock and a steady increase in demand and market value. The purpose of the current investigation was to evaluate the impact of extreme water temperature changes on growth, hemato-biochemical responses, pepsin enzyme activity and gill histomorphology of B. gonionotus. Four distinct temperatures (22, 26, 30 and 34 °C) were applied in the laboratory (22, 26, 30 and 34 °C) in triplicate glass aquariums (150 L each). At 30 and 22 °C, respectively, the highest and the lowest length and weight gain, specific, daily and relative growth rates were noted. At 30 °C the lowest FCR was recorded (1.42 ± 0.04). The values related to hematology and biochemistry were found to be within normal ranges; nevertheless, there was a notable variation in the parameters when the temperature changed. Hematological results revealed that RBC, HB, PLT, HCT and PMV levels were significantly higher in groups 30 °C with respect to others. It was evident that cold and heat shock stress was present due to the decline in hematocrit levels and rise in WBC values. Regarding the biochemical responses, the level of triglycerides, cholesterol, AP, Ca+, HDL, and HDL/LDL ratio increased significantly higher at 30 °C. Glucose, total protein, albumin, Na+, K+, Cl−1, AST, bilirubin, uric acid, and LDL levels were significantly higher at 22 °C compared to other temperatures. There was a higher pepsin activity between 26 and 30 °C while the digestive somatic index (IDS) was disproportionate. Histological examination demonstrated the well-shaped gill tissues at 26 and 30 °C compared to distinctive pathology in other temperature treatments. As an end note, the results of the experiment indicated that B. gonionotus should be cultured at 26–30 °C to maximize the overall productivity and the health condition of this economically important fish species.

LncRNAs, Critical Regulators of Cellular Stress in Cancer: A New Player in the Old Game

Due to deregulated control of the cell cycle, proliferation and metabolism, cancer cells are constantly exposed to a wide range of stresses, including DNA damage, nutrient deprivation, heat shock, hypoxia, and oxidative stresses, often, in a non-exclusive manner. Maintaining homeostasis, survival, and proliferation under these adverse conditions is a hallmark of cancer cells. Understanding the factors that enable cancer cells to endure such harsh environments is an important topic in cancer pathology. Recently, the range of these factors have expanded from regulatory proteins, mostly described as oncogenes and tumor suppressors, to non-coding RNAs, particularly long non-coding RNAs (lncRNA). LncRNAs have been found to play crucial roles in regulating stress responses at the molecular level, with implications on cell survival and tumor initiation and progression. In this review, we explore recent studies that underscore the importance of lncRNA in regulating cellular stress responses, homeostasis, and survival.

Characterizing primary transcriptional responses to short term heat shock in Down syndrome.

Heat shock stress induces genome-wide changes in transcription regulation, activating a coordinated cellular response to enable survival. We noticed many heat shock genes are up-regulated in blood samples from individuals with trisomy 21. We characterized the immediate transcriptional response to heat shock of two lymphoblastoid cell lines derived from brothers with and without trisomy 21. The trisomy 21 cells displayed a more robust heat shock response after just one hour at 42°C than the matched disomic cells.

The Snf5-Hsf1 transcription module synergistically regulates stress responses and pathogenicity by maintaining ROS homeostasis in Sclerotinia sclerotiorum.

The SWI/SNF complex is guided to the promoters of designated genes by its co-operator to activate transcription in a timely and appropriate manner to govern development, pathogenesis, and stress responses in fungi. Nevertheless, knowledge of the complexes and their co-operator in phytopathogenic fungi is still fragmented. We demonstrate that the heat shock transcription factor SsHsf1 guides the SWI/SNF complex to promoters of heat shock protein (hsp) genes and antioxidant enzyme genes using biochemistry and pharmacology. This is accomplished through direct interaction with the complex subunit SsSnf5 under heat shock and oxidative stress. This results in the activation of their transcription and mediates histone displacement to maintain reactive oxygen species (ROS) homeostasis. Genetic results demonstrate that the transcription module formed by SsSnf5 and SsHsf1 is responsible for regulating morphogenesis, stress tolerance, and pathogenicity in Sclerotinia sclerotiorum, especially by directly activating the transcription of hsp genes and antioxidant enzyme genes counteracting plant-derived ROS. Furthermore, we show that stress-induced phosphorylation of SsSnf5 is necessary for the formation of the transcription module. This study establishes that the SWI/SNF complex and its co-operator cooperatively regulate the transcription of hsp genes and antioxidant enzyme genes to respond to host and environmental stress in the devastating phytopathogenic fungi.

Arabidopsis HSFA9 Acts as a Regulator of Heat Response Gene Expression and the Acquisition of Thermotolerance and Seed Longevity.

Heat-shock transcription factors (HSFs) are crucial for regulating plant responses to heat and various stresses, as well as for maintaining normal cellular functions and plant development. HSFA9 and HSFA2 are two of the Arabidopsis class A HSFs and their expressions are dramatically induced in response to heat shock (HS) stress among all 21 Arabidopsis HSFs. However, the detailed biological roles of their cooperation have not been fully characterized. In this study, we employed an integrated approach that combined bioinformatics, molecular genetics and computational analysis to identify and validate the molecular mechanism that controls seed longevity and thermotolerance in Arabidopsis. The acquisition of tolerance to deterioration was accompanied by a significant transcriptional switch that involved the induction of primary metabolism, reactive oxygen species and unfolded protein response, as well as the regulation of genes involved in response to dehydration, heat and hypoxia. In addition, the cis-regulatory motif analysis in normal stored and controlled deterioration treatment (CDT) seeds confirmed the CDT-repressed genes with heat-shock element (HSE) in their promoters. Using a yeast two-hybrid and molecular dynamic interaction assay, it is shown that HSFA9 acted as a potential regulator that can interact with HSFA2. Moreover, the knock-out mutants of both HSFA9 and HSFA2 displayed a significant reduction in seed longevity. These novel findings link HSF transcription factors with seed deterioration tolerance and longevity.

Stress Pathways Induced by Volatile Anesthetics and Failure of Preconditioning in a Mitochondrial Complex I Mutant.

Carriers of mutations in the mitochondrial electron transport chain are at increased risk of anesthetic-induced neurotoxicity. To investigate the neurotoxicity mechanism and to test preconditioning as a protective strategy, this study used a Drosophila melanogaster model of Leigh syndrome. Model flies carried a mutation in ND23 (ND2360114) that encodes a mitochondrial electron transport chain complex I subunit. This study investigated why ND2360114 mutants become susceptible to lethal, oxygen-modulated neurotoxicity within 24 h of exposure to isoflurane but not sevoflurane. This study used transcriptomics and quantitative real-time reverse transcription polymerase chain reaction to identify genes that are differentially expressed in ND2360114 but not wild-type fly heads at 30 min after exposure to high- versus low-toxicity conditions. This study also subjected ND2360114 flies to diverse stressors before isoflurane exposure to test whether isoflurane toxicity could be diminished by preconditioning. The ND2360114 mutation had a greater effect on isoflurane- than sevoflurane-mediated changes in gene expression. Isoflurane and sevoflurane did not affect expression of heat shock protein (Hsp) genes (Hsp22, Hsp27, and Hsp68) in wild-type flies, but isoflurane substantially increased expression of these genes in ND2360114 mutant flies. Furthermore, isoflurane and sevoflurane induced expression of oxidative (GstD1 and GstD2) and xenobiotic (Cyp6a8 and Cyp6a14) stress genes to a similar extent in wild-type flies, but the effect of isoflurane was largely reduced in ND2360114 flies. In addition, activating stress response pathways by pre-exposure to anesthetics, heat shock, hyperoxia, hypoxia, or oxidative stress did not suppress isoflurane-induced toxicity in ND2360114 mutant flies. Mutation of a mitochondrial electron transport chain complex I subunit generates differential effects of isoflurane and sevoflurane on gene expression that may underlie their differential effects on neurotoxicity. Additionally, the mutation produces resistance to preconditioning by stresses that protect the brain in other contexts. Therefore, complex I activity modifies molecular and physiologic effects of anesthetics in an anesthetic-specific manner.