Specific Stress-responsive Genes Research Articles

Crosstalk in proline biosynthesis regulates proline augmentation and resilience to salt stress in Panicum miliaceum L.

The development and productivity of most agricultural plants can be adversely affected by the presence of salts in soil. It is vital in these situations to increase agricultural yield, especially in barren soil, by developing plants that can endure and thrive in salty environment. For reducing the detrimental salt-induced effects, plants must actively control osmotic balance by accumulating suitable solutes like proline, polyols, and glycine betaine and by activating specific stress-responsive genes and enzymes within their cells. Proline is an important osmolyte which build up endogenously in plants in response to stressful situations and its accumulation is dependent on type of species and severity of stress. Although proline biosynthesis genes and enzymes have been extensively studied, but the preferred substrate in this process is yet not clear. In present study, we aimed to elucidate the preferred pathway of proline biosynthesis and the effect on physiological parameters under salt and Se application in proso millet. It was found that salt stress negatively impacted these parameters, while as the addition of Se improved these parameters. In comparison to control 150 mM NaCl treatment led to a reduction of upto 38.6% in FW and 18.91% in DW, whereas 200 mM NaCl led to reduction of upto 52.29% in FW and 18.91% in DW. The osmolytes, total soluble sugars (TSS), glycine betaine (GB) and total proline content (TPC) increased under salt stress by 53.7%, 2.14% and 113.79% at 150 mM NaCl and 54.89%, 0.53% and 87.1% at 200 mM NaCl. But, the application of Se significantly improved the above parameters. It was observed that the low level of Se (1 µM) had a role in enhancing the activity of P5CS, P5CR, and OAT enzymes while decreasing the activity of ProDH and P5CDH enzymes. It was found that genes responsible for proline biosynthesis were expressed efficiently in response to salt stress which further increased with Se application. During salt stress proline biosynthesis (PmP5CS, PmP5CR and PmOAT) genes were up-regulated which improved further with Se treatment. While as, the proline degrading (PmP5CDH and PmProDH) genes were down-regulated at both salt and se treatments. Overall, the Se treatment appeared to be beneficial for modulating the plant responses by providing tolerance.

Highlight Induced Transcriptional Priming against a Subsequent Drought Stress in Arabidopsis thaliana.

In plants, priming allows a more rapid and robust response to recurring stresses. However, while the nature of plant response to a single stress can affect the subsequent response to the same stress has been deeply studied, considerably less is known on how the priming effect due to one stress can help plants cope with subsequent different stresses, a situation that can be found in natural ecosystems. Here, we investigate the potential priming effects in Arabidopsis plants subjected to a high light (HL) stress followed by a drought (D) stress. The cross-stress tolerance was assessed at the physiological and molecular levels. Our data demonstrated that HL mediated transcriptional priming on the expression of specific stress response genes. Furthermore, this priming effect involves both ABA-dependent and ABA-independent responses, as also supported by reduced expression of these genes in the aba1-3 mutant compared to the wild type. We have also assessed several physiological parameters with the aim of seeing if gene expression coincides with any physiological changes. Overall, the results from the physiological measurements suggested that these physiological processes did not experience metabolic changes in response to the stresses. In addition, we show that the H3K4me3 epigenetic mark could be a good candidate as an epigenetic mark in priming response. Overall, our results help to elucidate how HL-mediated priming can limit D-stress and enhance plant responses to stress.

Modification of Phosphorylation Sites in the Yeast Lysine Methyltransferase Set5 Exerts Influences on the Mitogen-Activated Protein Kinase Hog1 under Prolonged Acetic Acid Stress.

Responses to acetic acid toxicity in the budding yeast Saccharomyces cerevisiae have widespread implications in the biorefinery of lignocellulosic biomass and food preservation. Our previous studies revealed that Set5, the yeast lysine methyltransferase and histone H4 methyltransferase, was involved in acetic acid stress tolerance. However, it is still mysterious how Set5 functions and interacts with the known stress signaling network. Here, we revealed that elevated phosphorylation of Set5 during acetic acid stress is accompanied by enhanced expression of the mitogen-activated protein kinase (MAPK) Hog1. Further experiments uncovered that the phosphomimetic mutation of Set5 endowed yeast cells with improved growth and fermentation performance and altered transcription of specific stress-responsive genes. Intriguingly, Set5 was found to bind the coding region of HOG1 and regulate its transcription, along with increased expression and phosphorylation of Hog1. A protein-protein interaction between Set5 and Hog1 was also revealed. In addition, modification of Set5 phosphosites was shown to regulate reactive oxygen species (ROS) accumulation, which is known to affect yeast acetic acid stress tolerance. The findings in this study imply that Set5 may function together with the central kinase Hog1 to coordinate cell growth and metabolism in response to stress. IMPORTANCE Hog1 is the yeast homolog of p38 MAPK in mammals that is conserved across eukaryotes, and it plays crucial roles in stress tolerance, fungal pathogenesis, and disease treatments. Here, we provide evidence that modification of Set5 phosphorylation sites regulates the expression and phosphorylation of Hog1, which expands current knowledge on upstream regulation of the Hog1 stress signaling network. Set5 and its homologous proteins are present in humans and various eukaryotes. The newly identified effects of Set5 phosphorylation site modifications in this study benefit an in-depth understanding of eukaryotic stress signaling, as well as the treatment of human diseases.

Crop Wild Relatives: A Valuable Source of Tolerance to Various Abiotic Stresses

Global climate change is one of the major constraints limiting plant growth, production, and sustainability worldwide. Moreover, breeding efforts in the past years have focused on improving certain favorable crop traits, leading to genetic bottlenecks. The use of crop wild relatives (CWRs) to expand genetic diversity and improve crop adaptability seems to be a promising and sustainable approach for crop improvement in the context of the ongoing climate challenges. In this review, we present the progress that has been achieved towards CWRs exploitation for enhanced resilience against major abiotic stressors (e.g., water deficiency, increased salinity, and extreme temperatures) in crops of high nutritional and economic value, such as tomato, legumes, and several woody perennial crops. The advances in -omics technologies have facilitated the elucidation of the molecular mechanisms that may underlie abiotic stress tolerance. Comparative analyses of whole genome sequencing (WGS) and transcriptomic profiling (RNA-seq) data between crops and their wild relative counterparts have unraveled important information with respect to the molecular basis of tolerance to abiotic stressors. These studies have uncovered genomic regions, specific stress-responsive genes, gene networks, and biochemical pathways associated with resilience to adverse conditions, such as heat, cold, drought, and salinity, and provide useful tools for the development of molecular markers to be used in breeding programs. CWRs constitute a highly valuable resource of genetic diversity, and by exploiting the full potential of this extended allele pool, new traits conferring abiotic-stress tolerance may be introgressed into cultivated varieties leading to superior and resilient genotypes. Future breeding programs may greatly benefit from CWRs utilization for overcoming crop production challenges arising from extreme environmental conditions.

Perturbed fatty-acid metabolism is linked to localized chromatin hyperacetylation, increased stress-response gene expression and resistance to oxidative stress.

Oxidative stress is associated with cardiovascular and neurodegenerative diseases, diabetes, cancer, psychiatric disorders and aging. In order to counteract, eliminate and/or adapt to the sources of stress, cells possess elaborate stress-response mechanisms, which also operate at the level of regulating transcription. Interestingly, it is becoming apparent that the metabolic state of the cell and certain metabolites can directly control the epigenetic information and gene expression. In the fission yeast Schizosaccharomyces pombe, the conserved Sty1 stress-activated protein kinase cascade is the main pathway responding to most types of stresses, and regulates the transcription of hundreds of genes via the Atf1 transcription factor. Here we report that fission yeast cells defective in fatty acid synthesis (cbf11, mga2 and ACC/cut6 mutants; FAS inhibition) show increased expression of a subset of stress-response genes. This altered gene expression depends on Sty1-Atf1, the Pap1 transcription factor, and the Gcn5 and Mst1 histone acetyltransferases, is associated with increased acetylation of histone H3 at lysine 9 in the corresponding gene promoters, and results in increased cellular resistance to oxidative stress. We propose that changes in lipid metabolism can regulate the chromatin and transcription of specific stress-response genes, which in turn might help cells to maintain redox homeostasis.

Identification of heat-responsive miRNAs to reveal the miRNA-mediated regulatory network of heat stress response in Betula luminifera

This paper proposes a miRNA-mediated regulatory network of heat stress response in a tree, Betula luminifera. Plants are sessile organisms that must gauge stressful conditions to ensure survival and reproductive success. In nature, plants often encounter chronic or recurring abiotic stresses, such as heat stress, although the strategies to cope with high temperature are poorly understood in woody plants. In this study, we investigated the potential roles of microRNAs (miRNAs) in heat stress response in Betula luminifera. Using next-generation deep sequencing, we identified a total of 206 miRNAs, comprising 115 known and 84 novel miRNAs, and seven potential miRNA candidates. Of these miRNAs, 98 (57 known and 41 novel miRNAs) were differentially expressed under heat stress. A total of 101 miRNA-target pairs consisting of 44 miRNAs and 71 target genes were verified by degradome sequencing. Target annotation suggested that these miRNAs might be important in the regulation of specific stress-responsive genes, including many transcription factors and a series of genes encoding important enzymes of functional proteins targeted by miRNAs. Further functional analysis suggested that these target genes were related to protein synthesis, transport and turnover, cell wall organization, protein folding, antioxidation, defense response, and modulation of attenuated plant growth and development under heat stress. The expression patterns of 15 randomly selected miRNAs derived from quantitative reverse transcription PCR had similar trends as those derived from high-throughput sequencing, as well as the expression patterns of six target genes under heat stress. These results improve our understanding of the miRNA-mediated regulatory network of heat stress response in B. luminifera, which will contribute to improving heat stress-resistant breeding in woody plants.

5-HT2A receptor deficiency alters the metabolic and transcriptional, but not the behavioral, consequences of chronic unpredictable stress

Chronic stress enhances risk for psychiatric disorders, and in animal models is known to evoke depression-like behavior accompanied by perturbed neurohormonal, metabolic, neuroarchitectural and transcriptional changes. Serotonergic neurotransmission, including serotonin2A (5-HT2A) receptors, have been implicated in mediating specific aspects of stress-induced responses. Here we investigated the influence of chronic unpredictable stress (CUS) on depression-like behavior, serum metabolic measures, and gene expression in stress-associated neurocircuitry of the prefrontal cortex (PFC) and hippocampus in 5-HT2A receptor knockout (5-HT2A−/−) and wild-type mice of both sexes. While 5-HT2A−/− male and female mice exhibited a baseline reduced anxiety-like state, this did not alter the onset or severity of behavioral despair during and at the cessation of CUS, indicating that these mice can develop stress-evoked depressive behavior. Analysis of metabolic parameters in serum revealed a CUS-evoked dyslipidemia, which was abrogated in 5-HT2A−/− female mice with a hyperlipidemic baseline phenotype. 5-HT2A−/− male mice in contrast did not exhibit such a baseline shift in their serum lipid profile. Specific stress-responsive genes (Crh, Crhr1, Nr3c1, and Nr3c2), trophic factors (Bdnf, Igf1) and immediate early genes (IEGs) (Arc, Fos, Fosb, Egr1-4) in the PFC and hippocampus were altered in 5-HT2A−/− mice both under baseline and CUS conditions. Our results support a role for the 5-HT2A receptor in specific metabolic and transcriptional, but not behavioral, consequences of CUS, and highlight that the contribution of the 5-HT2A receptor to stress-evoked changes is sexually dimorphic.

Hydrogen Peroxide Cycling in High-Temperature Acidic Geothermal Springs and Potential Implications for Oxidative Stress Response

Hydrogen peroxide (H2O2), superoxide (O2•-), and hydroxyl radicals (OH•) are produced in natural waters via ultraviolet (UV) light-induced reactions between dissolved oxygen (O2) and organic carbon, and further reaction of H2O2 and Fe(II) (i.e., Fenton chemistry). The temporal and spatial dynamics of H2O2 and other dissolved compounds (Fe(II), Fe(III), H2S, O2) were measured during a diel cycle (dark/light) in surface waters of three acidic geothermal springs (Beowulf Spring, One Hundred Springs Plain, and Echinus Geyser Spring; pH = 3-3.5, T = 68-80 °C) in Norris Geyser Basin, Yellowstone National Park. In situ analyses showed that H2O2 concentrations were lowest (ca. 1 μM) in geothermal source waters containing high dissolved sulfide (and where oxygen was below detection) and increased by two-fold (ca. 2-3 μM) in oxygenated waters corresponding to Fe(III)-oxide mat formation down the water channel. Small increases in dissolved oxygen and H2O2 were observed during peak photon flux, but not consistently across all springs sampled. Iron-oxide microbial mats were sampled for molecular analysis of ROS gene expression in two primary autotrophs of acidic Fe(III)-oxide mat ecosystems: Metallosphaera yellowstonensis (Archaea) and Hydrogenobaculum sp. (Bacteria). Expression (RT-qPCR) assays of specific stress-response genes (e.g., superoxide dismutase, peroxidases) of the primary autotrophs were used to evaluate possible changes in transcription across temporal, spatial and/or seasonal samples. Data presented here documented the presence of H2O2 and general correlation with dissolved oxygen. Moreover, two dominant microbial populations expressed ROS response genes throughout the day, but showed less expression of key genes during peak sunlight. Oxidative stress response genes (especially external peroxidases) were highly-expressed in microorganisms within Fe(III)-oxide mat communities, suggesting a significant role for these proteins during survival and growth in situ.

High-throughput sequencing reveals differential regulation of miRNAs in fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.

Non-target site resistance (NTSR) to herbicides is an increasing concern for weed control. The majority of previous studies have focused on metabolic resistance mechanisms of NTSR, but no research exists on gene regulation mechanisms behind herbicide resistance, such as microRNA (miRNA). Here, we identified 3 American sloughgrass (Beckmannia syzigachne Steud.) populations containing fenoxaprop-P-ethyl-resistant plants. We then constructed small RNA libraries and subjected them to deep sequencing and bioinformatics analyses. Forty known and 36 potentially novel, predicted miRNAs were successfully identified. Of these, we identified 3 conserved, predicted candidate NTSR-determinant miRNAs and their potential corresponding target genes, as well as 4 novel potential miRNAs with high count. Target gene prediction and annotation indicated that these 7 differentially expressed miRNAs potentially play a role in regulating specific stress-responsive genes, very likely related to herbicide resistance. Expression profiles were determined with quantitative real-time PCR. The present study is a novel, large-scale characterization of weed miRNAs. The results should further our understanding of miRNA expression profiles associated with herbicide resistance, allowing for the development of more effective weed management strategies.

Transcriptomic profiling of Arabidopsis thaliana mutant pad2.1 in response to combined cold and osmotic stress.

The contribution of glutathione (GSH) in stress tolerance, defense response and antioxidant signaling is an established fact. In this study transcriptome analysis of pad2.1, an Arabidopsis thaliana mutant, after combined osmotic and cold stress treatment has been performed to explore the intricate position of GSH in the stress and defense signaling network in planta. Microarray data revealed the differential regulation of about 1674 genes in pad2.1 amongst which 973 and 701 were significantly up- and down-regulated respectively. Gene enrichment, functional pathway analysis by DAVID and MapMan analysis identified various stress and defense related genes viz. members of heat shock protein family, peptidyl prolyl isomerase (PPIase), thioredoxin peroxidase (TPX2), glutathione-S-transferase (GST), NBS-LRR type resistance protein etc. as down-regulated. The expression pattern of the above mentioned stress and defense related genes and APETALA were also validated by comparative proteomic analysis of combined stress treated Col-0 and pad2.1. Functional annotation noted down-regulation of UDP-glycosyl transferase, 4-coumarate CoA ligase 8, cinnamyl alcohol dehydrogenase 4 (CAD4), ACC synthase and ACC oxidase which are the important enzymes of phenylpropanoid, lignin and ethylene (ET) biosynthetic pathway respectively. Since the only difference between Col-0 (Wild type) and pad2.1 is the content of GSH, so, this study suggested that in addition to its association with specific stress responsive genes and proteins, GSH provides tolerance to plants by its involvement with phenylpropanoid, lignin and ET biosynthesis under stress conditions.

Identification of novel and salt-responsive miRNAs to explore miRNA-mediated regulatory network of salt stress response in radish (Raphanus sativus L.).

BackgroundSalt stress is one of the most representative abiotic stresses that severely affect plant growth and development. MicroRNAs (miRNAs) are well known for their significant involvement in plant responses to abiotic stresses. Although miRNAs implicated in salt stress response have been widely reported in numerous plant species, their regulatory roles in the adaptive response to salt stress in radish (Raphanus sativus L.), an important root vegetable crop worldwide, remain largely unknown.ResultsSolexa sequencing of two sRNA libraries from NaCl-free (CK) and NaCl-treated (Na200) radish roots were performed for systematical identification of salt-responsive miRNAs and their expression profiling in radish. Totally, 136 known miRNAs (representing 43 miRNA families) and 68 potential novel miRNAs (belonging to 51 miRNA families) were identified. Of these miRNAs, 49 known and 22 novel miRNAs were differentially expressed under salt stress. Target prediction and annotation indicated that these miRNAs exerted a role by regulating specific stress-responsive genes, such as squamosa promoter binding-like proteins (SPLs), auxin response factors (ARFs), nuclear transcription factor Y (NF-Y) and superoxide dismutase [Cu-Zn] (CSD1). Further functional analysis suggested that these target genes were mainly implicated in signal perception and transduction, regulation of ion homeostasis, basic metabolic processes, secondary stress responses, as well as modulation of attenuated plant growth and development under salt stress. Additionally, the expression patterns of ten miRNAs and five corresponding target genes were validated by reverse-transcription quantitative PCR (RT-qPCR).ConclusionsWith the sRNA sequencing, salt-responsive miRNAs and their target genes in radish were comprehensively identified. The results provide novel insight into complex miRNA-mediated regulatory network of salt stress response in radish, and facilitate further dissection of molecular mechanism underlying plant adaptive response to salt stress in root vegetable crops.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1416-5) contains supplementary material, which is available to authorized users.

P.1.a.021 A molecular pathway analysis of the genes in 22q11.2 provides information on the genetic structure of psychosis

Chronic stress enhances risk for psychiatric disorders, and in animal models is known to evoke depression-like behavior accompanied by perturbed neurohormonal, metabolic, neuroarchitectural and transcriptional changes. Serotonergic neurotransmission, including serotonin2A (5-HT2A) receptors, have been implicated in mediating specific aspects of stress-induced responses. Here we investigated the influence of chronic unpredictable stress (CUS) on depression-like behavior, serum metabolic measures, and gene expression in stress-associated neurocircuitry of the prefrontal cortex (PFC) and hippocampus in 5-HT2A receptor knockout (5-HT2A−/−) and wild-type mice of both sexes. While 5-HT2A−/− male and female mice exhibited a baseline reduced anxiety-like state, this did not alter the onset or severity of behavioral despair during and at the cessation of CUS, indicating that these mice can develop stress-evoked depressive behavior. Analysis of metabolic parameters in serum revealed a CUS-evoked dyslipidemia, which was abrogated in 5-HT2A−/− female mice with a hyperlipidemic baseline phenotype. 5-HT2A−/− male mice in contrast did not exhibit such a baseline shift in their serum lipid profile. Specific stress-responsive genes (Crh, Crhr1, Nr3c1, and Nr3c2), trophic factors (Bdnf, Igf1) and immediate early genes (IEGs) (Arc, Fos, Fosb, Egr1-4) in the PFC and hippocampus were altered in 5-HT2A−/− mice both under baseline and CUS conditions. Our results support a role for the 5-HT2A receptor in specific metabolic and transcriptional, but not behavioral, consequences of CUS, and highlight that the contribution of the 5-HT2A receptor to stress-evoked changes is sexually dimorphic.

Acquisition of thermotolerant yeast Saccharomyces cerevisiae by breeding via stepwise adaptation

A thermotolerant Saccharomyces cerevisiae yeast strain, YK60-1, was bred from a parental strain, MT8-1, via stepwise adaptation. YK60-1 grew at 40°C, a temperature at which MT8-1 could not grow at all. YK60-1 exhibited faster growth than MT8-1 at 30°C. To investigate the mechanisms how MT8-1 acquired thermotolerance, DNA microarray analysis was performed. The analysis revealed the induction of stress-responsive genes such as those encoding heat shock proteins and trehalose biosynthetic enzymes in YK60-1. Furthermore, nontargeting metabolome analysis showed that YK60-1 accumulated more trehalose, a metabolite that contributes to stress tolerance in yeast, than MT8-1. In conclusion, S. cerevisiae MT8-1 acquired thermotolerance by induction of specific stress-responsive genes and enhanced intracellular trehalose levels.

The exoribonuclease Polynucleotide Phosphorylase influences the virulence and stress responses of yersiniae and many other pathogens

Microbes are incessantly challenged by both biotic and abiotic stressors threatening their existence. Therefore, bacterial pathogens must possess mechanisms to successfully subvert host immune defenses as well as overcome the stress associated with host-cell encounters. To achieve this, bacterial pathogens typically experience a genetic re-programming whereby anti-host/stress factors become expressed and eventually translated into effector proteins. In that vein, the bacterial host-cell induced stress-response is similar to any other abiotic stress to which bacteria respond by up-regulating specific stress-responsive genes. Following the stress encounter, bacteria must degrade unnecessary stress responsive transcripts through RNA decay mechanisms. The three pathogenic yersiniae (Yersinia pestis, Y. pseudo-tuberculosis, and Y. enterocolitica) are all psychrotropic bacteria capable of growth at 4°C; however, cold growth is dependent on the presence of an exoribonuclease, polynucleotide phosphorylase (PNPase). PNPase has also been implicated as a virulence factor in several notable pathogens including the salmonellae, Helicobacter pylori, and the yersiniae [where it typically influences the type three secretion system (TTSS)]. Further, PNPase has been shown to associate with ribonuclease E (endoribonuclease), RhlB (RNA helicase), and enolase (glycolytic enzyme) in several Gram-negative bacteria forming a large, multi-protein complex known as the RNA degradosome. This review will highlight studies demonstrating the influence of PNPase on the virulence potentials and stress responses of various bacterial pathogens as well as focusing on the degradosome-dependent and -independent roles played by PNPase in yersiniae stress responses.

Ribonucleases and bacterial virulence

SummaryBacterial stress responses provide them the opportunity to survive hostile environments, proliferate and potentially cause diseases in humans and animals. The way in which pathogenic bacteria interact with host immune cells triggers a complicated series of events that include rapid genetic re‐programming in response to the various host conditions encountered. Viewed in this light, the bacterial host‐cell induced stress response (HCISR) is similar to any other well‐characterized environmental stress to which bacteria must respond by upregulating a group of specific stress‐responsive genes. Post stress, bacteria must resume their pre‐stress genetic program, and, as a consequence, must degrade unnecessary stress responsive transcripts through RNA decay mechanisms. Further, there is a well‐established role for several ribonucleases in the cold shock response whereby they modulate the changing transcript landscape in response to the stress, and during acclimation and subsequent genetic re‐programming post stress. Recently, ribonucleases have been implicated as virulence‐associated factors in several notable Gram‐negative pathogens including, the yersiniae, the salmonellae, Helicobacter pylori, Shigella flexneri and Aeromonas hydrophila. This review will focus on the roles played by ribonucleases in bacterial virulence, other bacterial stress responses, and on their novel therapeutic applications.

Molecular and physiological analysis of drought stress in Arabidopsis reveals early responses leading to acclimation in plant growth.

Plant drought stress response and resistance are complex biological processes that need to be analyzed at a systems level using genomics and physiological approaches to dissect experimental models that address drought stresses encountered by crops in the field. Toward this goal, a controlled, sublethal, moderate drought (mDr) treatment system was developed in Arabidopsis (Arabidopsis thaliana) as a reproducible assay for the dissection of plant responses to drought. The drought assay was validated using Arabidopsis mutants in abscisic acid (ABA) biosynthesis and signaling displaying drought sensitivity and in jasmonate response mutants showing drought resistance, indicating the crucial role of ABA and jasmonate signaling in drought response and acclimation. A comparative transcriptome analysis of soil water deficit drought stress treatments revealed the similarity of early-stage mDr to progressive drought, identifying common and specific stress-responsive genes and their promoter cis-regulatory elements. The dissection of mDr stress responses using a time-course analysis of biochemical, physiological, and molecular processes revealed early accumulation of ABA and induction of associated signaling genes, coinciding with a decrease in stomatal conductance as an early avoidance response to drought stress. This is accompanied by a peak in the expression of expansin genes involved in cell wall expansion, as a preparatory step toward drought acclimation by the adjustment of the cell wall. The time-course analysis of mDr provides a model with three stages of plant responses: an early priming and preconditioning stage, followed by an intermediate stage preparatory for acclimation, and a late stage of new homeostasis with reduced growth.

The significance of genome-wide transcriptional regulation in the evolution of stress tolerance

It is widely recognized that stress plays an important role in directing the adaptive adjustment of an organism to changing environments. However, very little is known about the evolution of mechanisms that promote stress-induced variation. Adaptive transcriptional responses have been implicated in the evolution of tolerance to natural and anthropogenic stressors in the environment. Recent technological advances in transcriptomics provide a mechanistic understanding of biological pathways or processes involved in stress-induced phenotypic change. Furthermore, these studies are (semi) quantitative and provide insight into the reaction norms of identified target genes in response to specific stressors. We argue that plasticity in gene expression reaction norms may be important in the evolution of stress tolerance and adaptation to environmental stress. This review highlights the consequences of transcriptional plasticity of stress responses within a single generation and concludes that gene promoters containing a TATA box are more capable of rapid and variable responses than TATA-less genes. In addition, the consequences of plastic transcriptional responses to stress over multiple generations are discussed. Based on examples from the literature, we show that constitutive over expression of specific stress response genes results in stress adapted phenotypes. However, organisms with an innate capacity to buffer stress display plastic transcriptional responses. Finally, we call for an improved integration of the concept of phenotypic plasticity with studies that focus on the regulation of transcription.

Upregulated ex vivo expression of stress-responsive inflammatory pathway genes by LPS-challenged CD14 + monocytes in frail older adults

Frailty has been increasingly recognized as an important clinical syndrome in old age. The frailty syndrome is characterized by chronic inflammation, decreased functional and physiologic reserve, and increased vulnerability to stressors, leading to disability and mortality. However, molecular mechanisms that contribute to inflammation activation and regulation in frail older adults have not been investigated. To begin to address this, we conducted a pathway-specific gene array analysis of 367 inflammatory pathway genes by lipopolysaccharide (LPS)-challenged CD14 + monocytes from 32 community-dwelling frail and age-, race-, and sex-paired nonfrail older adults (mean age 83 years, range 72–94). The results showed that ex vivo LPS-challenge induced average 2.0-fold or higher upregulated expression of 116 genes in frail participants and 85 genes in paired nonfrail controls. In addition, frail participants had 2-fold or higher upregulation in LPS-induced expression of 7 stress-responsive genes than nonfrail controls with validation by quantitative real time RT-PCR. These findings suggest upregulated expression of specific stress-responsive genes in monocyte-mediated inflammatory pathway in the syndrome of frailty with potential mechanistic and interventional implications.

Expression analysis of stress-specific responsive genes in two-stage continuous cultures of Escherichia coli using cDNA microarray and real-time RT-PCR analysis

For the continuous cultivation of the three Escherichia coli strains, which harbor luciferase operon under control of promoter recA (DPD2794), katG (DK1), and their wild type host RFM443, multi-channel two-stage continuous mini-bioreactor system was employed. Stressful conditions were initiated by pulse-injections of mitomycin C (MMC) and hydrogen peroxide (HP) into the second mini-bioreactors of each channel in order to analyze specific gene expression along with bioluminescence emission. When stressed, the recombinant strains responded through changes in their bioluminescence levels via an activation of the promoters from specific stress-responsive genes ( recA or katG). Likewise, changes of expression levels of target genes ( recA and katG) and other relevant genes in host E. coli RFM443 were also observed by using cDNA microarray and further quantified with real-time RT-PCR assay. The target gene expression of the host strain analyzed by using cDNA microarray and real-time RT-PCR assays were matched well with bioluminescent profiles at the conditions triggered by different toxic chemicals. The results from this study indicated that changes in bioluminescence level the continuous water toxicity monitoring system using recombinant strains are due to the exact activation of the stress-specific target genes controlled by the stress-specific promoter. In addition, DNA microarray and real-time RT-PCR techniques can be implemented to make system performance validated.

Functional analysis of oxidative stress-activated mitogen-activated protein kinase cascade in plants

Despite the recognition of H(2)O(2) as a central signaling molecule in stress and wounding responses, pathogen defense, and regulation of cell cycle and cell death, little is known about how the H(2)O(2) signal is perceived and transduced in plant cells. We report here that H(2)O(2) is a potent activator of mitogen-activated protein kinases (MAPKs) in Arabidopsis leaf cells. Using epitope tagging and a protoplast transient expression assay, we show that H(2)O(2) can activate a specific Arabidopsis mitogen-activated protein kinase kinase kinase, ANP1, which initiates a phosphorylation cascade involving two stress MAPKs, AtMPK3 and AtMPK6. Constitutively active ANP1 mimics the H(2)O(2) effect and initiates the MAPK cascade that induces specific stress-responsive genes, but it blocks the action of auxin, a plant mitogen and growth hormone. The latter observation provides a molecular link between oxidative stress and auxin signal transduction. Finally, we show that transgenic tobacco plants that express a constitutively active tobacco ANP1 orthologue, NPK1, display enhanced tolerance to multiple environmental stress conditions without activating previously described drought, cold, and abscisic acid signaling pathways. Thus, manipulation of key regulators of an oxidative stress signaling pathway, such as ANP1/NPK1, provides a strategy for engineering multiple stress tolerance that may greatly benefit agriculture.