Stress Adaptation Processes Research Articles

HY5 Contributes to Light-Regulated Root System Architecture Under a Root-Covered Culture System.

Light is essential for plant organogenesis and development. Light-regulated shoot morphogenesis has been extensively studied; however, the mechanisms by which plant roots perceive and respond to aboveground light are largely unknown, particularly because the roots of most terrestrial plants are usually located underground in darkness. To mimic natural root growth conditions, we developed a root-covered system (RCS) in which the shoots were illuminated and the plant roots could be either exposed to light or cultivated in darkness. Using the RCS, we observed that root growth of wild-type plants was significantly promoted when the roots were in darkness, whereas it was inhibited by direct light exposure. This growth change seems to be regulated by ELONGATED HYPOCOTYL 5 (HY5), a master regulator of photomorphogenesis. Light was found to regulate HY5 expression in the roots, while a HY5 deficiency partially abolished the inhibition of growth in roots directly exposed to light, suggesting that HY5 expression is induced by direct light exposure and inhibits root growth. However, no differences in HY5 expression were observed between illuminated and dark-grown cop1 roots, indicating that HY5 may be regulated by COP1-mediated proteasome degradation. We confirmed the crucial role of HY5 in regulating root development in response to light under soil-grown conditions. A transcriptomic analysis revealed that light controls the expression of numerous genes involved in phytohormone signaling, stress adaptation, and metabolic processes in a HY5-dependent manner. In combination with the results of the flavonol quantification and exogenous quercetin application, these findings suggested that HY5 regulates the root response to light through a complex network that integrates flavonol biosynthesis and reactive oxygen species signaling. Collectively, our results indicate that HY5 is a master regulator of root photomorphogenesis.

Mechanical Stress and Alteration of Cellular Morphology Influences O‐GlcNAc Modification

Protein O‐linked N‐acetylglucosamine modification (O‐GlcNAc) is the result of a post‐translational modification that involves the reversible transfer of an N‐acetyl‐glucosamine molecule to Ser/Thr OH‐group of intracellular proteins. O‐GlcNAc modification is increasingly recognized as a key regulatory element, capable to modify the functionality and the life‐cycle of hundreds of proteins. O‐GlcNAc's participation in stress adaptation processes was evidenced after several environmental challenges such as heat shock, hypoxia or oxidative stress. However, intracellular O‐GlcNAc modification was not yet studied under mechanical stress, despite the fact that physical stress is a constant challenge for many cells in our body.In our present work, we used human periodontal ligament (PDL) cells isolated from teeth extracted for orthodontic indications. PDL cells were cultivated under standard cell culture conditions and exposed to various amount of compression force for 12 hours.We have analyzed cell survival by flow‐cytometry and protein O‐GlcNAc by Western‐blot. Since cytoskeletal filaments are essential to the structural integrity of the cells both in normal condition and under mechanical stress, we also studied the intracellular distribution of O‐GlcNAc in relation to actin, alpha‐tubulin, vimentin and the cellular shape. We have found that O‐GlcNAc elevated under moderate mechanical load (1.5 – 3 g/cm2) but did not changed significantly under higher load ( ≥ 7 g/cm2). Intracellular distribution of O‐GlcNAc in non‐loaded cell demonstrated an accumulation at several membrane protrusion sites which showed the most overlap with tubulin and no overlap at all with vimentin. Under mechanical stress, the cells retracted these protrusions and O‐GlcNAc distribution became more centralized as well.In conclusion, we found that O‐GlcNAc regulation responds to mechanical challenges and our data suggest that O‐GlcNAc is coupled to cellular morphology.Support or Funding InformationThis work was funded by the Research Fund of the University of Pécs, Faculty of Medicine (grant No.: AOK‐KA 2/2015 (06.30)) and the EU founded Hungarian project GINOP 2.3.2. –15 (grant No.: 2.3.2. –15‐2016‐00050).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Family of People with Multiple Sclerosis: The Process of Family Stress Adaptation

Background: Multiple Sclerosis (MS) affects everyday functioning of individuals with MS, and their family dynamics. Furthermore, MS is a chronic disease with unpredictable course imposing a stressful experience on the entire family. Changes in family functioning patterns are necessary so that they can appropriately respond to complex demands imposed by the disease. Objectives: This study aimed to evaluate predictive values of family resources in the encounter with stressful life events and family adaptation. These data are required to provide adequate family support systems. Methods: The sample consisted of 62 people with MS. The following instruments were used: Family Adaptation Scale, Family Social Support Index, Financial Well-Being Scale, and Family Problem Solving Communication Scale. Results: The results of this research indicate that subjective assessment of the quality of family relationships, measures of the quality of family communication (β = 0.353, P < 0.001), and measures of perceived family social support (β = 0.272, P < 0.05) are the only predictors of successful family adaptation. Conclusions: The results infer that the processes essential for successful adaptation of people with MS occurs within their nuclear family. Therefore, adaptation to accidental crisis created by MS onset can be promoted by strengthening support and communication within the nuclear family.

Perceived Stress and University Adaptation Process: The Mediating Role of Mindfulness

Perceived Stress and University Adaptation Process: The Mediating Role of Mindfulness

Diurnal cortisol and alpha-amylase in the daily lives of older adults with vital exhaustion

ObjectiveVital exhaustion (VE) is characterised by unusual fatigue, increased irritability, and a feeling of demoralisation. It has been found a major risk factor for cardiovascular diseases, and one that is independent of subclinical or clinical manifestations of coronary heart disease or lifestyle-related risk factors. Stress-induced alterations in the hypothalamic-pituitary–adrenal (HPA) axis and sympathetic nervous system may mediate the link between VE and increased cardiovascular risk. However, no studies have yet assessed both systems simultaneously and in high-risk populations, such as older adults. MethodsA total of 72 older adults (34 women, mean age 61.7±7.3) who were free of any major physical or mental illnesses filled out the Maastricht Vital Exhaustion Questionnaire (MVEQ) and the Perceived Stress Scale (PSS). To determine cortisol and alpha-amylase, participants collected saliva samples upon awakening, +30min thereafter, and at 11am, 3pm, and 8pm. ResultsParticipants with higher VE reported lower perceived stress (β=−0.515, p<0.001). Individuals reporting higher VE also exhibited more diminished cortisol concentrations across the day, although only by trend (β=−0.218, p=0.092). There was no significant association between VE and diurnal alpha-amylase activity. Moreover, women had lower diurnal cortisol (β=−0.381, p=0.004) and alpha-amylase (β=−0.329, p=0.011) when compared to men. ConclusionsOur findings provide initial evidence for psychosocial stress to be linked to VE in older adults, while evidence for HPA alterations remains tentative. Future research is warranted to determine whether VE related hypocortisolaemia represents a specific stage of the stress adaptation process that may put individuals at risk for incident cardiovascular diseases.

Epigenetic Regulation of Abiotic Stress Tolerance in Plants

Sequence specific, genome-wide changes are being reported in plants which often correlate with regulation of gene expression at transcription levels. Many of such changes occur during stress exposure, and both gene expression and chromatin changes may revert to the pre-stress state shortly thereafter. There are reports for stress-induced chromatin changes that are transmitted to the progenies. Such changes alter gene expression without having any change in the DNA sequence. These epigenetic changes include modification in DNA base, histones and small non-coding RNAs. Some of the cytosine residues in nuclear genome may get methylated at 5’ position by the action of DNA methyl transferase. Histones are also subjected to post-translational modifications which affect transcription, replication, chromosome condensation/segregation, as well as DNA repair. Methylation of a promoter may repress gene transcription, while methylation of coding region of a gene may cause post-transcriptional gene silencing. Epigenetic changes may also be inherited over the generations in the form of epialleles, which are considered as a source of genetic variability for crop improvement. The roles of epigenetic changes in plant’s response to stress are becoming increasingly evident, suggesting that epigenetic mechanisms play important role in stress tolerance, acclimatization, adaptation and evolution processes. Therefore, it is worth investigating the epigenetic mechanisms of gene regulation in plants, and their possible exploitation in crop improvement.

Immunometabolism in Tuberculosis.

Immunometabolism, the study of the relationship between bioenergetic pathways and specific functions of immune cells, has recently gained increasing appreciation. In response to infection, activation of the host innate and adaptive immune cells is accompanied by a switch in the bioenergetic pathway from oxidative phosphorylation to glycolysis, a metabolic remodeling known as the Warburg effect, which is required for the production of antimicrobial and pro-inflammatory effector molecules. In this review, we summarize the current understanding of the Warburg effect and discuss its association with the expression of host immune responses in tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb). We also discuss potential mechanisms underlying the Warburg effect with a focus on the expression and regulation of hypoxia-inducible factor 1 alpha (HIF-1α), the regulatory subunit of HIF-1, a major transcription regulator involved in cellular stress adaptation processes, including energy metabolism and antimicrobial responses. We also propose a novel hypothesis that Mtb perturbs the Warburg effect of immune cells to facilitate its survival and persistence in the host. A better understanding of the dynamics of metabolic states of immune cells and their specific functions during TB pathogenesis can lead to the development of immunotherapies capable of promoting Mtb clearance and reducing Mtb persistence and the emergence of drug resistant strains.

Commentary: Conservation of AtTZF1, AtTZF2, and AtTZF3 homolog gene regulation by salt stress in evolutionarily distant plant species.

Commentary: Conservation of AtTZF1, AtTZF2, and AtTZF3 homolog gene regulation by salt stress in evolutionarily distant plant species.

Tert‐Butyl hydroperoxide‐induced differing plasma membrane and oxidative stress processes in yeast strains BY4741 and erg5Δ

The molecular mechanism of tert-butyl hydroperoxide (t-BuOOH) elicited cytotoxicity and the background of t-BuOOH sensitivity were studied in the Saccharomyces cerevisiae ergosterol-less gene deletion mutant erg5Δ and its parental strain BY4741. In comparison to BY4741, untreated erg5Δ cells exhibited alterations in sterol and fatty acid compositions of the plasma membrane, as reflected by the inherent amphotericin B resistance, an elevated level (31%) of plasma membrane rigidity and a decreased uptake of glycerol. Surprisingly, the untreated erg5Δ cells exhibited an unbalanced intracellular redox state, accompanied by the continuous upregulation of the antioxidant enzymes Mn superoxide dismutase, catalase, and glutathione S-transferase, which resulted in decreased specific concentrations of superoxide and peroxides and elevated levels of the hydroxyl radical and thiols. The 2.5-fold sensitivity of erg5Δ to t-BuOOH suggested that the oxidative stress adaptation processes of the mutant could not restore the redox homeostasis of the cells and there is an overlap between sterol and redox homeostases. t-BuOOH treatment of both strains induced adaptive modification of the sterol and fatty acid compositions, increased the plasma membrane fluidity and elevated the specific activities of most antioxidant enzymes through specific regulation processes in a strain-dependent manner.

Molecular cloning, characterization, and stress-responsive expression of genes encoding glycine-rich RNA-binding proteins in Camelina sativa L.

Camelina sativa L. is an oil-seed crop that has potential for biofuel applications. Although the importance of C.sativa as a biofuel crop has increased in recent years, reports demonstrating the stress responsiveness of C.sativa and characterizing the genes involved in stress response of C.sativa have never been published. Here, we isolated and characterized three genes encoding glycine-rich RNA-binding proteins (GRPs) from camelina: CsGRP2a, CsGRP2b, and CsGRP2c. The three CsGRP2 proteins were very similar in amino acid sequence and contained a well-conserved RNA-recognition motif at the N-terminal region and glycine-rich domain at the C-terminal region. To understand the functional roles of CsGRP2s under stress conditions, we investigated the expression patterns of CsGRP2s under various environmental stress conditions. The expressions of the three CsGRP2s were highly up-regulated under cold stress. The expression of CsGRP2a was up-regulated under salt or dehydration stress, whereas the transcript levels of CsGRP2b and CsGRP2c were decreased under salt or dehydration stress conditions. The three CsGRP2s had the ability to complement cold-sensitive Escherichia coli mutants at low temperatures and harbored transcription anti-termination and nucleic acid-melting activities, indicating that the CsGRP2s possess RNA chaperone activity. The CsGRP2a protein was localized to both the nucleus and the cytoplasm. Expression of CsGRP2a in cold-sensitive Arabidopsis grp7 mutant plants resulted in decreased electrolyte leakage at freezing temperatures. Collectively, these results suggest that the stress-responsive CsGRP2s play a role as an RNA chaperone during the stress adaptation process in camelina.

Ecophysiological tolerance of Lemna gibba L. exposed to cadmium

In this study, an experiment was carried out to study the process of stress adaptation in Lemna gibba L. grown under cadmium stress (0–20mg Cd L−1). The level of photosynthetic pigments and soluble proteins decreased only upon exposure to high Cd concentrations (for pigments 5mg Cd L−1; for soluble proteins 10mg Cd L−1). At the same time, the level of malondialdehyde (MDA) increased with increasing Cd concentration. These results suggested an alleviation of stress that was presumably the result of antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST) as well as ascorbate peroxidase (APX), which increased linearly with increasing Cd levels. In addition, the proline content in L. gibba increased with increasing cadmium levels. These findings suggest that Lemna is equipped with an efficient antioxidant mechanism against Cd induced oxidative stress which protects the plant's photosynthetic machinery from damage.We also found that moderate Cd treatment (0.05–5mg L−1 Cd) alleviated oxidative stress in plants, while the addition of higher amounts of Cd (10–20mg L−1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system.

Streptococcus mutans Protein Synthesis during Mixed-Species Biofilm Development by High-Throughput Quantitative Proteomics

Biofilms formed on tooth surfaces are comprised of mixed microbiota enmeshed in an extracellular matrix. Oral biofilms are constantly exposed to environmental changes, which influence the microbial composition, matrix formation and expression of virulence. Streptococcus mutans and sucrose are key modulators associated with the evolution of virulent-cariogenic biofilms. In this study, we used a high-throughput quantitative proteomics approach to examine how S. mutans produces relevant proteins that facilitate its establishment and optimal survival during mixed-species biofilms development induced by sucrose. Biofilms of S. mutans, alone or mixed with Actinomyces naeslundii and Streptococcus oralis, were initially formed onto saliva-coated hydroxyapatite surface under carbohydrate-limiting condition. Sucrose (1%, w/v) was then introduced to cause environmental changes, and to induce biofilm accumulation. Multidimensional protein identification technology (MudPIT) approach detected up to 60% of proteins encoded by S. mutans within biofilms. Specific proteins associated with exopolysaccharide matrix assembly, metabolic and stress adaptation processes were highly abundant as the biofilm transit from earlier to later developmental stages following sucrose introduction. Our results indicate that S. mutans within a mixed-species biofilm community increases the expression of specific genes associated with glucan synthesis and remodeling (gtfBC, dexA) and glucan-binding (gbpB) during this transition (P<0.05). Furthermore, S. mutans up-regulates specific adaptation mechanisms to cope with acidic environments (F1F0-ATPase system, fatty acid biosynthesis, branched chain amino acids metabolism), and molecular chaperones (GroEL). Interestingly, the protein levels and gene expression are in general augmented when S. mutans form mixed-species biofilms (vs. single-species biofilms) demonstrating fundamental differences in the matrix assembly, survival and biofilm maintenance in the presence of other organisms. Our data provide insights about how S. mutans optimizes its metabolism and adapts/survives within the mixed-species community in response to a dynamically changing environment. This reflects the intricate physiological processes linked to expression of virulence by this bacterium within complex biofilms.

Generation of an expressed sequence tag (EST) library from salt‐stressed roots of Jatropha curcas for identification of abiotic stress‐responsive genes

Improving salinity and drought tolerance of crop plants has been an important aim of modern agricultural development, which depends on understanding the functions of genes expressed during the process of stress adaptation. EST resources are an efficient and cost-effective solution to gene discovery. Jatropha curcas is emerging as the most promising tree oil seed as a source of biodiesel. To identify genes that respond to abiotic stress, in the present study, we report 1240 ESTs generated from root cDNA libraries of J.curcas. ESTs were clustered and assembled into a collection of 865 unigenes, with 107 contigs and 758 singleton sequences. The putative functions of several ESTs could be assigned by similarity to plant gene sequence comparisons. It was found that 23 full-length CDS (34%) and the majority of transcription factors had sequence similarity to genes known to be involved in abiotic and biotic stress tolerance. The expression pattern of nine selected genes revealed that these genes are differentially expressed in various tissues during adaptation to stress. The data could serve as a critical resource to enable plant improvement programmes towards enhancing the adaptability of J.curcas to growth on marginal lands.

Nickel-Induced Changes in Lipid Peroxidation, Antioxidative Enzymes, and Metal Accumulation in Lemna Gibba

In this study, an experiment was carried out to study the process of stress adaptation in Lemna gibba grown under nickel stress (0–20 mg Ni L−1). The results showed that Ni concentrations in plants increased with increasing Ni supply levels and reached a maximum of 142.82 mg.kg1 DW at 0.5 mg.L−1 Ni treatments. The level of photosynthetic pigments (Chl a, Chl b, and total Chl) and soluble proteins increased upon exposure to high Ni concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Ni concentration. These results suggested an alleviation of stress that was presumably the results of antioxidants such as superoxide dismutase (SOD), catalase (CAT) which generally increased linearly with increasing Ni levels. In addition, the proline content in L. gibba increased with increasing nickel levels.Our present work concluded that Lemna gibba has a high level of nickel tolerance and accumulation. We also found that moderate nickel treatment (0.05–5 mg.L−1) alleviated oxidative stress in plants, while the addition of higher amounts of nickel (10–20 mg.L−1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system. Therefore, L. gibba may be used as a phytoremediator in moderately polluted aquatic ecosystems.

Effects of lead on the growth, lead accumulation and physiological responses of Pluchea sagittalis

This work aimed to study the process of stress adaptation in root and leaves of different developmental stages (apex, middle and basal regions) of Pluchea sagittalis (Lam.) Cabrera plants grown under exposure to five Pb levels (0, 200, 400, 600 and 1000μM) for 30days. Pb concentration and content in roots, stems, and leaves of different developmental stages increased with external Pb level. Consumption of nutrient solution, transpiration ratio, leaf fresh weight, leaf area, and shoot length decreased upon addition of Pb treatments. However, dry weight of shoot parts and roots did not decrease upon addition of Pb treatments. Based on index of tolerance, the roots were much more tolerant to Pb than shoots. δ-aminolevulinic acid dehydratase activity was decreased by Pb treatments, whereas carotenoid and chlorophyll concentrations were not affected. Lipid peroxidation and hydrogen peroxide concentration both in roots and leaves increased with increasing Pb levels. Pb treatments increased ascorbate peroxidase activity in all plant parts, while superoxide dismutase activity increased in leaves and did not change in roots. Catalase activity in leaves from the apex shoot was not affected by Pb, but in other plant parts it was increased. Pb toxicity caused increase in non-protein thiol groups concentration in shoot parts, whereas no significant difference was observed in roots. Both root and shoot ascorbic acid concentration increased with increasing Pb level. Therefore, it seems that Pb stress triggered an efficient defense mechanism against oxidative stress in P. sagittalis but its magnitude was depending on the plant organ and of their physiological status. In addition, these results suggest that P. sagittalis is Pb-tolerant. In conclusion, P. sagittalis is able to accumulate on average 6730 and 550μg Pb g(-1) dry weight, respectively, in the roots and shoot, a physiological trait which may be exploited for the phytoremediation of contaminated soils and waters.

Changes in proline accumulation and antioxidative enzyme activities in Groenlandia densa under cadmium stress

In this study an experiment was carried out to study the process of stress adaptation in Groenlandia densa (opposite-leaved pondweed) grown under cadmium stress (0–20 mg L −1 Cd). The results showed that Cd concentrations in plants increased with increasing Cd supply levels and reached a maximum of 0.43 mg kg −1 DW at 0.5 mg L −1 Cd concentrations. The level of photosynthetic pigments and soluble proteins decreased only upon exposure to high Cd concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Cd concentration. These results suggested an alleviation of stress that was presumably the result of by antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST) as well as ascorbate peroxidase (APX), which increased linearly with increasing Cd levels. Cellular antioxidants levels showed a decline suggesting a defensive mechanism to protect against oxidative stress caused by Cd. In addition, the proline content in G. densa increased with increasing cadmium levels. These findings suggest that G. densa is equipped with an efficient antioxidant mechanism against Cd-induced oxidative stress which protects the plant's photosynthetic machinery from damage. Our present work concluded that G. densa has a high level of Cd tolerance and accumulation. We also found that moderate Cd treatment (0.05–5 mg L −1 Cd) alleviated oxidative stress in plants, while the addition of higher amounts of Cd (10–20 mg L −1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system.

Reduced Host Cell Invasiveness and Oxidative Stress Tolerance in Double and TriplecspGene Family Deletion Mutants ofListeria monocytogenes

The cold shock protein (Csp) family comprises small, highly conserved proteins that bind nucleic acids to modulate various bacterial gene expressions. In addition to cold adaptation functions, this group of proteins is thought to facilitate various cellular processes to promote normal growth and stress adaptation responses. Three proteins making up the Listeria monocytogenes Csp family (CspA, CspB, and CspD) promote both cold and osmotic stress adaptation functions in this bacterium. The contribution of these three Csps in the host cell invasion processes of L. monocytogenes was investigated based on human Caco-2 and murine macrophage in vitro cell infection models. The DeltacspB, DeltacspD, DeltacspAB, DeltacspAD, DeltacspBD, and DeltacspABD strains were all significantly impaired in Caco-2 cell invasion compared with the wild-type strain, whereas in the murine macrophage infection assay only, the double (DeltacspBD) and triple (DeltacspABD) csp mutants were also significantly impaired in cell invasion compared with the wild-type strain. The DeltacspBD and DeltacspABD mutants displayed the most severely impaired invasion phenotypes. The invasion ability of these two mutant strains was also further analyzed using cold-stress-exposed organisms. In both cell infection models a significant reduction in invasiveness was observed after cold stress exposure of Listeria organisms. The negative impact of cold stress on subsequent cell invasion ability was, however, more severe in cold-sensitive csp mutants (DeltacspBD and DeltacspABD) compared with the wild type. The impaired macrophage invasion and intracellular growth of DeltacspBD and DeltacspABD also led us to examine oxidative stress resistance capacity in these two mutant strains. Both strains also displayed higher oxidative stress sensitivity relative to the wild-type strain. Our data indicate that besides cold and osmotic stress adaptation roles, Csp family proteins also promote efficient host cell invasion and oxidative stress adaptation processes in L. monocytogenes.

Metabolic Pathway Relationships Revealed by an Integrative Analysis of the Transcriptional and Metabolic Temperature Stress-Response Dynamics in Yeast

The integrated analysis of omics datasets covering different levels of molecular organization has become a central task of systems biology. We investigated the transcriptional and metabolic response of yeast exposed to increased (37 degrees C) and lowered (10 degrees C) temperatures relative to optimal reference conditions (28 degrees C) in the context of known metabolic pathways. Pairwise metabolite correlation levels were found to carry more pathway-related information and to extend to farther distances within the metabolic pathway network than associated transcript level correlations. Metabolites were detected to correlate stronger to their cognate transcripts (metabolite is reactant of the enzyme encoded by the transcript) than to more remote or randomly chosen transcripts reflecting their close metabolic relationship. We observed a pronounced temporal hierarchy between metabolic and transcriptional molecular responses under heat and cold stress. Changes of metabolites were most significantly correlated to transcripts encoding metabolic enzymes, when metabolites were considered leading in time-lagged correlation analyses. By applying the concept of Granger causality, we detected directed relationships between metabolites and their cognate transcripts. When interpreted as substrate-to-product directions, most of these directed Granger causality pairs agreed with the KEGG-annotated preferred reaction direction. Thus, the introduced Granger causality approach may prove useful for determining the preferred direction of metabolic reactions in cellular systems. The metabolites glutamic acid and serine were identified as central causative metabolites influencing transcript levels at later time points. Selected examples are presented illustrating the intertwined relationships between metabolites and transcripts in the yeast temperature stress adaptation process.

Antioxidant defense mechanism in hydroponically grown Zea mays seedlings under moderate lead stress

The present study was designed to study the process of stress adaptation in roots and shoot of Zea mays seedlings grown under hydroponic conditions during exposure to lead (Pb) (0–200 μM) for 1–7 d. The alterations in growth and in the level of various biochemical parameters were accessed vis-à-vis Pb accumulation. The accumulation of Pb increased in a concentration-duration-dependent manner, however its translocation from root to shoot was low. At the same time, the level of malondialdehyde (MDA) increased with increasing Pb concentration. However, growth parameters, such as dry weight and root length did not show a significant decline to any of the Pb concentrations. In addition, the level of photosynthetic pigments decreased only upon exposure to high Pb concentrations. These results suggested an alleviation of the stress that was presumably being achieved by antioxidants viz., superoxide dismutase (SOD) and catalase (CAT) as well as ascorbic acid (AsA), which increased linearly with increasing Pb levels and exposure time. However, the level of non-protein thiols (NP-SH) in roots, in general, showed a decline beyond 4 d that could be attributed to their consumption for the purpose of Pb detoxification. In conclusion, Zea mays can be used as an indicator species for Pb, and the various antioxidants might play a key role in the detoxification of Pb induced toxic effects.

Identification and functional validation of a unique set of drought induced genes preferentially expressed in response to gradual water stress in peanut

Peanut, found to be relatively drought tolerant crop, has been the choice of study to characterize the genes expressed under gradual water deficit stress. Nearly 700 genes were identified to be enriched in subtractive cDNA library from gradual process of drought stress adaptation. Further, expression of the drought inducible genes related to various signaling components and gene sets involved in protecting cellular function has been described based on dot blot experiments. Fifty genes (25 regulators and 25 functional related genes) selected based on dot blot experiments were tested for their stress responsiveness using northern blot analysis and confirmed their nature of differential regulation under different field capacity of drought stress treatments. ESTs generated from this subtracted cDNA library offered a rich source of stress-related genes including signaling components. Additional 50% uncharacterized sequences are noteworthy. Insights gained from this study would provide the foundation for further studies to understand the question of how peanut plants are able to adapt to naturally occurring harsh drought conditions. At present functional validation cannot be deemed in peanut, hence as a proof of concept seven orthologues of drought induced genes of peanut have been silenced in heterologous N. benthamiana system, using virus induced gene silencing method. These results point out the functional importance for HSP70 gene and key regulators such as Jumonji in drought stress response.Electronic supplementary materialThe online version of this article (doi:10.1007/s00438-009-0432-z) contains supplementary material, which is available to authorized users.