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At least 865 records · Page 48Linked to original sources
PubMed1971

The effects of drought stress on respiration of isolated corn mitochondria.

Mitochondria were isolated from etiolated corn shoots (Zea mays L.) that were stressed to a measured water potential. The rates of mitochondrial respiration in state III, state IV, and without phosphate or ADP on a milligram protein basis decreased as water stress increased with succinate, malatepyruvate, or reduced nicotinamide adenine dinucleotide as substrates. Coupling (as determined by respiratory control and ADP/O ratios) did not decrease with increasing water stress. At water potentials greater than -35 bars all respiration had ceased.

Journal Article↗
PubMed1981

Water Relations of Cotton Plants under Nitrogen Deficiency: III. STOMATAL CONDUCTANCE, PHOTOSYNTHESIS, AND ABSCISIC ACID ACCUMULATION DURING DROUGHT.

Nitrogen nutrition exerted a strong effect on stomatal sensitivity to water stress in cotton. In well-watered plants grown with 0.31 millimolar N in the nutrient solution, stomata closed at a water potential of -9 bars even though the wilting point was below -15 bars. For each doubling of nutrient N level, the water potential for stomatal closure decreased by about 2 bars. Elevated intercellular CO(2) concentrations caused only slight stomatal closure regardless of N nutrition. Exogenous abscisic acid (ABA) greatly increased stomatal sensitivity to elevated CO(2) concentrations.PLANTS SUBJECTED TO WATER STRESS GAVE THE FOLLOWING RESPONSES: (a) decreased stomatal conductance at ambient external CO(2) concentration; (b) increased stomatal sensitivity to elevated CO(2) concentrations; (c) decreased mesophyll conductance to CO(2); and (d) increased endogenous ABA content. All of these responses to stress occurred at a higher water potential in N-deficient plants than in normal plants. The results show that N nutrition and water stress interact to control ABA accumulation and the events regulated by that accumulation.

Journal Article↗
PubMed1986

The Response of Leaf Water Potential and Crassulacean Acid Metabolism to Prolonged Drought in Sedum rubrotinctum.

Plants of Sedum rubrotinctum R. T. Clausen were studied in a green-house over a 2-year period without watering. Only the apical leaves survived and were turgid at the end of the experiment. The midday leaf water potential of these apical leaves was -1.20 megapascals, while the leaf water potential of comparable leaves on well-watered control plants was -0.20 megapascals. The unwatered plants appear to have maintained turgor by means of an osmotic adjustment. After 2 years without water the plants no longer exhibited a nocturnal accumulation of titratable acidity. However, the daytime levels of titratable acidity of the unwatered plants were more than 2-fold greater than the levels in well-watered control plants. Well-watered plants of S. rubrotinctum exhibited seasonal shifts in biomass stble carbon isotope ratios, indicating a greater proportion of day versus night CO(2) uptake in the winter than in the summer. The imposition of water stress prevented the expression of this seasonal rhythm and restricted the plants to dark CO(2) uptake.

Journal Article↗
PubMed2005

Role of an Arabidopsis AP2/EREBP-type transcriptional repressor in abscisic acid and drought stress responses.

The phytohormone abscisic acid (ABA) modulates the expression of many genes important to plant growth and development and to stress adaptation. In this study, we found that an APETALA2/EREBP-type transcription factor, AtERF7, plays an important role in ABA responses. AtERF7 interacts with the protein kinase PKS3, which has been shown to be a global regulator of ABA responses. AtERF7 binds to the GCC box and acts as a repressor of gene transcription. AtERF7 interacts with the Arabidopsis thaliana homolog of a human global corepressor of transcription, AtSin3, which in turn may interact with HDA19, a histone deacetylase. The transcriptional repression activity of AtERF7 is enhanced by HDA19 and AtSin3. Arabidopsis plants overexpressing AtERF7 show reduced sensitivity of guard cells to ABA and increased transpirational water loss. By contrast, AtERF7 and AtSin3 RNA interference lines show increased sensitivity to ABA during germination. Together, our results suggest that AtERF7 plays an important role in ABA responses and may be part of a transcriptional repressor complex and be regulated by PKS3.

Abscisic Acid↗
PubMed1990

Characterization of a rice gene showing organ-specific expression in response to salt stress and drought.

Protein changes induced by salinity stress were investigated in the roots of the salt-sensitive rice cultivar Taichung native 1. We found eight proteins to be induced and obtained partial sequences of one with a molecular mass of 15 kilodaltons and an isoelectric point of 5.5. Using an oligonucleotide probe based on this information, a cDNA clone, salT, was selected and found to contain an open reading frame coding for a protein of 145 amino acid residues. salT mRNA accumulates very rapidly in sheaths and roots from mature plants and seedlings upon treatment with Murashige and Skoog salts (1%), air drying, abscisic acid (20 microM), polyethylene glycol (5%), sodium chloride (1%), and potassium chloride (1%). Generally, no induction was seen in the leaf lamina even when the stress should affect all parts of the plant uniformly. The organ-specific response of salT is correlatable with the pattern of Na+ accumulation during salt stress.

Amino Acid Sequence↗
PubMed1994

A novel cis-acting element in an Arabidopsis gene is involved in responsiveness to drought, low-temperature, or high-salt stress.

Two genes, rd29A and rd29B, which are closely located on the Arabidopsis genome, are differentially induced under conditions of dehydration, low temperature, high salt, or treatment with exogenous abscisic acid (ABA). It appears that rd29A has at least two cis-acting elements, one involved in the ABA-associated response to dehydration and the other induced by changes in osmotic potential, and that rd29B contains at least one cis-acting element that is involved in ABA-responsive, slow induction. We analyzed the rd29A promoter in both transgenic Arabidopsis and tobacco and identified a novel cis-acting, dehydration-responsive element (DRE) containing 9 bp, TACCGACAT, that is involved in the first rapid response of rd29A to conditions of dehydration or high salt. DRE is also involved in the induction by low temperature but does not function in the ABA-responsive, slow expression of rd29A. Nuclear proteins that specifically bind to DRE were detected in Arabidopsis plants under either high-salt or normal conditions. Different cis-acting elements seem to function in the two-step induction of rd29A and in the slow induction of rd29B under conditions of dehydration, high salt, or low temperature.

Abscisic Acid↗
PubMed2004

Drug use patterns and mental health of regular amphetamine users during a reported 'heroin drought'.

AIMS: The present study extends the findings of a pilot study conducted among regular amphetamine users in Newcastle, NSW, in 1998. It compares key features between current participants in a state capital city (Brisbane) and a regional city (Newcastle) and between the 1998 and current Newcastle sample. DESIGN: Cross-sectional survey. Setting Brisbane and Newcastle, Australia. PARTICIPANTS: The survey was conducted among 214 regular amphetamine users within the context of a randomized controlled trial of brief interventions for amphetamine use. MEASUREMENTS: Demographic characteristics, past and present alcohol and other drug use and mental health, treatment, amphetamine-related harms and severity of dependence. FINDINGS: The main findings were as follows: (i). the rate of mental health problems was high among regular amphetamine users and these problems commonly emerged after commencement of regular amphetamine use; (ii). there were regional differences in drug use with greater accessibility to a wider range of drugs in a state capital city and greater levels of injecting risk-taking behaviour outside the capital city environment; and (iii). there was a significant increase in level of amphetamine use and percentage of alcohol users, a trend for a higher level of amphetamine dependence and a significant reduction in the percentage of people using heroin and benzodiazepines among the 2002 Newcastle cohort compared to the 1998 cohort. CONCLUSIONS: Further longitudinal research is needed to elucidate transitions from one drug type to another and from recreational to injecting and regular use and the relationship between drug use and mental health in prospective studies among users. IMPLICATIONS: Intervention research should evaluate the effectiveness of interventions aimed at: preventing transition to injecting and regular use of amphetamines; toward reducing levels of depression among amphetamine users and interventions among people with severe psychopathology and personality disorders; and toward reducing the prevalence of tobacco dependence among amphetamine users.

Adolescent↗
PubMed2004

Disruption of AtMRP4, a guard cell plasma membrane ABCC-type ABC transporter, leads to deregulation of stomatal opening and increased drought susceptibility.

ATP-binding cassette (ABC) transporters are membrane proteins responsible for cellular detoxification processes in plants and animals. Recent evidence shows that this class of transporters may also be involved in many other cellular processes. Because of their homology with human multidrug resistance-associated proteins (MRP), cystic fibrosis transmembrane conductance regulator (CFTR) and sulfonylurea receptor (SUR), some plant ABC transporters have been implicated in the regulation of ion channel activities. This paper describes an investigation of the AtMRP4 gene and its role in stomatal regulation. Reporter gene studies showed that AtMRP4 is highly expressed in stomata and that the protein is localized to the plasma membrane. Stomatal aperture in three independent atmrp4 mutant alleles was larger than in wild-type plants, both in the light and in the dark, resulting in increased water loss but no change in the photosynthetic rate. In baker's yeast, AtMRP4 shows ATP-dependent, vanadate-sensitive transport of methotrexate (MTX), an antifolate and a substrate of mammalian MRPs. Treatment with MTX reduced stomatal opening in wild-type plants, but had no effect in atmrp4 mutants. These results indicate the involvement of AtMRP4 in the complex regulation of stomatal aperture.

Arabidopsis↗
PubMed2005

The plant Mo-hydroxylases aldehyde oxidase and xanthine dehydrogenase have distinct reactive oxygen species signatures and are induced by drought and abscisic acid.

The plant molybdenum-cofactor (Moco) and flavin-containing enzymes, xanthine dehydrogenase (XDH; EC 1.2.1.37) and aldehyde oxidase (AO; EC 1.2.3.1) are thought to play important metabolic roles in purine metabolism and hormone biosynthesis, respectively. Their animal counterparts contribute to reactive oxygen species (ROS) production in numerous pathologies and here we examined these enzymes as potential sources of ROS in plants. Novel in-gel assay techniques and Moco sulfurase mutants, lacking a sulfur ligand in their Moco active center, were employed to demonstrate that the native tomato and Arabidopsis XDHs are capable of producing O, but not H2O2, while the animal counterpart was shown to produce both, O and H2O2. Superoxide production was dependent on Moco sulfuration when using hypoxanthine/xanthine but not NADH as substrates. The activity was inhibited by diphenylene iodonium (DPI), a suicide inhibitor of FAD containing enzymes. Analysis of XDH in an Arabidopsis Atxdh1 T-DNA insertion mutant and RNA interference lines revealed loss of O activity, providing direct molecular evidence that plant XDH generates superoxides. Contrary to XDH, AO activity produced only H2O2 dissimilar to native animal AO, that can produce O as well. Surprisingly, H2O2 accumulation was not sensitive to DPI. Plant ROS production and transcript levels of AO and XDH were rapidly upregulated by application of abscisic acid and in water-stressed leaves and roots. These results, supported by in vivo measurement of ROS accumulation, indicate that plant AO and XDH are possible novel sources for ROS increase during water stress.

Abscisic Acid↗
PubMed2006

Cross-talk between ethylene and drought signalling pathways is mediated by the sunflower Hahb-4 transcription factor.

Hahb-4 is a member of the Helianthusannuus (sunflower) subfamily I of HD-Zip proteins that is transcriptionally regulated by water availability and abscisic acid. Transgenic Arabidopsis thaliana plants overexpressing this transcription factor (TF) exhibit a characteristic phenotype that includes a strong tolerance to water stress. Here we show that this TF is a new component of ethylene signalling pathways, and that it induces a marked delay in senescence. Plants overexpressing Hahb-4 are less sensitive to external ethylene, enter the senescence pathway later and do not show the typical triple response. Furthermore, transgenic plants expressing this gene under the control of its own inducible promoter showed an inverse correlation between ethylene sensitivity and Hahb-4 levels. Potential targets of Hahb-4 were identified by comparing the transcriptome of Hahb-4-transformed and wild-type plants using microarrays and quantitative RT-PCR. Expression of this TF has a major repressive effect on genes related to ethylene synthesis, such as ACO and SAM, and on genes related to ethylene signalling, such as ERF2 and ERF5. Expression studies in sunflower indicate that Hahb-4 transcript levels are elevated in mature/senescent leaves. Expression of Hahb-4 is induced by ethylene, concomitantly with several genes homologous to the targets identified in the transcriptome analysis (HA-ACOa and HA-ACOb). Transient transformation of sunflower leaves demonstrated the action of Hahb-4 in the regulation of ethylene-related genes. We propose that Hahb-4 is involved in a novel conserved mechanism related to ethylene-mediated senescence that functions to improve desiccation tolerance.

Arabidopsis↗