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PubMed1993

The plant hormone abscisic acid mediates the drought-induced expression but not the seed-specific expression of rd22, a gene responsive to dehydration stress in Arabidopsis thaliana.

Nine cDNA clones, corresponding to genes that are responsive to dehydration (named RD), have been isolated from Arabidopsis thaliana. The sequence of a putative protein encoded by one of the RD cDNA clones, RD22, exhibits considerable homology to an unidentified seed protein (USP) of Vicia faba. Northern analysis showed that RD22 mRNA is induced by salt stress as well as by water deficit but not by cold or heat stress. RD22 mRNA appeared after the application of abscisic acid (ABA), an indication that transcription of RD22 mRNA is induced by endogenous ABA, the production of which is triggered by drought and salt stress. The induction of RD22 mRNA by ABA was inhibited by cycloheximide. Thus, it appears that protein synthesis is required for the induction of this mRNA by ABA. By contrast, protein synthesis was not required for the ABA-responsive induction RD29 mRNA, which corresponds to another dehydration-responsive gene of A. thaliana. These results suggest that there are at least two mechanisms for the induction of dehydration-responsive genes by ABA. RD22 mRNA was also expressed during the early and middle stages of seed development, showing a pattern of expression similar to that of USP. The seed-specific expression of RD22 seems not to be regulated by ABA. Structural analysis of the RD22 genomic clone revealed that the structural gene (designated rd22) contains three introns, and only a single copy of the gene is present in the A. thaliana genome, while the gene for USP from V. faba is actually a family of genes with 10 to 20 members.(ABSTRACT TRUNCATED AT 250 WORDS)

Abscisic Acid↗
PubMed1994

Two genes that encode Ca(2+)-dependent protein kinases are induced by drought and high-salt stresses in Arabidopsis thaliana.

Two cDNA clones, cATCDPK1 and cATCDPK2, encoding Ca(2+)-dependent, calmodulin-independent protein kinases (CDPK) were cloned from Arabidopsis thaliana and their nucleotide sequences were determined. Northern blot analysis indicated that the mRNAs corresponding to the ATCDPK1 and ATCDPK2 genes are rapidly induced by drought and high-salt stress but not by low-temperature stress or heat stress. Treatment of Arabidopsis plants with exogenous abscisic acid (ABA) had no effect on the induction of ATCDPK1 or ATCDPK2. These findings suggest that a change in the osmotic potential of the environment can serve as a trigger for the induction of ATCDPK1 and ATCDPK2. Putative proteins encoded by ATCDPK1 and ATCDPK2 which contain open reading frames of 1479 and 1488 bp, respectively, are designated ATCDPK1 and ATCDPK2 and show 52% identity at the amino acid sequence level. ATCDPK1 and ATCDPK2 exhibit significant similarity to a soybean CDPK (51% and 73%, respectively). Both proteins contain a catalytic domain that is typical of serine/threonine protein kinases and a regulatory domain that is homologous to the Ca(2+)-binding sites of calmodulin. Genomic Southern blot analysis suggests the existence of a few additional genes that are related to ATCDPK1 and ATCDPK2 in the Arabidopsis genome. The ATCDPK2 protein expressed in Escherichia coli was found to phosphorylate casein and myelin basic protein preferentially, relative to a histone substrate, and required Ca2+ for activation.

Adaptation, Biological↗
PubMed1989

Interrelationship of kernel water activity, soil temperature, maturity, and phytoalexin production in preharvest aflatoxin contamination of drought-stressed peanuts.

Samples of Florunner peanuts were collected throughout a period of late-season drought stress with mean geocarposphere temperatures of 29 and 25 degrees C, and determinations of maturity, kernel water activity (aw), percent moisture, capacity for phytoalexin production, and aflatoxin contamination were made. Results showed an association between the loss of the capacity of kernels to produce phytoalexins and the appearance of aflatoxin contamination. Kernel aw appeared to be the most important factor controlling the capacity of kernels to produce phytoalexins. Mature peanuts possessed additional resistance to contamination that could not be attributed solely to phytoalexin production. Kernel moisture loss was accelerated in the 29 degrees C treatment compared to the 25 degrees C treatment, and data indicated that the higher soil temperature also favored growth and aflatoxin production by Aspergillus flavus in peanuts susceptible to contamination.

Aflatoxins↗
PubMed2006

Candidate genes for drought tolerance and improved productivity in rice (Oryza sativa L.).

Candidate genes are sequenced genes of known biological action involved in the development or physiology of a trait. Twenty-one putative candidate genes were designed after an exhaustive search in the public databases along with an elaborate literature survey for candidate gene products and/or regulatory sequences associated with enhanced drought resistance. The downloaded sequences were then used to design primers considering the flanking sequences as well. Polymerase chain reaction (PCR) performed on 10 diverse cultivars that involved Japonica, Indica and local accessions, revealed 12 polymorphic candidate genes. Seven polymorphic candidate genes were then utilized to genotype 148 individuals of CT9993 x IR62266 doubled haploid (DH) mapping population. The segregation data were tested for deviation from the expected Mendelian ratio (1:1) using a Chi-square test (less than 1%). Based on this, four candidate genes were assessed to be significant and the remaining three, as non-significant. All the significant candidate genes were biased towards CT9993, the female parent in the DH mapping population. Single-marker analysis strongly associated (less than 1%) them to different traits under both well-watered and low-moisture stress conditions. Two candidate genes, EXP15 and EXP13, were found to be associated with root number and silicon content in the stem respectively, under both well-watered and low-moisture stress conditions.

Genetic Markers↗
PubMed1999

Drought Stress Syndrome in Wheat Is Provoked by Ethylene Evolution Imbalance and Reversed by Rewatering, Aminoethoxyvinylglycine, or Sodium Benzoate.

In this work we present evidence that the drought stress syndrome in the flag leaves and ears of wheat plants, provoked by the production of ethylene (shortening the grain filling period and lowering the grain weight) is reversed by the application of a free radical scavenger, sodium benzoate or the ethylene synthesis inhibitor, aminoethoxyvinylglycine. Rehydration by watering also attenuated the detrimental effect of the water deficit. Consequently, the grain filling period was longer, the grain weight increased, and the total protein content was higher than that in plants watered regularly.

Journal Article↗
PubMed2006

Mapping QTLs and QTL x environment interaction for CIMMYT maize drought stress program using factorial regression and partial least squares methods.

The study of QTL x environment interaction (QEI) is important for understanding genotype x environment interaction (GEI) in many quantitative traits. For modeling GEI and QEI, factorial regression (FR) models form a powerful class of models. In FR models, covariables (contrasts) defined on the levels of the genotypic and/or environmental factor(s) are used to describe main effects and interactions. In FR models for QTL expression, considerable numbers of genotypic covariables can occur as for each putative QTL an additional covariable needs to be introduced. For large numbers of genotypic and/or environmental covariables, least square estimation breaks down and partial least squares (PLS) estimation procedures become an attractive alternative. In this paper we develop methodology for analyzing QEI by FR for estimating effects and locations of QTLs and QEI and interpreting QEI in terms of environmental variables. A randomization test for the main effects of QTLs and QEI is presented. A population of F2 derived F3 families was evaluated in eight environments differing in drought stress and soil nitrogen content and the traits yield and anthesis silking interval (ASI) were measured. For grain yield, chromosomes 1 and 10 showed significant QEI, whereas in chromosomes 3 and 8 only main effect QTLs were observed. For ASI, QTL main effects were observed on chromosomes 1, 2, 6, 8, and 10, whereas QEI was observed only on chromosome 8. The assessment of the QEI at chromosome 1 for grain yield showed that the QTL main effect explained 35.8% of the QTL + QEI variability, while QEI explained 64.2%. Minimum temperature during flowering time explained 77.6% of the QEI. The QEI analysis at chromosome 10 showed that the QTL main effect explained 59.8% of the QTL + QEI variability, while QEI explained 40.2%. Maximum temperature during flowering time explained 23.8% of the QEI. Results of this study show the possibilities of using FR for mapping QTL and for dissecting QEI in terms of environmental variables. PLS regression is efficient in accounting for background noise produced by other QTLs.

Chromosome Mapping↗
PubMed2000

MRI in a patient with the Worster-Drought syndrome.

We describe a patient with the Worster-Drought syndrome (congenital suprabulbar paresis), thought to be a failure of development of the corticobulbar tracts. MRI showed bilateral perisylvian cortical dysplasia.

Bulbar Palsy, Progressive↗
PubMed1997

Genetic variation in two cultures of Bradyrhizobium japonicum 110 differing in their ability to impart drought tolerance to soybean.

The polymerase chain reaction with arbitrary primers (RAPD) discriminated between two separately maintained cultures of Bradyrhizobium japonicum USDA 110 differing in symbiotic performance under drought conditions. Since strain 110 is used in inoculum production, the use of RAPD to monitor inoculum cultures could help to preserve their genetic composition and prevent the loss of important symbiotic properties. The use of RAPD could also be extended to other B. japonicum strains currently used in inoculum production.

Genetic Variation↗
PubMed2006

Zinc finger protein 1 (ThZF1) from salt cress (Thellungiella halophila) is a Cys-2/His-2-type transcription factor involved in drought and salt stress.

Zinc finger proteins (ZFPs) play important roles in growth and development in both animals and plants. Recently, some Arabidopsis genes encoding distinct ZFPs have been identified. However, the physiological role of their homologues with putative zinc finger motif remains unclear. In the present study, a novel gene, ThZF1, was characterized from salt stressed cress (Thellungiella halophila, Shan Dong), encoding a functional transcription factor. ThZF1 contains two conserved C(2)H(2) regions and shares conserved domains, including DNA-binding motif, with Arabidopsis thaliana ZFP family members. The transcript of the ThZF1 gene was induced by salinity and drought. Transient expression analysis of ThZF1-GFP fusion protein revealed that ThZF1 was localized preferentially in nucleus. A gel-shift assay showed that ThZF1 specially bind to the wild-type (WT) EP2 element, a cis-element present in the promoter regions of several target genes regulated by ZFPs. Furthermore, a functional analysis demonstrated that ThZF1 was able to activate HIS marker gene in yeast. Finally, ectopic expression of ThZF1 in Arabidopsis mutant azf2 suggested that ThZF1 may have similar roles as Arabidopsis AZF2 in plant development as well as regulation of downstream gene.

Amino Acid Sequence↗
PubMed2006

Overexpression of barley hva1 gene in creeping bentgrass for improving drought tolerance.

The objectives of this study were to test the feasibility of introducing barley hva1 gene, a LEA3 member, into perennial grass species using the Agrobacterium-mediated transformation technique and to determine whether heterologous expression of hva1 would alleviate water-deficit injury in grass species. Creeping bentgrass (Agrostis stolonifera var. palustris), a drought-intolerant grass species, was transformed transiently or stably using three different promoters in conjunction with the downstream report/target genes. Two abscisic acid (ABA)-inducible promoters, ABA1 and ABA2 derived from ABA-response complex (ABRC3) were used to examine stress-responsive expression of the green fluorescent protein (GFP). Transient expression of GFP demonstrated the inducibility of ABA1 and ABA2 promoters in response to exogenous ABA application. The ABA2 promoter was further studied for stress-responsive expression of hva1 and a maize Ubi-1 promoter was tested for constitutive expression of the gene. In the T(0) generation, the Ubi-1::hva1 transformants displayed variable expression levels of HVA1 protein under normal growth conditions. The hva1 gene in the ABA2::hva1 transformants maintained low expression under well-watered conditions, but was upregulated under water-deficit conditions. The tolerance to water deficit of T(0) transgenic lines was assessed by measuring leaf relative water content and visually rating the severity of leaf wilting during to water stress. Under water-stressed conditions, some transgenic lines maintained high water content in leaves and showed significantly less extent of leaf wilting compared with non-transgenic control plants. These results indicated that the introduction of barley hva1 gene using constitutive or stress-inducible promoters lessened water-deficit injury in creeping bentgrass, suggesting that heterologous expression of LEA3 protein genes may enhance the survival ability of creeping bentgrass in water limiting environments.

Abscisic Acid↗
PubMed2004

Reduction of the thylakoid electron transport chain by stromal reductants--evidence for activation of cyclic electron transport upon dark adaptation or under drought.

The reduction of P700(+), the primary electron donor of photosystem I (PSI), following a saturating flash of white light in the presence of the photosystem II (PSII) inhibitor 3-(3.4-dichlorophenyl)-1,1-dimethylurea (DCMU), was examined in barley plants exposed to a variety of conditions. The decay kinetic fitted to a double exponential decay curve, implying the presence of two distinct pools of PSI. A fast component, with a rate constant for decay of around 0.03-0.04 ms(-1) was observed to be sensitive to the duration of illumination. This rate constant was slower than, but comparable to, that observed in non-inhibited samples (i.e. where linear flow was active). It was substantially faster than values typically reported for experiments where PSII activity is inhibited. The magnitude of this component rose in leaves that were dark-adapted or exposed to drought. This component was assigned to PSI centres involved in cyclic electron transport. The remaining slowly decaying P700(+) population (rate constant of around 0.001-0.002 ms(-1)) was assigned to centres normally involved in linear electron transport (but inhibited here because of the presence of DCMU), or inactivated centres involved in the cyclic pathway. Processes that might regulate the relative flux through cyclic electron transport are discussed.

Adaptation, Physiological↗
PubMed1998

Gene structure and expression analysis of the drought- and abscisic acid-responsive CDeT11-24 gene family from the resurrection plant Craterostigma plantagineum Hochst.

In order to understand the molecular mechanisms which are responsible for desiccation tolerance in the resurrection plant Craterostigma plantagineum Hochst. a thorough analysis of the CDeT11-24 gene family was performed. CDeT11-24 comprises a small gene family whose genes are expressed in response to dehydration, salt stress and abscisic acid (ABA) treatment in leaves. The gene products are constitutively expressed in roots and disappear only when the plants are transferred to water. It is therefore suggested that the proteins are involved in sensing water status. The predicted proteins are very hydrophilic; they share some features with late-embryogenesis-abundant proteins, and sequence similarities were found with two ABA- and drought-regulated Arabidopsis genes. The analysis of beta-glucuronidase reporter genes driven by the CDeT11-24 promoter showed high activity in mature seeds in both transgenic Arabidopsis and tobacco. In vegetative tissues the promoter activity in response to ABA was restricted to young Arabidosis seedlings. The responsiveness to ABA during later developmental stages was regained in the presence of the Arabidopsis gene product ABI3. Dehydration-induced promoter activity was only observed in Arabidopsis leaves at a particular developmental stage. This analysis indicates that some components in the signal transduction pathway of the resurrection plant are not active in tobacco or Arabidopsis.

Abscisic Acid↗
PubMed2000

Drought induces fructan synthesis and 1-SST (sucrose:sucrose fructosyltransferase) in roots and leaves of chicory seedlings (Cichorium intybus L.).

Seeds of Cichorium intybus L. var. foliosum cv. Flash were sown in acid-washed vermiculite and grown in a controlled-environment growth chamber. After 1 month of growth, plantlets did not contain sucrose:sucrose 1-fructosyltransferase (1-SST), the key enzyme in fructan biosynthesis. No fructan could be observed. Some of the plants were submitted to drought for 2 weeks. Glucose, fructose and sucrose concentrations increased in roots and leaves of stressed plants and the fructan concentration in roots and leaves was ten times higher than in control plants. The onset of fructan synthesis coincided with the increase in 1-SST activity in roots. Expression of the 1-SST gene could be observed in roots and leaves of stressed plants.

Blotting, Northern↗
PubMed2003

Regeneration niche partitioning in neotropical pioneers: effects of gap size, seasonal drought and herbivory on growth and survival.

Adaptive trade-offs underlie the specialisation that permits habitat partitioning in species rich plant communities. We investigated the influence of the trade-offs that determine differences in growth and survival among six species of neotropical pioneer trees in gaps in semideciduous forest in Panama. Seedlings of Miconia argentea, Cecropia insignis, Luehea seemannii, Trema micrantha, Ochroma pyramidale and Croton bilbergianus were planted into artificial small (25 m(2)), medium (64 m(2)) and large (225 m(2)) gaps in secondary forest in the Barro Colorado Nature Monument. Trema and Ochroma suffered >/=50% mortality across all gap sizes, while Cecropia had high mortality only during the dry season and in the small gaps, and Miconia and Croton suffered low to zero mortality across all environments. The highest growth rates in large gaps were attained by Cecropia seedlings and in the smaller gaps by Miconia seedlings, although there were indications that Trema and Ochroma required gaps that were larger than any used in this study. Variation in growth and mortality could not be attributed to differences in foliar herbivore damage. Instead, there was strong evidence of a trade-off between maximum growth in the wet season and the ability to survive seasonal drought, particularly in small gaps. We conclude that variation in allocation in response to multiple limiting resources may be as important as allocation to growth and defence in determining the habitat preferences of neotropical pioneers.

Adaptation, Physiological↗
PubMed2003

Influence of a Bacillus sp. on physiological activities of two arbuscular mycorrhizal fungi and on plant responses to PEG-induced drought stress.

The effects of bacterial inoculation (Bacillus sp.) on the development and physiology of the symbiosis between lettuce and the arbuscular mycorrhizal (AM) fungi Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe and Glomus intraradices (Schenck and Smith) were investigated. Plant growth, mineral nutrition and gas-exchange values in response to bacterial inoculation after PEG-induced drought stress were also evaluated. In AM plants, inoculation with Bacillus sp. enhanced fungal development and metabolism, measured as succinate dehydrogenase (SDH) and alkaline phosphatase (ALP) activities, more than plant growth. Under non-stressed conditions, G. intraradices colonization increased all plant physiological values to a higher extent when in dual inoculation with the bacterium. Under stress conditions, the bacterium had an important stimulatory effect on G. intraradices development. Under such conditions, the effects of the bacterium on photosynthetic rate, water use efficiency (WUE) and stomatal conductance of lettuce plants differed with the fungus species. Plant-gas exchange was enhanced in G. intraradices- and reduced in G. mosseae-colonized plants when co-inoculated with Bacillus sp. Thus, the effects of each fungus on plant physiology were modulated by the bacterium. Stress was detrimental, particularly in G. intraradices-colonized plants without the bacterium, reducing intra and extraradical mycelium growth and vitality (SDH), as well as plant-gas exchange. Nevertheless, Bacillus sp. inoculation improved all these plant and fungal parameters to the same level as in non-stressed plants. The highest amount of alive and active AM mycelium for both fungi was obtained after co-inoculation with Bacillus sp. These results suggest that selected free-living bacteria and AM fungi should be co-inoculated to optimize the formation and functioning of the AM symbiosis in both normal and adverse environments.

Bacillus↗
PubMed2006

Drought tolerance genes in rice.

Quantitative trait loci (QTLs) for drought tolerance (DT) can be readily identified in available databases and in this paper, these QTLs were summarized in the form of a consensus map. An in silico strategy was then deployed to mine for candidate genes associated with DT QTLs using rice dbEST and rice genome databases. DT QTLs on rice chromosomes 1, 2, 4, 8, and 9 were selected to test the method. The result showed candidate genes associated with DT could be readily identified.

Acclimatization↗
PubMed2004

Hv-WRKY38: a new transcription factor involved in cold- and drought-response in barley.

WRKY proteins constitute a large family of plant specific transcription factors implicated in many different processes. Here we describe Hv-WRKY38, a barley gene coding for a WRKY protein, whose expression is involved in cold and drought stress response. Hv-WRKY38 was early and transiently expressed during exposure to low non-freezing temperature, in ABA-independent manner. Furthermore, it showed a continuous induction during dehydration and freezing treatments. A WRKY38:YFP fusion protein was found to localise into the nucleus upon introduction into epidermal onion cells. Bacterially expressed Hv-WRKY38 was able to bind in vitro to the W-box element (T)TGAC(C/T) also recognisable by other WRKY proteins. Hv-WRKY38 genomic DNA was sequenced and mapped onto the centromeric region of the barley chromosome 6H. Arabidopsis and rice sequences homologous to Hv-WRKY38 were also identified. Our results indicate that Hv-WRKY38 transcription factor may play a regulatory role in abiotic stress response.

Amino Acid Sequence↗
PubMed2006

Identification and functional expression of the pepper pathogen-induced gene, CAPIP2, involved in disease resistance and drought and salt stress tolerance.

A novel pathogen-induced gene, designated CAPIP2, was isolated from pepper leaves infected with Xanthomonas campestris pv. vesicatoria. CAPIP2:GFP fusion proteins were primarily localized in the cytoplasm. The CAPIP2 transcripts were constitutively expressed in the pepper leaves, flowers, and fruits, but were not detected in the stems and roots. CAPIP2 gene expression was induced strongly in the pepper leaves during pathogen infection, and also after exposure to abiotic elicitors and environmental stresses. Ectopic CAPIP2 expression in Arabidopsis was accompanied by the expression of Arabidopsis PR-1 and PDF1.2 genes. Overexpression of the CAPIP2 gene in Arabidopsis transgenic plants conferred enhanced resistance to Pseudomonas syringae pv. tomato DC3000. The CAPIP2 transgenic Arabidopsis also manifested increased tolerance to high salt, drought and oxidative stress during seed germination and seedling state. These results suggest that pepper CAPIP2 gene may function as a defense-related gene against both biotic and abiotic stresses.

Amino Acid Sequence↗