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Abiotic Stress (abiotic + stress)
Terms modified by Abiotic Stress Selected AbstractsUnderstanding Abiotic Stresses and the SolutionJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2008Qi Xie Professor [source] The 6-phosphogluconate Dehydrogenase Genes Are Responsive to Abiotic Stresses in RiceJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2007Fu-Yun Hou Abstract Glucose-6-phosphate dehydrogenase (G6PDH, E.C. 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH, EC 1.1.1.44) are both key enzymes of the pentose phosphate pathway (PPP). The OsG6PDH1 and Os6PGDH1 genes encoding cytosolic G6PDH and cytosolic 6PGDH were isolated from rice (Oryza sativa L.). We have shown that Os6PGDH1 gene was up-regulated by salt stress. Here we reported the isolation and characterization of Os6PGDH2 from rice, which encode the plastidic counterpart of 6PGDH. Genomic organization analysis indicated that OsG6PDH1 and OsG6PDH2 genes contain multiple introns, whereas two Os6PGDH1 and Os6PGDH2 genes have no introns in their translated regions. In a step towards understanding the functions of the pentose phosphate pathway in plants in response to various abiotic stresses, the expressions of four genes in the rice seedlings treated by drought, cold, high salinity and abscisic acid (ABA) were investigated. The results show that OsG6PDH1 and OsG6PDH2 are not markedly regulated by the abiotic stresses detected. However, the transcript levels of both Os6PGDH1 and Os6PGDH2 are up-regulated in rice seedlings under drought, cold, high salinity and ABA treatments. Meanwhile, the enzyme activities of G6PDH and 6PGDH in the rice seedlings treated by various abiotic stresses were investigated. Like the mRNA expression patterns, G6PDH activity remains constant but the 6PGDH increases steadily during the treatments. Taken together, we suggest that the pentose phosphate pathway may play an important role in rice responses to abiotic stresses and the second key enzyme of PPP, 6PGDH, may function as a regulator controlling the efficiency of the pathway under abiotic stresses. (Handling editor: Kang Chong) [source] Influence of drought, salt stress and abscisic acid on the resistance of tomato to Botrytis cinerea and Oidium neolycopersiciPLANT PATHOLOGY, Issue 2 2006E. A. Achuo Abiotic stress may affect plant response to pathogen attack through induced alterations in growth regulator and gene expression. Abscisic acid (ABA) mediates several plant responses to abiotic stress. The effects of drought, salt stress and ABA on the interaction of tomato (Lycopersicon esculentum) with the biotrophic fungus Oidium neolycopersici and the necrotrophic fungus Botrytis cinerea were investigated. Drought stress resulted in a twofold increase in endogenous ABA as well as a 50% reduction in B. cinerea infection and a significant suppression of O. neolycopersici on tomato cv. Moneymaker. Salt stress did not affect B. cinerea infection, but significantly reduced infection by O. neolycopersici, with no obvious increase in endogenous ABA. Compared with the wild type, the ABA-deficient sitiens mutant was more resistant to O. neolycopersici and B. cinerea. Exogenous ABA resulted in increased susceptibility of sitiens to both pathogens, but did not increase the basal susceptibility of wild-type plants. It is concluded that, in tomato, drought and salt stress stimulate different, but possibly overlapping, pathogen-defence pathways which may not necessarily involve ABA. Meanwhile, basal endogenous ABA levels suppress the resistance of tomato to O. neolycopersici and B. cinerea, but an ABA increase above the basal level, resulting from exogenous application, does not increase susceptibility to these pathogens. [source] Abiotic stress and plant responses from the whole vine to the genesAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010G.R. CRAMER Abstract Drought, salinity and extreme temperatures significantly limit the distribution of grapes around the world. In this review, the literature of grape responses to abiotic stress with particular reference to whole plant and molecular responses observed in recent studies is discussed. A number of short-term and long-term studies on grapevine shoots and berries have been conducted using a systems biology approach. Transcripts, proteins and metabolites were profiled. Water deficit, salinity and chilling altered the steady-state abundance of a large number of transcripts. Common responses to these stresses included changes in hormone metabolism, particularly abscisic acid (ABA), photosynthesis, growth, transcription, protein synthesis, signalling and cellular defences. Some of the transcriptional changes induced by stress were confirmed by proteomic and metabolomic analyses. More than 2000 genes were identified whose transcript abundance was altered by both water deficit and ABA. Different gene sets were used to map molecular pathways regulated by ABA, water deficit, salinity and chilling in grapevine. This work supports the hypothesis that ABA is a central regulator of abiotic stress tolerance mechanisms. ABA affects signalling pathways that trigger important molecular activities involving metabolism, transcription, protein synthesis, and cellular defence and also regulates important physiological responses such as stomatal conductance, photoprotection and growth. Systems biology approaches are providing more comprehensive understanding of the complex plant responses to abiotic stress. The molecular sets generated from mapping the ABA-inducible stress responses provide numerous targets for genetic and cultural manipulation for improved plant protection and grape quality. [source] Abiotic stresses and plant responses to climate changeAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010Article first published online: 7 JAN 2010 First page of article [source] Genome-wide identification, classification, evolutionary expansion and expression analyses of homeobox genes in riceFEBS JOURNAL, Issue 11 2008Mukesh Jain Homeobox genes play a critical role in regulating various aspects of plant growth and development. In the present study, we identified a total of 107 homeobox genes in the rice genome and grouped them into ten distinct subfamilies based upon their domain composition and phylogenetic analysis. A significantly large number of homeobox genes are located in the duplicated segments of the rice genome, which suggests that the expansion of homeobox gene family, in large part, might have occurred due to segmental duplications in rice. Furthermore, microarray analysis was performed to elucidate the expression profiles of these genes in different tissues and during various stages of vegetative and reproductive development. Several genes with predominant expression during various stages of panicle and seed development were identified. At least 37 homeobox genes were found to be differentially expressed significantly (more than two-fold; P < 0.05) under various abiotic stress conditions. The results of the study suggest a critical role of homeobox genes in reproductive development and abiotic stress signaling in rice, and will facilitate the selection of candidate genes of agronomic importance for functional validation. [source] Condition-specific competition allows coexistence of competitively superior exotic oysters with native oystersJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008Frederick R. Krassoi Summary 1Trade-offs between competitive ability and tolerance of abiotic stress are widespread in the literature. Thus, condition-specific competition may explain spatial variability in the success of some biological invaders and why, in environments where there is small-scale environmental variability, competitively inferior and superior species can coexist. 2We tested the hypothesis that differences in abiotic stress alter the outcome of competitive interactions between the native Sydney rock oysters Saccostrea glomerata and exotic Pacific oysters Crassostrea gigas by experimentally testing patterns of intra- and interspecific competition across a tidal elevation gradient of abiotic stress at three sites on the east coast of Australia. 3At low and mid-intertidal heights, exotic C. gigas were able to rapidly overgrow and smother native S. glomerata, which grew at c. 60% of the exotic's rate. In high intertidal areas, where C. gigas displayed about 80% mortality but similar growth rates to S. glomerata, the native oyster was not affected by the presence of the exotic species. 4Asymmetrical effects of the exotic species on the native could not be replicated by manipulating densities of conspecifics, confirming that effects at low and mid-intertidal heights were due to interspecific competition. 5Our results suggest that the more rapid growth of C. gigas than S. glomerata comes at the cost of higher mortality under conditions of abiotic stress. Thus, although C. gigas may rapidly overgrow S. glomerata at low and mid tidal heights, the native oyster will not be competitively excluded by the exotic due to release from competition at high intertidal elevations. 6The success of trade-offs in explaining spatial variation in the outcome of competitive interactions between C. gigas and S. glomerata strengthen the claim that these may be a useful tool in the quest to produce general predictive models of invasion success. [source] Asymmetric coexistence: bidirectional abiotic and biotic effects between goose barnacles and musselsJOURNAL OF ANIMAL ECOLOGY, Issue 4 2006TAKASHI KAWAI Summary 1Species coexistence depends on the net effect of interacting species, representing the sum of multiple interaction components that may act simultaneously and vary independently depending on ambient environmental conditions. Consequently, for a comprehensive understanding of the compound nature of species interactions and coexistence, a mechanistic approach that allows a separate evaluation of each interaction component is required. 2Two sessile filter-feeders, the goose barnacle Capitulum mitella and the mussel Septifer virgatus, coexist on moderately wave-exposed rocky shores in south-western Japan. In the upper intertidal, Capitulum positively influenced Septifer survivorship and growth through amelioration of thermal stress and of physical disturbance. On the other hand, these species are potential competitors as they have similar body sizes and modes of resource utilization. These opposite processes, facilitation and competition, are based on abiotic characteristics and biotic functions of the two species, respectively. 3In order to quantify the bidirectional abiotic, biotic and net effects, a series of experimental manipulations was conducted involving the use of living neighbours with both abiotic and biotic effects, and artificial mimics to simulate abiotic effects without biotic effects. 4Capitulum had strong positive abiotic effects on the mussel survivorship in most experimental periods, while the biotic effect was negligible or weakly negative, suggesting that the net effect of Capitulum on mussel survival was largely attributable to the abiotic effect. In contrast, a significantly negative biotic effect on the mussel growth rate was always present, though this was cancelled out by the larger, positive abiotic effect. In the case of Septifer, its abiotic and biotic effects on the survivorship of goose barnacles were negligible, while those on the growth rate showed temporal variation. 5With respect to the relationship between species interaction and environmental conditions, the strength of abiotic facilitative effect of Capitulum on mussel survival increased with increasing abiotic stress, while the strength of biotic effect was negligible or weakly negative. As regards the effects of mussels on goose barnacles, our study indicated no obvious relationship. These results point to the importance of decomposing interaction for an accurate, mechanistic understanding of species relations and coexistence. [source] Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesisJOURNAL OF ECOLOGY, Issue 6 2009Christian Smit Summary 1. ,The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and strength of species interactions change along stress gradients, and to calls for new empirical and theoretical work. 2. ,In the latest attempt in this journal, it is successfully argued how the SGH should be expanded by considering different life strategies of species (stress tolerance versus competitive ability) and characteristics of abiotic stress (resource versus non-resource based) over wider stress gradients (opposed to low,high contrasts), but the crucial role of biotic stress by consumers is largely ignored in this refinement. 3. ,We point out that consumers strongly alter the outcome of species interactions in benign and harsh environments, and show how inclusion of consumer-incurred biotic stress alters the predicted outcome of interactions along resource- and non-resource-based stress gradients for stress-tolerant and competitive benefactors and beneficiaries. 4. ,Synthesis. New studies should include stress gradients consisting of both abiotic and biotic components to disentangle their impacts, and to improve our understanding of how species interactions change along environmental gradients. [source] Refining the stress-gradient hypothesis for competition and facilitation in plant communitiesJOURNAL OF ECOLOGY, Issue 2 2009Fernando T. Maestre Summary 1The stress-gradient hypothesis (SGH) predicts that the frequency of facilitative and competitive interactions will vary inversely across abiotic stress gradients, with facilitation being more common in conditions of high abiotic stress relative to more benign abiotic conditions. With notable exceptions, most tests of the SGH have studied the interaction between a single pair or a few pairs of species, and thus have evaluated shifts in the magnitude and direction of pair-wise interactions along stress gradients, rather than shifts in the general frequency of interactions. 2The SGH has been supported by numerous studies in many ecosystems, has provided a crucial foundation for studying the interplay between facilitation and competition in plant communities, and has a high heuristic value. However, recent empirical research indicates that factors like the variation among species and the nature of the stress gradient studied add complexity not considered in the SGH, creating an opportunity to extend the SGH's general conceptual framework. 3We suggest that one approach for extending the SGH framework is to differentiate between the original idea of how ,common' interactions might be along stress gradients and the ubiquitous empirical approach of studying shifts in the strength of pair-wise interactions. Furthermore, by explicitly considering the life history of the interacting species (relative tolerance to stress vs. competitive ability) and the characteristics of the stress factor (resource vs. non-resource) we may be able to greatly refine specific predictions relevant to the SGH. 4We propose that the general pattern predicted by the SGH would hold more frequently for some combinations of life histories and stress factor, particularly when the benefactor and beneficiary species are mostly competitive and stress-tolerant, respectively. However, we also predict that other combinations are likely to yield different results. For example, the effect of neighbours can be negative at both ends of the stress gradient when both interacting species have similar ,competitive' or ,stress-tolerant' life histories and the abiotic stress gradient is driven by a resource (e.g. water). 5Synthesis. The extension of the SGH presented here provides specific and testable hypotheses to foster research and helps to reconcile potential discrepancies among previous studies. It represents an important step in incorporating the complexity and species-specificity of potential outcomes into models and theories addressing how plant,plant interactions change along stress gradients. [source] Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forestJOURNAL OF ECOLOGY, Issue 2 2007JONATHAN A. MYERS Summary 1To survive in forest understoreys, seedlings must depend on carbohydrate reserves when they experience negative carbon balance imposed by occasional light reduction and tissue loss to herbivores and diseases. We present the first experimental evidence in support of this hypothesis, using seven woody neotropical species. 2We transplanted seedlings that had recently expanded their first photosynthetic cotyledon or leaf to the forest understorey (1% of full sun) and quantified initial biomass and total non-structural carbohydrate (TNC) in stems, roots and storage cotyledons. We then randomly assigned seedlings to control and two stress treatments: light reduction (0.08% of full sun for 8 weeks) and complete defoliation. 3First-year survival of control seedlings, a comparative measure of shade tolerance, differed widely among species. The two stress treatments reduced survival and relative growth rates (RGR) of all species. Shade-tolerant species were little impacted by the stress treatments, whereas the two least shade-tolerant species experienced 100% mortality. 4In all treatments, 8-week and first-year survival was positively correlated with initial TNC pool size in stems and roots. By contrast, survival was generally not correlated with initial TNC concentration in any organ, TNC pools in cotyledons, seed mass or seedling biomass. 5TNC in stems and roots, but not in cotyledons, decreased in response to light reduction and defoliation over 8 weeks. Leaf area recovery of defoliated seedlings was positively correlated with initial TNC pools in stems and roots. 6First-year survival in each treatment was negatively correlated with 0,8 week RGR of control seedlings, suggesting higher stress tolerance of species with inherently slow growth rates in shade. RGR of control seedlings from 0 to 8 weeks was negatively correlated with initial TNC pools, but not concentrations, in stems and roots. After 8 weeks, RGR was positive for all species, without clear relationships with survival or TNC. 7We conclude that carbohydrate storage in stems and roots enhances long-term survival in shade by enabling seedlings to cope with periods of biotic and abiotic stress. Carbohydrate storage is a key functional trait that can explain species differences in growth and survival that lead to species coexistence through niche assembly processes and life-history trade-offs. [source] Influence of environmental factors on the growth and interactions between salt marsh plants: effects of salinity, sediment and waterloggingJOURNAL OF ECOLOGY, Issue 3 2000Jonathan M. Huckle Summary 1,Artificial environmental gradients were established in a series of pot experiments to investigate the effect of salinity, sediment type and waterlogging on the growth, and interactions between Spartina anglica and Puccinellia maritima. In each experiment, one environmental variable was manipulated and plants grown in pairwise combinations to examine the effect of the environmental factor on the intensity of intra- and interspecific interactions, quantified using the Relative Neighbour Effect (RNE) index. 2,Puccinellia was found to exert an asymmetric, one-way competitive dominance above ground over Spartina in experiments where gradients of sediment type and waterlogging were established. The intensity of the competition was highest in conditions with the least abiotic stress and lower or non-existent where stress was increased. 3,The intensity of the above-ground competition was greatest in loam and least in sand sediments. Reduction in competitive intensity in sand was accompanied by an increase in below-ground Spartina biomass and it is suggested that the production of rhizomes is a potential mechanism by which this species can expand vegetatively into areas without competition. 4,Interspecific competition on Spartina from Puccinellia also varied in intensity in the waterlogging experiment, being more intense in non-immersed treatments, where abiotic stress was reduced. 5,The competitive dominance of Puccinellia and the competition avoidance mechanism shown by Spartina in these experiments help to explain the successional interactions between the species along environmental gradients in natural salt marsh communities. [source] Positive Interactions: Crucial Organizers in a Plant CommunityJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2006Dong-Liang Cheng Abstract For more than a century, ecologists have concentrated on competition as a crucial process for community organization. However, more recent experimental investigations have uncovered the striking influence of positive interactions on the organization of plant communities. Complex combinations of competition and positive interactions operating simultaneously among plant species seem to be widespread in nature. In the present paper, we reviewed the mechanism and ecological importance of positive interactions in plant communities, emphasizing the certainties and uncertainties that have made it an attractive area of research. Positive interactions, or facilitation, occur when one species enhances the survival, growth, or richness of another. The importance of facilitation in plant organization increases with abiotic stress and the relative importance of competition decreases. Only by combining plant interactions and the many fields of biology can we fully understand how and when the positive interactions occur. (Managing editor: Ya-Qin Han) [source] RAMET DYNAMICS FOR THE CLONAL SEAWEED PTEROCLADIELLA CAPILLACEA (RHODOPHYTA): A COMPARISON WITH CHONDRUS CRISPUS AND WITH MAZZAELLA CORNUCOPIAE (GIGARTINALES)JOURNAL OF PHYCOLOGY, Issue 6 2000Ricardo Scrosati Little is known about the dynamics and the ecological interactions among ramets (fronds) from populations of clonal red seaweeds. Small ramets are very difficult to tag, so their growth cannot be monitored directly. The temporal variation of the relationship between stand biomass and ramet density offers information on ramet performance. We calculated this relationship for an intertidal population of Pterocladiella capillacea (Gmelin) Santelices et Hommersand (Gelidiales) from Baja California, Mexico. Biomass and density were positively correlated on an annual basis, indicating that biomass accumulated without involving self-thinning among ramets. This contrasts with nonclonal seaweeds, for which self-thinning among individuals occurs during growth, but agrees with other clonal red seaweeds, such as Chondrus crispus Stackhouse and Mazzaella cornucopiae (Postels et Ruprecht) Hommersand (both Gigartinales). The growth pattern for these members of the Gelidiales and of the Gigartinales holds despite differences in holdfast morphology and ramet branching degree and despite differences in the capacity of coalescence during early stages, known only for the Gigartinales. The positive slope for the dynamic biomass,density relationship, on a bilogarithmic scale, was statistically steeper for M. cornucopiae than for P. capillacea and for C. crispus. This suggests that the addition of new ramets during the growth season may be relatively more beneficial for biomass accumulation rates for M. cornucopiae. This would be expected for high-intertidal species subjected to strong abiotic stress, for which ramet crowding constitutes a key protection. Pterocladiella capillacea occurs at the mid-intertidal zone and C. crispus at the subtidal zone, so ramets would be relatively less important in that respect. [source] Facilitation of tree saplings by nurse plants: Microhabitat amelioration or protection against herbivores?JOURNAL OF VEGETATION SCIENCE, Issue 2 2008Lorena Gómez-Aparicio Abstract Question: Positive interactions are predicted to be common in communities developing under high physical stress or high herbivory pressure due to neighbour amelioration of limiting physical and consumer stresses, respectively. However, when both stress sources meet in the same community, the relative importance of the two facilitation mechanisms is poorly understood. We ask: What is the relative importance of abiotic vs. biotic mechanisms of facilitation of tree saplings by shrubs in Mediterranean mountain forests? Location: Sierra Nevada, SE Spain (1800,1850 m a.s.l.) Methods: Saplings of four tree taxa (Acer opalus ssp. grana-tense, Quercus ilex, Pinus nigra ssp. salzmanii and P. sylvestris var. nevadensis) were planted following a 2 × 2 factorial design: two levels of herbivory (control and ungulate exclusion) and two microhabitats (under shrubs and in open areas). Sapling survival and growth were monitored for five years. Results: Shrubs had positive effects on sapling survival both in control and ungulate excluded plots. This effect was species-specific, with shrubs increasing the survival of Acer opalus and Quercus ilex three and twofold, respectively, but having a minor effect on the Pinus species. Herbivory damage was also species-specific, being much higher for Acer opalus than for any other species. Shrubs did not protect saplings of any species against ungulates. Thus, all Acer saplings (the most damaged species) suffered herbivory outside the exclosures, which largely reduced sapling height. Conclusions: Protection from abiotic stress (summer drought and winter frost) was much more relevant than protection from biotic stress (herbivory). However, we propose that the final balance between the two mechanisms can be expected to vary strongly between sites, depending on the relative magnitude of the different sources of stress and the intrinsic traits (e.g. palatability) of the species interacting. [source] Adaptive differences in gene expression associated with heavy metal tolerance in the soil arthropod Orchesella cinctaMOLECULAR ECOLOGY, Issue 15 2009DICK ROELOFS Abstract Field-selected tolerance to heavy metals has been reported for Orchesella cincta (Arthropoda: Collembola) populations occurring at metal-contaminated mining sites. This tolerance correlated with heritable increase in metal excretion efficiency, less pronounced cadmium (Cd)-induced growth reduction and overexpression of the metallothionein gene. We applied transcriptomics to determine differential gene expression caused by this abiotic stress in reference and Cd-tolerant populations. Many cDNAs responded to Cd exposure in the reference population. Significantly fewer clones were Cd responsive in tolerant animals. Analysis of variance revealed transcripts that interact between Cd exposure and population. Hierarchical cluster analysis of these clones identified two major groups. The first one contained cDNAs that were up-regulated by Cd in the reference culture but non-responsive or down-regulated in tolerant animals. This cluster was also characterized by elevated constitutive expression in the tolerant population. Gene ontology analysis revealed that these cDNAs were involved in structural integrity of the cuticle, anti-microbial defence, calcium channel-blocking, sulphur assimilation and chromatin remodelling. The second group consisted of cDNAs down-regulated in reference animals but not responding or slightly up-regulated in tolerant animals. Their functions involved carbohydrate metabolic processes, Ca2+ -dependent stress signalling, redox state, proteolysis and digestion. The reference population showed a strong signature of stress-induced genome-wide perturbation of gene expression, whereas the tolerant animals maintained normal gene expression upon Cd exposure. We confirmed the micro-evolutionary processes occurring in soil arthropod populations and suggest a major contribution of gene regulation to the evolution of a stress-adapted phenotype. [source] A comparison between virus replication and abiotic stress (heat) as modifiers of host gene expression in peaMOLECULAR PLANT PATHOLOGY, Issue 3 2000Margarita Escaler Pea embryonic tissues respond to active replication of pea seed-borne mosaic potyvirus (PSbMV) by the down-regulation of a range of genes and the induction of others. Both of these responses can be seen when tissues are subjected to abiotic stress, particularly heat. We have compared the effects of the two inducers to assess whether the host alterations following virus replication represent generic responses to stress, or more specific effects. Five classes of response were identified: (i) genes induced by both stresses (e.g. heat shock protein 70, hsp70); (ii) genes induced by virus replication but unaffected by heat (e.g. glutathione reductase 2, gor2); (iii) genes induced by heat but unaffected by virus replication (e.g. heat shock factor, hsf); (iv) genes down-regulated by virus replication and unaffected by heat (e.g. vicilin, vic); and (v) genes unaffected by both inducers (e.g. actin, act and ,-tubulin, tub). A change in the appearance and organization of the endoplasmic reticulum (ER) was also seen in cells actively replicating PSbMV RNA. Heat treatment of pea embryonic tissues also produced altered ER, although the changes were different from those seen following virus infection. Collectively, these data show that, while there are some common features of the responses to virus infection and heat, there are also substantial differences. Hence, it appears that the host response to virus replication is not a general stress response. [source] Programmed responses to virus replication in plantsMOLECULAR PLANT PATHOLOGY, Issue 1 2000A. J. Maule Despite their economic importance, we understand very little about the mechanism leading to symptom formation in compatible virus infections. By applying a spatial analysis to advancing infection fronts, we have been able to relate molecular events in small groups of cells to a sequence of virus-induced changes. This sequence starts ahead of the main front of virus replication and virus protein accumulation and lasts beyond the time at which virus replication has ceased. The host changes include alterations in gene expression, physiology and cellular ultrastructure. The relationship between these effects has been analysed in comparative studies between different virus infections in different hosts and abiotic stress. The research points to there being common features for different viruses leading to common effects. Also, although many of the consequences of virus infection are similar to the effects of heat shock, there are sufficient differences to suggest that the two inducers use distinct control pathways. The immediate challenge for the future is to establish synchronous infections of tissues so that the complex relationship between the virus and the host can be investigated using temporal rather than spatial analyses. [source] Interspecific and intraspecific interactions between salt marsh plants: integrating the effects of environmental factors and density on plant performanceOIKOS, Issue 2 2002Jonathan M. Huckle There has been much debate about the role of plant interactions in the structure and function of vegetation communities. Here the results of a pot experiment with controlled environments are described where three environmental variables (nutrients, sediment type and waterlogging) were manipulated factorially to identify their effects on the growth and intensity of interactions occurring between Spartina anglica and Puccinellia maritima. The two species were grown in split-plot planting treatments, representing intraspecific and interspecific addition series experiments, to determine individual and interactive effects of environmental factors and plant interactions on plant biomass. Above-ground growth of both species involved interactions between the environmental and planting treatments, while below-ground, environmental factors affected the biomass irrespective of planting treatments. It was suggested that this difference in growth response is evidence that in our experiment plant interactions between the two species occur primarily at the above-ground level. The intensity of plant interactions varied in a number of ways. First, interactions between Spartina and Puccinellia were distinctly asymmetrical, Puccinellia exerting a competitive effect on Spartina, with no reciprocal effect, and with a facilitative effect of Spartina on Puccinellia in low nutrient conditions. Second, the interactions varied in intensity in different environmental conditions. Interspecific competitive effects of Puccinellia on Spartina were more intense in conditions favourable to growth of Puccinellia and reduced or non-existent in environments with more abiotic stress. Third, intraspecific competition was found to be less intense for both species than interspecific interactions. Finally, the intensity of plant interactions involving both species was more intense above ground than below ground, with a disproportionate reduction in the intensity of interspecific competition below relative to above ground in treatments with less productive sediments and greater immersion. This is interpreted as reflecting a potential mechanism by which Spartina may be able to evade competitive neighbours. [source] Epigenetic chromatin modifiers in barley: I. Cloning, mapping and expression analysis of the plant specific HD2 family of histone deacetylases from barley, during seed development and after hormonal treatmentPHYSIOLOGIA PLANTARUM, Issue 3 2009Kyproula Demetriou Epigenetic phenomena have been associated with modifications of chromatin structure. These are achieved, in part, by histone post-translational modifications including acetylations and deacetylations, the later being catalyzed by histone deacetylaces (HDACs). Eukaryotic HDACs are grouped into three major families, RPD3/HDA1, SIR2 and the plant-specific HD2. HDAC genes have been analyzed from model plants such as Arabidopsis, rice and maize and have been shown to be involved in various cellular processes including seed development, vegetative and reproductive growth and responses to abiotic and biotic stress, but reports on HDACs from other crops are limited. In this work two full-length cDNAs (HvHDAC2-1 and HvHDAC2-2) encoding two members of the plant-specific HD2 family, respectively, were isolated and characterized from barley (Hordeum vulgare), an agronomically important cereal crop. HvHDAC2-1 and HvHDAC2-2 were mapped on barley chromosomes 1H and 3H, respectively, which could prove useful in developing markers for marker-assisted selection in breeding programs. Expression analysis of the barley HD2 genes demonstrated that they are expressed in all tissues and seed developmental stages examined. Significant differences were observed among tissues and seed stages, and between cultivars with varying seed size, suggesting an association of these genes with seed development. Furthermore, the HD2 genes from barley were found to respond to treatments with plant stress-related hormones such as jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA) implying an association of these genes with plant resistance to biotic and abiotic stress. The expression pattern of HD2 genes suggests a possible role for these genes in the epigenetic regulation of seed development and stress response. [source] Overexpression of the apple alcohol acyltransferase gene alters the profile of volatile blends in transgenic tobacco leavesPHYSIOLOGIA PLANTARUM, Issue 3 2008Dapeng Li Alcohol acyltransferases (AATs) are key enzymes in ester biosynthesis. Previous studies have found that AAT may be a stress-related gene. To investigate further the function of the apple alcohol acyltransferase gene (MdAAT2), transgenic tobacco plants overexpressing MdAAT2 were generated. Gas chromatography,mass spectroscopy analysis showed that the volatile blends were altered in these transgenic tobacco leaves. Although no apple-fruity volatile esters were detected in transgenic tobacco leaves, methyl caprylate, methyl caprate, and methyl dodecanoate were newly generated, and the concentrations of methyl benzoate and methyl tetradecanoate were significantly increased, suggesting that MdAAT2 may use medium-chain fatty acyl CoA and benzoyl-CoA as acyl donors together with methanol acceptors as substrates. Surprisingly, the concentrations of linalool were significantly increased in transgenic tobacco leaves, which may mediate the repellent effect on Myzus persicae (Sulzer) aphids. Using methyl jasmonate (MeJA) and wounding treatments, we found that MdAAT2 may substitute for the partial ability of MeJA to induce the production of linalool in transgenic plants. These data suggest that MdAAT2 may be involved in the response to the MeJA signal and may play a role in the response to biotic and abiotic stress. [source] Reactive oxygen signaling and abiotic stressPHYSIOLOGIA PLANTARUM, Issue 3 2008Gad Miller Reactive oxygen species (ROS) play a dual role in plant biology acting on the one hand as important signal transduction molecules and on the other as toxic by-products of aerobic metabolism that accumulate in cells during different stress conditions. Because of their toxicity as well as their important signaling role, the level of ROS in cells is tightly controlled by a vast network of genes termed the ,ROS gene network'. Using mutants deficient in key ROS-scavenging enzymes, we have defined a signaling pathway that is activated in cells in response to ROS accumulation. Interestingly, many of the key players in this pathway, including different zinc finger proteins and WRKY transcription factors, are also central regulators of abiotic stress responses involved in temperature, salinity and osmotic stresses. Here, we describe our recent findings and discuss how ROS integrate different signals originating from different cellular compartments during abiotic stress. [source] The role of abscisic acid and auxin in the response of poplar to abiotic stressPLANT BIOLOGY, Issue 2 2010J. Popko Abstract The plant hormones auxin and abscisic acid may at first sight appear to be a conflicting pair of plant regulators. Abscisic acid content increases during stress and protects plant water status. The content of free auxin in the developing xylem of poplar declines during stress, while auxin conjugates increase. This indicates that specific down-regulation of a signal transduction chain is important in plant adaptation to stress. Diminished auxin content may be a factor that adapts growth and wood development of poplar during adverse environmental conditions. To allow integration of environmental signals, abscisic acid and auxin must interact. Data are accumulating that abscisic acid,auxin cross-talk exists in plants. However, knowledge of the role of plant hormones in the response of trees to stress is scarce. Our data show that differences in the localisation of ABA synthesis exist between the annual, herbaceous plant Arabidopsis and the perennial woody species, poplar. [source] The Plant's Capacity in Regulating Resource DemandPLANT BIOLOGY, Issue 6 2005R. Matyssek Abstract: Regulation of resource allocation in plants is the key to integrate understanding of metabolism and resource flux across the whole plant. The challenge is to understand trade-offs as plants balance allocation between different and conflicting demands, e.g., for staying competitive with neighbours and ensuring defence against parasites. Related hypothesis evaluation can, however, produce equivocal results. Overcoming deficits in understanding underlying mechanisms is achieved through integrated experimentation and modelling the various spatio-temporal scaling levels, from genetic control and cell metabolism towards resource flux at the stand level. An integrated, interdisciplinary research concept on herbaceous and woody plants and its outcome to date are used, while drawing attention to currently available knowledge. This assessment is based on resource allocation as driven through plant-pathogen and plant-mycorrhizosphere interaction, as well as competition with neighbouring plants in stands, conceiving such biotic interactions as a "unity" in the control of allocation. Biotic interaction may diminish or foster effects of abiotic stress on allocation, as changes in allocation do not necessarily result from metabolic re-adjustment but may obey allometric rules during ontogeny. Focus is required on host-pathogen interaction under variable resource supply and disturbance, including effects of competition and mycorrhization. Cost/benefit relationships in balancing resource investments versus gains turned out to be fundamental in quantifying competitiveness when related to the space, which is subject to competitive resource exploitation. A space-related view of defence as a form of prevention of decline in competitiveness may promote conversion of resource turnover across the different kinds of biotic interaction, given their capacity in jointly controlling whole plant resource allocation. [source] Engineering of enhanced glycine betaine synthesis improves drought tolerance in maizePLANT BIOTECHNOLOGY JOURNAL, Issue 6 2004Ruidang Quan Summary Glycine betaine plays an important role in some plants, including maize, in conditions of abiotic stress, but different maize varieties vary in their capacity to accumulate glycine betaine. An elite maize inbred line DH4866 was transformed with the betA gene from Escherichia coli encoding choline dehydrogenase (EC 1.1.99.1), a key enzyme in the biosynthesis of glycine betaine from choline. The transgenic maize plants accumulated higher levels of glycine betaine and were more tolerant to drought stress than wild-type plants (non-transgenic) at germination and the young seedling stage. Most importantly, the grain yield of transgenic plants was significantly higher than that of wild-type plants after drought treatment. The enhanced glycine betaine accumulation in transgenic maize provides greater protection of the integrity of the cell membrane and greater activity of enzymes compared with wild-type plants in conditions of drought stress. [source] Over-expression of a Populus peroxisomal ascorbate peroxidase (PpAPX) gene in tobacco plants enhances stress tolerancePLANT BREEDING, Issue 4 2009Y-J. Li Abstract Ascorbate peroxidase (APX) plays an important role in the metabolism of hydrogen peroxide in higher plants. We studied the effect of over-expressing a Populus peroxisomal ascorbate peroxidase (PpAPX) gene under the control of the cauliflower mosaic virus 35S promoter or the rd29 promoter in transgenic tobacco. High levels of PpAPX gene expression were observed in 35S-PpAPX transgenic plants, with a 50% increase in APX activity. The constitutive expression of PpAPX in the tobacco exhibited no morphological abnormalities, while significantly increased root growth was observed in transgenic plants, when compared to control plants. Several independently transformed lines were propagated and evaluated for resistance to methyl viologen (MV), drought and salt stress. Visual assessment of transgenic and control lines exposed to MV (50 or 100 ,mol) confirmed that over-expression of APX minimized leaf damage. APX activity was nearly 80% higher in the leaves of transgenic plants in response to drought or salt stresses. Moreover, the transgenic tobacco also showed significantly improved drought resistance and salt tolerance at the vegetative stage. RNA blot analysis indicated that the PpAPX transcript level was very low under normal growing conditions in rd29Ap-PpAPX plants, but clearly increased under drought stress. Our results show that PpAPX does not play a significant role under normal growing conditions, but did ameliorate oxidative injury under abiotic stress. The Ad29 promoter should be used as an inducible promoter in transgenic works. [source] Glycinebetaine accumulation is more effective in chloroplasts than in the cytosol for protecting transgenic tomato plants against abiotic stressPLANT CELL & ENVIRONMENT, Issue 8 2007EUNG-JUN PARK ABSTRACT Tomato (Lycopersicon esculentum Mill. cv. Moneymaker) plants were transformed with a gene for choline oxidase (codA) from Arthrobacter globiformis. The gene product (CODA) was targeted to the chloroplasts (Chl,codA), cytosol (Cyt,codA) or both compartments simultaneously (ChlCyt,codA). These three transgenic plant types accumulated different amounts and proportions of glycinebetaine (GB) in their chloroplasts and cytosol. Targeting CODA to either the cytosol or both compartments simultaneously increased total GB content by five- to sixfold over that measured from the chloroplast targeted lines. Accumulation of GB in codA transgenic plants was tissue dependent, with the highest levels being recorded in reproductive organs. Despite accumulating, the lowest amounts of GB, Chl,codA plants exhibited equal or higher degrees of enhanced tolerance to various abiotic stresses. This suggests that chloroplastic GB is more effective than cytosolic GB in protecting plant cells against chilling, high salt and oxidative stresses. Chloroplastic GB levels were positively correlated with the degree of oxidative stress tolerance conferred, whereas cytosolic GB showed no such a correlation. Thus, an increase in total GB content does not necessarily lead to enhanced stress tolerance, but additional accumulation of chloroplastic GB is likely to further raise the level of stress tolerance beyond what we have observed. [source] An , -amylase (At4g25000) in Arabidopsis leaves is secreted and induced by biotic and abiotic stressPLANT CELL & ENVIRONMENT, Issue 4 2007ELIZABETH A. DOYLE ABSTRACT Leaves are reported to contain a secreted , -amylase that accumulates during senescence or after biotic or abiotic stress; however, a gene encoding this enzyme has not been described. Because a secreted amylase is isolated from plastidic starch, the function of this enzyme is difficult to predict, but circumstantial evidence suggests that it may degrade starch after cell death. The Arabidopsis thaliana genome contains three , -amylase genes, one of which, AMY1 (At4g25000), has a putative signal sequence suggesting that the protein may be secreted. Two independent T-DNA insertion mutants in AMY1 lacked an amylase band on starch zymograms, which was previously named ,A1'. Washed leaf protoplasts contained reduced A1 activity suggesting that the enzyme is secreted. Native AMY1, fused to a weakly fluorescent form of GFP, was sensitive to proteinase K infiltrated into leaf apoplastic spaces, while a cytosolic form of GFP was unaffected until cell breakage, confirming that the AMY1 protein is secreted. Amylase A1 was transcriptionally induced in senescing leaves and in leaves exposed to heat stress, treated with abscisic acid or infected with Pseudomonas syringae pv. tomato expressing avrRpm1. The A1 amylase was also extremely heat resistant and its expression was up-regulated in cpr5-2, an activated defence response mutant. [source] Over-expression of different aldehyde dehydrogenase genes in Arabidopsis thaliana confers tolerance to abiotic stress and protects plants against lipid peroxidation and oxidative stressPLANT CELL & ENVIRONMENT, Issue 6 2006SIMEON O. KOTCHONI ABSTRACT Aldehyde dehydrogenases (ALDHs) play a major role in the detoxification processes of aldehydes generated in plants when exposed to abiotic stress. In previous studies, we have shown that the Arabidopsis thaliana ALDH3I1 gene is transcriptionally activated by abiotic stress, and over-expression of the ALDH3I1 gene confers stress tolerance in transgenic plants. The A. thaliana genome contains 14 ALDH genes expressed in different sub-cellular compartments and are presumably involved in different reactions. The purpose of this study was to compare the potential of a cytoplasmic and a chloroplastic stress-inducible ALDH in conferring stress tolerance under different conditions. We demonstrated that constitutive or stress-inducible expression of both the chloroplastic ALDH3I1 and the cytoplasmic ALDH7B4 confers tolerance to osmotic and oxidative stress. Stress tolerance in transgenic plants is accompanied by a reduction of H2O2 and malondialdehyde (MDA) derived from cellular lipid peroxidation. Involvement of ALDHs in stress tolerance was corroborated by the analysis of ALDH3I1 and ALDH7B4 T-DNA knockout (KO) mutants. Both mutant lines exhibited higher sensitivity to dehydration and salt than wild-type (WT) plants. The results indicate that ALDH3I1 and ALDH7B4 not only function as aldehyde-detoxifying enzymes, but also as efficient reactive oxygen species (ROS) scavengers and lipid peroxidation-inhibiting enzymes. The potential of ALDHs to interfere with H2O2 was also shown for recombinant bacterial proteins. [source] Genetic dissection of cotton physiological responses to arid conditions and their inter-relationships with productivityPLANT CELL & ENVIRONMENT, Issue 3 2004Y. SARANGA ABSTRACT Testing of the extent to which different complex traits share common genetic control provides a means to distinguish associations that are truly diagnostic of genetic potential for improved adaptation to abiotic stress, from incidental phenotypic correlations. In two generations of progeny from a cross between Gossypium hirsutum and Gossypium barbadense, quantitative trait loci (QTL) mapping was used to evaluate correspondence in genetic control of selected physiological measures and productivity under water-limited and well-watered environments, respectively. A total of 33 QTLs were detected for five physiological variables [osmotic potential (OP), carbon isotope ratio (,13C; indicator of water use efficiency), canopy temperature, chlorophyll a and b], and 46 QTLs for five measures of crop productivity [dry matter, seed cotton yield (SC), harvest index, boll weight, and boll number]. QTL likelihood intervals for high SC and low OP corresponded in three genomic regions, two of which mapped to homoeologous locations on the two subgenomes of tetraploid cotton. QTLs for ,13C showed only incidental association with productivity, indicating that high water use efficiency can be associated with either high or low productivity. Different cotton species have evolved different alleles related to physiological responses and productivity under water deficit, which may permit the development of genotypes that are better-adapted to arid conditions. [source] | |||||||||||||||||||||||||||||||