Plants

1644 KiB

Open AccessArticle

Identification of Chimeric Repressors that Confer Salt and Osmotic Stress Tolerance in Arabidopsis

by Daisuke Kazama, Masateru Itakura, Takamitsu Kurusu, Nobutaka Mitsuda, Masaru Ohme-Takagi and Yuichi Tada

Plants 2013, 2(4), 769-785; https://doi.org/10.3390/plants2040769 - 5 Dec 2013

Cited by 18 | Viewed by 8774

Abstract

We produced transgenic Arabidopsis plants that express chimeric genes for transcription factors converted to dominant repressors, using Chimeric REpressor gene-Silencing Technology (CRES-T), and evaluated the salt tolerance of each line. The seeds of the CRES-T lines for ADA2b, Msantd, DDF1, DREB26, AtGeBP, and [...] Read more.

We produced transgenic Arabidopsis plants that express chimeric genes for transcription factors converted to dominant repressors, using Chimeric REpressor gene-Silencing Technology (CRES-T), and evaluated the salt tolerance of each line. The seeds of the CRES-T lines for ADA2b, Msantd, DDF1, DREB26, AtGeBP, and ATHB23 exhibited higher germination rates than Wild type (WT) and developed rosette plants under up to 200 mM NaCl or 400 mM mannitol. WT plants did not grow under these conditions. In these CRES-T lines, the expression patterns of stress-related genes such as RD29A, RD22, DREB1A, and P5CS differed from those in WT plants, suggesting the involvement of the six transcription factors identified here in the stress response pathways regulated by the products of these stress-related genes. Our results demonstrate additional proof that CRES-T is a superior tool for revealing the function of transcription factors. Full article

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506 KiB

Open AccessArticle

Experimental Measurements and Mathematical Modeling of Cytosolic Ca²⁺ Signatures upon Elicitation by Penta-N-acetylchitopentaose Oligosaccharides in Nicotiana tabacum Cell Cultures

by Kalina Mrozek, Karsten Niehaus and Petra Lutter

Plants 2013, 2(4), 750-768; https://doi.org/10.3390/plants2040750 - 27 Nov 2013

Cited by 4 | Viewed by 7646

Abstract

Plants have developed sophisticated recognition systems for different kinds of pathogens. Pathogen-associated molecular patterns (PAMPs) can induce various defense mechanisms, e.g., the production of reactive oxygen species (ROS) as an early event. Plant defense reactions are initiated by a signal transduction cascade involving [...] Read more.

Plants have developed sophisticated recognition systems for different kinds of pathogens. Pathogen-associated molecular patterns (PAMPs) can induce various defense mechanisms, e.g., the production of reactive oxygen species (ROS) as an early event. Plant defense reactions are initiated by a signal transduction cascade involving the release of calcium ions (Ca²⁺) from both external and internal stores to the plant cytoplasm. This work focuses on the analysis of cytosolic Ca²⁺ signatures, experimentally and theoretically. Cytosolic Ca²⁺ signals were measured in Nicotiana tabacum plant cell cultures after elicitation with penta-N-acetylchitopentaose oligosaccharides (Ch5). In order to allow a mathematical simulation of the elicitor-triggered C^a2+ release, the Li and Rinzel model was adapted to the situation in plants. The main features of the Ca2+ response, like the specific shape of the C^a2+ transient and the dose-response relationship, could be reproduced very well. Repeated elicitation of the same cell culture revealed a refractory behavior with respect to the Ca²⁺ transients for this condition. Detailed analysis of the obtained data resulted in further modifications of the mathematical model, allowing a predictive simulation of Ch5-induced C^a2+ transients. The promising results may contribute to a deeper understanding of the underlying mechanisms governing plant defense. Full article

(This article belongs to the Special Issue Calcium Signaling in Plants)

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1503 KiB

Open AccessArticle

The Clubroot Pathogen (Plasmodiophora brassicae) Influences Auxin Signaling to Regulate Auxin Homeostasis in Arabidopsis

by Linda Jahn, Stefanie Mucha, Sabine Bergmann, Cornelia Horn, Paul Staswick, Bianka Steffens, Johannes Siemens and Jutta Ludwig-Müller

Plants 2013, 2(4), 726-749; https://doi.org/10.3390/plants2040726 - 27 Nov 2013

Cited by 49 | Viewed by 12255

Abstract

The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of [...] Read more.

The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of auxin receptors, the TIR family and the auxin binding protein 1 (ABP1) in Arabidopsis thaliana are transcriptionally upregulated upon gall formation. Mutations in the TIR family resulted in more susceptible reactions to the root pathogen. As target genes for the different pathways we have investigated the transcriptional regulation of selected transcriptional repressors (Aux/IAA) and transcription factors (ARF). As the TIR pathway controls auxin homeostasis via the upregulation of some auxin conjugate synthetases (GH3), the expression of selected GH3 genes was also investigated, showing in most cases upregulation. A double gh3 mutant showed also slightly higher susceptibility to P. brassicae infection, while all tested single mutants did not show any alteration in the clubroot phenotype. As targets for the ABP1-induced cell elongation the effect of potassium channel blockers on clubroot formation was investigated. Treatment with tetraethylammonium (TEA) resulted in less severe clubroot symptoms. This research provides evidence for the involvement of two auxin signaling pathways in Arabidopsis needed for the establishment of the root galls by P. brassicae. Full article

(This article belongs to the Special Issue Auxin Signaling, Transport, and Metabolism)

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668 KiB

Open AccessArticle

Responses of African Grasses in the Genus Sporobolus to Defoliation and Sodium Stress: Tradeoffs, Cross-Tolerance, or Independent Responses?

by Daniel M. Griffith and T. Michael Anderson

Plants 2013, 2(4), 712-725; https://doi.org/10.3390/plants2040712 - 8 Nov 2013

Cited by 3 | Viewed by 6141

Abstract

In the Serengeti ecosystem of East Africa, grazing ungulates prefer areas with elevated grass Na, suggesting that some grasses tolerate both high soil Na and defoliation. We performed a factorial Na-by-defoliation greenhouse study with five abundant Sporobolus congeners to explore whether Serengeti grasses [...] Read more.

In the Serengeti ecosystem of East Africa, grazing ungulates prefer areas with elevated grass Na, suggesting that some grasses tolerate both high soil Na and defoliation. We performed a factorial Na-by-defoliation greenhouse study with five abundant Sporobolus congeners to explore whether Serengeti grasses possess traits which: (i) confer tolerance to both Na and defoliation (cross-tolerance); (ii) display a tradeoff; or (iii) act independently in their tolerances. Our expectation was that related grasses would exhibit cross-tolerance when simultaneously subjected to Na and defoliation. Instead, we found that physiological tolerances and growth responses to Na and defoliation did not correlate but instead acted independently: species characterized by intense grazing in the field showed no growth or photosynthetic compensation for combined Na and defoliation. Additionally, in all but the highest Na dosage, mortality was higher when species were exposed to both Na and defoliation together. Across species, mortality rates were greater in short-statured species which occur on sodic soils in heavily grazed areas. Mortality among species was positively correlated with specific leaf area, specific root length, and relative growth rate, suggesting that rapidly growing species which invest in low cost tissues have higher rates of mortality when exposed to multiple stressors. We speculate that the prevalence of these species in areas of high Na and disturbance is explained by alternative strategies, such as high fecundity, a wide range of germination conditions, or further dispersal, to compensate for the lack of additional tolerance mechanisms. Full article

(This article belongs to the Special Issue Interaction Between Abiotic and Biotic Stresses in Plants)

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667 KiB

Open AccessReview

The Role of Temperature in the Growth and Flowering of Geophytes

by Nadezda V. Khodorova and Michèle Boitel-Conti

Plants 2013, 2(4), 699-711; https://doi.org/10.3390/plants2040699 - 1 Nov 2013

Cited by 97 | Viewed by 15838

Abstract

Among several naturally occurring environmental factors, temperature is considered to play a predominant role in controlling proper growth and flowering in geophytes. Most of them require a “warm-cold-warm” sequence to complete their annual cycle. The temperature optima for flower meristem induction and the [...] Read more.

Among several naturally occurring environmental factors, temperature is considered to play a predominant role in controlling proper growth and flowering in geophytes. Most of them require a “warm-cold-warm” sequence to complete their annual cycle. The temperature optima for flower meristem induction and the early stages of floral organogenesis vary between nine and 25 °C, followed, in the autumn, by a several-week period of lower temperature (4–9 °C), which enables stem elongation and anthesis. The absence of low temperature treatment leads to slow shoot growth in spring and severe flowering disorders. Numerous studies have shown that the effects of the temperature surrounding the underground organs during the autumn-winter period can lead to important physiological changes in plants, but the mechanism that underlies the relationship between cold treatment and growth is still unclear. In this mini-review, we describe experimental data concerning the temperature requirements for flower initiation and development, shoot elongation, aboveground growth and anthesis in bulbous plants. The physiological processes that occur during autumn-winter periods in bulbs (water status, hormonal balance, respiration, carbohydrate mobilization) and how these changes might provoke disorders in stem elongation and flowering are examined. A model describing the relationship between the cold requirement, auxin and gibberellin interactions and the growth response is proposed. Full article

(This article belongs to the Special Issue Developmental Biology and Biotechnology of Plant Sexual Reproduction)

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1238 KiB

Open AccessCommunication

Decrease in Available Soil Water Storage Capacity Reduces Vitality of Young Understorey European Beeches (Fagus sylvatica L.)—A Case Study from the Black Forest, Germany

by Tamalika Chakraborty, Somidh Saha and Albert Reif

Plants 2013, 2(4), 676-698; https://doi.org/10.3390/plants2040676 - 23 Oct 2013

Cited by 17 | Viewed by 7838

Abstract

Growth and survival of young European beech (Fagus sylvatica L.) is largely dependent on water availability. We quantified the influence of water stress (measured as Available Soil Water Storage Capacity or ASWSC) on vitality of young beech plants at a dry site. [...] Read more.

Growth and survival of young European beech (Fagus sylvatica L.) is largely dependent on water availability. We quantified the influence of water stress (measured as Available Soil Water Storage Capacity or ASWSC) on vitality of young beech plants at a dry site. The study site was located in a semi-natural sessile oak (Quercus petraea (Mattuschka) Liebl.) stand adjacent to beech stands on a rocky gneiss outcrop in southwestern Germany. Plant vitality was measured as crown dieback and estimated by the percentage of dead above ground biomass. The magnitude of crown dieback was recorded in different vertical parts of the crown. Biomass was calculated from the harvested plants following allometric regression equations specifically developed for our study site. Stem discs from harvested plants were used for growth analysis. We found that soil depth up to bedrock and skeleton content significantly influenced ASWSC at the study site. A significant negative correlation between ASWSC and crown dieback was found. Highest rates of crown dieback were noticed in the middle and lower crown. The threshold of crown dieback as a function of drought stress for young beech plants was calculated for the first time in this study. This threshold of crown dieback was found to be 40% of above ground biomass. Beyond 40% crown dieback, plants eventually experienced complete mortality. In addition, we found that the extremely dry year of 2003 significantly hampered growth (basal area increment) of plants in dry plots (ASWSC < 61 mm) in the study area. Recovery in the plants’ radial growth after that drought year was significantly higher in less dry plots (ASWSC > 61 mm) than in dry plots. We concluded that a decrease in ASWSC impeded the vitality of young beech causing partial up to complete crown dieback in the study site. Full article

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654 KiB

Open AccessReview

Calcium: The Missing Link in Auxin Action

by Steffen Vanneste and Jiří Friml

Plants 2013, 2(4), 650-675; https://doi.org/10.3390/plants2040650 - 21 Oct 2013

Cited by 73 | Viewed by 14803

Abstract

Due to their sessile lifestyles, plants need to deal with the limitations and stresses imposed by the changing environment. Plants cope with these by a remarkable developmental flexibility, which is embedded in their strategy to survive. Plants can adjust their size, shape and [...] Read more.

Due to their sessile lifestyles, plants need to deal with the limitations and stresses imposed by the changing environment. Plants cope with these by a remarkable developmental flexibility, which is embedded in their strategy to survive. Plants can adjust their size, shape and number of organs, bend according to gravity and light, and regenerate tissues that were damaged, utilizing a coordinating, intercellular signal, the plant hormone, auxin. Another versatile signal is the cation, Ca²⁺, which is a crucial second messenger for many rapid cellular processes during responses to a wide range of endogenous and environmental signals, such as hormones, light, drought stress and others. Auxin is a good candidate for one of these Ca²⁺-activating signals. However, the role of auxin-induced Ca²⁺ signaling is poorly understood. Here, we will provide an overview of possible developmental and physiological roles, as well as mechanisms underlying the interconnection of Ca²⁺ and auxin signaling. Full article

(This article belongs to the Special Issue Calcium Signaling in Plants)

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406 KiB

Open AccessArticle

Verbesina alternifolia Tolerance to the Holoparasite Cuscuta gronovii and the Impact of Drought

by Bethany Evans and Victoria Borowicz

Plants 2013, 2(4), 635-649; https://doi.org/10.3390/plants2040635 - 18 Oct 2013

Cited by 6 | Viewed by 7145

Abstract

Holoparasites are nonphotosynthetic plants that acquire all resources from hosts. The holoparasite Cuscuta gronovii is native to much of the US with a broad host range including Verbesina alternifolia, an understory perennial. Both species grow in moderate to moist soils and occur [...] Read more.

Holoparasites are nonphotosynthetic plants that acquire all resources from hosts. The holoparasite Cuscuta gronovii is native to much of the US with a broad host range including Verbesina alternifolia, an understory perennial. Both species grow in moderate to moist soils and occur in habitats that may experience prolonged or episodic drought. We applied the Wise-Abrahamson Limiting Resource Model (LRM) developed for plant-herbivore relations to examine the effects of pattern of drought stress on tolerance of V. alternifolia to parasitism by C. gronovii. Individual plants were assigned one of six treatments that were combinations of parasite (none or addition of parasite) and drought stress (well-watered, continuously-stressed, or pulse-stressed). After pulse-stressed plants had experienced two wet-dry cycles all plants were harvested. Parasitism strongly reduced both shoot and root mass and well-watered hosts exhibited the greatest decline, indicating reduced tolerance to parasitism when water was readily available. This is consistent with the LRM if parasitism limits photosynthates available to the host. However, parasitism increased allocation to shoot and this effect did not differ between well-watered and drought-stressed plants, indicating equal tolerance. This outcome is in accord with an alternative prediction of the LRM if hosts are not carbon limited. Total pot productivity was reduced by parasitism and drought stress, and this effect was greater for pulse-stressed than for continuously-stressed hosts. We discuss the applicability of the LRM for understanding the effects of drought on tolerance to parasitism. Full article

(This article belongs to the Special Issue Interaction Between Abiotic and Biotic Stresses in Plants)

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376 KiB

Open AccessReview

Interaction between Calcium and Actin in Guard Cell and Pollen Signaling Networks

by Dong-Hua Chen, Biswa R. Acharya, Wei Liu and Wei Zhang

Plants 2013, 2(4), 615-634; https://doi.org/10.3390/plants2040615 - 15 Oct 2013

Cited by 12 | Viewed by 8595

Abstract

Calcium (Ca²⁺) plays important roles in plant growth, development, and signal transduction. It is a vital nutrient for plant physical design, such as cell wall and membrane, and also serves as a counter-cation for biochemical, inorganic, and organic anions, and more [...] Read more.

Calcium (Ca²⁺) plays important roles in plant growth, development, and signal transduction. It is a vital nutrient for plant physical design, such as cell wall and membrane, and also serves as a counter-cation for biochemical, inorganic, and organic anions, and more particularly, its concentration change in cytosol is a ubiquitous second messenger in plant physiological signaling in responses to developmental and environmental stimuli. Actin cytoskeleton is well known for its importance in cellular architecture maintenance and its significance in cytoplasmic streaming and cell division. In plant cell system, the actin dynamics is a process of polymerization and de-polymerization of globular actin and filamentous actin and that acts as an active regulator for calcium signaling by controlling calcium evoked physiological responses. The elucidation of the interaction between calcium and actin dynamics will be helpful for further investigation of plant cell signaling networks at molecular level. This review mainly focuses on the recent advances in understanding the interaction between the two aforementioned signaling components in two well-established model systems of plant, guard cell, and pollen. Full article

(This article belongs to the Special Issue Calcium Signaling in Plants)

551 KiB

Open AccessReview

Calcium Signals from the Vacuole

by Gerald Schönknecht

Plants 2013, 2(4), 589-614; https://doi.org/10.3390/plants2040589 - 14 Oct 2013

Cited by 51 | Viewed by 9885

Abstract

The vacuole is by far the largest intracellular Ca²⁺ store in most plant cells. Here, the current knowledge about the molecular mechanisms of vacuolar Ca²⁺ release and Ca²⁺ uptake is summarized, and how different vacuolar Ca²⁺ channels and Ca [...] Read more.

The vacuole is by far the largest intracellular Ca²⁺ store in most plant cells. Here, the current knowledge about the molecular mechanisms of vacuolar Ca²⁺ release and Ca²⁺ uptake is summarized, and how different vacuolar Ca²⁺ channels and Ca²⁺ pumps may contribute to Ca²⁺ signaling in plant cells is discussed. To provide a phylogenetic perspective, the distribution of potential vacuolar Ca²⁺ transporters is compared for different clades of photosynthetic eukaryotes. There are several candidates for vacuolar Ca²⁺ channels that could elicit cytosolic [Ca²⁺] transients. Typical second messengers, such as InsP₃ and cADPR, seem to trigger vacuolar Ca²⁺ release, but the molecular mechanism of this Ca²⁺ release still awaits elucidation. Some vacuolar Ca²⁺ channels have been identified on a molecular level, the voltage-dependent SV/TPC1 channel, and recently two cyclic-nucleotide-gated cation channels. However, their function in Ca²⁺ signaling still has to be demonstrated. Ca²⁺ pumps in addition to establishing long-term Ca²⁺ homeostasis can shape cytosolic [Ca²⁺] transients by limiting their amplitude and duration, and may thus affect Ca²⁺ signaling. Full article

(This article belongs to the Special Issue Calcium Signaling in Plants)

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1483 KiB

Open AccessReview

Towards the Physics of Calcium Signalling in Plants

by Teresa Vaz Martins, Matthew J. Evans, Hugh C. Woolfenden and Richard J. Morris

Plants 2013, 2(4), 541-588; https://doi.org/10.3390/plants2040541 - 27 Sep 2013

Cited by 31 | Viewed by 12015

Abstract

Calcium is an abundant element with a wide variety of important roles within cells. Calcium ions are inter- and intra-cellular messengers that are involved in numerous signalling pathways. Fluctuating compartment-specific calcium ion concentrations can lead to localised and even plant-wide oscillations that can [...] Read more.

Calcium is an abundant element with a wide variety of important roles within cells. Calcium ions are inter- and intra-cellular messengers that are involved in numerous signalling pathways. Fluctuating compartment-specific calcium ion concentrations can lead to localised and even plant-wide oscillations that can regulate downstream events. Understanding the mechanisms that give rise to these complex patterns that vary both in space and time can be challenging, even in cases for which individual components have been identified. Taking a systems biology approach, mathematical and computational techniques can be employed to produce models that recapitulate experimental observations and capture our current understanding of the system. Useful models make novel predictions that can be investigated and falsified experimentally. This review brings together recent work on the modelling of calcium signalling in plants, from the scale of ion channels through to plant-wide responses to external stimuli. Some in silico results that have informed later experiments are highlighted. Full article

(This article belongs to the Special Issue Calcium Signaling in Plants)

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Plants, Volume 2, Issue 4 (December 2013) – 11 articles , Pages 541-785

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