1,720,999 research outputs found
Peroxisomal PEX7 Receptor Affects Cadmium-Induced ROS and Auxin Homeostasis in Arabidopsis Root System
Full text linkPeroxisomes are important in plant physiological functions and stress responses. Through the production of reactive oxygen and nitrogen species (ROS and RNS), and antioxidant defense enzymes, peroxisomes control cellular redox homeostasis. Peroxin (PEX) proteins, such as PEX7 and PEX5, recognize peroxisome targeting signals (PTS1/PTS2) important for transporting proteins from cytosol to peroxisomal matrix. pex7-1 mutant displays reduced PTS2 protein import and altered peroxisomal metabolism. In this research we analyzed the role of PEX7 in the Arabidopsis thaliana root system exposed to 30 or 60 μM CdSO4. Cd uptake and translocation, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) levels, and reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels and catalase activity were analyzed in pex7-1 mutant primary and lateral roots in comparison with the wild type (wt). The peroxisomal defect due to PEX7 mutation did not reduce Cd-uptake but reduced its translocation to the shoot and the root cell peroxisomal signal detected by 8-(4-Nitrophenyl) Bodipy (N-BODIPY) probe. The trend of nitric oxide (NO) and peroxynitrite in pex7-1 roots, exposed/not exposed to Cd, was as in wt, with the higher Cd-concentration inducing higher levels of these RNS. By contrast, PEX7 mutation caused changes in Cd-induced hydrogen peroxide (H2O2) and superoxide anion (O2●−) levels in the roots, delaying ROS-scavenging. Results show that PEX7 is involved in counteracting Cd toxicity in Arabidopsis root system by controlling ROS metabolism and affecting auxin levels. These results add further information to the important role of peroxisomes in plant responses to Cd
Coronary occlusion secondary to blunt chest trauma: a first attempt at balloon angioplasty.
No full textThere have been only 58 angiographically documented reports of transmural myocardial infarction due to closed-chest trauma. None of these cases has been treated by percutaneous transluminal coronary angioplasty. We report the case of a 40-year-old man who developed an anterior-wall myocardial infarction secondary to blunt chest trauma suffered in an automobile accident. Angiographic study performed 2 months after the injury revealed an isolated total obstruction of the left anterior descending coronary artery. The patient was judged a good candidate for balloon angioplasty, but total reocclusion occurred within 24 hours of the procedure and a 2nd attempt did not restore patency. Surgical revascularization was performed a week later. A year after his injury, the patient remains asymptomatic and is back at work. Despite the failure of percutaneous transluminal coronary angioplasty in its 1st application to coronary artery repair after blunt chest trauma, we believe it to be the treatment of choice in young patients and in single-vessel disease
Nitric oxide alleviates cadmium- but not arsenic-induced damages in rice roots
Full text linkNitric oxide (NO) has signalling roles in plant stress responses. Cadmium (Cd) and arsenic (As) soil pollutants alter plant development, mainly the root-system, by increasing NO-content, triggering reactive oxygen species (ROS), and forming peroxynitrite by NO-reaction with the superoxide anion. Interactions of NO with ROS and peroxynitrite seem important for plant tolerance to heavy metal(oid)s, but the mechanisms underlying this process remain unclear. Our goal was to investigate NO-involvement in rice (Oryza sativa L.) root-system after exposure to Cd or As, to highlight possible differences in NO-behaviour between the two pollutants. To the aim, morpho-histological, chemical and epifluorescence analyses were carried out on roots of different origin in the root-system, under exposure to Cd or As, combined or not with sodium nitroprusside (SNP), a NO-donor compound. Results show that increased intracellular NO levels alleviate the root-system alterations induced by Cd, i.e., inhibition of adventitious root elongation and lateral root formation, increment in lignin deposition in the sclerenchyma/endodermis cell-walls, but, even if reducing As-induced endodermis lignification, do not recover the majority of the As-damages, i.e., enhancement of AR-elongation, reduction of LR-formation, anomalous tissue-proliferation. However, NO decreases both Cd and As uptake, without affecting the pollutants translocation-capability from roots to shoots. Moreover, NO reduces the Cd-induced, but not the As-induced, ROS levels by triggering peroxynitrite production. Altogether, results highlight a different behaviour of NO in modulating rice root-system response to the toxicity of the heavy metal Cd and the metalloid As, which depends by the NO-interaction with the specific pollutant
Cadmium and arsenic affect root development in Oryza sativa L. involving auxin jasmonate crosstalk
No full textNitric oxide and phytohormones interaction in the response of the rice root system to Cadmium or Arsenic
No full textSoil pollution by cadmium (Cd) and arsenic (As) is a worldwide concern due to their toxicity chemical stability. Oryza sativa L. (rice) is a model organism for monocot plants and is also one of the most relevant sources of toxic metals for humans. Changes in the root intracellular content and distribution of phytohormones, such as auxin or brassinosteroids represent a tool through which plants change their architecture in response to the stress. In addition to phytohormones, plants can rely on a plethora of small signal molecules such as nitrogen monoxide (nitric oxide – NO) able to promptly sense and transduce the stress signals, thanks also to their interaction with plant hormones. However, the complex relationship between NO and auxin or brassinosteroid, during the plant response to toxic metals is still poorly understood. The aim of the study was to evaluate if exogenous supplementations with a specific NO-donor (sodium nitroprusside, SNP) compound mitigate Cd or As stress in the root system of rice seedlings grown in vitro, as well as to understand if the molecule interacts with auxin or brassinosteroids during the root stress response. Our results show that exogenous treatments with SNP mitigate the inhibition of the rice root system induced by Cd, but not that induced by As, through an increase of the intracellular NO levels. Moreover, by the use of the OsDR5::GUS system, we show that SNP treatments restore the IAA distribution in the adventitious root apices altered by both the pollutants. In addition, exogenous brassinosteroid treatments strongly increase the root endogenous NO levels, reduced by As, and the transcripts of OsNOS1, a gene involved in NO biosynthesis. However, the brassinosteroid-mediated increase of NO does not mitigate the morpho/histological anomalies induced by the pollutants in the root system
Nitric oxide cooperates with auxin to mitigate the alterations in the root system caused by cadmium and arsenic
Full text linkOryza sativa L. is a worldwide food-crop frequently growing in cadmium (Cd)/arsenic (As) polluted soils, with its root-system as the first target of the pollutants. Root-system development involves the establishment of optimal indole-3-acetic acid (IAA) levels, also requiring the conversion of the IAA natural precursor indole-3-butyric acid (IBA) into IAA, causing nitric oxide (NO) formation. Nitric oxide is a stress-signaling molecule. In rice, a negative interaction of Cd or As with endogenous auxin has been demonstrated, as some NO protective effects. However, a synergism between the natural auxins (IAA and/or IBA) and NO was not yet determined and might be important for ameliorating rice metal(oid)-tolerance. With this aim, the stress caused by Cd/As toxicity in the root cells and the possible recovery by either NO or auxins (IAA/IBA) were evaluated after Cd or As (arsenate) exposure, combined or not with the NO-donor compound sodium-nitroprusside (SNP). Root fresh weight, membrane electrolyte leakage, and H2O2 production were also measured. Moreover, endogenous IAA/IBA contents, transcription-levels of OsYUCCA1 and OsASA2 IAA-biosynthetic-genes, and expression of the IAA-influx-carrier OsAUX1 and the IAA-responsive DR5::GUS construct were analyzed, and NO-epifluorescence levels were measured. Results showed that membrane injury by enhanced electrolyte leakage occurred under both pollutants and was reduced by the treatment with SNP only in Cd-presence. By contrast, no membrane injury was caused by either exogenous NO or IAA or IBA. Cd- and As-toxicity also resulted into a decreased root fresh weight, mitigated by the combination of each pollutant with either IAA or IBA. Cd and As decreased the endogenous NO-content, increased H2O2 formation, and altered auxin biosynthesis, levels and distribution in both adventitious (ARs) and mainly lateral roots (LRs). The SNP-formed NO counteracted the pollutants’ effects on auxin distribution/levels, reduced H2O2 formation in Cd-presence, and enhanced AUX1-expression, mainly in As-presence. Each exogenous auxin, but mainly IBA, combined with Cd or As at 10 μM, mitigated the pollutants’ effects by increasing LR-production and by increasing NO-content in the case of Cd. Altogether, results demonstrate that NO and auxin(s) work together in the rice root system to counteract the specific toxic-effects of each pollutant
Transition dynamics in plastid interconversion in land plants
Full text linkIn land plants, plastids acquired different functions and structures in parallel with the increasing genetic, developmental, and morphological diversity attained by the plant tissues. There are transition dynamics among the morpho-functional features of the different plastid types. This review is focused on plastid structure and interconversion with a focus on recent findings and a special attention to plastid types that are less known than chloroplasts. The morpho-physiological and biochemical differences, which explain the multiple functions of each plastid type and the transcriptional and post-translational modulation of plastid capabilities are here described. The structural dynamism of plastids is also discussed through their ability to produce protrusions called stromules and the activity of lipoprotein particles known as plastoglobules. As a consequence of the proteome differences among plastid types, the conversion from one type of plastid to another requires an organellar proteome reorganization with a turnover of plastid proteins, but also a differentially regulated import of nuclear-encoded proteins. Plastid degradation by macroautophagy and microautophagy pathways is also described. Taken together, all this information allows us to interpret plastids as sensors in development and plastid interconversion as a way that the plant uses to modify its growth
Plastid dynamism integrates development and environment
Full text linkIn land plants plastid type differentiation occurs concomitantly with cellular differentiation and the transition from one type to another is under developmental and environmental control. Plastid dynamism is based on a bilateral communication between plastids and nucleus through anterograde and retrograde signaling. Signaling occurs through the interaction with specific phytohormones (abscisic acid, strigolactones, jasmonates, gibberellins, brassinosteroids, ethylene, salicylic acid, cytokinin and auxin). The review is focused on the modulation of plastid capabilities at both transcriptional and post-translational levels at the crossroad between development and stress, with a particular attention to the chloroplast, because the most studied plastid type. The role of plastid-encoded and nuclear-encoded proteins for plastid development and stress responses, and the changes of plastid fate through the activity of stromules and plastoglobules, are discussed. Examples of plastid dynamism in response to soil stress agents (salinity, lead, cadmium, arsenic, and chromium) are described. Albinism and root greening are described based on the modulation activities of auxin and cytokinin. The physiological and functional responses of the sensory epidermal and vascular plastids to abiotic and biotic stresses along with their specific roles in stress sensing are described together with their potential modulation of retrograde signaling pathways. Future research perspectives include an in-depth study of sensory plastids to explore their potential for establishing a transgenerational memory to stress. Suggestions about anterograde and retrograde pathways acting at interspecific level and on the lipids of plastoglobules as a novel class of plastid morphogenic agents are provided
Oligogalacturonides enhance cytokinin-induced vegetative shoot formation in tobacco explants, inhibit polyamine biosynthetic gene expression, and promote long-term remobilisation of cell calcium
No full textAbstract Long-sized oligogalacturonides (OGs) are cell
wall fragments that induce defence and developmental
responses. The Ca2+-dependent “egg-box” conformation is
required for their activity, and polyamines may prevent
them from adopting this conformation. Although OGs are
known to inhibit auxin-induced growth processes, their
eVect on cytokinin-induced ones requires investigation. In
the present work OGs were shown to promote cytokinin
(benzyladenine, BA)-induced vegetative shoot formation
from tobacco leaf explants, independent of the presence of
CaCl2 in the medium and of auxin (indoleacetic acid, IAA)
supply. The eVect of polyamines, putrescine (PU) and spermidine
(SD) supplied with/without their biosynthetic inhibitors
(DFMO, CHA) was also investigated, and showed that
spermidine enhanced adventitious vegetative shoot formation,
but only on medium containing Ca2+ and IAA. Treatments
with inhibitors blocked this promotive eVect. OGs
did not alter free polyamine concentrations, but caused a
moderate increase of conjugated ones, and exhibited an
early inhibitory eVect on polyamine biosynthetic gene
expression. OGs, but not SD, caused long-term changes in
calcium-associated epiXuorescent signals in the cell walls,
and, later, inside the cells of speciWc tissues. Electron
microscopy analysis (ESI system) demonstrated that
calcium accumulated in the cell walls and vacuoles of OGcultured explants
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