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Balsera M.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Soll J.,Ludwig Maximilians University of Munich | Buchanan B.B.,University of California at Berkeley
Trends in Plant Science

The import of chloroplast proteins synthesized in the cytosol of a plant cell is mediated by two multiprotein complexes or translocons located at the outer and inner membranes of the chloroplast envelope, respectively, TOC and TIC. These complexes integrate different signals to assure the timely transport of proteins into the chloroplast in accordance with the metabolic and developmental needs of the cell. The past few years have witnessed the emergence of redox as a regulator of the protein transport process. Here, we discuss evidence that the metabolic redox state of the chloroplast regulates the import of preproteins by altering either the activity or composition of participating transport components. It appears that, through these redox changes, chloroplasts communicate with other compartments of the plant cell. © 2010 Elsevier Ltd. Source

Garcia-Sanchez A.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Alonso-Rojo P.,University of Salamanca | Santos-Frances F.,University of Salamanca
Science of the Total Environment

High levels of total and bioavailable As in soils in mining areas may lead to the potential contamination of surface water and groundwater, being toxic to human, plants, and animals. The soils in the studied area (Province of Salamanca, Spain) recorded a total As concentration that varied from 5.5. mg/kg to 150. mg/kg, and water-soluble As ranged from 0.004. mg/kg to 0.107. mg/kg, often exceeding the guideline limits for agricultural soil (50. mg/kg total As, 0.04. mg/kg water-soluble As). The range of As concentration in pond water was <0.001μg/l-60μg/l, with 40% of samples exceeding the maximum permissible level (10μg/l) for drinking water. Estimated bioavailable As in soil varied from 0.045. mg/kg to 0.760. mg/kg, around six times higher than water-soluble As fraction, which may pose a high potential risk in regard to its entry into food chain. Soil column leaching tests show an As potential mobility constant threatening water contamination by continuous leaching. The vertical distribution of As through soil profiles suggests a deposition mechanism of this element on the top-soils that involves the wind or water transport of mine tailings. A similar vertical distribution of As and organic matter (OM) contents in soil profiles, as well as, significant correlations between As concentrations and OM and N contents, suggests that type and content of soil OM are major factors for determining the content, distribution, and mobilization of As in the soil. Due to the low supergenic mobility of this element in mining environments, the soil pollution degree in the studied area is moderate, in spite of the elevated As contents in mine tailings. © 2010 Elsevier B.V. Source

Martinez-Hidalgo P.,University of Salamanca | Galindo-Villardon P.,University of Salamanca | Igual J.M.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Martinez-Molina E.,University of Salamanca
Scientific Reports

Biotic interactions can improve agricultural productivity without costly and environmentally challenging inputs. Micromonospora strains have recently been reported as natural endophytes of legume nodules but their significance for plant development and productivity has not yet been established. The aim of this study was to determine the diversity and function of Micromonospora isolated from Medicago sativa root nodules. Micromonospora-like strains from field alfalfa nodules were characterized by BOX-PCR fingerprinting and 16S rRNA gene sequencing. The ecological role of the interaction of the 15 selected representative Micromonospora strains was tested in M. sativa. Nodulation, plant growth and nutrition parameters were analyzed. Alfalfa nodules naturally contain abundant and highly diverse populations of Micromonospora, both at the intra- and at interspecific level. Selected Micromonospora isolates significantly increase the nodulation of alfalfa by Ensifer meliloti 1021 and also the efficiency of the plant for nitrogen nutrition. Moreover, they promote aerial growth, the shoot-to-root ratio, and raise the level of essential nutrients. Our results indicate that Micromonospora acts as a Rhizobia Helper Bacteria (RHB) agent and has probiotic effects, promoting plant growth and increasing nutrition efficiency. Its ecological role, biotechnological potential and advantages as a plant probiotic bacterium (PPB) are also discussed. Source

Balsera M.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Uberegui E.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Schurmann P.,Laboratoire Of Biologie Moleculaire Et Cellulaire | Buchanan B.B.,University of California at Berkeley
Antioxidants and Redox Signaling

Significance: The post-translational modification of thiol groups stands out as a key strategy that cells employ for metabolic regulation and adaptation to changing environmental conditions. Nowhere is this more evident than in chloroplasts - the O2-evolving photosynthetic organelles of plant cells that are fitted with multiple redox systems, including the thioredoxin (Trx) family of oxidoreductases functional in the reversible modification of regulatory thiols of proteins in all types of cells. The best understood member of this family in chloroplasts is the ferredoxin-linked thioredoxin system (FTS) by which proteins are modified via light-dependent disulfide/dithiol (S-S/2SH) transitions. Recent Advances: Discovered in the reductive activation of enzymes of the Calvin-Benson cycle in illuminated chloroplast preparations, recent studies have extended the role of the FTS far beyond its original boundaries to include a spectrum of cellular processes. Together with the NADP-linked thioredoxin reductase C-type (NTRC) and glutathione/glutaredoxin systems, the FTS also plays a central role in the response of chloroplasts to different types of stress. Critical Issues: The comparisons of redox regulatory networks functional in chloroplasts of land plants with those of cyanobacteria - prokaryotes considered to be the ancestors of chloroplasts - and different types of algae summarized in this review have provided new insight into the evolutionary development of redox regulation, starting with the simplest O2-evolving organisms. Future Directions: The evolutionary appearance, mode of action, and specificity of the redox regulatory systems functional in chloroplasts, as well as the types of redox modification operating under diverse environmental conditions stand out as areas for future study. © Copyright 2014, Mary Ann Liebert, Inc. 2014. Source

Sanchez Marquez S.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Bills G.F.,Fundacion MEDINA | Herrero N.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca | Zabalgogeazcoa I.,CSIC - Institute of Natural Resources and Agriculture Biology of Salamanca
Fungal Ecology

Many fungi behave as endophytes in grasses. Unlike the well known . Epichloë/. Neotyphodium species, most other endophytes are not capable of systemic colonization of plant organs, or seed transmission. The species diversity of the non-systemic endophytic mycobiota of grasses is large, dominated by ascomycetes. The relative abundance of species is very unequal, a few dominant taxa like . Acremonium, . Alternaria, . Cladosporium, . Epicoccum and . Penicillium spp., occur in many grasses and locations. In contrast, many rare species are isolated only once in endophyte surveys. The possible ecological functions of endophytes are diverse, and often unknown. Latent pathogens represent a small fraction of endophytic mycobiotas, indicating that many non-pathogenic fungal taxa are able to enter plants overriding defence reactions. Some dominant species behave as latent saprotrophs, sporulating when the host tissue dies. Endofungal viruses and bacteria occur among endophytic species, but their effect in their hosts is largely unknown. © 2011 Elsevier Ltd and The British Mycological Society. Source

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