Variability of nuclear and mitochondrial ribosomal DNA of a truffle species (Tuber aestivum)

The intraspecific genetic variability of #Tuber aestivum$ was studied using molecular markers at various geographical scales. We used the polymerase chain reaction (PCR) coupled with restriction fragment length polymorphism (RFLP) analysis to examine the variation of the nuclear and mitochondrial ribosomal DNA (rDNA). RFLPs were found in the nuclear internal transcribed spacer (ITS) and three alleles were detected in the six populations analysed. No variability was found in mitochondrial rDNA. We found, in a very few cases, that truffles sharing different ITS genotypes could be present within a single symbiotic tree. (Résumé d'auteur

Sinorhizobium medicae sp. nov., isolated from annual Medicago spp.

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Rhizostabilzation of a mine tailing higly contaminated: Previous study of Cd localization and speciation in Anthyllis vulneraria

cited By 0International audienceThe plant Anthyllis vulneraria has been identified in mine tailings and the aim of this study is to determine the mechanisms developed by the plant and its symbiotic association Mesorhizobium metallidurans to tolerate Cd. We particulary intend to determine the distribution and speciation of Cd in plant using a combination of μXRF (X-ray fluorescence) and Cd XANES and μXANES (X-ray Absorption Near Edge Structure). © Owned by the authors, published by EDP Sciences, 2013

Stimulation of the ionic transport system in Brassica napus by a plant growth-promoting rhizobacterium (Achromobacter sp.)

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CadA of Mesorhizobium metallidurans isolated from a zinc-rich mining soil is a P(IB-2)-type ATPase involved in cadmium and zinc resistance

Mesorhizobium metallidurans STM 2683(T) is a nitrogen-fixing bacterium that nodulates Anthyllis vulneraria in mine tailings highly contaminated in zinc, lead and cadmium. To study the mechanisms whereby this bacterium copes with metals, we functionally screened a cosmid genomic library of M. metallidurans for zinc or cadmium tolerance. A cosmid clone harbored a gene encoding P(IB)-type ATPase homologous to CadA that leads to cadmium and zinc resistance in Escherichia coli. The CadA protein structure presents one duplication of the two N-terminal metal binding domains (i.e. a heavy metal-associated domain followed by a histidine-rich domain) which allows specific binding to zinc and cadmium cations. A cadA-deleted strain of M. metallidurans failed to grow at high zinc concentrations (2 mM) and its growth was delayed at lower zinc concentrations. Expression studies using a transcriptional fusion of cadA promoter to gfp showed that cadA is specifically induced in a dose-dependent manner by zinc and cadmium in M. metallidurans in vitro conditions and into A. vulneraria nodules after Zn stress. Metal induction sensitivity was increased in the strain where cadA gene was deleted. This study identified cadA as a first mesorhizobial resistance determinant involved in detoxification of cadmium and zinc and which confers upon M. metallidurans greater capacity for coping with high zinc concentrations. This improves the knowledge of this bacterium for potential use as a symbiotic inoculant of Anthyllis in phytostabilization strategies of metal-rich sites

Purification, characterization and subcellular localization of ACC oxidase from fruits

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Immunocytolocalisation of ACC oxidase in tomato fruits

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Ancient Heavy Metal Contamination in Soils as a Driver of Tolerant Anthyllis vulneraria Rhizobial Communities.

Anthyllis vulneraria is a legume associated with nitrogen-fixing rhizobia that together offer an adapted biological material for mine-soil phytostabilization by limiting metal pollution. To find rhizobia associated with Anthyllis at a given site, we evaluated the genetic and phenotypic properties of a collection of 137 rhizobia recovered from soils presenting contrasting metal levels. Zn-Pb mine soils largely contained metal-tolerant rhizobia belonging to Mesorhizobium metallidurans or to another sister metal-tolerant species. All of the metal-tolerant isolates harbored the cadA marker gene (encoding a metal-efflux PIB-type ATPase transporter). In contrast, metal-sensitive strains were taxonomically distinct from metal-tolerant populations and consisted of new Mesorhizobium genospecies. Based on the symbiotic nodA marker, the populations comprise two symbiovar assemblages (potentially related to Anthyllis or Lotus host preferences) according to soil geographic locations but independently of metal content. Multivariate analysis showed that soil Pb and Cd concentrations differentially impacted the rhizobial communities and that a rhizobial community found in one geographically distant site was highly divergent from the others. In conclusion, heavy metal levels in soils drive the taxonomic composition of Anthyllis-associated rhizobial populations according to their metal-tolerance phenotype but not their symbiotic nodA diversity. In addition to heavy metals, local soil physicochemical and topoclimatic conditions also impact the rhizobial beta diversity. Mesorhizobium communities were locally adapted and site specific, and their use is recommended for the success of phytostabilization strategies based on Mesorhizobium-legume vegetation. Phytostabilization of toxic mine spoils limits heavy metal dispersion and environmental pollution by establishing a sustainable plant cover. This eco-friendly method is facilitated by the use of selected and adapted cover crop legumes living in symbiosis with rhizobia that can stimulate plant growth naturally through biological nitrogen fixation. We studied microsymbiont partners of a metal-tolerant legume, Anthyllis vulneraria, which is tolerant to very highly metal-polluted soils in mining and nonmining sites. Site-specific rhizobial communities were linked to taxonomic composition and metal tolerance capacity. The rhizobial species Mesorhizobium metallidurans was dominant in all Zn-Pb mines but one. It was not detected in unpolluted sites where other distinct Mesorhizobium species occur. Given the different soil conditions at the respective mining sites, including their heavy-metal contamination, revegetation strategies based on rhizobia adapting to local conditions are more likely to succeed over the long term compared to strategies based on introducing less-well-adapted strains

REVUELTA DOMÍNGUEZ, F. I.; PÉREZ SÁNCHEZ, L. «Interactividad en los entornos de formación on-line». Barcelona: UOC, 2009

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