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ABSTRACT: Environmental and Experimental Botany j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e n v e x p b o t Arbuscular mycorrhizal fungi modulate the leaf transcriptome of a Populus alba L. a b s t r a c t Significant improvement of growth associated with increased, rather than decreased, uptake of Cu and Zn has been observed in poplar plants inoculated with Glomus spp. as compared with non-mycorrhizal plants. The beneficial effect exerted by these arbuscular mycorrhizal fungi (AMF) is likely to be controlled by specific gene expression patterns in the plant. Until now, however, very little is known about the tran-scriptional changes which occur in response to heavy metals (HMs) in mycorrhizal vs. non-mycorrhizal poplar plants. In order to identify such HM-and/or AMF-induced changes in leaves of white poplar (Pop-ulus alba L.) plants grown, in the greenhouse, on Cu-and Zn-polluted soil, the cDNA-Amplified Fragment Length Polymorphism (AFLP) approach was adopted, resulting in the identification of a number of new differentially regulated genes. Transcript derived fragments (TDFs) mostly belonged to stress-related functional categories of defence and secondary metabolism. Genes belonging to different functional cat-egories, plus other genes known to be related to HM stress (metallothioneins, phytochelatin synthase, glutathione synthase, arginine decarboxylase), were analysed by quantitative (q)RT-PCR. Transcript lev-els were generally down-regulated, or unaffected, in polluted soil compared with controls, the main exceptions being phytochelatin synthase and clathrin, and strongly up-regulated in the presence of AMF, especially Glomus mosseae.
Environmental and Experimental Botany 08/2012; 75:25-35. · 2.98 Impact Factor
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ABSTRACT: The localization, viability, and culturability of Pseudomonas fluorescens 92rkG5 were analyzed on three morphological root zones (root tip + elongation, root hair, and collar) of 3-, 5-, and 7-day-old
tomato plants. Qualitative information about the localization and viability was collected by confocal laser scanning microscopy.
Quantitative data concerning the distribution, viability, and culturability were obtained through combined dilution plating
and flow cytometry. Colonization by P. fluorescens affected root development in a complex way, causing a general increase in the length of the collar and early stimulation
of the primary root growth (3rd day), followed by a reduction in length (7th day). The three root zones showed different distribution,
organization, and viability of the bacterial cells, but the distribution pattern within each zone did not change with time.
Root tips were always devoid of bacteria, whereas with increasing distance from the apex, microcolonies or strings of cells
became more and more prominent. Viability was high in the elongation zone, but it declined in the older parts of the roots.
The so-called viable but not culturable cells were observed on the root, and their proportion in the distal (root tip + elongation)
zone dramatically increased with time. These results suggest the existence of a specific temporal and spatial pattern of root
colonization, related to cell viability and culturability, expressed by the plant-beneficial strain P. fluorescens 92rkG5.
Microbial Ecology 04/2012; 50(2):289-297. · 2.91 Impact Factor
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ABSTRACT: We performed a field trial to evaluate the response of different poplar clones to heavy metals. We found that poplar plants of the same clone, propagated by cuttings, had a marked variability of survival and growth in different zones of the field that were characterized by very similar physical-chemical prosperities. Since metal uptake and its accumulation by plants can be affected by soil microorganisms, we investigated soil microbial populations that were collected in proximity to the roots of large and small poplar plants. We used microbiological and molecular tools to ascertain whether bacterial strains or species were associated with large, or small poplars, and whether these were different from those present in the bulk (without plants) soil. We found that the culturable fraction of the bacteria differed in the three cases (bulk soil, small or large poplars). While some taxa were always present, two species (Chryseobacterium soldanellicola and Variovorax paradoxus) were only found in the soil where poplars (large or small) were growing, independently from the plant size. Bacterial strains of the genus Flavobacterium were prevalent in the soil with large poplar plants. The existence of different microbial populations in the bulk and in the poplar grown soils was confirmed by the DGGE profiles of the bacterial culturable fractions. Cluster analysis of the DGGE profiles highlighted the clear separation of the culturable fraction from the whole microbial community. The isolation and identification of poplar-associated bacterial strains from the culturable fraction of the microbial community provided the basis for further studies aimed at the combined use of plants and soil microorganisms in the remediation of heavy metal polluted soils.
Science of The Total Environment 04/2012; 425:262-70. · 3.29 Impact Factor
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ABSTRACT: Arbuscular mycorrhizal (AM) fungi establish a mutualistic symbiosis with the roots of most plant species. While receiving photosynthates, they improve the mineral nutrition of the plant and can also increase its tolerance towards some pollutants, like heavy metals. Although the fungal symbionts exclusively colonize the plant roots, some plant responses can be systemic. Therefore, in this work a clone of Populus alba L., previously selected for its tolerance to copper and zinc, was used to investigate the effects of the symbiosis with the AM fungus Glomus intraradices on the leaf protein expression. Poplar leaf samples were collected from plants maintained in a glasshouse on polluted (copper and zinc contaminated) or unpolluted soil, after four, six and sixteen months of growth. For each harvest, about 450 proteins were reproducibly separated on 2DE maps. At the first harvest the most relevant effect on protein modulation was exerted by the AM fungi, at the second one by the metals, and at the last one by both treatments. This work demonstrates how importantly the time of sampling affects the proteome responses in perennial plants. In addition, it underlines the ability of a proteomic approach, targeted on protein identification, to depict changes in a specific pattern of protein expression, while being still far from elucidating the biological function of each protein.
PLoS ONE 01/2012; 7(6):e38662. · 4.09 Impact Factor
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ABSTRACT: We have isolated a cDNA clone, Le-MI-13 (Lycopersicon esculentum mycorrhizal induced) by differential screening of a cDNA library prepared from mRNA extracted from tomato roots colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae. The Le-MI-13 clone encodes a polypeptide that shows a high degree of amino acid sequence similarity with members of the recently identified multigene family, the cullins. Northern blot analyses demonstrated that the Le-MI-13 transcript accumulated in tomato roots forming arbuscular mycorrhizal symbiosis. Only very little Le-MI-13 transcript was detected in control roots. Tomato roots infected by the pathogenic fungus Phytophthora nicotianae var. parasitica did not accumulate Le-MI-13 transcript, indicating that upregulation of the Le-MI-13 gene is specific to roots forming arbuscular mycorrhizal symbiosis. Indirect evidence suggesting that a Le-MI-13-mediated cell-cycle-like control might operate in AM-colonized cells came from flow cytometry and static micro fluorimetry analysis. There was a strong correlation between nuclear polyploidization and AM colonization.Key words: tomato, arbuscular mycorrhizae, Phytophthora, cullins, polyploidy.
Canadian Journal of Botany 02/2011; 80(6):607-616. · 1.40 Impact Factor
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ABSTRACT: It is increasingly evident that plant tolerance to stress is improved by mycorrhiza. Thus, suitable plant-fungus combinations may also contribute to the success of phytoremediation of heavy metal (HM)-polluted soil. Metallothioneins (MTs) and polyamines (PAs) are implicated in the response to HM stress in several plant species, but whether the response is modulated by arbuscular mycorrhizal fungi (AMF) remains to be clarified. The aim of the present study was to check whether colonization by AMF could modify growth, metal uptake/translocation, and MT and PA gene expression levels in white poplar cuttings grown on HM-contaminated soil, and to compare this with plants grown on non-contaminated soil.
In this greenhouse study, plants of a Populus alba clone were pre-inoculated, or not, with either Glomus mosseae or G. intraradices and then grown in pots containing either soil collected from a multimetal- (Cu and Zn) polluted site or non-polluted soil. The expression of MT and PA biosynthetic genes was analysed in leaves using quantitative reverse transcription-PCR. Free and conjugated foliar PA concentrations were determined in parallel.
On polluted soil, AMF restored plant biomass despite higher Cu and Zn accumulation in plant organs, especially roots. Inoculation with the AMF caused an overall induction of PaMT1, PaMT2, PaMT3, PaSPDS1, PaSPDS2 and PaADC gene expression, together with increased free and conjugated PA levels, in plants grown on polluted soil, but not in those grown on non-polluted soil.
Mycorrhizal plants of P. alba clone AL35 exhibit increased capacity for stabilization of soil HMs, together with improved growth. Their enhanced stress tolerance may derive from the transcriptional upregulation of several stress-related genes, and the protective role of PAs.
Annals of Botany 11/2010; 106(5):791-802. · 4.03 Impact Factor
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ABSTRACT: Arbuscular mycorrhizae (AM) are the most widespread mutualistic symbioses between the roots of most land plants and a phylum of soil fungi. AM are known to influence plant performance by improving mineral nutrition, protecting against pathogens and enhancing resistance or tolerance to biotic and abiotic stresses. The aim of this study was to investigate the frond proteome of the arsenic hyperaccumulator fern Pteris vittata in plants that had been inoculated with one of the two AM fungi (Glomus mosseae or Gigaspora margarita) with and without arsenic treatment. A protective role for AM fungi colonisation in the absence of arsenic was indicated by the down-regulation of oxidative damage-related proteins. Arsenic treatment of mycorrhizal ferns induced the differential expression of 130 leaf proteins with specific responses in G. mosseae- and Gi. margarita-colonised plants. Up-regulation of multiple forms of glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, and enolase, primarily in G. mosseae-inoculated plants, suggests a central role for glycolytic enzymes in arsenic metabolism. Moreover, a putative arsenic transporter, PgPOR29, has been identified as an up-regulated protein by arsenic treatment.
Proteomics 09/2010; 10(21):3811-34. · 4.43 Impact Factor
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ABSTRACT: The present study addresses the optimization of gemcitabine-cisplatin protocols currently adopted in the clinical management of malignant pleural mesothelioma (MPM), using cell lines derived from different histological subtypes of MPM as an in vitro model.
MPM cell lines were exposed either to single drugs or to their combinations, using a fixed dose ratio. Possible mechanisms for synergistic interactions were investigated by cell cycle analysis, western blot analysis of p53 phosphorylation status, and neutral comet assay to detect double strand breaks.
Four-hour pre-treatment with gemcitabine followed by 68-h exposure to cisplatin was found to exert synergistic activity in both epithelioid and sarcomatoid MPM subtypes, inducing a strong S-phase arrest that correlated with accumulation of double-strand breaks (DSBs).
The antiproliferative effects of the gemcitabine/cisplatin combination in mesothelioma cells can be maximized by pre-treatment with gemcitabine, suggesting that this drug increases cisplatin-induced DSBs by inhibiting DNA adduct repair.
Cancer Chemotherapy and Pharmacology 04/2010; 67(2):265-73. · 2.83 Impact Factor
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Alma Balestrazzi,
Silvia Botti,
Samantha Zelasco,
Stefania Biondi,
Cinzia Franchin,
Paolo Calligari,
Milvia Racchi,
Adelaide Turchi, Guido Lingua,
Graziella Berta,
Daniela Carbonera
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ABSTRACT: Marker-free transgenic white poplar (Populus alba L., cv 'Villafranca') plants, expressing the PsMT (A1) gene from Pisum sativum for a metallothionein-like protein, were produced by Agrobacterium tumefaciens-mediated transformation. The 35SCaMV-PsMT (A1)-NosT cassette was inserted into the ipt-type vector pMAT22. The occurrence of the abnormal ipt-shooty phenotype allowed the visual selection of transformants, while the yeast site-specific recombination R/RS system was responsible for the excision of the undesired vector sequences with the consequent recovery of normal marker-free transgenic plants. Molecular analyses confirmed the presence of the 35SCaMV-PsMT (A1)-NosT cassette and transgene expression. Five selected lines were further characterized, revealing the ability to withstand heavy metal toxicity. They survived 0.1 mM CuCl(2), a concentration which strongly affected the nontransgenic plants. Moreover, root development was only slightly affected by the ectopic expression of the transgene. Reactive oxygen species were accumulated to a lower extent in leaf tissues of multi-auto-transformation (MAT)-PsMT(A1) plants exposed to copper and zinc, compared to control plants. Tolerance to photo-oxidative stress induced by paraquat was another distinctive feature of the MAT-PsMT(A1) lines. Finally, low levels of DNA damage were detected by quantifying the amounts of 8-hydroxy-2'-deoxyguanosine in leaf tissues of the transgenic plants exposed to copper.
Plant Cell Reports 07/2009; 28(8):1179-92. · 2.27 Impact Factor
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ABSTRACT: Heavy metal pollution is a major worldwide environmental concern that has recently motivated researchers to develop a variety of novel approaches towards its cleanup. As an alternative to traditional physical and chemical methods of environmental cleanup, scientists have developed phytoremediation approaches that include the use of plants to remove or render harmless a range of compounds. Both plant growth promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) can be used to facilitate the process of phytoremediation and the growth of plants in metal-contaminated soils. This review focuses on the recent literature dealing with the effects of plant growth-promoting bacteria and AM fungi on the response of plants to heavy metal stress and points the way to strategies that may facilitate the practical realization of this technology.
Canadian Journal of Microbiology 06/2009; 55(5):501-14. · 1.36 Impact Factor
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ABSTRACT: The symbiosis between plant roots and arbuscular mycorrhizal (AM) fungi has been shown to affect both the diversity and productivity of agricultural communities. In this study, we characterized the AM fungal communities of Solanum tuberosum L. (potato) roots and of the bulk soil in two nearby areas of northern Italy, in order to verify if land use practices had selected any particular AM fungus with specificity to potato plants. The AM fungal large-subunit (LSU) rRNA genes were subjected to nested PCR, cloning, sequencing, and phylogenetic analyses. One hundred eighty-three LSU rRNA sequences were analyzed, and eight monophyletic ribotypes, belonging to Glomus groups A and B, were identified. AM fungal communities differed between bulk soil and potato roots, as one AM fungal ribotype, corresponding to Glomus intraradices, was much more frequent in potato roots than in soils (accounting for more than 90% of sequences from potato samples and less than 10% of sequences from soil samples). A semiquantitative heminested PCR with specific primers was used to confirm and quantify the AM fungal abundance observed by cloning. Overall results concerning the biodiversity of AM fungal communities in roots and in bulk soils from the two studied areas suggested that potato roots were preferentially colonized by one AM fungal species, G. intraradices.
Applied and environmental microbiology 10/2008; 74(18):5776-83. · 3.69 Impact Factor
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ABSTRACT: Bacteria producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase modulate plant ethylene levels. Decreased ethylene levels increase plant tolerance to environmental stresses and promote legume nodulation. On the contrary, the role of ethylene in mycorrhizal symbiosis establishment is still controversial. In this work, the ACC deaminase-producing strain Pseudomonas putida UW4 AcdS+ and its mutant AcdS(-), impaired in ACC deaminase synthesis, were inoculated alone or in combination with the AM fungus Gigaspora rosea on cucumber. Mycorrhizal and bacterial colonization as well as plant growth and morphometric parameters were measured. The influence of each microorganism on the photosynthetic efficiency was evaluated on the second and fourth leaf. The strain AcdS+, but not the AcdS(-) mutant, increased AM colonization and arbuscule abundance. The mycorrhizal fungus, but not the bacterial strains, promoted plant growth. However, the AcdS+ strain, inoculated with G. rosea, induced synergistic effects on plant biomass, total root length and total leaf projected area. Finally, the photosynthetic performance index was increased by the strain UW4 AcdS+ inoculated in combination with G. rosea BEG9. These results suggest a key role of this enzyme in the establishment and development of AM symbiosis.
FEMS Microbiology Ecology 07/2008; 64(3):459-67. · 3.41 Impact Factor
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ABSTRACT: The effects of a high concentration of zinc on two registered clones of poplar (Populus alba Villafranca and Populus nigra Jean Pourtet), inoculated or not with two arbuscular mycorrhizal fungi (Glomus mosseae or Glomus intraradices) before transplanting them into polluted soil, were investigated, with special regard to the extent of root colonization by the fungi, plant growth, metal accumulation in the different plant organs, and leaf polyamine concentration. Zinc accumulation was lower in Jean Pourtet than in Villafranca poplars, and it was mainly translocated to the leaves; the metal inhibited mycorrhizal colonization, compromised plant growth, and, in Villafranca, altered the putrescine profile in the leaves. Most of these effects were reversed or reduced in plants pre-inoculated with G. mosseae. Results indicate that poplars are suitable for phytoremediation purposes, confirming that mycorrhizal fungi can be useful for phytoremediation, and underscore the importance of appropriate combinations of plant genotypes and fungal symbionts.
Environmental Pollution 06/2008; 153(1):137-47. · 3.75 Impact Factor
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ABSTRACT: Poplar is a good candidate for phytoremediation purposes because of its rapid growth, extensive root system, and ease of propagation and transformation; however its tolerance to heavy metals has not been fully investigated yet. In the present work, an in vitro model system with shoot cultures was used to investigate the tolerance to high concentrations of zinc (Zn) of a commercial clone (Villafranca) of Populus alba. Based on chlorophyll content (leaf chlorosis) and the rate of adventitious root formation from shoot cuttings as parameters of damage, 0.5-4mM zinc concentrations were all toxic albeit to different extents. Northern blot and reverse transcriptase (RT)-PCR analyses were used to examine the expression profiles of types 1, 2 and 3 PaMT genes in stems, leaves and roots of plants exposed to Zn treatments. In leaves, MT1 and MT3 mRNA levels were enhanced by Zn, while MT2 transcripts were not affected. The PaMT expression profiles were differentially affected by Zn in an organ-specific manner, and the relationship with Zn concentration and exposure time was rarely linear. The developmental and molecular data reveal that the in vitro model is a sensitive and reliable system to study heavy metal stress responses.
Chemosphere 05/2007; 67(6):1117-26. · 3.21 Impact Factor
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ABSTRACT: An in vitro model system of micropropagated shoots of the commercial clone ‘Villafranca’ of Populus alba (L.) was used to investigate polyamine (PA) biosynthesis and accumulation in response to high concentrations of zinc (Zn) and copper (Cu). Based on leaf symptoms, rate of adventitious root formation and ethylene production, 0.5–1 mM Zn was transiently toxic while 2–4 mM Zn concentrations were increasingly toxic. Free and conjugated putrescine and spermidine accumulated in a dose–response manner and proportionally to toxicity. The expression profiles of the PA biosynthetic genes were analysed by reverse transcriptase polymerase chain reaction in plants exposed to Zn. In both leaves and stems, PaADC and PaODC transcript levels were early enhanced by all Zn concentrations, while those of PaSAMDC were not. In adventitious roots, free and conjugated PA levels also rose, although their composition and reciprocal ratios were different from those of leaves and no changes in transcript levels of PA biosynthetic genes were detected. Several Cu concentrations (5–500 μM) were tested in shoots showing severe leaf toxicity, strongly impaired adventitious root formation and high ethylene production. No changes in PA levels were detected until end of culture. The different timing of the PA response to Zn and Cu, despite their rapid uptake and translocation already at 24 h, is discussed in relation to the extent of leaf toxicity.
Physiologia Plantarum 03/2007; 130(1):77 - 90. · 3.11 Impact Factor
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ABSTRACT: The essential oils of basil are widely used in the cosmetic, pharmaceutical, food, and flavoring industries. Little is known about the potential of arbuscular mycorrhizal (AM) fungi to affect their production in this aromatic plant. The effects of colonization by three AM fungi, Glomus mosseae BEG 12, Gigaspora margarita BEG 34, and Gigaspora rosea BEG 9 on shoot and root biomass, abundance of glandular hairs, and essential oil yield of Ocimum basilicum L. var. Genovese were studied. Plant P content was analyzed in the various treatments and no differences were observed. The AM fungi induced various modifications in the considered parameters, but only Gi. rosea significantly affected all of them in comparison to control plants or the other fungal treatments. It significantly increased biomass, root branching and length, and the total amount of essential oil (especially alpha-terpineol). Increased oil yield was associated to a significantly larger number of peltate glandular trichomes (main sites of essential oil synthesis) in the basal and central leaf zones. Furthermore, Gi. margarita and Gi. rosea increased the percentage of eugenol and reduced linalool yield. Results showed that different fungi can induce different effects in the same plant and that the essential oil yield can be modulated according to the colonizing AM fungus.
Mycorrhiza 11/2006; 16(7):485-94. · 2.63 Impact Factor
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ABSTRACT: Aromatic hydrocarbons are pollutants which have mutagenic and carcinogenic properties as well as relatively high hydrosolubility. Their presence in soils makes techniques such as bioremediation an important topic for research. In this work, the effect of arbuscular mycorrhiza (AM) on the persistence of benzene, toluene, ethylbenzene and xylene (BTEX) in artificially contaminated substrates was evaluated. Leek plants were grown with three AM fungal species using a specially designed mesocosm system, in which internal air and substrate samples were analyzed by gas chromatography for BTEX content. Strong reductions in the BTEX concentration in substrates were generally observed in the presence of mycorrhizal plants. Residual BTEX content ranged between nearly total disappearance (<2%) and 40% of the original concentration, whereas there was a high persistence of hydrocarbons in the samples of substrate alone or with non-mycorrhizal plants. These results provide first evidence for an influence of AM activity in reducing pollution of substrates by aromatic hydrocarbons.
Mycorrhiza 01/2006; 16(1):43-50. · 2.63 Impact Factor
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ABSTRACT: The localization, viability, and culturability of Pseudomonas fluorescens 92 rkG5 were analyzed on three morphological root zones (root tip + elongation, root hair, and collar) of 3-, 5-, and 7-day-old tomato plants. Qualitative information about the localization and viability was collected by confocal laser scanning microscopy. Quantitative data concerning the distribution, viability, and culturability were obtained through combined dilution plating and flow cytometry. Colonization by P. fluorescens affected root development in a complex way, causing a general increase in the length of the collar and early stimulation of the primary root growth (3rd day), followed by a reduction in length (7th day). The three root zones showed different distribution, organization, and viability of the bacterial cells, but the distribution pattern within each zone did not change with time. Root tips were always devoid of bacteria, whereas with increasing distance from the apex, microcolonies or strings of cells became more and more prominent. Viability was high in the elongation zone, but it declined in the older parts of the roots. The so-called viable but not culturable cells were observed on the root, and their proportion in the distal (root tip + elongation) zone dramatically increased with time. These results suggest the existence of a specific temporal and spatial pattern of root colonization, related to cell viability and culturability, expressed by the plant-beneficial strain P. fluorescens 92 rkG5.
Microbial Ecology 09/2005; 50(2):289-97. · 2.91 Impact Factor
