Articles de revues : « Alnus-Frankia symbiosis »

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Anne-Emmanuelle, Hay, Boubakri Hasna, Buonomo Antoine, Rey Marjolaine, Meiffren Guillaume, Cotin-Galvan Laetitia, Comte Gilles et Herrera-Belaroussi Aude. « Control of Endophytic Frankia Sporulation by Alnus Nodule Metabolites ». Molecular Plant-Microbe Interactions® 30, n^o 3 (mars 2017) : 205–14. http://dx.doi.org/10.1094/mpmi-11-16-0235-r.

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A unique case of microbial symbiont capable of dormancy within its living host cells has been reported in actinorhizal symbioses. Some Frankia strains, named Sp+, are able to sporulate inside plant cells, contrarily to Sp− strains. The presence of metabolically slowed-down bacterial structures in host cells alters our understanding of symbiosis based on reciprocal benefits between both partners, and its impact on the symbiotic processes remains unknown. The present work reports a metabolomic study of Sp+ and Sp− nodules (from Alnus glutinosa), in order to highlight variabilities associated with in-planta sporulation. A total of 21 amino acids, 44 sugars and organic acids, and 213 secondary metabolites were detected using UV and mass spectrometric–based profiling. Little change was observed in primary metabolites, suggesting that in-planta sporulation would not strongly affect the primary functionalities of the symbiosis. One secondary metabolite (M27) was detected only in Sp+ nodules. It was identified as gentisic acid 5-O-β-d-xylopyranoside, previously reported as involved in plant defenses against microbial pathogens. This metabolite significantly increased Frankia in-vitro sporulation, unlike another metabolite significantly more abundant in Sp− nodules [M168 = (5R)-1,7-bis-(3,4-dihydroxyphenyl)-heptane-5-O-β-d-glucopyranoside]. All these results suggest that the plant could play an important role in the Frankia ability to sporulate in planta and allow us to discuss a possible sanction emitted by the host against less cooperative Sp+ symbionts.

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Markham, John H., et Chris P. Chanway. « Does past contact reduce the degree of mutualism in the Alnus rubra - Frankia symbiosis ? » Canadian Journal of Botany 77, n^o 3 (20 août 1999) : 434–41. http://dx.doi.org/10.1139/b98-227.

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Although most vascular plants have symbiotic relationships with soil microbes, and there is an extensive theoretical literature on the evolution of mutualism, there has been little experimental examination of the evolution of mutualism between plants and their microbial symbionts. We inoculated red alder (Alnus rubra Bong.) seedlings from three high- and three low-elevation populations with crushed nodule suspensions containing the nitrogen fixing bacterium Frankia from either the parent trees (familiar strains) or the other plant population sampled within the parent watershed (unfamiliar strains). The inoculated seedlings were planted on three high- and three low-elevation sites. Growth was monitored over the second and third year following planting, after which the whole plants were harvested. The proportion of nitrogen derived from fixation was estimated from the ratio of stable nitrogen isotopes in the harvested leaves. On low-elevation sites, which had high soil nitrogen, plants with familiar Frankia strains were half the size and derived less fixed nitrogen from their symbionts compared with plants inoculated with unfamiliar Frankia strains. On high-elevation sites, which had low soil nitrogen, the type of inoculum had little effect on plant performance, although plants with familiar inoculum were consistently larger than plants with unfamiliar inoculum. These results suggest that the degree of mutualism in this symbiosis depends on environmental conditions and may decrease with time.Key words: coevolution, Frankia, Alnus rubra, mutualism, nitrogen fixation, symbiosis.

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Pujic, Petar, Nicole Alloisio, Guylaine Miotello, Jean Armengaud, Danis Abrouk, Pascale Fournier et Philippe Normand. « The Proteogenome of Symbiotic Frankia alni in Alnus glutinosa Nodules ». Microorganisms 10, n^o 3 (18 mars 2022) : 651. http://dx.doi.org/10.3390/microorganisms10030651.

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Omics are the most promising approaches to investigate microbes for which no genetic tools exist such as the nitrogen-fixing symbiotic Frankia. A proteogenomic analysis of symbiotic Frankia alni was done by comparing those proteins more and less abundant in Alnus glutinosa nodules relative to N2-fixing pure cultures with propionate as the carbon source. There were 250 proteins that were significantly overabundant in nodules at a fold change (FC) ≥ 2 threshold, and 1429 with the same characteristics in in vitro nitrogen-fixing pure culture. Nitrogenase, SuF (Fe–Su biogenesis) and hopanoid lipids synthesis determinants were the most overabundant proteins in symbiosis. Nitrogenase was found to constitute 3% of all Frankia proteins in nodules. Sod (superoxide dismutase) was overabundant, indicating a continued oxidative stress, while Kats (catalase) were not. Several transporters were overabundant including one for dicarboxylates and one for branched amino acids. The present results confirm the centrality of nitrogenase in the actinorhizal symbiosis.

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Mastronunzio, J. E., Y. Huang et D. R. Benson. « Diminished Exoproteome of Frankia spp. in Culture and Symbiosis ». Applied and Environmental Microbiology 75, n^o 21 (11 septembre 2009) : 6721–28. http://dx.doi.org/10.1128/aem.01559-09.

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ABSTRACT Frankia species are the most geographically widespread gram-positive plant symbionts, carrying out N2 fixation in root nodules of trees and woody shrubs called actinorhizal plants. Taking advantage of the sequencing of three Frankia genomes, proteomics techniques were used to investigate the population of extracellular proteins (the exoproteome) from Frankia, some of which potentially mediate host-microbe interactions. Initial two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of culture supernatants indicated that cytoplasmic proteins appeared in supernatants as cells aged, likely because older hyphae lyse in this slow-growing filamentous actinomycete. Using liquid chromatography coupled to tandem mass spectrometry to identify peptides, 38 proteins were identified in the culture supernatant of Frankia sp. strain CcI3, but only three had predicted export signal peptides. In symbiotic cells, 42 signal peptide-containing proteins were detected from strain CcI3 in Casuarina cunninghamiana and Casuarina glauca root nodules, while 73 and 53 putative secreted proteins containing signal peptides were identified from Frankia strains in field-collected root nodules of Alnus incana and Elaeagnus angustifolia, respectively. Solute-binding proteins were the most commonly identified secreted proteins in symbiosis, particularly those predicted to bind branched-chain amino acids and peptides. These direct proteomics results complement a previous bioinformatics study that predicted few secreted hydrolytic enzymes in the Frankia proteome and provide direct evidence that the symbiosis succeeds partly, if not largely, because of a benign relationship.

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Wall, Luis Gabriel, et Kerstin Huss-Danell. « Regulation of nodulation in Alnus incana-Frankia symbiosis ». Physiologia Plantarum 99, n^o 4 (avril 1997) : 594–600. http://dx.doi.org/10.1111/j.1399-3054.1997.tb05362.x.

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Wall, Luis Gabriel, et Kerstin Huss-Danell. « Regulation of nodulation in Alnus incana-Frankia symbiosis* ». Physiologia Plantarum 99, n^o 4 (avril 1997) : 594–600. http://dx.doi.org/10.1034/j.1399-3054.1997.990411.x.

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Gabbarini, Luciano Andrés, et Luis Gabriel Wall. « Diffusible factors involved in early interactions of actinorhizal symbiosis are modulated by the host plant but are not enough to break the host range barrier ». Functional Plant Biology 38, n^o 9 (2011) : 671. http://dx.doi.org/10.1071/fp11003.

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Nodulation kinetics were analysed in two nitrogen-fixing actinorhizal symbioses that show different pathways for infection: Alnus acuminata H. B. K., which is infected by Frankia ArI3, and Discaria trinervis (Hooker et Arnot) Reiche, which is infected by Frankia BCU110501. Both pairs are incompatible in cross-inoculation experiments. The dose–response effects in nodulation were studied in A. acuminata seedlings using different concentrations of compatible and incompatible bacteria in co-inoculation experiments. Restriction fragment length polymorphism PCR analysis and plant-trapping analysis showed no co-occupation in A. acuminata nodules when plants were co-inoculated with Frankia BCU110501 and Frankia ArI3. Despite the lack of co-occupation, the noninfective BCU110501 could modify the nodulation parameters of the non-host A. acuminata when infective ArI3 was present in the inoculum. The results suggest that although BCU110501 was not able to induce nodulation in A. acuminata, its interaction with the plant could induce autoregulation as if some level of infection or partial recognition could be achieved. We explored the possibility that physiological complementation of the heterologous Frankia BCU110501 for nodulation of A. acuminata originated in the homologous Frankia ArI3 in the presence of compatible root exudates. Despite the possibility of full activation between bacteria and the host, there was no co-infection of Frankia BCU110501 in Alnus or of Frankia ArI3 in Discaria either. These negative results suggest a physical recognition barrier in actinorhizal symbiosis that operates after early interactions, involving something other than root exudates and diffusible factors of bacterial or plant origin, regardless of the infection pathway.

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Clawson, Michael L., Jeffrey Gawronski et David R. Benson. « Dominance ofFrankiastrains in stands ofAlnus incanasubsp.rugosaandMyrica pensylvanica ». Canadian Journal of Botany 77, n^o 9 (18 décembre 1999) : 1203–7. http://dx.doi.org/10.1139/b99-070.

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To address issues of dominance and diversity of Frankia spp. strains, we sequenced 16S rRNA genes from root nodules and strains collected from Alnus incana subsp. rugosa (Du Roi) R.T. Clausen and Myrica pensylvanica Loisel. stands. Of 22 strains isolated previously from A. incana, 16 had the same partial rDNA sequence; the remaining 6 strains composed five additional groups. The groups identified by 16S rDNA analysis corresponded to phenotypic groups established previously by one- and two-dimensional polyacrylamide gel analysis, colony and hyphal morphology, and carbon source utilization patterns. Dominance of one strain was also evident in nodules collected from a single M. pensylvanica stand. The dominant strain had a partial 16S rDNA sequence identical to that of Frankia alni strain CpI1.Key words: Frankia, Myrica, Alnus, actinorhizal, root nodules, nitrogen fixation, symbiosis, 16S rRNA.

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Alloisio, Nicole, Clothilde Queiroux, Pascale Fournier, Petar Pujic, Philippe Normand, David Vallenet, Claudine Médigue, Masatoshi Yamaura, Kentaro Kakoi et Ken-ichi Kucho. « The Frankia alni Symbiotic Transcriptome ». Molecular Plant-Microbe Interactions® 23, n^o 5 (mai 2010) : 593–607. http://dx.doi.org/10.1094/mpmi-23-5-0593.

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The actinobacteria Frankia spp. are able to induce the formation of nodules on the roots of a large spectrum of actinorhizal plants, where they convert dinitrogen to ammonia in exchange for plant photosynthates. In the present study, transcriptional analyses were performed on nitrogen-replete free-living Frankia alni cells and on Alnus glutinosa nodule bacteria, using whole-genome microarrays. Distribution of nodule-induced genes on the genome was found to be mostly over regions with high synteny between three Frankia spp. genomes, while nodule-repressed genes, which were mostly hypothetical and not conserved, were spread around the genome. Genes known to be related to nitrogen fixation were highly induced, nif (nitrogenase), hup2 (hydrogenase uptake), suf (sulfur-iron cluster), and shc (hopanoids synthesis). The expression of genes involved in ammonium assimilation and transport was strongly modified, suggesting that bacteria ammonium assimilation was limited. Genes involved in particular in transcriptional regulation, signaling processes, protein drug export, protein secretion, lipopolysaccharide, and peptidoglycan biosynthesis that may play a role in symbiosis were also identified. We also showed that this Frankia symbiotic transcriptome was highly similar among phylogenetically distant plant families Betulaceae and Myricaceae. Finally, comparison with rhizobia transcriptome suggested that F. alni is metabolically more active in symbiosis than rhizobia.

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Gabbarini, Luciano Andrés, et Luis Gabriel Wall. « Diffusible factors from Frankia modify nodulation kinetics in Discaria trinervis, an intercellular root-infected actinorhizal symbiosis ». Functional Plant Biology 38, n^o 9 (2011) : 662. http://dx.doi.org/10.1071/fp11015.

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Frankia BCU110501 induces nitrogen-fixing root nodules in Discaria trinervis (Gillies ex Hook. & Arn.) Reiche (Rhamnaceae) via intercellular colonisation, without root hair deformation. It produces diffusible factors (DFs) that might be involved in early interactions with the D. trinervis roots, playing a role in the nodulation process. The induction of root nodule development in actinorhizal symbiosis would depend on the concentration of factors produced by the bacteria and the plant. A detailed analysis of nodulation kinetics revealed that these DFs produce changes at the level of initial rate of nodulation and also in nodulation profile. Diluted Frankia BCU110501 inoculum could be activated in less than 96 h by DFs produced by Frankia BCU110501 cells that had been previously washed. Biochemical characterisation showed that Frankia BCU110501 DFs have a molecular weight of <12 kDa, are negatively charged at pH 7.0 and seem to contain a peptide bond necessary for their activity. Frankia BCU110501, belonging to Frankia Clade 3, does not induce nodules in Alnus acuminata H.B.K. ssp. acuminata but is able to deform root hairs, as do Frankia strains from Clade 1. The root hair deforming activity of Frankia BCU110501 DFs show the same biochemical characteristics of the DFs involved in nodulation of D. trinervis. These results suggest that Frankia symbiotic factors have a basic structure regardless of the infection pathway of the host plant.

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Schrader, James A., et William R. Graves. « Nodulation and Growth of Alnus nitida and Alnus maritima Inoculated with Species-specific and Nonspecific Frankia ». Journal of Environmental Horticulture 26, n^o 1 (1 mars 2008) : 29–34. http://dx.doi.org/10.24266/0738-2898-26.1.29.

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Abstract Actinorhizal plants form N2-fixing symbioses with soil-borne bacteria of the genus Frankia. Potential exists for development of sustainable, actinorhizal nursery crops that obtain most of their required N through N2 fixation, but information on host-symbiont specificity, presence of compatible Frankia in soils, and techniques to inoculate during plant production is lacking. Our objectives were to determine the effect of inoculum type and source and the effect of supplemental N on nodulation, growth, and N content of two actinorhizal species, Alnus nitida (Spach) Endl. and Alnus maritima (Marsh.) Muhl. ex Nutt. Plants of both species were subjected to one of four inoculum treatments (two crushed-nodule inocula: species-specific and cross inoculation, and two soil inocula: soil collected beneath native Alnus rubra Bong. in Washington state and native prairie soil from Iowa), were supplied fertilizer with or without N, and were grown in a greenhouse for 22 weeks. Inoculated plants nodulated, grew larger and faster, and accrued greater N content than uninoculated controls in both fertilizer treatments. Plants that received species-specific inoculum grew larger, acquired more dry weight from symbioses, and accumulated higher N content than cross-inoculated plants. Plants of A. nitida inoculated with soil from Washington state grew larger and accumulated more dry weight from symbioses than those inoculated with prairie soil, but A. maritima grew similarly with soil inoculum from both sources. Our results demonstrate that A. nitida and A. maritima can benefit from N2-fixing symbiosis during production and that potential exists for development of superior inocula and inoculation techniques.

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Pawlowski, Katharina, Susan Swensen, Changhui Guan, Az-Eddine Hadri, Alison M. Berry et Ton Bisseling. « Distinct Patterns of Symbiosis-Related Gene Expression in Actinorhizal Nodules from Different Plant Families ». Molecular Plant-Microbe Interactions® 16, n^o 9 (septembre 2003) : 796–807. http://dx.doi.org/10.1094/mpmi.2003.16.9.796.

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Phylogenetic analyses suggest that, among the members of the Eurosid I clade, nitrogen-fixing root nodule symbioses developed multiple times independently, four times with rhizobia and four times with the genus Frankia. In order to understand the degree of similarity between symbiotic systems of different phylogenetic subgroups, gene expression patterns were analyzed in root nodules of Datisca glomerata and compared with those in nodules of another actinorhizal plant, Alnus glutinosa, and with the expression patterns of homologous genes in legumes. In parallel, the phylogeny of actinorhizal plants was examined more closely. The results suggest that, although relationships between major groups are difficult to resolve using molecular phylogenetic analysis, the comparison of gene expression patterns can be used to inform evolutionary relationships. In this case, stronger similarities were found between legumes and intracellularly infected actinorhizal plants (Alnus) than between actinorhizal plants of two different phylogenetic subgroups (Alnus/Datisca).

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Berry, A. M., L. McIntyre et M. E. McCully. « Fine structure of root hair infection leading to nodulation in the Frankia–Alnus symbiosis ». Canadian Journal of Botany 64, n^o 2 (1 février 1986) : 292–305. http://dx.doi.org/10.1139/b86-043.

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Root hair infection by Frankia (Actinomycetales) is the means by which nitrogen-fixing root nodules are initiated upon the actinorhizal host, Alnus rubra. Structural details of the infectious process and the changes in host root hair cells are demonstrated at the prenodule stage for the first time using light and transmission electron microscopy. The Frankia hypha is the infective agent, extending from the rhizosphere through the root hair wall in a highly deformed region of the hair. There is no evidence of pleomorphism of the Frankia hypha. The primary wall fibrils of the root hair appear disorganized at the site of penetration. There is extensive secondary wall formation in the infected hair. At the site of penetration, root hair cell wall ingrowths occur that are structurally consistent with transfer cell wall formation. The ingrowths are continuous with the encapsulating wall layer surrounding the Frankia hypha The host cytoplasm is rich in ribosomes, secretory products, and organelles, including Golgi bodies, mitochondria, plastids, and profiles of endoplasmic reticulum. In an aborted infection sequence, some structural features of the host response to Frankia are observable, while other aspects of successful infection do not occur. Limited transfer cell wall is formed at the site of near infection. The root hair cytoplasm is senescent, however, and a callosic plug appears to surround the pathway of infection.

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Chen, Haoran, Sylvie Renault et John Markham. « The Effect of Frankia and Hebeloma crustiliniforme on Alnus alnobetula subsp. Crispa Growing in Saline Soil ». Plants 11, n^o 14 (16 juillet 2022) : 1860. http://dx.doi.org/10.3390/plants11141860.

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The mining of the oil sands region of Canada’s boreal forest creates disturbed land with elevated levels of salts. Understanding how native plants respond to salt stress is critical in reclaiming these lands. The native species, Alnus alnobetula subsp. crispa forms nitrogen-fixing nodules with Frankia, and ectomycorrhizae with a number of fungal species. These relationships may make the plant particularly well suited for restoring disturbed land. We inoculated A. alnobetula subsp. crispa with Frankia and Hebeloma crustiliniforme and exposed the plants to 0, 50, or 100 mM NaCl for seven weeks. Frankia-inoculated plants had increased biomass regardless of salt exposure, even though salt exposure reduced nitrogen fixation and reduced the efficiency of nitrogen-fixing nodules. The nitrogen-fixing symbiosis also decreased leaf stress and increased root phosphatase levels. This suggests that N-fixing plants not only have increased nitrogen nutrition but also have increased access to soil phosphorus. Mycorrhizae did not affect plant growth but did reduce nodule numbers and nodule efficiency. These results suggest that the nitrogen-fixing trait is more critical than mycorrhizae. While salt stress inhibits nitrogen-fixing symbiosis, plants still benefit from nitrogen fixation when exposed to salt.

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Hay, Anne-Emmanuelle, Aude Herrera-Belaroussi, Marjolaine Rey, Pascale Fournier, Philippe Normand et Hasna Boubakri. « Feedback Regulation of N Fixation in Frankia-Alnus Symbiosis Through Amino Acids Profiling in Field and Greenhouse Nodules ». Molecular Plant-Microbe Interactions® 33, n^o 3 (mars 2020) : 499–508. http://dx.doi.org/10.1094/mpmi-10-19-0289-r.

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Symbiosis established between actinorhizal plants and Frankia spp., which are nitrogen-fixing actinobacteria, promotes nodule organogenesis, the site of metabolic exchange. The present study aimed to identify amino acid markers involved in Frankia-Alnus interactions by comparing nodules and associated roots from field and greenhouse samples. Our results revealed a high level of citrulline in all samples, followed by arginine (Arg), aspartate (Asp), glutamate (Glu), γ-amino-n-butyric acid (GABA), and alanine (Ala). Interestingly, the field metabolome approach highlighted more contrasted amino acid patterns between nodules and roots compared with greenhouse samples. Indeed, 12 amino acids had a mean relative abundance significantly different between field nodule and root samples, against only four amino acids in greenhouse samples, underlining the importance of developing “ecometabolome” approaches. In order to monitor the effects on Frankia cells (respiration and nitrogen fixation activities) of amino acid with an abundance pattern evocative of a role in symbiosis, in-vitro assays were performed by supplementing them in nitrogen-free cultures. Amino acids had three types of effects: i) those used by Frankia as nitrogen source (Glu, Gln, Asp), ii) amino acids stimulating both nitrogen fixation and respiration (e.g., Cit, GABA, Ala, valine, Asn), and iii) amino acids triggering a toxic effect (Arg, histidine). In this paper, a N-metabolic model was proposed to discuss how the host plant and bacteria modulate amino acids contents in nodules, leading to a fine regulation sustaining high bacterial nitrogen fixation.

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Kratsch, Heidi A., et William R. Graves. « Location and Anatomy of Nodules on Alnus maritima Subjected to Flooding ». Journal of the American Society for Horticultural Science 129, n^o 6 (novembre 2004) : 775–80. http://dx.doi.org/10.21273/jashs.129.6.0775.

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Although many species of Alnus Miller grow in wet soils, none is as closely associated with low-oxygen, waterlogged soils as Alnus maritima (Marsh.) Muhl. ex Nutt. (seaside alder). An actinorhizal species with promise for use in horticultural landscapes, land reclamation, and sustainable systems, A. maritima associates with Frankia Brunchorst, thereby forming root nodules in which gaseous nitrogen is fixed. Our objective was to determine how root-zone moisture conditions influence the occurrence, location, and anatomy of nodules on A. maritima. Plants of Alnus maritima subsp. maritima Schrader and Graves were established in root zones with compatible Frankia and subjected to four moisture regimens (daily watered/drained, partially flooded, totally flooded, and totally flooded with argon bubbled through the flood water) for 8 weeks. Oxygen content of the root zone, number and location of nodules on root systems, and dry weight and nitrogen content of shoots were determined. Root-zone oxygen content ranged from 17.3 kPa for daily watered/drained plants to 0.9 kPa for argon-treated plants. Across all treatments, 87% of the nodules were within the upper one-third (4 cm) of the root zone. Although shoot dry weights of daily watered/drained and partially flooded plants were not different, daily watered/drained plants had more nitrogen in their leaves (2.53 vs. 2.21 mg·g-1). Nodulation occurred in all treatments, but nodules on totally flooded roots (with or without argon) were limited to a single lobe; in contrast, multilobed nodules were prevalent on partially flooded and daily watered/drained plants. Frankia infection within submerged nodule lobes was limited to one or two layers of cortical cells. Submerged nodules developed large air spaces between cortical cells, and phenolic-containing cells appeared to inhibit Frankia expansion within the nodule. These data suggest that access to root-zone oxygen is critical to the Frankia-A. maritima subsp. maritima symbiosis, and that plants of this subspecies in the drained soils of managed landscapes may benefit more than plants in native wetland habitats from nodulation and nitrogen fixation.

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Sasakura, Fuyuko, Toshiki Uchiumi, Yoshikazu Shimoda, Akihiro Suzuki, Katsumi Takenouchi, Shiro Higashi et Mikiko Abe. « A Class 1 Hemoglobin Gene from Alnus firma Functions in Symbiotic and Nonsymbiotic Tissues to Detoxify Nitric Oxide ». Molecular Plant-Microbe Interactions® 19, n^o 4 (avril 2006) : 441–50. http://dx.doi.org/10.1094/mpmi-19-0441.

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Actinorhizal symbiosis is as important in biological nitrogen fixation as legume-rhizobium symbiosis in the global nitrogen cycle. To understand the function of hemoglobin (Hb) in actinorhizal symbiosis, we characterized a Hb of Alnus firma, AfHb1. A cDNA that encodes nonsymbiotic Hb (nonsym-Hb) was isolated from a cDNA library of A. firma nodules probed with LjHb1, a nonsym-Hb of Lotus japonicus. No homolog of symbiotic Hb (sym-Hb) could be identified by screening in the cDNA library or by polymerase chain reaction (PCR) using degenerate primers for other sym-Hb genes. The deduced amino acid sequence of AfHb1 showed 92% sequence similarity with a class 1 nonsym-Hb of Casuarina glauca. Quantitative reverse transcriptase-PCR analysis showed that AfHb1 was expressed strongly in the nodules and enhanced expression was detected under cold stress but not under hypoxia or osmotic stress. Moreover, AfHb1 was strongly induced by the application of nitric oxide (NO) donors, and the application of a NO scavenger suppressed the effect of NO donors. Acetylene reduction was strongly inhibited by the addition of NO donors. AfHb1 may support the nitrogen fixation ability of members of the genus Frankia as a NO scavenger.

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Bélanger, Pier-Anne, Jean-Philippe Bellenger et Sébastien Roy. « Strong modulation of nutrient distribution in Alnus glutinosa as a function of the actinorhizal symbiosis ». Botany 91, n^o 4 (avril 2013) : 218–24. http://dx.doi.org/10.1139/cjb-2012-0184.

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Micro- and macro-nutrient acquisition by plants and microorganisms is a cornerstone for their survival and has a direct impact on biogeochemical cycling. In this study, we investigated, in controlled conditions, how the availability of exogenous nitrate impacted nutrient acquisition and distribution in black alder (Alnus glutinosa (L.) Gaertn.) in the presence, or absence, of its nitrogen-fixing bacterial symbiont (Frankia sp.). Our findings show that alder physiology and distribution of nutrients between aerial and root tissues were strongly influenced by the presence of the symbiont. In both nodulated and non-nodulated alders, root allocation and total plant biomass were positively correlated, except when nodulated alders were subjected to low nitrate conditions (≤15 ppm). Alders receiving 45 ppm exogenous nitrate had a less developed actinorhizal symbiosis. These findings reflect the importance of root exploration in relation to plant dependence to exogenous nitrate. Nutrient composition of alder aerial tissues, in particular molybdenum, was significantly altered in the presence of Frankia. In the context of plant leaf-litter mutualism involving metals and N exchange, our findings of high Mo and P translocation to shoots of non-nodulated alders underscores how the state of the symbiosis in actinorhizal plants can influence the biogeochemical cycling of elements.

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Lundquist, Per-Olof, et Kerstin Huss-Danell. « Response of nitrogenase to altered carbon supply in a Frankia-Alnus incana symbiosis ». Physiologia Plantarum 83, n^o 3 (novembre 1991) : 331–38. http://dx.doi.org/10.1111/j.1399-3054.1991.tb00102.x.

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Lundquist, Per-Olof, et Kerstin Russ-Danell. « Response of nitrogenase to altered carbon supply in a Frankia-Alnus incana symbiosis ». Physiologia Plantarum 83, n^o 3 (novembre 1991) : 331–38. http://dx.doi.org/10.1034/j.1399-3054.1991.830301.x.

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Weber, Assi, Mervi-Leena Sarsa et Veronica Sundman. « Frankia-Alnus incana symbiosis : Effect of endophyte on nitrogen fixation and biomass production ». Plant and Soil 120, n^o 2 (décembre 1989) : 291–97. http://dx.doi.org/10.1007/bf02377079.

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Sellstedt, A. « Acetylene reduction, H2 evolution and 15N2 fixation in the Alnus incana-Frankia symbiosis ». Planta 167, n^o 3 (mars 1986) : 382–86. http://dx.doi.org/10.1007/bf00391343.

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Vergnaud, L., A. Chaboud, Y. Prin et M. Rougier. « Preinfection events in the establishment of Alnus-Frankia symbiosis : Development of a spot inoculation technique ». Plant and Soil 87, n^o 1 (février 1985) : 67–78. http://dx.doi.org/10.1007/bf02277649.

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Lundquist, Per-Olof, et Kerstin Huss-Danell. « Nitrogenase Activity and Amounts of Nitrogenase Proteins in a Frankia-Alnus incana Symbiosis Subjected to Darkness ». Plant Physiology 95, n^o 3 (1 mars 1991) : 808–13. http://dx.doi.org/10.1104/pp.95.3.808.

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Kratsch*, Heidi A., et William R. Graves. « Adaptations of Alnus maritima Nodules to Low Oxygen in the Root Zone ». HortScience 39, n^o 4 (juillet 2004) : 892D—892. http://dx.doi.org/10.21273/hortsci.39.4.892d.

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Alnus maritima (Marsh.) Muhl. ex Nutt. is unique among alders in its degree of preference for low-oxygen soils of wetlands. An actinorhizal species with promise for use in sustainable horticulture, A. maritima develops a root-nodule symbiosis with nitrogen-fixing Frankia. Nodules of other actinorhizal species that are obligate wetland natives are adapted to low oxygen, and expression of hemoglobin is common to these taxa. Our objectives were to determine the range of oxygen tension under which Alnus maritima subsp. maritima fixes nitrogen and to investigate a potential role for hemoglobin in adaptation of nodules to low oxygen. Roots of plants, cultured aeroponically, were subjected to eight oxygen tensions from 0 to 32 kPa. After four weeks, plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate were measured. In addition, nodules were assayed spectrophotometrically for the presence of hemoglobin. A quadratic function best described the influence of oxygen on plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate with maximal values above 20 kPa. Alnus serrulata (Ait.) Willd. is sympatric with A. maritima subsp. maritima but is not an obligate inhabitant of wetlands. In a separate experiment, we found higher nitrogenase activity in A. maritima subsp. maritima than in A. serrulata (0.74 vs. 0.26 μmol/h per plant) at hypoxic oxygen tensions. Further, optical absorption spectra of nodule extracts confirmed hemoglobin within nodules of A. maritima subsp. maritima. Our data suggest that hemoglobin contributes to oxygen regulation in nodules of A. maritima subsp. maritima.

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Markham, John H., et Chris P. Chanway. « Does past contact reduce the degree of mutualism in the Alnus rubra - Frankia symbiosis ? » Canadian Journal of Botany 77, n^o 3 (1999) : 434–41. http://dx.doi.org/10.1139/cjb-77-3-434.

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Bissonnette, C., B. Fahlman, K. M. Peru, D. P. Khasa, C. W. Greer, J. V. Headley et S. Roy. « Symbiosis with Frankia sp. benefits the establishment of Alnus viridis ssp. crispa and Alnus incana ssp. rugosa in tailings sand from the Canadian oil sands industry ». Ecological Engineering 68 (juillet 2014) : 167–75. http://dx.doi.org/10.1016/j.ecoleng.2014.03.061.

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Lopez, Mary F., Patricia Young et John G. Torrey. « A comparison of carbon source utilization for growth and nitrogenase activity in two Frankia isolates ». Canadian Journal of Microbiology 32, n^o 4 (1 avril 1986) : 353–58. http://dx.doi.org/10.1139/m86-068.

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The carbon source requirements for the growth and nitrogen fixation of two morphologically distinct Frankia isolates were examined. Isolate ArI3 (from Alnus rubra) grew well on propionate, malate, acetate, and trehalose, and isolate CcI2 (from Casuarina cunninghamiana) grew best on pyruvate, acetate, and propionate. In general, the same carbon sources that supported growth supported both the development of vesicles and nitrogenase activity in long-term induction experiments in both isolates. However, ArI3 cultures induced on proprionate had 7 to 26 times the activity of other carbon sources and ArI3 cultures induced on acetate did not develop any detectable acetylene reduction. In a parallel set of experiments, cultures of both isolates were induced for nitrogenase activity on propionate and the resulting nitrogen fixing cultures were washed free of the organic acid by centrifugation. The washed cultures were incubated in the presence of various carbon sources to determine the ability of a particular substrate to supply energy directly for nitrogen fixation when vesicles and nitrogenase were already present. As was observed in the long-term induction experiments, pyruvate, propionate, and acetate supported the greatest activity in CcI2. Succinate and malate supported the greatest activity in ArI3, and propionate had very little stimulation of acetylene reduction. The reason for the lack of stimulation by propionate for washed cells of ArI3 was unclear but may have been due to toxic concentrations of the organic acid. In an attempt to compare the carbon utilization of ArI3 in pure culture with that in the alder symbiosis, oxygen uptake in the presence of various carbon sources of vesicles clusters isolate from Alnus rubra nodules inoculated with ArI3 was compared with the oxygen uptake of nitrogen-fixing pure cultures of ArI3. The oxygen uptake of the isolated vesicle clusters was stimulated by sucrose, trehalose, and glucose, but not by a variety of organic acids. In comparison, nitrogen-fixing pure cultures of ArI3 readily oxidized sugars and organic acids.

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Cérémonie, Hélène, Frédéric Debellé et Maria P. Fernandez. « Structural and functional comparison of Frankia root hair deforming factor and rhizobia Nod factor ». Canadian Journal of Botany 77, n^o 9 (18 décembre 1999) : 1293–301. http://dx.doi.org/10.1139/b99-060.

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The infectious processes of the Frankia-Alnus and Rhizobium-legume symbioses present strong similarities, suggesting the existence of analogies between Frankia root hair deforming factor and rhizobia Nod factors. Biochemical and functional analogies were tested using ACoN24d Frankia strain. The putative chitin-like nature of the Frankia deforming factor was explored by (i) gas chromatography coupled to mass spectrometry and thin layer chromatography, after radioactive labeling of the culture for detection of chitin oligomers, and (ii) following the root hair deforming activity of the supernatant after discriminating treatments (temperature, chitinase, butanol extraction). In parallel, the functional analogy was questioned by testing the mitotic activity of the Frankia supernatant onAlnus glutinosa (L.) roots. The implication in the symbiotic process of the Frankia factor was indirectly explored by testing the effect of a nodulation inhibitor (combined nitrogen) on root hair deformation. The studies of the combined nitrogen effect on root hair deformation indicate that the deformation induced in vitro by the Frankia factor is linked to the symbiotic process. Moreover, the various approaches used suggest that rhizobia Nod factors and Frankia root hair deforming factor are two structurally divergent symbiotic factors. However, functionnal differences between Frankia root hair factor and the Nod factors have to be confirmed.Key words: Frankia, root hair deforming factor, Nod factor, actinorhizal plants.

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Markham, John H. « Variability of nitrogen-fixing Frankia on Alnus species ». Botany 86, n^o 5 (mai 2008) : 501–10. http://dx.doi.org/10.1139/b08-023.

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Plants maintain mutualistic symbioses with multiple symbiont genotypes that differ in the benefits they provide. To investigate differences in the effect of nitrogen-fixing Frankia on Alnus species, spore-producing (sp+) nodules from Alnus rubra Bong. and Alnus incana subsp. rugosa (Du Roi) Clausen and non-spore-producing (sp–) nodules from Alnus viridis subsp. crispa (Ait.) Turrill, A. rubra, and A. incana subsp. rugosa were collected from each of four different populations and used to inoculate all three Alnus species. As expected, sp+ Frankia produced significantly more nodules on all three species. However, A. crispa, which normally does not have sp+ nodules in the field, was more susceptible to a high level of infection by sp+ Frankia in general, and by any source of sp+ Frankia in particular, whereas A. incana subsp. rugosa, which has the highest abundance of sp+ in the field, was less susceptible to high levels of infection. This suggests that A. incana subsp. rugosa develops resistance to high levels of infection. The infectivity of an sp+ Frankia source on A. viridis subsp. crispa and A. rubra was positively correlated with the proportion of sp+ nodules on the site it was collected from, suggesting that the variation in the abundance of sp+ in the field is caused by sp+ Frankia with different levels of infectivity. There was no effect of Frankia sources on nodule allocation. Plant growth was positively correlated with the specific nodule mass and the specific nodule activity, and negatively correlated with the nodule number per plant. Sp+ Frankia resulted in significantly smaller plants in A. rubra. While there was no overall sp+ type effect on the growth of A. viridis subsp. crispa, the largest plants always resulted when they were inoculated with sp–, and the smallest with sp+ Frankia. Neither spore type nor inoculum source had any effect on the performance of A. rugosa. These results suggest that Alnus species remain susceptible to infection by both Frankia spore types, but are able to modulate the effectiveness of these spore types when they are the common symbionts in the field.

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Higgins, Logan Massie, et Peter Gault Kennedy. « Symbiotic Frankia bacteria in Alnus forests in Mexico and the United States of America : is geographic location a good predictor of assemblage structure ? » Botany 90, n^o 6 (juin 2012) : 423–31. http://dx.doi.org/10.1139/b2012-006.

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While the biogeography of Alnus species is well characterized, that of their microbial symbionts remains less well understood. Little is known, for example, about how the genotypic richness of Alnus-associated Frankia bacteria varies at the continental scale, and the richness of Alnus-associated Frankia at tropical latitudes has yet to be explored. In this study, we conducted sequence-based analyses of the nifH gene comparing Frankia found in root nodules of two Alnus species in central Mexico with those associated with two Alnus species in the northwestern United States of America (USA). Similar to Frankia assemblages in northwestern USA and other geographic locations, genotypic richness within the Mexican samples was low, with five genotypes total using a ≥97% nifH sequence similarity cutoff. The vast majority of Mexican sequences belonged to genotypes also very common in northwestern USA Alnus forests, although two novel Mexican genotypes were identified. Phylogenetic analyses confirmed that all of the genotypes present in Mexico belong to larger clades of Alnus-associated Frankia. Genotype- and distance-based community analyses indicated that neither geographic location nor the phylogenetic relationships among hosts are strong predictors of Frankia assemblage structure. Our results suggest that factors other than classic biogeography are more influential in determining the continental-scale distribution and diversity of Alnus-associated Frankia.

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Batzli, Janet McCray, Jeff F. Zimpfer, Valérie Huguet, Charles A. Smyth, Maria Fernandez et Jeffrey O. Dawson. « Distribution and abundance of infective, soilborne Frankia and host symbionts Shepherdia, Alnus, and Myrica in a sand dune ecosystem ». Canadian Journal of Botany 82, n^o 5 (1 mai 2004) : 700–709. http://dx.doi.org/10.1139/b04-044.

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We describe presence, abundance, and distribution of three sympatric nitrogen-fixing shrubs and their symbiotic diazatroph, Frankia, in a sand dune ecosystem differing in successional stage, vegetative cover, edaphic characteristics, and topography. Distribution of actinorhizal Myrica gale L., Alnus incana (L.) Moench subsp. rugosa (Du Roi) Clausen, and Shepherdia canadensis (L.) Nutt. was analyzed among 120 sampling locations representing a gradient of successional stages in a sand dune system along Lake Michigan. In a greenhouse study, seedlings of these species were employed to bioassay the presence and abundance of infective Frankia in soils. Shepherdia-infective Frankia was detected in 80% of the plots, while Alnus- and Myrica-infective Frankia were found in 65% and 64% of the plots, respectively, with no Frankia found in 18% of the plots. Only 14% of the plots supported actinorhizal host-plant species. Infective Frankia were present in soils of young dunes prior to the establishment of any actinorhizal hosts. Shepherdia-infective Frankia were more abundant in soils from drier, earlier successional sites, while Alnus- and Myrica-infective Frankia were more abundant in moister soils of later successional communities. A previous study had revealed that nodular Frankia strains at this site were host specific for Shepherdia and largely so for Myrica and Alnus, which had only a small proportion of shared strains (Huguet et al. 2001). The likelihood of host-plant nodulation by soilborne Frankia was increased by the presence of actinorhizal plants in general, but not by the presence of their respective specific host plants. Submerged soils had no infectious capacity, whereas soils with greater in situ moisture content and soils subject to intermittent saturation tended to have lower infectious capacities overall. Our results suggest that soilborne, infective Frankia genotypes are not only host specific, but are also associated with spatially and chronologically distinct sets of ecological conditions.Key words: speckled alder, sweet gale, Canada buffalo berry, actinorhizal, nitrogen fixation, Frankia, root nodules.

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Laplaze, Laurent, Ana Ribeiro, Claudine Franche, Emile Duhoux, Florence Auguy, Didier Bogusz et Katharina Pawlowski. « Characterization of a Casuarina glauca Nodule-Specific Subtilisin-like Protease Gene, a Homolog of Alnus glutinosa ag12 ». Molecular Plant-Microbe Interactions® 13, n^o 1 (janvier 2000) : 113–17. http://dx.doi.org/10.1094/mpmi.2000.13.1.113.

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In search of plant genes expressed during early interactions between Casuarina glauca and Frankia, we have isolated and characterized a C. glauca gene that has strong homology to subtilisin-like protease gene families of several plants including the actinorhizal nodulin gene ag12 of another actinorhizal plant, Alnus glutinosa. Based on the expression pattern of cg12 in the course of nodule development, it represents an early actinorhizal nodulin gene. Our results suggest that subtilisin-like proteases may be a common element in the process of infection of plant cells by Frankia in both Betulaceae (Alnus glutinosa) and Casuarinaceae (Casuarina glauca) symbioses.

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Hammad, Y., J. Maréchal, B. Cournoyer, P. Normand et A. M. Domenach. « Modification of the protein expression pattern induced in the nitrogen-fixing actinomyceteFrankiasp. strain ACN14a-tsr by root exudates of its symbiotic hostAlnus glutinosaand cloning of thesodFgene ». Canadian Journal of Microbiology 47, n^o 6 (1 juin 2001) : 541–47. http://dx.doi.org/10.1139/w01-046.

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Two-dimensional (2-D) polyacrylamide gel electrophoresis was used to detect proteins induced in Frankia sp. strain ACN14a-tsr by root exudates of its symbiotic host, Alnus glutinosa. The 5 most prominent proteins were purified from 2-D gels and characterized by N-terminal sequencing. All of these proteins had a high percentage of similarity with known stress proteins. One protein match was the Fe superoxide dismutase (Fe-SOD), another was a tellurite resistance protein (Ter), the third was a bacterioferritin comigratory protein (Bcp); and two matches, differing only by their isoelectric point, were the same small heat shock protein (Hsp), a major immune reactive protein found in mycobacteria. This suggests that the symbiotic microorganism Frankia, first responds with a normal stress response to toxic root products of its symbiotic host plant. To confirm its identity, the gene corresponding to the Fe-SOD protein, sodF was isolated from a genomic library by a PCR-approach and sequenced. It is the first stress response gene characterized in Frankia.Key words: Frankia, Alnus glutinosa, root-exudates, superoxide dismutase, tellurite resistance, bacterioferritin comigratory protein, heat shock protein.

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Abeysekera, R. M., William Newcomb, W. B. Silvester et John G. Torrey. « A freeze-fracture electron microscopic study of Frankia in root nodules of Alnus incana grown at three oxygen tensions ». Canadian Journal of Microbiology 36, n^o 2 (1 février 1990) : 97–108. http://dx.doi.org/10.1139/m90-019.

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Nodulated plants of Alnus incana ssp. rugosa and ssp. incana were grown with the roots exposed to 5, 21, and 40 kPa O2. The nodules were studied by freeze-fracture transmission electron microscopy to determine the effect of varying O2 tension on the numbers of lipid laminae in the Frankia envelope. Lipid laminae were present in the cell envelopes of hyphae, stalks, and symbiotic vesicles. The mean number of lipid laminae in hyphal envelopes varied from five to nine. Stalks of symbiotic vesicles contained mean numbers of 35–59 lipid laminae over the range of pO2's studied. Symbiotic vesicle envelopes showed mean numbers of lipid laminae varying from 48 to 94. The numbers of lipid laminae were observed to increase significantly in the distal regions of the symbiotic vesicles in response to raised pO2 while the numbers on the proximal portions remained unchanged. The increase in the numbers of lipid laminae in response to raised pO2 was not sufficient to account for the expected increase in resistance to O2 required at the symbiotic vesicle envelope if lipid laminae formed the exclusive diffusion barrier to O2. These results suggest that lipid laminae surrounding symbiotic vesicles may not constitute the only O2 protection mechanism in Alnus nodules. Key words: Alnus incana, Frankia, nitrogen fixation, actinorhizal nodules, Actinomycetes.

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Vikman, Per-Åke. « The symbiotic vesicle is a major site for respiration in Frankia from Alnus incana root nodules ». Canadian Journal of Microbiology 38, n^o 8 (1 août 1992) : 779–84. http://dx.doi.org/10.1139/m92-127.

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A technique was developed for preparation of Frankia symbiotic vesicles, free of hyphae. The symbiotic vesicles were isolated by isopycnic centrifugation of disrupted Frankia vesicle clusters prepared from root nodules of Alnus incana (L.) Moench. Activities in symbiotic vesicles were compared with activities in intact symbiotic vesicle clusters on a total protein basis. Respiratory capacity was tested with 6-phosphogluconate, malate + glutamate, and NADH as added substrates. With all three substrates, specific respiration was doubled after symbiotic vesicle isolation. Nitrogenase was used as a symbiotic vesicle specific marker and its specific activity increased similarly to respiration. Activities of four respiratory enzymes were assayed on crude cell-free extracts obtained after sonication of symbiotic vesicle preparations. According to the increased specific rates after symbiotic vesicle isolation, NAD+:6-phosphogluconate dehydrogenase (EC 1.1.1.44) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) were mainly localized in symbiotic vesicles. NAD+:malate dehydrogenase (EC 1.1.1.37) and glutamate-oxaloacetate transaminase (EC 2.6.1.1) were also present in symbiotic vesicles, but their specific activities were not increased compared with the symbiotic vesicle clusters. The magnitude of increased activities suggested that the symbiotic vesicle is a major site for hexose respiration in symbiotic Frankia. An apparent Km for O2 between 20 and 30 μM indicated that symbiotic vesicles in symbiotic vesicle clusters have a restricted oxygen diffusion rate. Key words: Frankia, symbiotic vesicles, respiration, nitrogenase, oxygen diffusion.

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Domenach, A. M., et F. Kurdali. « Influence des réserves azotées sur la formation des feuilles d’Alnus glutinosa et ses conséquences dans l'estimation de la fixation d'azote ». Canadian Journal of Botany 67, n^o 3 (1 mars 1989) : 865–71. http://dx.doi.org/10.1139/b89-116.

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The influence of nitrogen reserves on leaf formation of 5- to 6-year-old plants of Alnus glutinosa (L.) Gaertn. was investigated using a 15N labelling method. Nitrogen reserves were derived essentially from the root system and along with N fixation by Frankia, supported the growth of the young leaves. The reserves represent 10% of the total nitrogen in the leaves at the end of the growing period under natural or environmentally controlled conditions. The percentage of fixed nitrogen in alder leaves was estimated to be 87% taking into account the nitrogen reserves and using the isotopic comparison with a nonfixing plant (Populus alba L.). Several conditions requiring the use of 15N methods to estimate the symbiotic nitrogen fixation by Frankia were formulated. The selection of samples for analysis must be from the most recently formed leaves at the end of the growing season to avoid the influence of nitrogenous reserves. Key words: nitrogen reserves, Alnus glutinosa, Populus alba, Frankia, 15N fixation.

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Roy, Melanie, Adrien C. Pozzi, Raphaëlle Gareil, Melissande Nagati, Sophie Manzi, Imen Nouioui, Nino Sharikadze et al. « Alder and the Golden Fleece : high diversity of Frankia and ectomycorrhizal fungi revealed from Alnus glutinosa subsp. barbata roots close to a Tertiary and glacial refugium ». PeerJ 5 (18 juillet 2017) : e3479. http://dx.doi.org/10.7717/peerj.3479.

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Background Recent climatic history has strongly impacted plant populations, but little is known about its effect on microbes. Alders, which host few and specific symbionts, have high genetic diversity in glacial refugia. Here, we tested the prediction that communities of root symbionts survived in refugia with their host populations. We expected to detect endemic symbionts and a higher species richness in refugia as compared to recolonized areas. Methods We sampled ectomycorrhizal (EM) root tips and the nitrogen-fixing actinomycete Frankia communities in eight sites colonized by Alnus glutinosa subsp. barbata close to the Caucasus in Georgia. Three sites were located in the Colchis, one major Eurasian climatic refugia for Arcto-Tertiary flora and alders, and five sites were located in the recolonized zone. Endemic symbionts and plant ITS variants were detected by comparing sequences to published data from Europe and another Tertiary refugium, the Hyrcanian forest. Species richness and community structure were compared between sites from refugia and recolonized areas for each symbionts. Results For both symbionts, most MOTUs present in Georgia had been found previously elsewhere in Europe. Three endemic Frankia strains were detected in the Colchis vs two in the recolonized zone, and the five endemic EM fungi were detected only in the recolonized zone. Frankia species richness was higher in the Colchis while the contrary was observed for EM fungi. Moreover, the genetic diversity of one alder specialist Alnicola xanthophylla was particularly high in the recolonized zone. The EM communities occurring in the Colchis and the Hyrcanian forests shared closely related endemic species. Discussion The Colchis did not have the highest alpha diversity and more endemic species, suggesting that our hypothesis based on alder biogeography may not apply to alder’s symbionts. Our study in the Caucasus brings new clues to understand symbioses biogeography and their survival in Tertiary and ice-age refugia, and reveals that isolated host populations could be of interest for symbiont diversity conservation.

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Pozzi, Adrien C. Meynier, Aude Herrera-Belaroussi, Guillaume Schwob, Hector H. Bautista-Guerrero, Lorine Bethencourt, Pascale Fournier, Audrey Dubost, Danis Abrouk, Philippe Normand et Maria P. Fernandez. « Proposal of 'Candidatus Frankia alpina', the uncultured symbiont of Alnus alnobetula and A. incana that forms spore-containing nitrogen-fixing root nodules ». International Journal of Systematic and Evolutionary Microbiology 70, n^o 10 (1 octobre 2020) : 5453–59. http://dx.doi.org/10.1099/ijsem.0.004433.

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The members of the genus Frankia are, with a few exceptions, a group of nitrogen-fixing symbiotic actinobacteria that nodulate mostly woody dicotyledonous plants belonging to three orders, eight families and 23 genera of pioneer dicots. These bacteria have been characterized phylogenetically and grouped into four molecular clusters. One of the clusters, cluster 1 contains strains that induce nodules on Alnus spp. (Betulaceae), Myrica spp., Morella spp. and Comptonia spp. (Myricaceae) that have global distributions. Some of these strains produce not only hyphae and vesicles, as other cluster 1 strains do, but also numerous sporangia in their host symbiotic tissues, hence their phenotype being described as spore-positive (Sp+). While Sp+ strains have resisted repeated attempts at cultivation, their genomes have recently been characterized and found to be different from those of all described species, being markedly smaller than their phylogenetic neighbours. We thus hereby propose to create a 'Candidatus Frankia alpina' species for some strains present in nodules of Alnus alnobetula and A. incana that grow in alpine environments at high altitudes or in subarctic environments at high latitudes.

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Domenach, A. M., F. Kurdali, C. Danière et R. Bardin. « Détermination de l'identité isotopique de l'azote fixé par le Frankia associé au genre Alnus ». Canadian Journal of Botany 66, n^o 7 (1 juillet 1988) : 1241–47. http://dx.doi.org/10.1139/b88-177.

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To use the 15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on the Frankia strains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in 15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness of Frankia strains and 15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in 15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.

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Vikman, Per-Ake, et Kerstin Huss-Danell. « Capacity for hexose respiration in symbiotic Frankia from Alnus incana ». Physiologia Plantarum 70, n^o 2 (juin 1987) : 349–54. http://dx.doi.org/10.1111/j.1399-3054.1987.tb06154.x.

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Brunner, I. L., F. Brunner et O. K. Miller Jr. « Ectomycorrhizal synthesis with Alaskan Alnus tenuifolia ». Canadian Journal of Botany 68, n^o 4 (1 avril 1990) : 761–67. http://dx.doi.org/10.1139/b90-101.

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The ability of Alnus tenuifolia to form ectomycorrhizae with potential ectomycorrhizal fungi was investigated. Alnus tenuifolia seedlings raised in growth pouches were inoculated with Frankia to induce nodulation and then with a putative ectomycorrhizal fungus. The fungi used were collected in nearly pure A. tenuifolia stands in Alaska or were found in Alnus nepalensis stands in Nepal. Five species of putative ectomycorrhizal symbionts of alders were tested. Alpova diplophloeus and Paxillus filamentosus formed both mantle and Hartig net. Cortinarius cf. saturninus developed a mantle but no Hartig net. Hebeloma cf. crustuliniforme and Gyrodon lividus developed neither mantle nor Hartig net. This is the first report of synthesis of P. filamentosus and C. cf. saturninus with Alnus. The ectomycorrhizal status of the genus Gyrodon is discussed, since in vitro synthesis has not yet been demonstrated. Synthesis with A. diplophloeus and H. crustuliniforme did not result in ectomycorrhizal formations with nonnodulated alder seedlings.

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Bernèche-D'Amours, Audrey, Mariana Gabriela Ghinet, Julie Beaudin, Ryszard Brzezinski et Sébastien Roy. « Sequence analysis ofrpoBandrpoDgene fragments reveals the phylogenetic diversity of actinobacteria of genus Frankia ». Canadian Journal of Microbiology 57, n^o 3 (mars 2011) : 244–49. http://dx.doi.org/10.1139/w10-106.

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Partial rpoD, rpoB, and 16S rRNA gene sequences were obtained from databases and (or) amplified from 12 strains of Frankia . These strains belonged to either Cluster 1 (Alnus-, Myrica-, Comptonia-, and Casuarina-infective strains) or Cluster 3 (Elaeagnus-infective strain). An rpoD gene-based PCR approach was designed to allow the detection of frankiae in complex samples. Additionally, partial gene sequences obtained using 2 rpoB gene primer sets (named rpoB-1 and rpoB-2) were used to generate phylogenetic eurograms to find a molecular tool able to assess biodiversity among Frankia strains. The rpoB-2 primer set allowed separation of closely related strains and groupings representative of host plant compatibility groups. One exception to this was for strains ACN10a and ACN14a, isolated from the same geographical location. Results obtained showed that rpoB-2 is a tool of great interest to evaluate relatedness of Frankia strains, and assess biodiversity in this genus. Additionally, since rpoB-2 phylogenetic profiles of the Frankia strains studied reflected the species of host plants they were isolated from, the study of rpoB (a house-keeping gene) shows promise for future ecological studies on these symbioses.

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Gentili, Francesco G., et Kerstin Huss-Danell. « The δ15N value of N2 fixing actinorhizal plants and legumes grown with N2 as the only nitrogen source ». Symbiosis 79, n^o 3 (novembre 2019) : 213–19. http://dx.doi.org/10.1007/s13199-019-00650-2.

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AbstractThe aim of this study was to investigate the effects of different plant parts and the age of plants at harvest as well as N2 fixing bacterial strains on the N concentration in symbiotic plant parts, especially on the δ15N signature of the actinorhizal plants and legumes. The 15N natural abundance method was used. Two actinorhizal plants were studied: Alnus incana (L.) infected with the Frankia strains ArI3 or “lsF” (local source of Frankia) and Hippophaë rhamnoides (L.) infected with the Frankia strains T1 or E15b. Two legume species were studied: Hedysarum coronarium (L.), infected with a soil suspension, and Robinia pseudoacacia (L.), infected with a crushed nodule suspension. It was particularly interesting that in A. incana, the two Frankia strains affected not only N concentration and δ15N signature of leaves and roots, but also had an impact on plant growth at first harvest. In Hippophaë rhamnoides plants inoculated with the Frankia strains T1 and E15b, N concentrations and δ15N values did not differ at any harvest time. However, plants nodulated by the Frankia strain T1 showed a higher nitrogen fixation rate and higher plant dry matter at all harvesting times. Based on our results for the quantification of N2 fixation with the “B” value, that is the δ15N value of the N2 fixing plants relying only on N2 fixation, plant parts, ages and strains should be carefully considered.

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Huguet, V., J. M. Batzli, J. F. Zimpfer, F. Gourbière, J. O. Dawson et M. P. Fernandez. « Nodular symbionts ofShepherdia,Alnus, andMyricafrom a sand dune ecosystem : trends in occurrence of soilborneFrankiagenotypes ». Canadian Journal of Botany 82, n^o 5 (1 mai 2004) : 691–99. http://dx.doi.org/10.1139/b04-043.

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A successional sand dune system along the Lake Michigan shoreline was chosen to study the impact of edaphic factors, vegetation cover, and topographic position on Frankia strain distribution and infectivity. On this site, three actinorhizal species, Myrica gale L., Alnus incana (L.) Moench subsp. rugosa (Du Roi) Clausen, and Shepherdia canadensis (L.) Nutt., grew in different communities. Soil samples were collected on plots devoid of actinorhizal plants and serially diluted to inoculate the three native host plants in a greenhouse study. Strains present in the nodules formed were then genetically characterized using PCR-RFLP of the 16S23S intergenic spacer (IGS). An additional study site was included to estimate the impact of the sympatric presence of the three host species on soil infectivity and strain diversity. On this second site, soils used as inocula were collected in the rhizosphere of M. gale and S. canadensis. The M. gale and A. incana nodular strains belonged to an homogeneous cluster, whereas the S. cana densis nodular strains were separated into two distinct genetic clusters, irrespective of edaphic conditions and proximity to the host's root systems. A χ2analysis conducted on Shepherdia-infective strains showed the dominance of two distinct genotypes, with one of them being specific to newly formed dunes lacking plant cover and the other specific to older, stable dunes with dense vegetative cover.Key words: Frankia, Myrica, Shepherdia, Alnus, IGS 16S23S, sand dunes.

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Markham, John H. « The effect of Frankia and Paxillus involutus on the performance of Alnus incana subsp. rugosa in mine tailings ». Canadian Journal of Botany 83, n^o 11 (novembre 2005) : 1384–90. http://dx.doi.org/10.1139/b05-108.

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The purpose of this study was to determine whether symbiotic nitrogen-fixing bacteria and mycorrhizal fungi act synergistically to improve plant performance when grown on heavy metal mine tailings. Seedlings were inoculated with Frankia, Paxillus involutus (Batsch) Fr., or a combination of both and grown in 100% peat, a 1:1 mix of peat and tailings, or 100% tailings for 20 weeks. Mortality of plants grown on pure tailings (15.0%) and peat–tailings (17.9%) was significantly greater than mortality of plants grown on peat (3.5%). The rate of nodulation and mycorrhizae formation decreased from 90.0% and 66.7%, respectively, on the peat, to 11.9% and 2.6% on the tailings. Frankia-inoculated plants grown on peat–tailings showed twice the mortality rate (38.5%) of any other inoculation treatment. Plants grown on media containing tailings had greater root/shoot ratios than plants grown on peat. Inoculating plants grown in the presence of tailings with either Frankia and (or) P. involutus increased root thickness. Inoculating plants with both symbionts increased colonization rates and shoot yield on the peat and peat–tailings media, suggesting that these symbionts act synergistically to improve plant performance. However, inoculating plants with Frankia decreased shoot relative growth rate in the early part of the experiment when plants were not fixing nitrogen, which, coupled with the higher mortality effect, suggests that nodule development is a stress for plants. It may be advisable that plants have fully functioning nodules before transplanting if they are to be used in revegetation programs.

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Rosendahl, Lis, et Kerstin Huss-Danell. « Effects of elevated oxygen tensions on acetylene reduction in Alnus incana-Frankia symbioses ». Physiologia Plantarum 74, n^o 1 (septembre 1988) : 89–94. http://dx.doi.org/10.1111/j.1399-3054.1988.tb04946.x.

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Sellstedt, Anita. « Occurrence and activity of hydrogenase in symbiotic Frankia from field-collected Alnus incana ». Physiologia Plantarum 75, n^o 2 (février 1989) : 304–8. http://dx.doi.org/10.1111/j.1399-3054.1989.tb06186.x.

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Prin, Yves, et Mireille Rougier. « Cytological and histochemical characteristics of the axenic root surface of Alnus glutinosa ». Canadian Journal of Botany 64, n^o 10 (1 octobre 1986) : 2216–26. http://dx.doi.org/10.1139/b86-296.

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The aim of the present study was to investigate the Alnus root surface using seedlings grown axenically. This study has focused on root zones where infection by the symbiotic actinomycete Frankia takes place. The zones examined extend from the root cap to the emerging root hair zone. The root cap ensheaths the Alnus root apex and extends over the root surface as a layer of highly flattened cells closely appressed to the root epidermal cell wall. These cells contain phenolic compounds as demonstrated by various histochemical tests. They are externally bordered by a thin cell wall coated by a thin mucilage layer. The root cap is ruptured when underlying epidermal cells elongate, and cell remnants are still found in the emerging root hair zone. Young emerging root hairs are bordered externally by a cell wall covered by a thin mucilage layer which reacts positively to the tests used for the detection of polysaccharides, glycoproteins, and anionic sites. The characteristics of the Alnus root surface and the biological function of mucilage and phenols present at the root surface are discussed in relation to the infection process.

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Sellstedt, Anita, Kerstin Huss-Danell et Ann-Sofi Ahlqvist. « Nitrogen fixation and biomass production in symbioses between Alnus incana and Frankia strains with different hydrogen metabolism ». Physiologia Plantarum 66, n^o 1 (janvier 1986) : 99–107. http://dx.doi.org/10.1111/j.1399-3054.1986.tb01240.x.

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