Nygren CM, Eberhardt U, Karlsson M, Parrent JL, Lindahl BD, Taylor AF.. Growth on nitrate and occurrence of nitrate reductase-encoding genes in a phylogenetically diverse range of ectomycorrhizal fungi. New Phytol 180: 875-889

Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, PO Box 7026, SE-750 07 Uppsala, Sweden.
New Phytologist (Impact Factor: 7.67). 10/2008; 180(4):875-89. DOI: 10.1111/j.1469-8137.2008.02618.x
Source: PubMed


Ectomycorrhizal (ECM) fungi are often considered to be most prevalent under conditions where organic sources of N predominate. However, ECM fungi are increasingly exposed to nitrate from anthropogenic sources. Currently, the ability of ECM fungi to metabolize this nitrate is poorly understood. Here, growth was examined among 106 isolates, representing 68 species, of ECM fungi on nitrate as the sole N source. In addition, the occurrence of genes coding for the nitrate reductase enzyme (nar gene) in a broad range of ectomycorrhizal fungi was investigated. All isolates grew on nitrate, but there was a strong taxonomic signature in the biomass production, with the Russulaceae and Amanita showing the lowest growth. Thirty-five partial nar sequences were obtained from 43 tested strains comprising 31 species and 10 genera. These taxa represent three out of the four clades of the Agaricales within which ECM fungi occur. No nar sequences were recovered from the Russulaceae and Amanita, but Southern hybridization showed that the genes were present. The results demonstrate that the ability to utilize nitrate as an N source is widespread in ECM fungi, even in those fungi from boreal forests where the supply of nitrate may be very low.

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Available from: Andy FS Taylor, Jan 27, 2014
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    • "Soil fungi from temperate and boreal forests and from agricultural soils show a widespread capacity to grow on NO 3 − (Yamanaka, 1999; Nygren et al., 2008; Gorfer et al., 2011). While the majority of ECM fungi are reported to prefer NH 4 + as an inorganic nitrogen source, the capacity to grow on NO 3 − is also widely distributed among them (Nygren et al., 2008) and some ECM species even prefer NO 3 − over NH 4 + (Scheromm et al., 1990; Aouadj et al., 2000). Most importantly, the ECM interaction can drive the whole nitrogen uptake by the host tree that takes place via the extraradical (ERM) mycelium of the fungal partner (Gobert and Plassard, 2002; Gobert and Plassard , 2007; Guescini et al., 2003; Bailly et al., 2007). "
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    ABSTRACT: Arbuscular mycorrhiza (AM), ectomycorrhiza (ECM) and nitrogen (N) fixation through rhizobia symbioses (RS) play a critical role for plant nutrient use efficiency in natural ecosystems, usually characterized by nutrient limitation, especially regarding nitrogen and phosphate. Substantial evidence has accumulated about how the rational use of microsymbionts’ properties should significantly contribute to decreasing fertilizer and pesticide use in agriculture and forestry. Understanding the mechanisms underlying high N use efficiency by mycorrhizal/rhizobial plants and carbon allocation in a context of mutualistic biotrophic interactions is critical for managing both croplands and forests while taking care of the ecosystem services rendered by microbial symbionts. Availability, uptake and exchange of nutrients in biotrophic interactions drive plant growth and modulate biomass allocation, and these parameters are central to plant yield, a major outcome in the context of high biomass production. To unravel the symbiotic N “transportome” blueprint from various host plant combinations, it is critical to facilitate the first steps favoring the manipulation of crops toward greater nitrogen use efficiency and mycorrhizal or rhizobial ability. The present review addresses current knowledge on inorganic N transport in mycorrhizal/rhizobial symbiosis.
    Critical Reviews in Plant Sciences 06/2015; 34(1-3). DOI:10.1080/07352689.2014.897897 · 5.44 Impact Factor
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    • "Genomic DNA was isolated using a hexadecyltrimethylammonium bromide (CTAB)-based method [53]. Phusion DNA polymerase (Finnzymes, Vantaa, Finland) was used for PCR amplification of a 1 kb 5′-flank and 3′-flank region of the Hyd1, Hyd2 and Hyd3 genes from genomic DNA of C. rosea using primer pairs Hyd1 ko-1 F/1R and Hyd1 ko-2 F/2R; Hyd2 ko-1 F/1R and Hyd2 ko-2 F/2R; and Hyd3 ko-1 F/1R and Hyd3 ko-2 F/2R, respectively (Additional file 1: Table S2). "
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    ABSTRACT: Filamentous fungi produce small cysteine rich surface active amphiphilic hydrophobins on the outer surface of cell walls that mediate interactions between the fungus and the environment. The role of hydrophobins in surface hydrophobicity, sporulation, fruit body formation, recognition and adhesion to host surface and virulence have been reported. The aim of the present study was to characterize the biological function of hydrophobins in the fungal biocontrol agent Clonostachys rosea in order to understand their potential roles in biocontrol mechanisms. Based on the presence of hydrophobin domains, cysteine spacing patterns and hydropathy plots, we identified three class II hydrophobin genes in C. rosea. Gene expression analysis showed basal expression of Hyd1, Hyd2 and Hyd3 in all conditions tested with the exception of induced Hyd1 expression in conidiating mycelium. Interestingly, up-regulation of Hyd1, Hyd2 and Hyd3 was found during C. rosea self interaction compared to interactions with the fungal plant pathogens Botrytis cinerea or Fusarium graminearum in dual culture assays. Phenotypic analysis of C. rosea deletion and complementation strains showed that Hyd1 and Hyd3 are jointly required for conidial hydrophobicity, although no difference in mycelia hydrophobicity was found between wild type (WT) and mutant strains. Interestingly, mutant strains showed increased growth rates, conidiation and enhanced tolerances of conidia to abiotic stresses. Antagonism tests using in vitro dual culture and detached leaf assays showed that the mutant strains were more aggressive towards B. cinerea, F. graminearum or Rhizoctonia solani, and that aggression was partly related to earlier conidial germination and enhanced tolerance of mutant strains to secreted fungal metabolites. Furthermore, in vitro Arabidopsis thaliana root colonization assays revealed reduced root colonization ability of the DeltaHyd3 strain, but not for the DeltaHyd1 strain. Furthermore, enhanced root colonization ability for the DeltaHyd1DeltaHyd3 strain was found in comparison to WT. These results show a role for hydrophobins in conidial hydrophobicity, control of conidial germination under stress conditions, and in root colonization in C. rosea. However, functional studies of Hyd2 remains to be performed in order to fully assess the role of hydrophobins in C. rosea.
    BMC Microbiology 01/2014; 14(1):18. DOI:10.1186/1471-2180-14-18 · 2.73 Impact Factor
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    • "Root colonization was determined by quantifying the DNA level of T. atroviride strains in Ar. thaliana roots using qPCR. DNA was isolated from the root samples as described above using the CTAB method (Nygren et al., 2008), quantified spectrophotometrically using NanoDrop (Thermo Scientific) and 100 ng was used for qPCR analysis. PR-2 was used as the target gene for Ar. "
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    ABSTRACT: Methylcitrate lyase (MCL), the signature enzyme of the methylcitrate cycle that cleaves methylisocitrate to pyruvate and succinate, is required for propionate metabolism, secondary metabolite production and for virulence in bacteria and fungi. Here we investigate the role of the methylcitrate cycle by generating a mcl deletion mutant in the fungal biocontrol agent Trichoderma atroviride. Gene expression analysis shows that a basal expression of mcl is observed in all growth conditions tested. Phenotypic analysis of a mcl deletion mutant suggests the requirement of MCL in propionate resistance, growth, conidial pigmentation and germination, and abiotic stress tolerance. A plate confrontation assay did not show a difference between the wild type and the Δmcl strain in antagonism towards B. cinerea. However, the Δmcl strain display reduced antagonism towards B. cinerea based on a secretion assay. Furthermore, an in vitro root colonization assay shows that the Δmcl strain had reduced ability to colonize Arabidopsis thaliana roots, which results in reduced induction of systemic resistance towards B. cinerea. These data show that MCL is important not only for growth and development in T. atroviride but also in antagonism, root colonization and induction of defence responses in plants.
    Microbiology 10/2013; 159(Pt_12). DOI:10.1099/mic.0.070466-0 · 2.56 Impact Factor
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