Small genetic differences between ericoid mycorrhizal fungi affect nitrogen uptake by Vaccinium

Institute of Biological Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK.
New Phytologist (Impact Factor: 7.67). 12/2008; 181(3):708-18. DOI: 10.1111/j.1469-8137.2008.02678.x
Source: PubMed


Ericoid mycorrhizal fungi have been shown to differ in their pattern of nitrogen (N) use in pure culture. Here, we investigate whether this functional variation is maintained in symbiosis using three ascomycetes from a clade not previously shown to include ericoid mycorrhizal taxa. Vaccinium macrocarpon and Vaccinium vitis-idaea were inoculated with three fungal strains known to form coils in Vaccinium roots, which differed in their patterns of N use in liquid culture. (15)N was used to trace the uptake of -N, -N and glutamine-N into shoots. (15)N transfer differed among the three fungal strains, including two that had identical internal transcribed spacer (ITS) sequences, and was quantitatively related to fungal growth in liquid culture at low carbon availability. These results demonstrate that functional differences among closely related ericoid mycorrhizal fungi are maintained in symbiosis with their hosts, and suggest that N transfer to plant shoots in ericoid mycorrhizas is under fungal control.

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    • "The presence of hyphae from the ascomycete strain AC21 [FM180477] mycobiont inside the C. vulgaris stem cells suggests antagonistic behavior, and may explain the observed growth suppression (Fig. 3b). Hence, the behaviour of the ascomycete strain AC21 [FM180477] in this experimental ex situ system seems to comply with the " mutualism-parasitism continuum " (Johnson et al. 1997) as previously reported by Grelet et al. (2009a) with the same fungal strain. Smith and Read (1997) pointed out that no increase, or a reduction, in growth of plants following colonization by micorrhizal fungi is often found under artificial systems. "
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    ABSTRACT: In view of the close association between ericaceous shrubs and ectomycorrhizal trees in forest ecosystems, the interaction between ectomycorrhizal basidiomycetes and the hair roots of four typical ericoid mycorrhizal hosts was investigated in vitro. Seedlings of Vaccinium myrtillus, V. vitis-idaea, V. macrocarpon and Calluna vulgaris were inoculated with each of four ectomycorrhizal basidiomycetes from different phylogenetic groups (Laccaria bicolor, Lactarius musteus, Suillus variegatus and Tomentellopsis submollis) in a low carbon and nutrient agar-cellophane culture system. Two ericoid mycorrhizal Helotiales ascomycetes (Meliniomyces bicolor in the Rhizoscyphus ericae aggregate and a mycobiont out of the Rhizoscyphus ericae aggregate) were included for comparison. Interactions between fungi and hair roots ranged from neutral to surface attachment, and the formation of intracellular hyphal coils. Root and shoot responses to inoculation were different between the host/fungus combinations. The ectomycorrhizal fungus L. bicolor formed extensive intracellular colonization, spreading cell-to-cell with multiple hyphal entry points and intracellular hyphal coils with single entry points in C. vulgaris and V. macrocarpon epidermal cells respectively, however, no significant effects on plant growth were detected. Meliniomyces bicolor formed intracellular hyphal coils in the epidermal cells of V. myrtillus and V. macrocarpon but not the other host spp. The M. bicolor isolate stimulate V. myrtillus root length about 2.5 times. Interestingly, although the unknown ascomycete strain out of the Rhizoscyphus ericae aggregate formed intracellular hyphal coils in epidermal cells of all host plants, it suppressed the growth of C. vulgaris, V. myrtillus, and V. vitis-idaea but not to V. macrocarpon. Further and more detailed experimentation under more ecological realistic conditions for a longer period of time is needed.
    Symbiosis 05/2012; 56(2). DOI:10.1007/s13199-012-0161-7 · 1.44 Impact Factor
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    • "The main effect of reducing C availability was to increase the relative ability of most strains to grow on glutamine and nitrate, in comparison to ammonium. Grelet et al. (2009b) investigated whether the functional variation was maintained in symbiosis. Vaccinium plants were inoculated with three genetically closely related ERM fungal strains known to differ in their N use in liquid culture. "
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    ABSTRACT: Ericoid mycorrhizal (ERM) fungi are a diverse assemblage of symbiotic fungi that features culturable ascomycetes in the Helotiales and Onygenales, but also so far unculturable basidiomycetes in the Sebacinales. They form a distinct endomycorrhizal association with some plant genera in the Ericaceae. ERM plants dominate in heathlands characterised by very poor nutrient status and considerable edaphic stress, and their success in these harsh environments is ascribed to the functional traits of their symbiotic fungi. ERM fungi are able to exploit recalcitrant organic substrates thanks to an arsenal of extracellular enzymes. They also display adaptive mechanisms of stress tolerance and are able to withstand high concentrations of toxic compounds such as heavy metals. ERM plants are also commonly found as understorey vegetation in woodland habitats, and molecular investigations on the genetic diversity of ERM fungi, together with cross-inoculation experiments under gnotobiotic conditions, indicate the potential networking ability of these fungi in mixed plant communities.
    Fungal Associations, 01/2012: pages 255-285; , ISBN: 978-3-642-30825-3
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    • "An additional strain of M. variabilis (isolate F), obtained from a Vaccinium hair root, was included for comparison. DNA extraction and ITS-PCR were performed as described in Grelet et al. (2009), and species designation was based on matching ITS sequences to those of known origin in GenBank. The position of each isolate within the 'H. "
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    ABSTRACT: * The overstorey coniferous trees and understorey ericaceous dwarf shrubs of northern temperate and boreal forests have previously been considered to form mycorrhizas with taxonomically and functionally distinct groups of fungi. * Here, we tested the hypothesis that Meliniomyces variabilis and Meliniomyces bicolor, isolated from Piceirhiza bicolorata ectomycorrhizas of pine, can function as ericoid mycorrhizal symbionts with Vaccinium vitis-idaea. We used split-compartment microcosms to measure the reciprocal exchange of (13)C and (15)N between V. vitis-idaea and three fungal isolates in the Hymenoscyphus ericae aggregate isolated from Scots pine ectomycorrhizas (M. variabilis and M. bicolor) or Vaccinium roots (M. variabilis). * The extramatrical fungal mycelium of labelled mycorrhizal plants was significantly enriched in (13)C, and the leaves were significantly enriched in (15)N, compared with nonmycorrhizal and nonlabelled controls. * These findings show for the first time that fungi in the H. ericae aggregate, isolated from pine ectomycorrhizas, can transfer C and N and can thus form functional ericoid mycorrhizas in an understorey ericaceous shrub.
    New Phytologist 04/2009; 182(2). DOI:10.1111/j.1469-8137.2009.02813.x · 7.67 Impact Factor
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