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David Read - One of the best experts on this subject based on the ideXlab platform.
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Symbiotic fungal associations in 'lower' land plants.
Philosophical Transactions of the Royal Society B, 2000Co-Authors: David Read, Jeffrey G. Duckett, Roberto Ligrone, R. Francis, A RussellAbstract:An analysis of the current state of knowledge of symbiotic fungal associations in ‘lower’ plants is provided. Three fungal phyla, the Zygomycota, Ascomycota and Basidiomycota, are involved in forming these associations, each producing a distinctive suite of structural features in well–defined groups of ‘lower’ plants. Among the ‘lower’ plants only mosses and Equisetum appear to lack one or other of these types of association. The salient features of the symbioses produced by each fungal group are described and the relationships between these associations and those formed by the same or related fungi in ‘higher’ plants are discussed. Particular consideration is given to the question of the extent to which root–fungus associations in ‘lower’ plants are analogous to ‘mycorrhizas’ of ‘higher’ plants and the need for analysis of the functional attributes of these symbioses is stressed. Zygomycetous fungi colonize a wide range of extant lower land plants (hornworts, many hepatics, lycopods, Ophioglossales, Psilotales and Gleicheniaceae), where they often produce structures analogous to those seen in the vesicular–arbuscular (VA) mycorrhizas of higher plants, which are formed by members of the order Glomales. A preponderance of associations of this kind is in accordance with palaeobotanical and molecular evidence indicating that glomalean fungi produced the archetypal symbioses with the first plants to emerge on to land. It is shown, probably for the first time, that glomalean fungi forming typical VA mycorrhiza with a higher plant ( Plantago lanceolata ) can colonize a thalloid liverwort ( Pellia epiphylla ), producing arbuscules and vesicles in the hepatic. The extent to which these associations, which are structurally analogous to mycorrhizas, have similar functions remains to be evaluated. Ascomycetous associations are found in a relatively small number of families of leafy liverworts. The structural features of the fungal colonization of rhizoids and underground axes of these plants are similar to those seen in mycorrhizal associations of ericaceous plants like Vaccinium . Cross inoculation experiments have confirmed that a typical mycorrhizal endophyte of ericaceous plants, Hymenoscyphus ericae , will form associations in liverworts which are structurally identical to those seen in nature. Again, the functional significance of these associations remains to be examined. Some members of the Jungermanniales and Metzgeriales form associations with basidiomycetous fungi. These produce intracellular coils of hyphae, which are similar to the pelotons seen in orchid mycorrhizas, which also involve basidiomycetes. The fungal associates of the autotrophic Aneura and of its heterotrophic relative Cryptothallus mirabilis have been isolated. In the latter case it has been shown that the fungal symbiont is an ectomycorrhizal associate of Betula , suggesting that the apparently obligate nature of the association between the hepatic and Betula in nature is based upon requirement for this particular heterotroph.
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the biology of mycorrhiza in the ericaceae xx plant and mycorrhizal necromass as nitrogenous substrates for the ericoid mycorrhizal fungus Hymenoscyphus ericae and its host
New Phytologist, 1998Co-Authors: S J Kerley, David ReadAbstract:In the ‘F’ horizons of acid mor-humus soils of heathland ecosystems, mycorrhizal roots of the dominant ericaceous species form a large fraction of the soil biomass. Rapid turnover of these roots provides the potential for recycling of substantial amounts of nitrogen contained in their fungal and plant components. Here, we first determine the amount of N in the biomass of ericoid roots growing in heathland and show it to constitute a large proportion of total soil N. In order to assess the accessibility of this N to ericaceous plants, experiments were then conducted using aseptically produced shoot and root necromass of Vaccinium macrocarpon Ait., the roots being grown with or without mycorrhizal colonization. These materials were provided as sole nitrogenous substrates in growth experiments using the ericoid mycorrhizal fungus Hymenoscyphus ericae (Read) Korf & Kernan in pure culture and V. macrocarpon in the mycorrhizal (M) or non-mycorrhizal (NM) condition as test organisms. The experiments were designed to test the hypothesis that the N contained in these substrates can be mobilized by the mycorrhizal endophyte. The ability of the endophyte to utilize the substrates was determined by measuring fungal yields and by assessing the presence of its extra-cellular protease and chitinase enzymes. Transfer of N to the host by the endophyte was determined through measurements of plant yield and tissue N contents. H. ericae produced a significantly greater yield on shoot and mycorrhizal root necromass than on non-mycorrhizal root necromass. The extra-cellular enzymes protease and chitinase were produced by the fungus when grown on the M root necromass. The fungus also transferred N to the host plant, up to 76% of N contained in the substrate being found in M plants whereas less than 5% was present in their NM counterparts.
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Lignin and soluble phenolic degradation by ectomycorrhizal and ericoid mycorrhizal fungi
Fungal Biology, 1997Co-Authors: Gary D. Bending, David ReadAbstract:The organic soil horizons of heathland and temperate forest ecosystems are characteristically rich in phenolics, which present barriers to organic N availability to the microflora. The abilities of ectomycorrhizal (ECM), ericoid mycorrhizal and wood decomposing saprotrophic fungi to degrade model compounds representing the insoluble phenolic lignin, and soluble phenolics, which provide physical and chemical barriers respectively to organic N availability, were compared. No clear relationship was found between ability to degrade lignin and soluble phenolics. The presumptive assays indicated that most mycorrhizal fungi have only low abilities to degrade these compounds relative to the wood decomposing fungi. In general, ericoid mycorrhiza fungi were capable of greater phenolic degradation than most ECM species, and degradative ability was associated with production of phenol-oxidizing enzymes. In no case was presumptive degradation of lignin or soluble phenolic, or production of phenol-oxidizing enzymes by mycorrhizal fungi as great as that of the wood decomposing fungi. In the case of the ericoid endophyte Hymenoscyphus ericae , phenol-oxidation was associated with production of an extracellular o-polyphenol oxidase (tyrosinase) which showed optimal activity at a pH of 5–5.5 and temperature of 30°C. The ecological significance of the results is discussed.
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the biology of mycorrhiza in the ericaceae xix fungal mycelium as a nitrogen source for the ericoid mycorrhizal fungus Hymenoscyphus ericae and its host plants
New Phytologist, 1997Co-Authors: S J Kerley, David ReadAbstract:SUMMARY Measurements of the chitin content of the rooting horizons of a typical mor-humus heathland soil, indicate that chitin can contain in excess of 20 % of the total nitrogen in the litter (L) horizon and 30 % in the fermentation (F) horizon. Much of this chitin-nitrogen is thought to be contained in the mycelial walls of soil fungi. Experiments were therefore designed to test the hypothesis that such sources of N could be rendered accessible to the ericaceous plants by their fungal endophytes. Mycelium of the ericoid endophyte Hymenoscyphus ericae (Read) Korf & Kernan and of the ectomycorrhizal fungus Suillus bovinus (Fr.) 0. Krantze were grown in liquid culture before being killed and added either in the intact condition, or after fractionation, as sole sources of N to sterile media upon which were grown H. ericae in pure culture, or mycorrhizal and non-mycorrhizal plants of Vaccinium macrocarpon Ait. and Calluna vulgaris L. The abilities of the test organisms to utilize the nitrogen contained in the intact mycelial necromass, or in its fractions, were assessed by determining their yields and nitrogen concentrations of their tissues. It was revealed that H. ericae was able to produce significantly higher yield when grown on intact fungal necromass than when provided with equivalent concentrations of N in the form of ammonium. Its yields on mycelial fractions were lower, but still significantly greater than those obtained in the controls lacking N. Significantly greater yields and N contents were also found in the ericaceous plants grown with these nitrogenous substrates in the mycorrhizal condition. Without H. ericae they had no access to the substrates. The possible ecological implications of these results are discussed.
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Effects of the soluble polyphenol tannic acid on the activities of ericoid and ectomycorrhizal fungi
Soil Biology & Biochemistry, 1996Co-Authors: Gary D. Bending, David ReadAbstract:Abstract Plants with ericoid and ectomycorrhizal (ECM) roots characteristically produce acidic polyphenol-rich residues which accumulate in soil, and may influence the activities of the fungal symbionts directly through toxic effects, or indirectly through effects on nitrogen availability. The ability of fungi representative of these mycorrhizal types to degrade solube polyphenolic materials and, hence, to reduce their nutritional effects was investigated using tannic acid (TA) as a model compound. The ericoid endophyte Hymenoscyphus ericae (Read), Korf and Kernan was able to readily degrade the compound, and as a result, to reduce its ability to bind protein. In contrast, the ECM fungi examined had only limited abilities to degrade TA. The presence of TA induced H. ericae but not the ECM fungi, to produce extracellular polyphenol oxidase. Mycelial yields and the extent of TA degradation by H. ericae were both enhanced by exogenous ammonium.
Andrew A Meharg - One of the best experts on this subject based on the ideXlab platform.
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carbon availability affects nitrogen source utilisation by Hymenoscyphus ericae
Fungal Biology, 2005Co-Authors: Gwenaelle Grelet, Andrew A Meharg, Ian J AlexanderAbstract:We compared the ability of five strains of the ericoid mycorrhizal fungus Hymenoscyphus ericae to utilise glutamine, ammonium or nitrate at high or low carbon (C) availability. The pattern of intraspecific variation in growth was affected by C availability. When C supply was high, growth differences between strains were explained by the total amount of nitrogen (N) taken up, suggesting variation in uptake kinetics. Under C-limiting conditions, strain differences were linked with their nitrogen use efficiency, implying intraspecific differences in N metabolism. The relationship between growth on glutamine and pH shifts in the media indicated that there was intraspecific variation in glutamine transporters. In addition, the correlation between pH changes and the amount of glutamine-N recovered as ammonium in the media indicated that there were intraspecific variations within the enzymatic pathways involved in glutamine metabolism. Our findings, compared with those of a previous study involving the same ericoid strains, draw attention to the temporal variation in nitrogen source utilisation by ericoid mycorrhizal fungi when maintained in axenic culture.
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calluna vulgaris root cells show increased capacity for amino acid uptake when colonized with the mycorrhizal fungus Hymenoscyphus ericae
New Phytologist, 2002Co-Authors: Sergei G Sokolovski, Andrew A Meharg, Frans J M MaathuisAbstract:Summary • Ericoid mycorrhizas are believed to improve N nutrition of many ericaceous plant species that typically occur in habitats with impoverished nutrient status, by releasing amino acids from organic N forms. Despite the ubiquity of mycorrhizal formation the mechanisms and regulation of nutrient transport in mycorrhizal associations are poorly understood. • We used an electrophysiological approach to study how amino acid transport characteristics of Calluna vulgaris were affected by colonization with the ericoid mycorrhiza fungus Hymenoscyphus ericae . • Both the Vmax and Km parameters of amino acid uptake were affected by fungal colonization in a manner consistent with an increased availability of amino acid to the plant. • The ecophysiological significance of altered amino acid transport in colonized root cells of C. vulgaris is discussed.
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arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae
New Phytologist, 2001Co-Authors: J M Sharples, Andrew A Meharg, Susan M Chambers, J W G CairneyAbstract:Summary • Differential resistance to arsenate (AsO43−) is demonstrated here among populations of the ericoid mycorrhizal fungus Hymenoscyphus ericae isolated from Calluna vulgaris in natural heathland soils and soils contaminated with AsO43−. • Isolates (c. 25) of the fungus from each of two As and Cu mine sites, and a natural heathland site, were screened for AsO43− and Cu2+ resistance by growing isolates in media containing a range of AsO43− and Cu2+ concentrations. • H. ericae populations from the mine sites demonstrated resistance to AsO43− compared with the heathland population; the mine-site populations producing significant growth at the highest AsO43− concentration (4.67 mol m−3), whereas growth of the heathland population was almost completely inhibited. EC50 values for mine-site isolates were estimated to be 5–41-times higher than the heathland population. All isolates produced identical responses to increasing Cu2+ concentrations, with no differences observed between mine-site and heathland isolates. • Populations of H. ericae on the contaminated mine sites have developed adaptive resistance to AsO43−. By contrast, Cu2+ resistance appears to be constitutive.
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mechanism of arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae
Plant Physiology, 2000Co-Authors: J M Sharples, Andrew A Meharg, Susan M Chambers, J W G CairneyAbstract:Arsenate resistance is exhibited by the ericoid mycorrhizal fungus Hymenoscyphus ericae collected from As-contaminated mine soils. To investigate the mechanism of arsenate resistance, uptake kinetics for arsenate (H 2 AsO 4 − ), arsenite (H 3 AsO 3 ), and phosphate (H 2 PO 4 − ) were determined in both arsenate-resistant and -non-resistant H. ericae . The uptake kinetics of H 2 AsO 4 − , H 3 AsO 3 , and H 2 PO 4 − in both resistant and non-resistant isolates were similar. The presence of 5.0 μm H 2 PO 4 − repressed uptake of H 2 AsO 4 − and exposure to 0.75 mm H 2 AsO 4 − repressed H 2 PO 4 − uptake in both H. ericae . Mine site H. ericae demonstrated an enhanced As efflux mechanism in comparison with non-resistant H. ericae and lost approximately 90% of preloaded cellular As (1-h uptake of 0.22 μmol g −1 dry weight h −1 H 2 AsO 4 − ) over a 5-h period in comparison with non-resistant H. ericae , which lost 40% of their total absorbed H 2 AsO 4 − . As lost from the fungal tissue was in the form of H 3 AsO 3 . The results of the present study demonstrate an enhanced H 3 AsO 3 efflux system operating in mine site H. ericae as a mechanism for H 2 AsO 4 − resistance. The ecological significance of this mechanism of arsenate resistance is discussed.
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Genetic diversity of root‐associated fungal endophytes from Calluna vulgaris at contrasting field sites
New Phytologist, 2000Co-Authors: J M Sharples, Andrew A Meharg, Susan M Chambers, John CairneyAbstract:A total of 107 putative ericoid mycorrhizal endophytes were isolated from hair roots of Calluna vulgaris from two abandoned arsenic/copper mine sites and a natural heathland site in southwest England. The endophytes were initially grouped as 14 RFLP types, based on the results of ITS-RFLP analysis using the restriction endonucleases Hinf I, Rsa I and Hae III. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with sequences for known ericoid mycorrhizal endophytes and selected ascomycetes. The majority of endophyte isolates (62–92%) from each site were identified as Hymenoscyphus ericae, but a number of other less common mycorrhizal RFLP types were also identified, all of which appear to have strong affinities with the order Leotiales. None of the less common RFLP types was isolated from C. vulgaris at more than one field site. Neighbour-joining analysis indicated similarities between the endophytes from C. vulgaris and mycorrhizal endophytes isolated from other Ericaceae and Epacridaceae hosts in North America and Australia.
Derek T Mitchell - One of the best experts on this subject based on the ideXlab platform.
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Nutritional influences on the solubilization of metal phosphate by ericoid mycorrhizal fungi.
Mycological research, 2020Co-Authors: Brian R Gibson, Derek T MitchellAbstract:Four ericoid mycobionts (two isolates of Hymenoscyphus ericae, and two dark, sterile ericoid mycobionts isolated from metal-contaminated mine sites) were grown on solid agar plates supplemented with zinc phosphate (0.25 %) containing different forms of nitrogen (nitrate, ammonium or alanine) and different concentrations of carbon (glucose) and phosphorus (K2HPO4). The influence of nutrient variation on solubilizing ability of the fungi was assessed by measuring the zones of solubilization appearing beneath the growing colonies. All four mycobionts were capable of zinc phosphate solubilization in the presence of all three nitrogen sources and in media containing no nitrogen. No solubilization was observed at 0 mM glucose-C but was observed with increasing glucose concentration from 300 to 600 mM C. Increasing phosphorus concentration (0-5 mM P) had no effect on the solubilizing ability of the isolates. All but one of the mycobionts were capable of solubilizing calcium phosphate (CaHPO4), while no solubilization was observed in media containing aluminium phosphate (AlPO4), iron phosphate (FePO4 x 4H2O) or copper phosphate (Cu3O8P2 x 2H2O) under conditions which were found to be optimal for zinc phosphate solubilization. Under conditions of glucose at 300 mM C and alanine as the N source in the zinc phosphate-amended agar medium, one of the mycobionts produced new crystals, which were morphologically distinct from the original zinc phosphate crystals. It is concluded that medium composition influences the metal-phosphate solubilizing ability of ericoid mycobionts. The results are discussed in relation to the possible mechanisms involved in solubilization and the potential benefits of metal-phosphate solubilization to ericoid mycobionts and their host plants.
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Sensitivity of Ericoid Mycorrhizal Fungi and Mycorrhizal Calluna vulgaris to Copper Mine Spoil from Avoca, County Wicklow
Biology & Environment: Proceedings of the Royal Irish Academy, 2006Co-Authors: Brian Gibson, Derek T MitchellAbstract:Ericoid mycorrhizal fungi were isolated from roots of Calluna vulgaris collected from mine spoil at abandoned copper mines at Avoca, County Wicklow, Ireland, and Parys Mountain, Anglesey, Wales. Two isolates were morphologically identical to Hymenoscyphus ericae and formed typical ericoid mycorrhizal associations. Four fungal isolates? the two mine-site isolates and two H. ericae isolates (obtained from uncontaminated sites) were grown in liquid media containing elevated levels of Cu and Zn. All isolates were determined to have a low sensitivity to these metals, with EC50 values (concentration of metal causing 50% reduction in mycelial dry mass) in the range 0.3-0.9mM Cu and 1.2-5.5mM Zn, but there were differences in metal sensitivity between isolates. There was a significant decline in the tolerance of each isolate to increasing concentrations of mine spoil (up to 10% in the agar medium). Mycorrhizal amelioration of heavy-metal toxicity was determined by growing mycorrhizal (M) and non-mycorrhizal (NM) rooted cuttings of C. vulgaris on mine spoil. Rooted cuttings obtained from an uncontaminated site showed no response to mycorrhizal colonisation. However, C. vulgaris obtained from the Avoca site and inoculated with H. ericae performed better than NM plants. The improved growth of these plants was associated with a reduction in Cu within the host's shoot. Inoculation of C. vulgaris with an ericoid mycorrhizal fungus isolated from the Avoca mine site also reduced Cu accumulation within shoots but there was no change in the growth and Zn accumulation of C. vulgaris on mine spoil. Results are discussed in relation to the potential benefit of the ericoid mycorrhizal association to C. vulgaris at metal contaminated sites. Brian R. Gibson, Division of Food Sciences, School of Biosciences,
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Phosphatases of ericoid mycorrhizal fungi: kinetic properties and the effect of copper on activity.
Fungal Biology, 2005Co-Authors: Brian Gibson, Derek T MitchellAbstract:Ericoid endomycorrhizal fungi (two isolates of Hymenoscyphus ericae obtained from unpolluted heathlands and two H. ericae -type endophytes isolated from Calluna vulgaris growing on Cu-contaminated mine spoil) were grown for 14 d on 10% Rorison's solution containing sodium phytate as the sole P source and either trace (0.16 μ) or elevated (0.25 mM) concentrations of Cu. The elevated levels of Cu in the medium had no effect on the growth of the two M. ericae -type endophytes from mine spoil sites but caused a significant reduction in growth of the two H. ericae isolates from unpolluted sites. Wall, cytoplasmic and extracellular fractions were assayed for phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activity. K m and V max values varied between the different endophytes and both were highest in the wall fractions. Wall-bound phosphatase activity, excluding PDEase of one H. ericae -type endophyte, was generally unaffected after the isolates had been grown on medium containing 0.25 mM Cu. Extracellular PDEase of the two H. ericae -type endophytes from mine spoil sites was stimulated by 0.25 mM Cu in the growth medium. Cu concentrations up to 5.0 mM in the assay medium did not inhibit wall-bound phosphatase activity whereas three of the isolates showed a stimulation of extracellular activity with increasing Cu. The results are discussed in relation to phosphatase activity of ericoid endophytes on Cu-contaminated substrates.
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Influence of pH on copper and zinc sensitivity of ericoid mycobionts in vitro.
Mycorrhiza, 2005Co-Authors: Brian Gibson, Derek T MitchellAbstract:The effect of pH on growth, metal uptake and toxicity in four isolates of ericoid mycobionts (two Hymenoscyphus ericae from unpolluted heathland sites and two H. ericae-type mycobionts from metal-contaminated mine spoil) was assessed in vitro. These isolates were incubated in liquid medium (10% Rorison’s medium, glucose at 10 g l−1) containing either 0.25 mM Cu or 2.0 mM Zn and adjusted to pH 2, 3, 4, 5 or 6. After 30 days incubation, dry mass and mycelial metal content were determined and growth was expressed as tolerance index, i.e. dry mass in the presence of metal as a percentage of dry mass in the absence of metal. Initial medium pH had a significant effect on both tolerance index and metal accumulation. Tolerance indices were highest at pH 2, with several isolates showing a stimulation of growth (i.e. tolerance index >100%) at this pH. Tolerance index decreased at higher initial pH values and growth of two mycobionts was completely inhibited (tolerance index=0) in the Cu-supplemented media at pH 6. Reduction in tolerance index coincided with an increase in mycelial accumulation of Cu and Zn. Practical and environmental implications of these results are discussed.
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Responses of mycorrhizal and non-mycorrhizal Erica cinerea and Vaccinium macrocarpon to Glomus mosseae
Mycorrhiza, 2004Co-Authors: Kenneth Byrne, Derek T MitchellAbstract:An investigation was carried out on the mycorrhizal colonisation, growth and nutrition of two members of the Ericaceae in close proximity to an arbuscular mycorrhizal (AM) association. This was undertaken by separating mycorrhizal (EM) and non-mycorrhizal (NEM) Erica cinerea and Vaccinium macrocarpon from AM (inoculated by Glomus mosseae ) and non-mycorrhizal (NAM) Plantago lanceolata using a 30 µm nylon mesh in a sand culture/pot system. Ericoid mycorrhizal colonisation by Hymenoscyphus ericae on root systems of E. cinerea and V. macrocarpon was in the range 14–22% and 58–69%, respectively. The presence of AM P. lanceolata had no effect on the ericoid mycorrhizal colonisation of E. cinerea and V. macrocarpon . NEM E. cinerea showed reductions in shoot biomass and shoot nitrogen concentrations after exposure to AM P. lanceolata after incubations of 6 and 9 weeks but there were no differences in dry mass, length, and nitrogen and phosphorus concentrations of the root systems between the treatment combinations. Reductions were also found, after incubations of 6 and 9 weeks, in shoot dry mass, leaf area and shoot nitrogen concentrations of NEM V. macrocarpon in the presence of AM P. lanceolata but no changes occurred in the length and dry mass of the root systems. There were no differences in maximum photosynthesis in V. macrocarpon between treatment combinations but NEM V. macrocarpon in the presence of AM P. lanceolata had the lowest transpiration rates and stomatal conductance and the highest nitrogen- and phosphorus-use efficiencies compared with the other treatment combinations. These results are discussed in relation to the type of interaction found in these compatible and incompatible mycorrhizal associations.
Ian J Alexander - One of the best experts on this subject based on the ideXlab platform.
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Reciprocal carbon and nitrogen transfer between an ericaceous dwarf shrub and fungi isolated from Piceirhiza bicolorata ectomycorrhizas.
New Phytologist, 2009Co-Authors: Gwenaelle Grelet, Ian C Anderson, David W. Johnson, Eric Paterson, Ian J AlexanderAbstract:Summary • 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. vitisidaea 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.
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carbon availability affects nitrogen source utilisation by Hymenoscyphus ericae
Fungal Biology, 2005Co-Authors: Gwenaelle Grelet, Andrew A Meharg, Ian J AlexanderAbstract:We compared the ability of five strains of the ericoid mycorrhizal fungus Hymenoscyphus ericae to utilise glutamine, ammonium or nitrate at high or low carbon (C) availability. The pattern of intraspecific variation in growth was affected by C availability. When C supply was high, growth differences between strains were explained by the total amount of nitrogen (N) taken up, suggesting variation in uptake kinetics. Under C-limiting conditions, strain differences were linked with their nitrogen use efficiency, implying intraspecific differences in N metabolism. The relationship between growth on glutamine and pH shifts in the media indicated that there was intraspecific variation in glutamine transporters. In addition, the correlation between pH changes and the amount of glutamine-N recovered as ammonium in the media indicated that there were intraspecific variations within the enzymatic pathways involved in glutamine metabolism. Our findings, compared with those of a previous study involving the same ericoid strains, draw attention to the temporal variation in nitrogen source utilisation by ericoid mycorrhizal fungi when maintained in axenic culture.
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interaction between an isolate from the Hymenoscyphus ericae aggregate and roots of pinus and vaccinium
New Phytologist, 2004Co-Authors: Luis Villarrealruiz, Ian C Anderson, Ian J AlexanderAbstract:Summary • A fungal isolate was obtained from Piceirhiza bicolorata-like ectomycorrhizas on Pinus sylvestris in a 160-yr-old natural woodland. • The fungus was identified by sequencing the PCR-amplified rDNA ITS regions. The sequence was compared with similar known taxa and grouped with Cadophora finlandia in the Hymenoscyphus ericae aggregate. • The fungus formed P. bicolorata-like ectomycorrhizas in aseptic synthesis with P. sylvestris seedlings. When seedlings of Vaccinium myrtillus were exposed to mycelium arising from these ectomycorrhizas, or to mycelium in pure culture, the hyphae entered the cells of the hair roots and formed coils characteristic of ericoid mycorrhizas. The presence of the fungus stimulated Vaccinium root growth and altered root architecture. • This is the first full report of the ability of a fungus from the H. ericae aggregate simultaneously to form both ectomycorrhizas and what appear to be ericoid mycorrhizas.
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Exclusion of grass roots from soil organic layers by Calluna: the role of ericoid mycorrhizas
Journal of Experimental Botany, 2000Co-Authors: David R. Genney, Ian J Alexander, Susan E. HartleyAbstract:phosphorus is the limiting nutrient (Fitter, 1977; West, 1996). It has also been demonstrated that plant diversity The role of ericoid mycorrhizal colonization in competi- increases with the number of VA mycorrhizal fungi pretion between the dwarf shrub Calluna vulgaris and sent in an alpine meadow community (van der Heijden coarse grass Nardus stricta was investigated. Nardus et al., 1998b). In acidic heathland ecosystems it is often was grown alone, or in competition with Calluna ,i n a nitrogen that limits growth, because mineralization rates layered organic/sand substrate with and without are low and nutrients are locked up in complex organic inoculation with the ericoid mycorrhizal endophyte compounds (Read, 1991). These heathland environments Hymenoscyphus ericae, and with and without the addi- are dominated by ericaceous dwarf shrubs (Aerts and tion of nitrogen. Root length and allocation between Heil, 1993) whose roots are colonized by ericoid mycordifferent substrate layers was assessed along with rhizal ( ErM ) fungi (Gimingham, 1972; Read and Stribley, plant biomass, nutrient uptake and mycorrhizal colon- 1973). ErM fungi are capable of utilizing nitrogen and ization. Calluna was the superior competitor for nutri- phosphorus from a wide range of organic substrates ents, probably because of its ability to concentrate (Haselwandter et al., 1990; Leake and Read, 1990; Myers root growth in the upper organic layer. In the presence and Leake, 1995), resulting in improved host nutrition of Calluna both the absolute amount and proportion ( Kerley and Read, 1998; Read and Stribley, 1973). of Nardus root length in the organic layer were Calluna vulgaris (L.) Hull is the ericaceous dwarf shrub reduced, and this reduction was greatest when Calluna that dominates many natural and semi-natural heathland was mycorrhizal. The presence of ericoid mycorrhizal communities in the oceanic north west of Europe colonization did not reduce Nardus shoot nutrient con- (Gimingham, 1960; Rodwell, 1991). In many areas, tent or concentration, suggesting that ericoid mycor- including Scotland, this Calluna heath has been replaced rhizal suppression of Nardus growth was not due to in recent decades by grassland (Marrs, 1993; Sydes, 1988; nutrient competition: alternative mechanisms of inter- Welch and Scott, 1995) of which the coarse grass Nardus ference are discussed. stricta (L.) is a frequent and dominant component (Hill et al., 1992; Welch, 1986; Welch and Scott, 1995). The
John Cairney - One of the best experts on this subject based on the ideXlab platform.
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Chitinolytic activities of ericoid mycorrhizal and other root-associated fungi from Epacris pulchella (Ericaceae).
Mycological research, 2005Co-Authors: Damian S. Bougoure, John CairneyAbstract:Ericoid mycorrhizal endophytes and other root-associated fungi from Epacris pulchella (Ericaceae) in an eastern Australian sclerophyll forest, along with Hymenoscyphus ericae, were tested for their abilities to produce extracellular chitinolytic activities during growth in axenic culture. Two root-associated fungi produced activities that were active against only a monomeric 4-methylumbelliferyl (4-MU) glycoside of N-acetylglucosamine, suggesting exo-acting beta-N-acetylhexosaminidase (EC 3.2.1.52) activity. All ericoid mycorrhizal fungi and two root-associated fungi produced activities against dimeric and trimeric 4-MU glycosides of N-acetylglucosamine, suggesting production of chitobiosidase and endo-acting chitinase (EC 3.2.1.14) respectively in addition to beta-N-acetylhexosaminidase. Specific activities for all ericoid mycorrhizal fungi, including H. ericae, were of the same order of magnitude, suggesting that their chitinolytic potential is broadly similar. Chitinase activities were only produced by an ericoid mycorrhizal fungus when chitin was included in the medium, however, no activity was produced if glucose was also present in the medium.
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Genetic diversity of root‐associated fungal endophytes from Calluna vulgaris at contrasting field sites
New Phytologist, 2000Co-Authors: J M Sharples, Andrew A Meharg, Susan M Chambers, John CairneyAbstract:A total of 107 putative ericoid mycorrhizal endophytes were isolated from hair roots of Calluna vulgaris from two abandoned arsenic/copper mine sites and a natural heathland site in southwest England. The endophytes were initially grouped as 14 RFLP types, based on the results of ITS-RFLP analysis using the restriction endonucleases Hinf I, Rsa I and Hae III. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with sequences for known ericoid mycorrhizal endophytes and selected ascomycetes. The majority of endophyte isolates (62–92%) from each site were identified as Hymenoscyphus ericae, but a number of other less common mycorrhizal RFLP types were also identified, all of which appear to have strong affinities with the order Leotiales. None of the less common RFLP types was isolated from C. vulgaris at more than one field site. Neighbour-joining analysis indicated similarities between the endophytes from C. vulgaris and mycorrhizal endophytes isolated from other Ericaceae and Epacridaceae hosts in North America and Australia.
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ITS rDNA sequence comparison of ericoid mycorrhizal endophytes from Woollsia pungens.
Fungal Biology, 2000Co-Authors: Susan M Chambers, John CairneyAbstract:The ITS regions of 14 isolates of endophytic fungi obtained from the root systems of four Woollsia pungens plants were sequenced and compared to sequences of Hymenoscyphus ericae, Oidiodendron maius and to sequences from other fungal taxa currently available in the GenBank and EMBL nucleotide databases. Sequence data suggested that six distinct taxa were present in the root systems of the four plants and that up to four of these were present in the root system of a single plant. One of the endophytes was identified as an Oidiodendron species, while most other isolates probably belong to the Leotiales.
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Molecular identification of Hymenoscyphus sp. from rhizoids of the leafy liverwort Cephaloziella exiliflora in Australia and Antarctica
Fungal Biology, 1999Co-Authors: Susan M Chambers, P.g. Williams, R.d. Seppelt, John CairneyAbstract:Fungi isolated from the leafy liverwort Cephaloziella exiliflora collected in Australia and continental Antarctica were compared with Hymenoscyphus ericae using internal transcribed spacer (ITS) region DNA sequences. The isolates displayed C. exiliflora are probably H. ericae. The data significantly extend the known host range and geographical distribution of H. ericae and indicate that the fungus has a global distribution.
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Utilisation of organic nitrogen and phosphorus sources by mycorrhizal endophytes of Woollsia pungens (Cav.) F. Muell. (Epacridaceae)
Mycorrhiza, 1999Co-Authors: A. Chen, Susan M Chambers, John CairneyAbstract:The ability of four ericoid mycorrhizal endophytes isolated from roots of Woollsia pungens (Cav.) F. Muell. (Epacridaceae) to utilise organic forms of nitrogen and phosphorus during growth in axenic culture was assessed. All isolates were able to utilise glutamine, arginine and bovine serum albumin (BSA), along with NH4+ or NO3–, in most cases yielding at least as much biomass as the ericoid mycorrhizal endophyte Hymenoscyphus ericae (Read) Korf & Kernan. All isolated endophytes were able to utilise BSA, arginine and glutamine as sole sources of N and C. With the exception of a single isolate (C40), which showed little growth on glutamine, biomass yields on glutamine as the sole N and C source was significantly greater for all isolates than on either of the other two organic N sources. Two isolates from W. pungens (C40 and A43) utilised DNA and sodium inositol hexaphosphate as sole P sources, in each case yielding significantly more biomass than H. ericae. The results suggest that mycorrhizal endophytes from epacrid plant hosts and those from ericaceous hosts have similar abilities to utilise organic forms of N and P.