Ectomycorrhizal Root Research Articles

Global patterns and determinants of bacterial communities associated with ectomycorrhizal root tips of Alnus species

Plant-soil interactions affect plant health, productivity and vegetation structure. Although recent advances in sequencing and computational tools have facilitated research on these complex interactions, we still have a poor understanding of the relative influence of biotic and abiotic factors on their community assembly. Here we aimed to determine the relative contributions of Alnus species and their associated mycorrhizal fungi, spatial, edaphic and climatic factors to the structure of root-associated bacterial communities. We used high-throughput identification of bacteria based on 369 ectomycorrhizal root tips of 19 Alnus species from 85 sites across the globe. We found that the Alnus species phylogeny was the primary determinant for the composition of root-associated bacterial communities, followed by edaphic, spatial and climate variables. Moreover, we observed Alnus species-specificity for some highly abundant bacterial phylotypes. These results reflect the importance of biotic variables in shaping root-associated bacterial communities and suggest that different processes underlie root-associated and soil bacterial communities on a global scale.

Novel Laccaria Species From Juglandaceae Forest in Panama With Notes on Their Ecology.

Since 2013 there have been 22 new species of Laccaria described worldwide. Only three of these represent species from the neotropics. In Panama, Laccaria is abundant in monodominant Oreomunnea mexicana (Juglandaceae) forests based on sporocarps and environmental sequencing of roots. This study uses a combination of morphological and phylogenetic evidence to document up to seven species of Laccaria from these forests, one previously described, three described as new, and three requiring more data before being formally described. Molecular data used for phylogenetic analysis include the nuclear ribosomal ITS and 28S regions, along with TEF1 and RPB2. Laccaria stellata, has previously been reported from O. mexicana cloud forests of Panama. Laccaria dallingii sp. nov., L. nitrophila sp. nov., and L. fortunensis sp. nov. are described as new based on morphology and phylogenetic analysis of multiple collections. A taxon referred to as “PAN sp3” is resolved sister to L. stellata. Phylogenetic analysis also resolved two separate clades of Panamanian Laccaria as sister to L. roseoalbescens, a species previously described from Mexico. These three taxa are not described in this paper as there is too little material from which to make effective morphological descriptions even though their placement in phylogenetic analysis identify them as being unique. Ecologically, all described species except for L. fortunensis were amplified from O. mexicana ectomycorrhizal root tips. L. nitrophila was one of the most recovered species from the roots of O. mexicana in a previous study, and it has been shown to respond positively to long term nitrogen addition. Our results expand the knowledge of Laccaria diversity for Central America and highlight that at least some species of Laccaria are nitrophilic in neotropical Juglandaceae forests as well as in temperate forests.

Winter soils of Mongolian forests have viable ectomycorrhizas and soil enzymatic activity

In forests in Mongolia, tree roots and ectomycorrhizal fungi must survive several months of soil freezing in winter. To investigate the ectomycorrhizal community after winter, we collected fine roots of Scots pine (Pinus sylvestris) and Siberian pine (Pinus sibirica) and associated soil from Nukht forest in the Bogd-Khan National Reserve, Mongolia. Soil samples were collected from frozen soil at the end of April 2016. We described the ectomycorrhizal community, and determined on ectomycorrhizal roots tips and in soils the potential activity of enzymes involved in the degradation of soil organic matter. In order to assess the temperature sensitivity of enzyme activity, potential soil enzyme activities were assayed at temperatures from 5 to 20 °C. We detected 24 different ectomycorrhizal morphotypes associated with Pinus sylvestris and Pinus sibirica, and 18 morphotypes were identified to taxa. The two Pinus species had dissimilar ectomycorrhizal communities, and only 2 ectomycorrhizal fungal taxa were common to both species. Most ectomycorrhizal taxa had measurable activity of at least one extracellular enzyme. A high contribution to the community extracellular enzyme activity was shown for both abundant and less abundant taxa. Among the eight tested soil enzymes, only the activity of leucine amino peptidase showed consistent higher Q10 values at 5–15 °C than at 10–20 °C, suggesting that the enzyme is adapted to colder temperatures. Total soil N was the strongest factor explaining differences in soil enzyme potential activity. A positive relationship was found between soil N and the soil potential enzyme activity of acid phosphatase. We suggest that viable ectomycorrhizas during winter provide an advantage to Pinus sibirica and Pinus sylvestris in acquiring nutrients as soil thaws in spring.

Temporal changes in enzyme activities associated with ectomycorrhizas and soil from secondary deciduous dipterocarp forest fragments

Ectomycorrhizal (ECM) fungi form a symbiotic association with host trees, functionally promoting the nutrient uptake in the hosts via their secretion of enzymes to degrade organic compounds. Because of the involvement in nutrient cycling, ECM fungi are important to the establishment of host trees and forest recovery. In Thailand, ECM fungi are mostly associated with host tree species in the Dipterocarpaceae found in deciduous dipterocarp forests (DDFs), some of which are secondary forests naturally recovering after abandonment of logging and agriculture. To determine the function of ECM fungi in secondary DDFs, temporal changes in the ECM community structure and potential activities of three enzymes involved in nitrogen, carbon, and phosphorus cycling (β-N-acetylglucosaminidase, β-glucosidase, and acid phosphatase) from ECM roots and soils were investigated in two secondary DDF fragments in the Saraburi and Nan provinces of Thailand. A total of 180 soil samples from each forest were collected at four times across the wet and dry seasons from June 2015 to May 2016. Soil moisture content, total nitrogen, organic matter, and available phosphorus contents were measured. The results showed temporal changes in the ECM fungal communities and relative enzyme activities throughout the study period, although differences between the wet and dry seasons were not detected. The enzyme profiles associated with ECM roots were significantly correlated to the ECM communities in both DDFs. Moreover, the total nitrogen and soil moisture content influenced the temporal variation of ECM and soil enzyme profiles. These findings suggest the effect of edaphic factors combined with the ECM communities on their enzyme activities in secondary DDFs in Thailand.

A Survey of the Potential Ectomycorrhizal Fungi Associated With Nursery Seedlings of Seven Species of Exotic Quercus in China

ABSTRACT Seven species of Quercus have been introduced into China from the United States for their ecological and economic values. The beneficial association between Quercus trees and ectomycorrhizal (ECM) fungi is well recognized. However, the ECM fungal communities associated with these exotic oak trees grown in new environments are currently unknown. The aims of this work were to investigate the mycorrhizal status of nursery seedlings and identify the fungal communities in them. All Quercus tree species examined exhibited well-developed ECM roots. However, neither the morphology nor the color of the observed ECM types was distinctive, suggesting reduced ECM fungal diversity. The combined application of isolation and amplicon-based sequencing approaches revealed that the mycorrhizal taxa represented 5 orders and 12 genera in the Basidiomycota, but only the dominant genus Scleroderma (Boletales) was detected by both approaches. In addition, Scleroderma exhibited the lowest degree of host specificity, but relatively high interspecific genetic diversity. Isolates assigned to Sistotrema displayed taxonomic novelties based on sequence similarity searches against the GenBank database. Non-metric multidimensional scaling analysis showed a degree of differentiation of ECM communities among Quercus species. Our results provide insights into the identities of exotic Quercus-associated ECM fungi and will improve symbiosis-based seedling nursing technology.

Temperature affected the formation of arbuscular mycorrhizas and ectomycorrhizas in Populus angustifolia seedlings more than a mild drought

Arbuscular mycorrhizal (AM) plants and fungi associate with lower soil organic matter, higher pH, lower phosphorus and higher nitrogen than ectomycorrhizal (EM) ones. However, soil conditions correlate with climatic factors, and we suggest that temperature and humidity have also direct roles in the success of mycorrhiza types. The hypothesis here is that EM perform better at low temperatures than AM, and AM resist drought better than EM.Narrowleaf cottonwood (Populus angustifolia E. James) forms both AM and EM. We grew seedlings in soil at 14, 20 and 26 °C in factorial combinations with adequate watering and a cyclic mild drought for 4 and 7 weeks.As hypothesized, the percent of EM root tips was largest at 14 °C, while the proportional root length with AM was largest at the two higher temperatures. However, unlike expectations, drought increased EM formation slightly, while the AM colonization was lower in the dry treatment. Plant growth was reduced more by low temperature than drought. Root branching was more prominent at low temperature and root length and mass growth at higher temperatures.Soil nutrient availability did not provide a direct explanation to the results, as both soluble soil N and P were the same in 14 and 20 °C, while the change in mycorrhiza colonization took place between these temperatures. Differences in root morphology (root branching vs length) may affect the proportions of the mycorrhiza types at different temperature regimes. The most likely explanation to the differential colonization is that temperature affects AM and EM fungi in a different way. In nature, temperature and humidity regimes are tightly correlated, and temperature as such may be a stronger determinant for the success of mycorrhiza types than has been previously considered. The poorer performance of AM in low-temperature and drought conditions may reflect stress avoidance rather than stress tolerance by AM fungi.

Role of the proteome in providing phenotypic stability in control and ectomycorrhizal poplar plants exposed to chronic mild Pb stress

Lead is a dangerous pollutant that accumulates in plant tissues and causes serious damage to plant cell macromolecules. However, plants have evolved numerous tolerance mechanisms, including ectomycorrhizae, to maintain cellular Pb2+ at the lowest possible level. When those mechanisms are successful, Pb-exposed plants should exhibit no negative phenotypic changes. However, actual molecular-level plant adjustments at Pb concentrations below the toxicity threshold are largely unknown, similar to the molecular effects of protective ectomycorrhizal root colonization. In this study, we (1) determined the molecular adjustments in plants exposed to Pb but without visible Pb stress symptoms and (2) examined ectomycorrhizal root colonization (the role of fungal biofilters) with respect to molecular-level Pb perception by plant root cells. Biochemical, microscopic, proteomic and metabolomic studies were performed to determine the molecular status of Populus × canescens microcuttings grown in agar medium enriched with 0.75 mM Pb(NO3)2. Noninoculated and inoculated with Paxillus involutus poplars were analyzed in two independent comparisons of the corresponding control and Pb treatments. After six weeks of growth, Pb caused no negative phenotypic effects. No Pb-exposed poplar showed impaired growth or decreased leaf pigmentation. Proteomic signals of intensified Pb sequestration in the plant cell wall and vacuoles, cytoskeleton modifications, H+-ATPase-14-3-3 interactions, and stabilization of protein turnover in chronically Pb-exposed plants co-occurred with high metabolomic stability. There were no differentially abundant root primary metabolites; only a few differentially abundant root secondary metabolites and no Pb-triggered ROS burst were observed. Our results strongly suggest that proteome adjustments targeting Pb sequestration and ROS scavenging, which are considerably similar but less intensive in ectomycorrhizal poplars than in control poplars due to the P. involutus biofilter (as confirmed in a mineral study), were responsible for the metabolomic and phenotypic stability of poplars exposed to chronic mild Pb stress.

The proportions of ectomycorrhizal roots are varied depending on the different host plant compositions in Scottish arctic/alpine coastal relict vegetation

The relative abundance of ectomycorrhizal (ECM) roots in pure and mixed stand compositions of Dryas octopetala, Salix repens and Arctostaphylos uva-ursi grown in Scottish coastal arctic/alpine relict habitat was described through ECM morphotyping and comparisons of fungal internal transcribed spacer sequences. Neither specific ECM morphotypes nor the morphotype communities were found in association with any stand compositions. The proportions of the ECM roots on S. repens , however, were significantly less in pure stand and were further decreased in mixed with A. uva-ursi . Possible factors contributing the reduction, including the effects by other host species grown in proximity, are discussed. • ECM morphotype abundance was described in three arctic/alpine host species. • Neither specific ECM morphotypes nor their communities were found. • The proportions of ECM root tips on S. repens were less compared with other two. • The ECM root tips on S. repens grown with A. uva-ursi were further reduced.

The effects of ectomycorrhizal fungal networks on seedling establishment are contingent on species and severity of overstorey mortality.

For tree seedlings in boreal forests, ectomycorrhizal (EM) fungal networks may promote, while root competition may impede establishment. Thus, disruption to EM fungal networks may decrease seedling establishment owing to the loss of positive interactions among neighbors. Widespread tree mortality can disrupt EM networks, but it is not clear whether seedling establishment will be limited by the loss of positive interactions or increased by the loss of negative interactions with surrounding roots. Depending upon the relative influence of these mechanisms, widespread tree mortality may have complicated consequences on seedling establishment, and in turn, the composition of future forests. To discern between these possible outcomes and the drivers of seedling establishment, we determined the relative importance of EM fungal networks, root presence, and the bulk soil on the establishment of lodgepole pine and white spruce seedlings along a gradient of beetle-induced tree mortality. We manipulated seedling contact with EM fungal networks and roots through the use of mesh-fabric cylinders installed in soils of lodgepole pine forests experiencing a range of overstorey tree mortality caused by mountain pine beetle. Lodgepole pine seedling survival was higher with access to EM fungal networks in undisturbed pine forests in comparison with that in beetle-killed stands. That is, overstorey tree mortality shifted fungal networks from being a benefit to a cost on seedling survival. In contrast, overstorey tree mortality did not change the relative strength of EM fungal networks, root presence and the bulk soil on survival and biomass of white spruce seedlings. Furthermore, the relative influence of EM fungal networks, root presence, and bulk soils on foliar N and P concentrations was highly contingent on seedling species and overstorey tree mortality. Our results highlight that following large-scale insect outbreak, soil-mediated processes can enable differential population growth of two common conifer species, which may result in species replacement in the future.

Fungal diversity in canopy soil of silver beech, Nothofagus menziesii(Nothofagaceae).

Adventitious roots in canopy soils associated with silver beech (Nothofagus menziesii Hook.f. (Nothofagaceae)) form ectomycorrhizal associations. We investigated the extent to which canopy ectomycorrhizal communities contribute to overall diversity of ectomycorrhizal fungi associated with silver beech. Hyphal ingrowth bags were buried for 12 months in canopy and terrestrial soils of five trees at one site. We used amplicon sequencing of the nuclear ribosomal internal transcribed spacer 2 region (ITS2) to assess diversity of both ectomycorrhizal and non-ectomycorrhizal OTUs in hyphal ingrowth bags. There was a significant difference in ectomycorrhizal fungal community diversity between the terrestrial and canopy hyphal ingrowth bag communities. Ectomycorrhizal community composition of the terrestrial and canopy environments was also significantly different. Some ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The hyphal ingrowth bags also accumulated non-ectomycorrhizal species. The non-ectomycorrhizal fungi also had significantly different diversity and community composition between the canopy and terrestrial environments. Like the ectomycorrhizal community, some non-ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The canopy soil microhabitat provides a novel environment for growth of ectomycorrhizal adventitious roots and enables the spatial partitioning of ectomycorrhizal and non-ectomycorrhizal fungal diversity in the forest.

Sibling spore isolates of Tricholoma matsutake vary significantly in their ectomycorrhizal colonization abilities on pine hosts in vitro and form multiple intimate associations in single ectomycorrhizal roots

Abstract Tricholoma matsutake is a commercially important edible ectomycorrhizal mushroom. The ecology of this species has emerged from studies of the genetic background of mycelial colonies in nature. Single putative colonies sometimes comprise several genets. This complex mycelial structure should be subjected to analysis to determine its ecophysiological significance. We tested the ectomycorrhization ability of nine T. matsutake sibling spore isolates. The ectomycorrhizal colonization ratio differed significantly among isolates, and was dependent on the soil nitrogen content. Mixed inoculations of three selected isolates into soils in which single pine seedlings were grown showed that the isolates interacted in the seedling roots. Paired inoculations of isolates #52/#99 and #52/#84, and a triple inoculation of isolates #52/#84/#99 resulted in levels of ectomycorrhizal colonization that significantly exceeded the colonization levels following single isolate inoculation. We suggest that mycelial interaction between sibling isolates is a significant phenomenon that operates within individual ectomycorrhizal pine root tips.

Temperature changes affect multi-trophic interactions among pines, mycorrhizal fungi, and soil nematodes in a microcosm experiment

Nematodes serve a key role in soil nutrient cycling by eating bacterial cells and fungal hyphae. However, little is known about how temperature changes affect multi-trophic interactions among host trees, root-associating fungi, and nematodes. The aim of this study was to identify abiotic and/or biotic factors that affect soil nematode communities. We constructed a pot microcosm with sandy soils from a coastal Pinus thunbergii forest. The soil-filled pots were incubated for 8 months at 20, 25, or 30 °C with or without pine seedlings. In the pots with seedlings, we measured the percentages of black, white, and brown ectomycorrhizal (ECM) formations on roots. Nematodes retrieved from the soils were morphologically identified to genus and differentiated by both trophic and community structures. The occurrence of ECM formation ranged from 85.7%–91.9%. Black ECM roots were significantly dominant at 30 °C (47.0 %), whereas white ones were significantly dominant at 20 °C (43.0 %) and 25 °C (53.0 %). The number of nematodes at 25 and 30 °C was significantly greater than that at 20 °C irrespective of the presence or absence of seedlings. In terms of trophic compositions, the relative abundance of fungivorous nematodes significantly increased from 10.4 % at 20 °C to 27.5 % at 25 °C to 44.6 % at 30 °C in the presence of pine seedlings. A non-metric multidimensional scaling scatter plot showed that the nematode communities clustered significantly among temperature treatments. Structural equation modeling indicated that nematode trophic compositions were directly regulated by temperature and the presence of pine seedlings. Our findings suggest that temperature has some cascading effects on the formation of nematode communities, and pine seedlings and associating ECM fungi contributed synergistically to the formation of their communities.

How deep can ectomycorrhizas go? A case study on Pisolithus down to 4 meters in a Brazilian eucalypt plantation.

Despite the strong ecological importance of ectomycorrhizal (ECM) fungi, their vertical distribution remains poorly understood. To our knowledge, ECM structures associated with trees have never been reported indepths below2 meters. In this study, fine roots and ECM root tips were sampled down to 4-m depth during the digging of two independent pits differing by their water availability. A meta-barcoding approach based on Illumina sequencing of internal transcribed spacers (ITS1 and ITS2) was carried out on DNA extracted from root samples (fine roots and ECM root tips separately). ECM fungi dominated the root-associated fungal community, with more than 90% of sequences assigned to the genus Pisolithus. The morphological and barcoding results demonstrated, for the first time, the presence of ECM symbiosis down to 4-m. The molecular diversity of Pisolithus spp. was strongly dependent on depth, with soil pH and soil water content as primary drivers of the Pisolithus spp. structure. Altogether, our results highlight the importance to consider the ECM symbiosis in deep soil layers to improve our understanding of fine roots functioning in tropical soils.

Effects of bacterial strains isolated from the ectomycorrhizal roots of Laccaria parva on sporocarp production by the fungus in vitro

Abstract The effects of bacteria isolated from ectomycorrhizas on sporocarp production of Laccaria parva were examined in vitro. Three bacterial strains of Bradyrhizobium were selected on the basis of their affinity for L. parva LL02 in previous confrontation tests: a positive or a negative strain that significantly increased or decreased hyphal extension areas, and a neutral strain that did not have significant effects on them. Mycelia of LL02 and a suspension of each bacterial strain were inoculated onto a surface-sterilized pine seedling in a glass bottle and then incubated for 3 mo in an illuminated incubator. Plant biomass did not differ significantly among the treatments, but the level of ectomycorrhizal colonization was low in the treatment inoculated with a negative strain (Neg treatment). The frequency with which mature sporocarps occurred was higher in treatments inoculated with positive (Pos treatment) or neutral strains (Neu treatment) compared with control and Neg treatments. The ratio of biomass accounted for by mature sporocarps was low in control and Neg treatments, and high in Pos and Neu treatments. These results indicate that bacteria colonizing ectomycorrhizas affect the production of sporocarps and that the affinity between fungi and bacteria is likely to underlie this interaction.

SlZRT2 Encodes a ZIP Family Zn Transporter With Dual Localization in the Ectomycorrhizal Fungus Suillus luteus.

Ectomycorrhizal (ECM) fungi are important root symbionts of trees, as they can have significant effects on the nutrient status of plants. In polluted environments, particular ECM fungi can protect their host tree from Zn toxicity by restricting the transfer of Zn while securing supply of essential nutrients. However, mechanisms and regulation of cellular Zn homeostasis in ECM fungi are largely unknown, and it remains unclear how ECM fungi affect the Zn status of their host plants. This study focuses on the characterization of a ZIP (Zrt/IrtT-like protein) transporter, SlZRT2, in the ECM fungus Suillus luteus, a common root symbiont of young pine trees. SlZRT2 is predicted to encode a plasma membrane-located Zn importer. Heterologous expression of SlZRT2 in yeast mutants with impaired Zn uptake resulted in a minor impact on cellular Zn accumulation and growth. The SlZRT2 gene product showed a dual localization and was detected at the plasma membrane and perinuclear region. S. luteus ZIP-family Zn uptake transporters did not show the potential to induce trehalase activity in yeast and to function as Zn sensors. In response to excess environmental Zn, gene expression analysis demonstrated a rapid but minor and transient decrease in SlZRT2 transcript level. In ECM root tips, the gene is upregulated. Whether this regulation is due to limited Zn availability at the fungal–plant interface or to developmental processes is unclear. Altogether, our results suggest a function for SlZRT2 in cellular Zn redistribution from the ER next to a putative role in Zn uptake in S. luteus.

Large, high-severity burn patches limit fungal recovery 13 years after wildfire in a ponderosa pine forest

Over the past three decades, wildfires in southwestern US ponderosa pine (Pinus ponderosa Lawson & C. Lawson) forests have increased in size and severity. These wildfires can remove large, contiguous patches of mature forests, alter dominant plant communities and increase woody debris, potentially altering fungal community composition. Additionally, post-fire conditions may shift dominant fungal functional groups from plant-symbiotic ectomycorrhizal (EM) fungi to more decomposer saprotrophic fungi. We investigated the long-term (13 years post-wildfire) effect of fire severity on 1) fungal sporocarp density, functional groups and community composition and 2) EM colonization and community composition from naturally regenerating ponderosa pine seedlings on the Pumpkin Fire that burned in 2000 in Arizona, USA. Plots were located in four burn severity classes: unburned, moderate-severity, and two high-severity (defined as 100% tree mortality) classes, either adjacent to residual live forest edges (edge plots), or >200 m from any residual live trees (interior plots). We found that high-severity burn plots had a unique sporocarp community composition, and a shift in dominant sporocarp functional groups, with 5–13 times lower EM sporocarp densities, and 4–7 times lower EM sporocarp species richness compared to unburned and moderate-severity plots. In contrast, saprotrophic sporocarp densities and richness were similar among burn severity classes, even with the large amount of coarse wood in the high-severity burn patches. Regenerating ponderosa pine seedlings had similar EM colonization and richness among severity classes, yet high-severity interior plots had a different community composition and a lower relative abundance of EM species compared to moderate-severity burn plots. Taken together, our results suggest that large patches of high-severity fire have long-term consequences for both EM sporocarp and root tip communities. Because EM fungal species vary in function, the limited species pool available in interior high-severity burn patches may influence pine recovery.

Amanita subjunquillea and its ectomycorrhizal association, reported as new for Pakistan

Amanita subjunquillea and its ectomycorrhizal association are reported for the first time from moist temperate Himalayan forests of Pakistan. The sample was studied based on morphological characters and nucleotide sequence analyses of the ITS region generated from basidiomata and ectomycorrhizal roots of Quercus floribunda. Our collection differs from the type in its dark orange pileus disc and pale yellow margins. Remaining morphological and molecular data are consistent with previously reported specimens. This represents the first report of A. subjunquillea from Pakistan.

Are Trechisporales ectomycorrhizal or non-mycorrhizal root endophytes?

Trechispora (Hydnodontaceae) is considered as a soil-inhabiting fungus. However, some species in the genus are frequently forming basidiomes on soil, a typical feature of ectomycorrhizal fungi. Ectomycorrhizal basidiomes are found in neotropical and subtropical region, but taxonomical information and DNA sequences of root fungi and basidiomes from native Atlantic Rainforest are poorly reported. Basidiomes and soil samples including roots, humus layer, and mineral soil were collected in the Atlantic Rainforest, in Florianopolis (South of Brazil). Sequences of the ITS region were obtained from all sample types and subjected to phylogenetic reconstruction. Two sequences amplified from apparently ectomycorrhizal roots belonged to Trechispora and suggested a root-associated ecology, at least biotrophic and possibly ectomycorrhizal. The analysis of isotope abundance in the same Brazilian site and in French Guiana showed that Trechispora thelephora has high 15N abundance and is often intermediate between ectomycorrhizal and saprotrophic species in 13C abundance. This is congruent with a plant biotrophic ecology, perhaps ectomycorrhizal. Future investigations in subtropical regions are needed to determine whether such a mode of nutrition is widespread among Trechispora.

Regulation of the leaf proteome by inoculation of Populus \xd7 canescens with two Paxillus involutus isolates differing in root colonization rates

During ectomycorrhizal symbioses, up to 30% of the carbon produced in leaves may be translocated to the fungal partner. Given that the leaf response to root colonization is largely unknown, we performed a leaf proteome analysis of Populus × canescens inoculated in vitro with two isolates of Paxillus involutus significantly differing in root colonization rates (65 ± 7% vs 14 ± 7%), together with plant growth and leaf biochemistry analyses to determine the response of plant leaves to ectomycorrhizal root colonization. The isolate that more efficiently colonized roots (isolate H) affected 9.1% of the leaf proteome compared with control plants. Simultaneously, ectomycorrhiza in isolate H-inoculated plants led to improved plant growth and an increased abundance of leaf proteins involved in protein turnover, stress response, carbohydrate metabolism, and photosynthesis. The protein increment was also correlated with increases in chlorophyll, foliar carbon, and carbohydrate contents. Although inoculation of P. × canescens roots with the other P. involutus isolate (isolate L, characterized by a low root colonization ratio) affected 6.8% of the leaf proteome compared with control plants, most proteins were downregulated. The proteomic signals of increased carbohydrate biosynthesis were not detected, and carbohydrate, carbon, and leaf pigment levels and plant biomass did not differ from the noninoculated plants. Our results revealed that the upregulation of the photosynthetic protein abundance and levels of leaf carbohydrate are positively related to rates of root colonization. Upregulation of photosynthetic proteins, chlorophyll, and leaf carbohydrate levels in ectomycorrhizal plants was positively related to root colonization rates and resulted in increased carbon translocation and sequestration underground.

Molecular and morphological evidence place Pholiota psathyrelloides from Patagonia within the ectomycorrhizal genus Psathyloma (Agaricales)

ABSTRACTPsathyloma is an agaricoid genus described recently to accommodate two species of brown-spored agarics from Australasia superficially similar to Psathyrella and Hebeloma. Phylogenetic analyses published along with the description of the genus determined that an unidentified species of Psathyloma was also present in Patagonia based on ITS sequences from ectomycorrhizal root tips of Nothofagaceae trees. Based on morphological and phylogenetic analyses of fresh mushroom collections from Patagonia, we determine that the unknown South American Psathyloma corresponds to Pholiota psathyrelloides, a species described by Rolf Singer in 1969 from Nothofagaceae forests in Argentina. Here we transfer this species to the genus Psathyloma and provide detailed morphological data and illustrations of fresh collections. Psathyloma is confirmed as an ectomycorrhizal genus with a disjunct southern Gondwanan distribution that is similar to what has been found for other Austral ectomycorrhizal fungal genera such as Austropaxillus and Descolea.