Welcome to IMC 2018 International Mycological Congress
Conference Calendar
An Overview of Bolete Systematics: Attention to details
- R. Halling
Abstract
Abstract
The taxonomy and systematics of Boletes has a long history. For much of that time, concepts of genera and species were based on morphological features and ecological preferences displayed by taxa in the Northern Hemisphere – primarily Europe and North America. Increased exploration of the tropics, southern hemisphere, and other under explored/remote areas has revealed previously undocumented complexity that has challenged existing taxonomic concepts. The application of contemporary technologies and methodologies has shifted the paradigm of bolete classification. The use of cladistic approaches to analyze DNA sequences via powerful computational tools has fundamentally changed bolete systematics from an alleged artificial system to one that is deemed less subjective based on hypotheses of evolutionary descent. Our recent efforts with the latter approach have resulted in a proliferation of taxonomic hypotheses; some withstanding further testing, others not. A verifiable framework is needed within which the details of morphology, sequence data, biogeographic and ecological factors can be evaluated.
Functional and evolutionary genetics of zinc tolerance in the ectomycorrhizal fungus Suillus luteus
- J. Ruytinx
- L. Coninx
- J. Colpaert
Abstract
Abstract
Suillus luteus is a cosmopolitan fungal species, symbiotically associated with pine trees. In primary successions of pines this species is abundant and involved in seedling establishment. On severely metal-contaminated soils, metal tolerant S. luteus populations evolved by natural selection. Tolerant individuals effectively protect their host tree from metal toxicity on these soils. However, the molecular and genetic mechanisms underlying adaptive metal tolerance in S. luteus are unknown. We hypothesize that tolerance phenotypes are due to an adaptation in the common metal homeostasis network. By comparative and functional genetics we identified several S. luteus genes encoding transporters involved in metal homeostasis. One of these transporters, SlZnT2, a CDF family transporter exhibits a differential gene expression among Zn-tolerant and Zn-sensitive phenotypes. The difference in expression level seems to be due to an extensive gene multiplication and differences in cis-regulation. Analyzing natural populations, tolerance phenotype is correlated with SlZnT2 gene copy number and associated with particular promoter genotypes. SlZnT2 is predicted to be localized on the tonoplast and to move Zn from the cytoplasm into the vacuole. Comparative genomics of different isolates representing distinct metal tolerance phenotypes is ongoing to identify the genetic loci associated with adaptive Cd and Cu tolerance. Altogether results of this study will be valuable to select ectomycorrhizal genotypes to support restoration of metal polluted soils.
Phylogenomics of the Boletaceae using generic level sampling and low coverage whole genome sequencing
- B. Dentinger
- R. Halling
- T. Henkel
Abstract
Abstract
Boletaceae is one of the largest and most successful families of ectomycorrhizal fungi. Despite their ubiquitous presence in ECM communities worldwide and high scientific interest among taxonomists, a robust intrafamilial phylogeny that implicates unequivocal generic level clades has remained frustratingly elusive. Bolete genera were traditionally defined based on morphology of north temperate taxa, but such character packages are ill-suited for the wealth of tropical species, many of which are new to science. Recent multigene phylogenetic analyses that included taxa from undersampled regions have revealed discrete terminal clades emerging from a largely unresolved backbone, a result that has persisted since the first Boletaceae phylogenies appeared in the 1990s. This pattern may reflect a recent evolutionary radiation or may be an artifact of inadequate phylogenetic resolution from too few genes and/or incomplete taxon sampling. Despite this lack of resolution between clades, this pattern has resulted in a proliferation of new genera, with more than 1/3 of current generic names having originated within the last eight years. This study attempts to reconcile generic-level classification with improved phylogenetic resolution from a molecular dataset generated using low coverage whole genome sequencing from ~100 species of Boletaceae, representing exemplars of most of the 65 currently accepted genera. Additional overlooked or undescribed taxa from tropical Africa and South America are included. Phylogenetic hypotheses and their implications for taxonomy and biogeography will be discussed.
Environmental adaptation in Suillus brevipes (Boletales)
- S. Branco
- K. Bi
- H. Liao
- P. Gladieux
- H. Badouin
- C. Ellison
- N. Ngyuen
- R. Vilgalys
- K. Peay
- J. Taylor
- T. Bruns
Abstract
Abstract
Recent advancements in sequencing technology allowed to better address the patterns and mechanisms involved in fungal environmental adaptation by identifying putative adaptive genes and providing a framework to further investigate the genetic basis of adaptation. Here, we report on ongoing studies investigating the physiological and genomic basis of environmental adaptation in species of the genus Suillus brevipes (Boletales). Whole genome scans in this widespread pine-associated species from across North America showed signatures of positive selection and genomic sites significantly associated with climate regimes and soil chemistry. Gene ontology enrichment analyses highlighted genes involved in transmembrane transport of substances and helicase activity that are potentially involved in both salt tolerance and cold stress response. We unveiled genomic regions underlying fungal adaptation and established links between phenotypes and genotypes, contributing for understanding how environmental conditions shape evolution.
Mutualistic coevolution mediating species and population level biodiversity of ectomycorrhizal fungi
- H. Liao
- S. Branco
- N. Nguyen
- P. Kennedy
- C. Hsu
- K. Chen
- A. Kuo
- K. Barry
- I. Grigoriev
- D. Hoyt
- R. Tappero
- R. Vilgalys
Abstract
Abstract
Species of the ectomycorrhizal bolete genus Suillus exhibit strong host-specific associations with members of the conifer family Pinaceae, suggesting a long history of fungal-plant coevolution with different species of pines, larches, and Douglas fir. Suillus species are often prominent members of the early successional ectomycorrhizal community of forests, and play a key role in their establishment, growth, spread, and ecosystem function. Using genomics-based approaches, we are developing the Suillus-Pinaceae symbiosis as a model for the study of ectomycorrhizal fungal diversity and function. Genome sequencing of over 50 Suillus species is underway to facilitate the study of the molecular evolutionary history of the entire genus for the first time. Using whole-genome sequencing, we are also examining finer-scale patterns of divergence within several globally distributed species (S. brevipes, S. luteus) using population genomics. To address molecular mechanisms involved in Suillus-Pinaceae coevolution we are using combined ‘omics-based approaches to study the genome-wide expression of interacting plant and fungal symbionts at several levels including (a) mycorrhizal compatibility interactions across a phylogenetically broad range of Suillus-Pinaceae species pairings (b) within-species variation (S. brevipes-Pinus spp.) across geographic and host ranges. RNA-Seq data is being used to estimate expression and diversity of global genes involved in fungal-host plant crosstalk (effector-receptor interaction), zinc uptake, symbiosis maintenance and C/N/P allocation. Our study indicates the genetic elements required for Suillus-plant crosstalk underwent very recent genome evolution. This implies that genetic coevolution has potential to affect both within- and across-species diversity. The research outcomes will have the significant impact on expanding the theory of mutualistic coevolution and allow us to predict the effects of host-driven biological diversity on ecosystem function.
Host range and specificity of ectomycorrhizal genus Suillus with different Pinaceae hosts
- A. Rojas
- Y. Ke
- K. Hameed
- H. Cotter
- H. Liao
- N. Nguyen
- P. Kennedy
- R. Vilgalys
Abstract
Abstract
Though many species of ectomycorrhizal fungi are often reported to exhibit host specificity with different plant taxa, experimental evidence is often lacking and the mechanisms controlling mycorrhizal compatibility are still largely unknown. One well-known example of host specificity is the bolete genus Suillus which forms ectomycorrhizae (ECM) almost exclusively with members of the conifer family Pinaceae. Many species of Suillus spp. are reported to only occur only in association with certain genera and subgenera of Pinaceae including Pinus subgenera Strobus and Pinus, Larix, Picea, Abies, or Pseudotsuga. Using basidiospore-seedling bioassays, we addressed the host-range and specificity of 98 collections of Suillus representing 37 morpho-species from 25 different locations across North America for their ability to form ECM with diverse host species of Pinaceae. Basidiospore suspensions (5 x106 spores/mL) were used to inoculate seedlings of 10 different Pinaceae host genotypes. Inoculated plants were grown in the Duke Phytotron under controlled conditions (20ºC, 16h/8h day/night, with regular overhead watering) and assessed for growth and mycorrhizal colonization after 180 days. Identity of Suillus spp. forming ECM was confirmed by PCR and by culturing of ECM-colonized root tips. Most Suillus species collected under a given species of Pinus also formed ECM with other species of the same host, though with different levels of colonization. Suillus spp. collected under Larix and Pseudotsuga showed high specificity for their original host, however, some strain had limited cross-compatibility with Pinus sylvestris. Overall, colonization levels were lower on Larix and Pseudotsuga with respect to the Pinus hosts included in the study. Using multilocus sequence genotyping, both dikaryotic and monokaryotic cultures were isolated from ECM root tips, suggesting that haploid mycelia are capable of forming persistent ECM.