Welcome to IMC 2018 International Mycological Congress
Conference Calendar
Fossil evidence of early Fungi and their role in the environment
- C. Strullu-Derrien
- T. Goral
- A. Spencer
- P. Kenrick
- J. Longcore
- M. Berbee
Abstract
Abstract
Fungi have been an important part of life on land for over 400 million years, playing crucial roles as decomposers as well as forming mutualistic or parasitic relationships with plants and other organisms. However direct fossil evidence of these associations is not visible before 407Ma because of the exceptional geological conditions required to preserve cellular and subcellular detail (e.g. rapid permineralization). Such conditions first occur in the 407 million-year-old Rhynie chert (Scotland, UK), which represents a privileged window into the paleontological past. Our objective is to document the early fungal diversity at this site and to understand the nature of the interactions between the fungi and other organisms. We are working principally with historical collections of thin sections that were made during the early part of the 20th century to document fossil plants. Now these sections have proven to be one of the best sources of material on early fungi. We first examined the fossils with standard light microscopy but have recently found that a combination of tools can be very effective for documenting early fungi and fungal associations. We use light microscopy with z-stacking montage, confocal laser scanning microscopy (CLSM) and digital 3D reconstructions obtained from the CLSM data with iso-surfaces digitally rendered using SPIERS and animations created in BlenderTM. This investigative approach allows us to characterize structures with a resolution of <1µm and to compare resulting images with relevant living groups and appropriate life history stages. Here we present an overview of our current knowledge regarding early steps taken by fungi in conquering the land. Evidence from the Rhynie chert shows that fungi were already diversified. Symbiotic associations (arbuscular mycorrhizae) attributable to Glomeromycotina have long been known and have been described in both stages of the life cycle of a Rhynie chert plant. Other plants were colonized by Glomeromycotina but did not show all the characteristic features of symbiosis. Zoosporic fungi were diverse with Chytridiomycota occurring in organic-rich sediments in wetter parts of the landscape while Blastocladiomycota were mostly associated with plants or plant debris. We recently demonstrated the occurrence of multiple colonizations of a single plant by different types of mycorrhizal fungi (Glomeromycotina and Mucoromycotina) and described fossil Blastocladiomycota, one of which is the earliest known fungal clade to develop hyphae, which likely served as a saprotrophic adaptation to patchy resource availability. A fossil Chytridiomycota has also been found showing that zoosporic fungi were likely important to the mobilisation of nutrients in early aquatic foodwebs. One of the driving forces behind the diversity of the early fungi could be the environments encountered. In the Rhynie chert, these ranged from terrestrial to fully freshwater and saline. This early fossil record is beginning to reveal fungal diversity and the important roles that fungi were playing in the earliest land communities. Interest in fossils is stimulated by our growing understanding of the diversity of modern early-diverging fungi, their life history stages and their roles in today’s ecosystems.
Evolution of diverse plant penetration strategies in pathogenic fungi.
- F. Trail
- C. Miguel-Rojas
- Z. Wang
- J. Townsend
Abstract
Abstract
Fungal spores are responsible for initiation and propagation of a majority of biotic plant diseases. Although spore germination is the first step in most fungal diseases, the genetics of spore germination has never been comparatively explored across multiple fungal lineages. Here we use comparative transcriptomics of spore germination among six fungi to determine how expression of orthologous genes has changed during evolution. and to predict genes whose knockouts will exhibit phenotypic differences in the spore germination and host penetration processes. We have chosen fungi which represent different approaches to plant penetration, including penetration using melanized appressoria, penetration through natural openings and direct penetration without melanization. To provide a basis for comparison among species and to identify infection-specific expression patterns, we compare transcriptional profiles during germination on a single defined medium as well as differences during germination on hosts. We used estimations of ancestral gene expression for orthologous genes common among all species to identify genes that undergo transcriptional shifts during the spore germination process, as well as those that are unique to infective germination, and those that are unique to specific fungi. Functional assays of a subset of genes exhibiting species-specific and infection-type specific upregulation were performed to determine the roles of these genes in conidial germination of these fungi. These experiments contribute to our understanding of how shifts in gene expression drive the evolution of conidial germination in a wide range of fungi.
Reassembling the ancient molecular toolkit for cellular morphogenesis in the Fungi
- J. Dee
- M. Berbee
Abstract
Abstract
Advancements in next-generation sequencing technologies and community sequencing initiatives, pairing mycologists with sequencing institutions such as the Joint Genome Institute, have gifted us with an unprecedented amount of sequence data from species all over the fungal tree of life and the rest of the eukaryotic domain. We now have an opportunity to view these data through the lens of evolution, evaluating how fungi have changed since their departure from the common ancestor that they share with animals. Investigations of morphogenetic protein function and localization in model yeast and hyphal fungi have provided a robust foundation for understanding the mechanisms of fungal morphogenesis. While parallel studies of protein function and localization cannot yet be pursued in some of the early diverging lineages including Chytridiomycota, Blastocladiomycota, and Zoopagomycota due to the lack of a tractable genetic transformation systems in target organisms, the first step is to identify and compare genes encoding proteins required for morphogenesis in these taxa. Here, we took a comparative approach, reviewing literature on septins, myosins, actin and actin binding proteins in Dikarya and other early diverging lineages. We conducted phylogenomic surveys revealing that seven families of actin binding proteins examined existed prior to the radiation of fungal phyla. Contrary to conventional notions of complexity in the fungi, most of the examined actin binding protein families were just as diverse in zoosporic Chytridiomycota as in Dikarya that have been examined thus far. While three of the actin binding genes that I surveyed here were maintained as single copy genes, the other four gene families underwent lineage specific duplications, which may have contributed to the evolution of morphological diversity in Chytridiomycota. In combination, phylogenetic analyses, molecular genetic analysis, and microscopy are beginning to tear away the curtains of time that mask the ever-changing molecular machinery that gave rise to hyphae and multicellularity in modern fungi.
The nature of early terrestrial communities
- P. Kenrick
- R. Mitchell
- C. Strullu-Derrien
- A. Spencer
- R. Garwood
Abstract
Abstract
Life on land during the early part of the Palaeozoic Era (396-541Myrs) has been likened to modern cryptogamic ground covers (CGCs), which today are photoautotrophic communities that grow on the surfaces of soils, rocks and plants. They are made up of variable proportions of bryophytes, lichens, algae, fungi and cyanobacteria, and they host various groups of animals, predominantly arthropods. Capable of tolerating widely varying environmental regimes encompassing extremes of aridity, temperature and UV flux, CGCs are widespread, and today they are thought to be responsible for an estimated 7% of net primary productivity and almost 50% of nitrogen fixation globally. Our objective is to investigate the nature of CGCs and their impacts on the environment and soil formation during what is arguably the acme of their development. This followed the origins of land plants, recently estimated to lie in an interval between mid-Cambrian (~515.2 Ma) and early Ordovician (~473.5 Ma), and preceded the evolution of forest ecosystems during the mid-Devonian (~385Ma). Early plant-bearing deposits are mostly allochthonous, so we are focusing initially on the 407 million-year-old Rhynie cherts (Scotland, UK) because the biota is fossilised more or less in situ and the preservation of the organisms and their associations is exceptional. As the roles of organisms in the formation of ancient CGC soils are largely unknown, we are developing an approach to characterizing these based on comparative analyses using modern analogues and a suite of analytical methods combining in situ imaging using X-ray micro-computed tomography in both the laboratory and synchrotron. The Rhynie cherts and their soil community contain many of the components of modern CGCs, including small-stature cryptogamic plants with rhizoidal rooting systems, fungi, cyanobacteria, green algae, fungus-like oomycetes, nematodes and a diverse community of arthropods. There is limited evidence for lichen-like associations, but more compelling fossils have recently been documented at contemporaneous sites elsewhere. Plant growth forms and symbiotic associations with fungi indicate that moss dominated CGCs—and especially peat forming systems—are not the best modern analogues. Liverworts are a more appropriate model for the plant component. Other key differences to many modern CGCs include the absence of annelids and ants; also absent were the most aggressive white rot lignin decomposing fungi of the Agaricomycetes, implying that there were key differences in the recycling of soil organic carbon. CGCs were the earliest soil forming communities and the organisms that they contained may have had the capacity to aggregate sediments and to weather minerals and clasts. Imaging and in situ chemical analyses of micro-dissolution features in soils and regoliths brings a novel perspective to studying early terrestrial communities and to understanding their broader impacts on Earth systems.
Proposal for practical classification of fungi within eukaryotes based on monophyly and comparable divergence time, and communication of higher-level taxa
- L. Tedersoo
Abstract
Abstract
Much of the ecological, taxonomic and biodiversity research relies on understanding of phylogenetic relationships among organisms. There are multiple available classification systems that all suffer from differences in naming, incompleteness, presence of multiple non-monophyletic entities and poor correspondence of divergence times. These issues render taxonomic comparisons across the main groups of eukaryotes and all life in general difficult at best. By using the monophyly criterion, roughly comparable time of divergence and information from multiple phylogenetic reconstructions, I propose an alternative classification system for the domain Eukarya to improve hierarchical taxonomical comparability for animals, plants, fungi and multiple protist groups. Following this rationale, I propose 32 kingdoms of eukaryotes that are treated in 10 subdomains. These kingdoms are further separated into 43, 115, 140 and 353 taxa at the level of subkingdom, phylum, subphylum and class, respectively (bioRxiv 2017:240929). In Fungi, nine subkingdoms and 19 fungal phyla are proposed. The kingdom Nucleariae (phyla Nuclearida and Fonticulida) is treated as a sister group to Fungi. In addition to widely accepted phyla, it is proposed to adopt phylum rank to Aphelidiomycota, Basidiobolomycota, Calcarisporiellomycota, Glomeromycota, Entomophthoromycota, Entorrhizomycota, Kickxellomycota, Monoblepharomycota, Mortierellomycota and Olpidiomycota given their deep divergence.
Elucidation of the “enigma” of Aenigmatospora
- Y. Degawa
- N. Tanaka
- H. Masumoto
- K. Seto
Abstract
Abstract
Sporulations of enigmatic fungus Aenigmatospora pulchra, described by Castañeda et al. (1999), were repeatedly observed on the dungs of millipedes. When the basal part of the conidiophore buried in the dung was gently washed in the water, the conidiophore stalk found to be connected to a large cylindrical cell. These cylindrical cells are superficially similar in shape and size with the arthrospores of Etenerobryus sp. (Eccrinales) inhabited in the hindgut of millipedes whose dungs harbor A. pulchra. Based on these morphological observation, Degawa (2005) speculated that A. pulchra must be an unknown stage of Enterobryus. However, as the results of recent careful reinvestigations, this hypothesis was denied. Here, we report the new discoveries. In the gut of millipedes, in addition to the genus Enterobryus, a similar shaped organism called Mononema often coexists. The genus Mononema is a fungus-like organism described by Balbiani (1889) and now included 3 spp. growing in the foregut of centipedes and millipedes. Lichtwardt (1986) excluded Mononema from the “Trichomycetes” and its real taxonomnic position is uncertain. Unidentified species of Mononema was frequently detected in the oesophagus of the field-collected millipedes individuals. Its arthrospores and the basal cylindrical cells of A. pulchra emerged on the dung of the same individuals are similar in shape and size. When the mature arthrospores were carefully picked up and put on the surface of plain agar, it sometimes germinated to produce incomplete conidiophores. As a result of sequencing the partial 18SrDNA of both of the arthrospores of Mononema and conidia of A. pulchra, they are almost identical and belonged to the Kickxellomycotina. These morphological observations and molecular data strongly support that A. pulchra was an unnoticed stage of the genus Mononema of the Kickxellomycotina and not Enterobryus. When the spore of A. pulchra was crashed under the cover glass, the endogenously produced double-walled spore was extruded from the echinulate wall, indicating that spores of A. pulchra are not “condia” but “unisporous sporangiole”. This feature also supports the phylogenetic position of A. pulchra-Mononema in the Kickxellomycotina.