Glomus (fungus)

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Glomus
Glomus australe fornerly Endogone australis.jpg
Glomus australe formerly Endogone australis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Glomeromycota
Class: Glomeromycetes
Order: Glomerales
Family: Glomeraceae
Genus: Glomus
Tul. & C.Tul. (1845)
Type species
Glomus macrocarpum
Tul. & C.Tul. (1845)
Species

ca. 85 species described

Synonyms [1]

Glomus is a genus of arbuscular mycorrhizal (AM) fungi, and all species form symbiotic relationships (mycorrhizae) with plant roots. Glomus is the largest genus of AM fungi, with ca. 85 species described, but is currently defined as non-monophyletic. [2]

Contents

Classification

Glomus is one of the genera in the family Glomeraceae, in the division Glomeromycota. Some members of the genus were originally described as Sclerocystis species, but this genus has been entirely transferred to Glomus. However, further taxonomic changes are likely as the phylogeny of AM fungi becomes better understood.

Glomus is likely related to the fossil fungus Glomites , discovered in the Rhynie chert deposits from the Early Devonian (400 million years ago).

Ecology

As with other AM fungi, all Glomus species are thought to be obligate symbionts, dependent on their mycorrhizal association with plant roots to complete their life cycle. They cannot be cultured in the laboratory in the absence of a plant host. Glomus species are found in nearly all terrestrial habitats, including arable land, deserts, grasslands, tropical forests, and tundras.

Arbuscular mycorrhizal fungi can provide numerous benefits to their plant hosts, including improved nutrient uptake, drought resistance, and disease resistance. However, the symbiosis is not mutualistic in all circumstances and may often be parasitic, with a detrimental effect on plant growth. Rarely, some plant species can parasitise the fungi. [3] Spores of Glomus prior to germinating produce an electric current. [4]

Life cycle

Glomus species were considered to be entirely asexual until recently (see Meiosis section below). Spores are produced at the tips of hyphae either within the host root or outside the root in the soil. Thought to be chlamydospores, these spores germinate and the germination tube that is produced grows through the soil until it comes into contact with roots. The fungus then penetrates the root and grows between root cells, or it may penetrate the cell wall and grow within root cells. Inside the root, the fungus forms arbuscules, which are highly branched hyphal structures that serve as sites of nutrient exchange with the plant. Arbuscules are formed within plant cell walls but are surrounded by an invaginated cell membrane, so remain within the apoplast. The fungus may also form vesicles, swollen structures which are thought to function as food storage organs.

Meiosis

Halary et al. [5] searched the genomes of four Glomus species for the presence of genes that encode proteins essential for meiosis. These proteins make up the conserved meiotic recombination machinery of eukaryotic cells. The study indicated that the Glomus species contain 51 genes encoding all the tools necessary for meiotic recombination and associated DNA repair processes. In particular, these species have seven genes that encode proteins whose only known function is in meiosis, including Dmc1 that is a meiosis-specific recombinase. Since meiosis is considered to be a hallmark of sexual reproduction, it might be expected that a sexual stage or a sexual apparatus should be present. However, as yet, none has been identified. In addition, mating type gene homologues and a putative sex hormone-sensing pathway were detected in these fungi. [6] Based on these findings it was suggested that Glomus species may be able to undergo a cryptic sexual cycle. [5] [7]

The population structure of Glomus etunicatum suggests that clonal expansion plays an important role in the ecological success of Glomus species, and that gene exchanges are not completely absent, although likely very rare. [8]

Agricultural significance

Several species of Glomus, including G. aggregatum , are cultured and sold as mycorrhizal inoculant for agricultural soils. One species, G. macrocarpum (and possibly also G. microcarpum), causes tobacco stunt disease. [9]

Species

See also

Related Research Articles

<span class="mw-page-title-main">Basidiomycota</span> Division of fungi

Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basidiomycota includes these groups: agarics, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and Cryptococcus, the human pathogenic yeast. Basidiomycota are filamentous fungi composed of hyphae and reproduce sexually via the formation of specialized club-shaped end cells called basidia that normally bear external meiospores. These specialized spores are called basidiospores. However, some Basidiomycota are obligate asexual reproducers. Basidiomycota that reproduce asexually can typically be recognized as members of this division by gross similarity to others, by the formation of a distinctive anatomical feature, cell wall components, and definitively by phylogenetic molecular analysis of DNA sequence data.

<span class="mw-page-title-main">Ascomycota</span> Division or phylum of fungi

Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defining feature of this fungal group is the "ascus", a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of the Ascomycota are asexual, meaning that they do not have a sexual cycle and thus do not form asci or ascospores. Familiar examples of sac fungi include morels, truffles, brewers' and bakers' yeast, dead man's fingers, and cup fungi. The fungal symbionts in the majority of lichens such as Cladonia belong to the Ascomycota.

<span class="mw-page-title-main">Mycorrhiza</span> Fungus-plant symbiotic association

A mycorrhiza is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, its root system. Mycorrhizae play important roles in plant nutrition, soil biology, and soil chemistry.

<span class="mw-page-title-main">Arbuscular mycorrhiza</span> Symbiotic penetrative association between a fungus and the roots of a vascular plant

An arbuscular mycorrhiza (AM) is a type of mycorrhiza in which the symbiont fungus penetrates the cortical cells of the roots of a vascular plant forming arbuscules. Arbuscular mycorrhiza is a type of endomycorrhiza along with ericoid mycorrhiza and orchid mycorrhiza.

<span class="mw-page-title-main">Glomeromycota</span> Phylum of fungi

Glomeromycota are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the thalli of bryophytes and the roots of vascular land plants. Not all species have been shown to form AMs, and one, Geosiphon pyriformis, is known not to do so. Instead, it forms an endocytobiotic association with Nostoc cyanobacteria. The majority of evidence shows that the Glomeromycota are dependent on land plants for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of the majority of plant species (>80%). They can also be found in wetlands, including salt-marshes, and associated with epiphytic plants.

Glomus aggregatum is an arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture. Like other species in this phylum it forms obligate symbioses with plant roots, where it obtains carbon (photosynthate) from the host plant in exchange for nutrients and other benefits.

<i>Geosiphon</i> Monotypic genus of photosynthetic, non-lichen fungi

Geosiphon is a genus of fungus in the family Geosiphonaceae. The genus is monotypic, containing the single species Geosiphon pyriformis, first described by Kützing in 1849 as Botrydium pyriforme. In 1915, Von Wettstein characterized Geosiphon pyriforme as a multinucleate alga containing endosymbiotic cyanobacteria, although he also noted the presence of chitin, a component of fungal cell walls. In 1933, Knapp was the first to suggest the fungal origin of the species and described it as a lichen with endosymbiotic cyanobacteria. It is the only member of the Glomeromycota known to not form a symbiosis with terrestrial plants in the form of arbuscular mycorrhiza.

<span class="mw-page-title-main">Glomerales</span> Order of fungi

Glomerales is an order of symbiotic fungi within the phylum Glomeromycota.

The mycorrhizosphere is the region around a mycorrhizal fungus in which nutrients released from the fungus increase the microbial population and its activities. The roots of most terrestrial plants, including most crop plants and almost all woody plants, are colonized by mycorrhiza-forming symbiotic fungi. In this relationship, the plant roots are infected by a fungus, but the rest of the fungal mycelium continues to grow through the soil, digesting and absorbing nutrients and water and sharing these with its plant host. The fungus in turn benefits by receiving photosynthetic sugars from its host. The mycorrhizosphere consists of roots, hyphae of the directly connected mycorrhizal fungi, associated microorganisms, and the soil in their direct influence.

<i>Rhizophagus</i> (fungus) Genus of fungi

Rhizophagus is a genus of arbuscular mycorrhizal (AM) fungi that form symbiotic relationships (mycorrhizas) with plant roots. The genome of Rhizophagus irregularis was recently sequenced.

<i>Rhizophagus irregularis</i> Species of arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture

Rhizophagus irregularis is an arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture. Rhizophagus irregularis is also commonly used in scientific studies of the effects of arbuscular mycorrhizal fungi on plant and soil improvement. Until 2001, the species was known and widely marketed as Glomus intraradices, but molecular analysis of ribosomal DNA led to the reclassification of all arbuscular fungi from Zygomycota phylum to the Glomeromycota phylum.

Orchid mycorrhizae are endomycorrhizal fungi which develop symbiotic relationships with the roots and seeds of plants of the family Orchidaceae. Nearly all orchids are myco-heterotrophic at some point in their life cycle. Orchid mycorrhizae are critically important during orchid germination, as an orchid seed has virtually no energy reserve and obtains its carbon from the fungal symbiont.

Dr. Mohamed Hijri is a biologist who studies arbuscular mycorrhizal fungi (AMF). He is a professor of biology and research at the Institut de recherche en biologie végétale at the University of Montreal.

<span class="mw-page-title-main">Mucoromycota</span> Diverse group of molds

Mucoromycota is a division within the kingdom fungi. It includes a diverse group of various molds, including the common bread molds Mucor and Rhizopus. It is a sister phylum to Dikarya.

<i>Funneliformis mosseae</i> Species of fungus

Funneliformis mosseae is a species of fungus in the family Glomeraceae, which is an arbuscular mycorrhizal (AM) fungi that forms symbiotic relationships with plant roots. Funneliformis mosseae has a wide distribution worldwide, and can be found in North America, South America, Europe, Africa, Asia and Australia. Funneliformis are characterized by having an easily visible septum in the area of the spore base and are often cylindrical or funnel-shaped. Funneliformis mosseae similarly resembles Glomus caledonium, however the spore wall of Funneliformis mosseae contains three layers, whereas Gl. caledonium spore walls are composed of four layers. Funneliformis is an easily cultivated species which multiplies well in trap culture, along with its high distribution, F. mosseae is not considered endangered and is often used for experimental purposes when combined with another host.

Rhizophagus clarus is an arbuscular mycorrhizal fungus in the family Glomeraceae. The species has been shown to improve nutrient absorption and growth in several agricultural crops but is not typically applied commercially.

The International Collection of (Vesicular) Arbuscular Mycorrhizal Fungi (INVAM) is the largest collection of living arbuscular mycorrhizal fungi (AMF) and includes Glomeromycotan species from 6 continents. Curators of INVAM acquire, grow, identify, and elucidate the biology, taxonomy, and ecology of a diversity AMF with the mission to expand availability and knowledge of these symbiotic fungi. Culturing AMF presents difficulty as these fungi are obligate biotrophs that must complete their life cycle while in association with their plant hosts, while resting spores outside of the host are vulnerable to predation and degradation. Curators of INVAM have thus developed methods to overcome these challenges to increase the availability of AMF spores. The inception of this living collection of germplasm occurred in the 1980s and it takes the form of fungi growing in association with plant symbionts in the greenhouse, with spores preserved in cold storage within their associated rhizosphere. AMF spores acquired from INVAM have been used extensively in both basic and applied research projects in the fields of ecology, evolutionary biology, agroecology, and in restoration. INVAM is umbrellaed under the Kansas Biological Survey at The University of Kansas, an R1 Research Institution. The Kansas Biological Survey is also home to the well-known organization Monarch Watch. INVAM is currently located within the tallgrass prairie ecoregion, and many collaborators and researchers associated with INVAM study the role of AMF in the mediation of prairie biodiversity. James Bever and Peggy Schultz are the Curator and Director of Operation team, with Elizabeth Koziol and Terra Lubin as Associate Curators.

<i>Gigaspora margarita</i> Arbuscular Mycorrhizal Fungi

Gigaspora margarita is an Arbuscular Mycorrhizal Fungi (AMF) which means it is an obligate symbiont that creates mutualistic relationships with many different plant species. Being an AMF, G. margarita does not produce a fruiting body. All of its mycelium will be found in the soil, associating with plant roots. Though hard to distinguish between different species of AMF, microscopic distinctions can be made. A prominent morphological distinction for species in the Gigasporaceae family is their large sized spores. Gigaspora margarita is characterized by its large, white, pearl-like spores found anywhere from 260 - 400 micrometers. This is where it gets its name as margarita in Latin means pearl.

Ambispora granatensis is an arbuscular mycorrhizal fungal species in the genus Ambispora, family Ambisporaceae. It forms spores of the acaulosporois and glomoid morphs, thus the Ambispora classification. It was discovered in Granada Spain in 2010 and has unique spore characteristics, which distinguishes the species from the others in its genus.

<i>Glomus macrocarpum</i> Species of fungus

Glomus macrocarpum is a vesicular-arbuscular endomycorrhizal plant pathogen in the Glomeraceae family of fungi. Also occasionally known as Endogone macrocarpa, G. macrocarpum is pathogenic to multiple plants, including tobacco and chili plants. G. macrocarpum was first discovered in the French woodlands by the Tulsane brothers in the early to mid 1800s. Their first known description of G. macrocarpum was published in the New Italian Botanical Journal in 1845. G. macrocarpum has since been documented in over 26 countries, including Australia, China, and Japan for example. G. macrocarpum is frequently found in grassy meadows, forests, greenhouses, and fruit orchards. It is known for its small, round-edged, and light brown to yellow-brown sporocarp. G. macrocarpum is sometimes known as the Glomerales truffle.

References

  1. "Glomus Tul. & C. Tul. 1845". MycoBank. International Mycological Association. Retrieved 24 January 2011.
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  3. Bidartondo, M.I.; Redecker, D.; Hijri, I.; Wiemken, A.; Bruns, T.D.; Dominguez, L.; Sersic A., Leake; J.R., Read, D.J. (2002). "Epiparasitic plants specialized on arbuscular mycorrhizal fungi" (PDF). Nature. 419 (6905): 389–392. Bibcode:2002Natur.419..389B. doi:10.1038/nature01054. hdl:11336/39185. PMID   12353033. S2CID   1636416.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. McCoy, Peter (2016). Radical Mycology: A Treatise on Seeing & Working with Fungi. Chthaeus Press. p. 102. ISBN   9780986399602.
  5. 1 2 Halary S, Malik SB, Lildhar L, Slamovits CH, Hijri M, Corradi N (2011). "Conserved meiotic machinery in Glomus spp., a putatively ancient asexual fungal lineage". Genome Biol Evol. 3: 950–8. doi:10.1093/gbe/evr089. PMC   3184777 . PMID   21876220.
  6. Halary S, Daubois L, Terrat Y, Ellenberger S, Wöstemeyer J, Hijri M (2013). "Mating type gene homologues and putative sex pheromone-sensing pathway in arbuscular mycorrhizal fungi, a presumably asexual plant root symbiont". PLOS ONE. 8 (11): e80729. Bibcode:2013PLoSO...880729H. doi: 10.1371/journal.pone.0080729 . PMC   3834313 . PMID   24260466.
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  9. Modjo, H.S.; Hendrix, J.W. (1986). "The mycorrhizal fungus Glomus macrocarpum as a cause of tobacco stunt disease". Phytopathology. 76 (7): 688–691. doi:10.1094/Phyto-76-688.