Entorrhizomycetes
Root-parasitic fungi forming galls on rushes and sedges.
Entorrhizomycetes is the only class within the fungal phylum Entorrhizomycota, which belongs to the subkingdom Dikarya alongside Basidiomycota and Ascomycota. This class contains three genera and consists of a small group of teliosporic root parasites that cause galls on plants from the rush family (Juncaceae) and the sedge family (Cyperaceae). Before 2015, this phylum was classified under the subdivision Ustilaginomycotina. A study that year, based on comprehensive five-gene analyses of the genus *Entorrhiza*, suggested that Entorrhizomycetes may be either a close sister group to the rest of Dikarya or to Basidiomycota.
In terms of taxonomy, the class is divided into two orders. The order Talbotiomycetales contains the family Talbotiomycetaceae and the genus *Talbotiomyces*. The order Entorrhizales includes the family Entorrhizaceae and the genera *Juncorrhiza* and *Entorrhiza* (the latter originally described as *Schinzia*).
All members of Entorrhizomycetes are obligate parasites on plant roots. They produce sori as galls on the roots of their hosts. These galls are tubercular, with a globoid, irregular, or elongated shape, and are made up of vascular bundles, parenchymatous cells, and fungal mycelium. Younger parts of the galls are pale, while older sections turn brown. The mycelium consists of dikaryotic, septate hyphae with fibrillate walls and no clamp connections. Initially, the mycelium grows between host cells, then produces coiled intracellular hyphae that end in globose cells. These cells detach and develop into teliospores. Teliospores germinate into tetrads through internal septation, and each compartment of the tetrad grows hyphae that end in sigmoid propagules. Observations show that young teliospores have two nuclei, older ones have one, and each tetrad compartment has one nucleus, indicating that karyogamy and meiosis occur in the teliospore. Teliospores are released when the host plant dies and the galls break apart. More galls form in waterlogged soils than in well-drained ones, which may suggest that these fungi disperse through soil moisture.
*Talbotiomyces* and *Juncorrhiza* were separated from the broader *Entorrhiza* group. *Entorrhiza* in the strict sense is identified by teliospores with longitudinally ridged or cerebriform ornamentation and infects plants in the Cyperaceae family. *Juncorrhiza* has teliospores with verrucose-tub
- classification
- Class within phylum Entorrhizomycota, subkingdom Dikarya
- number_of_genera
- 3
- host_families
- Juncaceae and Cyperaceae
- estimated_stem_age
- Approximately 560 million years ago (late Neoproterozoic)
- key_morphological_feature
- Teliospores that germinate into tetrads with pored septa
Lore & Background
All members of Entorrhizomycetes are obligate parasites on the roots of plants. Sori are produced as galls on the roots of hosts. Galls are tubercular with a globoid, irregular or elongated shape and are composed of vascular bundles, parenchymatous cells and fungal mycelium. Younger segments of the galls are pale in color whilst older segments turn brown. Mycelium consists of dikaryotic and septate hyphae with fibrillate walls that lack clamp connections. Initially, the mycelium grows intercellularily before producing coiled intracellular hyphae terminating in globose cells that detach and develop into teliospores. Teliospores germinate into tetrads through internal septation, and each tetrad compartment produce hyphae that terminate in sigmoid propagules. Bauer et al. noted that young teliospores have two nuclei, older teliospores have only one nucleus, and each tetrad compartment has one nucleus each, indicating that karyogamy and meiosis occurs in the teliospore.
Reader's Guide
Entorrhizomycetes holds a significant position in fungal evolution due to its uncertain phylogenetic placement as either a sister group to Basidiomycota or to all of Dikarya. Its teliospore tetrad structure has been speculated to represent the ancestral state of dikaryan meiosporangia, possibly evolving into phragmobasidia and then holobasidia during the transition from water-dispersal to air-dispersal. The class has a much lower number of species and more limited host range than its estimated age of approximately 560 million years would indicate. Possible explanations include extinction of lineages along with their hosts during mass extinction events, or that much diversity remains undiscovered—supported by the fact that host plants show no aboveground symptoms of infection and there may be species that do not cause galls. Divergence estimates between its orders and genera are incongruent with host plant stem ages, suggesting host-shift speciation rather than co-speciation.
Did You Know?
- Entorrhizomycetes was placed under the subdivision Ustilaginomycotina prior to 2015.
- Teliospores are liberated when the host plant dies and the galls disintegrate.
- The number of galls is higher in waterlogged soils compared to well-drained soils.
- Divergence between Entorrhiza and Juncorrhiza is estimated to approximately 42 million years ago.
Frequently Asked Questions
What is Entorrhizomycetes?
Entorrhizomycetes is a small class of root-parasitic fungi that constitutes the entire phylum Entorrhizomycota. It occupies a place in the subkingdom Dikarya, the same rank shared by Basidiomycota and Ascomycota.
What do Entorrhizomycetes do to their host plants?
These fungi infect the roots of rushes (family Juncaceae) and sedges (family Cyperaceae), inducing the formation of abnormal galls on the host. They are teliosporic parasites, so their life cycle is built around a teliospore stage.
What is the key morphological feature of Entorrhizomycetes?
Their teliospores germinate into tetrads—groups of four cells—separated by pored septa. This distinctive four-cell arrangement with perforated walls is the hallmark that sets the group apart morphologically.
How old is the Entorrhizomycetes lineage?
The stem lineage dates to roughly 560 million years ago, placing its origin in the late Neoproterozoic. That makes it one of the deeper-branching fungal lineages we currently recognize.
How many genera are in Entorrhizomycetes and how did its classification change?
The class contains just three genera, with Entorrhiza serving as the type. Prior to 2015 it was nested under Ustilaginomycotina, but a five-gene phylogenetic study of Entorrhiza led researchers to elevate it to its own phylum.
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