A type of fungi studied by a team of biologists from the Ruhr-UniversitÃ¤t Bochum (RUB) for their sexual reproduction strategies is commonly referred to as Sword-belt Mushrooms. In addition to the European sword-belt fungus (Cyclocybe aegerita), its Pacific relative, the so-called Tawaka (Cyclocybe parasitica), also possesses the unusual ability for agarics on their own to form complex multicellular structures for sexual reproduction. These fruiting bodies are normally produced as a collaborative effort between two sexual partners.
Hannah Enders and Dr Florian Hennicke describe the precise anatomy of these structures of the poplar fungus in the Mushroom Journal of 19 May 2021.
An edible wild mushroom
One of the organisms attacked by the fungus Cyclocybe parasitica is the Tawa tree (Beilschmiedia tawa), which is relevant to the timber industry in New Zealand. Cyclocybe parasitica is widespread in the Pacific region and has long been known to Maori, the indigenous people of New Zealand, as “Tawaka” as a wild edible mushroom.
Biology student Hannah Elders, supervised by Florian Hennicke in the Department of Plant and Fungi Evolution, studied the sexual behavior of the Tawaka fungus. The two researchers were able to show that the Pacific Tawaka, like its European cousin, the Sword-belt Mushroom (Cyclocybe aegerita), also edible, is able to develop a complex structure reserved for the sexual reproduction of two partner individuals, the so-called fruiting body, on its own. The specialized term for this is monocaryotic fruiting in the narrow sense.
Sister strains can form different monocaryotic fruiting structures on their own
Elders and Hennicke have not only identified a competent strain of this fungus that can produce almost fully developed fruiting bodies. They also characterized sister strains capable of producing precursors of these fruiting bodies to varying degrees, one of the precursors of which, the so-called stromatic type, was previously only known to bracket fungi. Additionally, tissue sectioning techniques and microscopy have successfully revealed the exact anatomical differences between the complex multicellular structures of these sister strains.
“The results of the work are also interesting in terms of reproductive biology, as they examine a decades-unresolved fungal research question in a new context: whether wild populations of sword-belt fungi, of which the main one reproductive strategy is based on the narrow-sense monocaryotic fruiting occurring in nature, “explains Florian Hennicke. They also discuss the question of how this type of reproduction would bring agarics better ecological fitness, ie say by recombining genetic information despite the absence of a mating partner. Improved ecological suitability conferred in this way may, for example, allow fungi to establish themselves in previously unsuitable habitat, as is normally possible with reproduction with a male and a female.
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