by Piter Kehoma Boll
Fungi show a variety of different fruiting bodies and they are almost always named based on what those fruiting bodies look like. This is the case of today’s fellow as well. Its scientific name is Aleuria aurantia and it is commonly known as the orange peel fungus. Due to English ambiguous language, such a name could mean a fungus that grows on orange peels as well, but that is not the case, as such a species is named green mold.
The orange peel fungus is found throughout the Holarctic region, i.e., North America, Europe and Northern Asia, and eventually elsewhere, probably due to human-driven dispersal. Its main habitat includes opean areas near conifer forests, where it lives as a saprotrophe, i.e., a decomposing fungus with the mycelia scattered through the soil.
The cup-shaped fruiting bodies appear more often in autumn. They have a strong orange color caused by carotenoids, especially β-carotene, γ-carotene and aleuriaxanthin. At first they are small and very regular, but grow up to 6 cm in diameter, when their structure often becomes irregular or torn apart, resembling pieces of orange peel thrown on the ground. The spores that they produce remain ungerminated in the soil until spring, when they start to grow. The cold temperatures of winter seem to be necessary for the spores to germinate, as spores in laboratory cultures only germinated successfully after remaining frozen for about 3 months.
The orange peel fungus has been a target species for pharmacological studies due to the presence of a lectin called Aleuria aurantia lectin (AAL). Lectins are a group of proteins that bind to sugars or sugar groups of other molecules such as glycoproteins and glycolipids. They are found in all groups of organisms and have different functions. In animals, for example, they are important in cell adhesion. They connect to glycoproteins on the cell membrane and tie neighbor cells to each other, preventing tissues to fall apart.
In many parasitic fungi, bacteria and viruses, lectins are important to recognize the host. They also seem to have a role during the production of spores in fungi. AAL from the orange peel fungus binds to fucose, a sugar that is commonly found on the surface of cells in mammals, insects and plants as part of their glycoproteins. The name fucose comes from the fact that this sugar forms the polysaccharide fucoidan found in several species of brown algae.
AAL has several practical uses. Due to its fucose-binding behavior, it can be used to detect the presence of fucose in different cells. Fucose is also related to some types of allergies and AAL has been studied as a potential compound to develop new antiallergics.
Other than its pharmacological properties, the orange peel fungus is also edible, though not that popular as food. Its fruiting bodies can be eaten fresh or dried for storage. Due to the presence of carotenoids, the orange peel fungus has potential antioxidant properties, although studies on its nutritious value seem to be lacking.
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