Potteromyces asteroxylicola parasitized on an extinct species of lycopsid plant called Asteroxylon mackiei, according to a paper published in the journal Nature Communications.
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Potteromyces asteroxylicola, holotype in white light: (a) location of the fungus (asterisks) along the aerial axis and enations of the plant Asteroxylon mackiei; arrowhead showing animal remains; (b) plant reaction induced by the fungal attack; (c, d) higher magnifications of the framed zone from (b) showing the plant cell proliferation in response to the fungal attack; arrowheads showing hyphae; (e) conidiophores in tuft; (f) higher magnification of (e); (g) conidiophores in high magnification, slightly shrunken at their distal end, and conidia. Scale bars – 900 µm in (a); 400 µm in (b); 120 µm in (c), 45 µm in (d), 85 µm in (e), 35 µm in (f, g). Image credit: Strullu-Derrien et al., doi: 10.1038/s41467-023-43276-1.
Potteromyces asteroxylicola existed during the Ealy Devonian epoch, approximately 407 million years ago.
The new species was discovered in microfossil samples from the Rhynie Chert, a crucial geological site in Scotland.
The site is known for a remarkably preserved Early Devonian community of plants and animals, including bacteria and fungi.
“Fungi are integral to well-functioning ecosystems, and their broader impact on Earth systems is widely acknowledged,” said lead author Dr. Christine Strullu-Derrien, a paleontologist at the Natural History Museum London, and her colleagues.
“Fossil evidence from the Rhynie Chert shows that fungi were already diverse in terrestrial ecosystems over 407 million years ago.”
Potteromyces asteroxylicola’s reproductive structures, known as conidiophores, had an unusual shape and formation unlike anything seen before.
Equally unusual was the fact this mysterious fungus was found attacking the lycopsid plant Asteroxylon mackiei.
The plant had responded by developing dome-shaped growths, showing that it must have been alive while the fungus making its attack.
“The fungus forms a stroma-like structure with conidiophores arising in tufts outside the cuticle on aerial axes and leaf-like appendages of Asteroxylon mackiei,” the paleontologists said.
“It causes a reaction in the plant that gives rise to dome-shaped surface projections.”
“This suite of features in the fungus together with the plant reaction tissues provides evidence of it being a plant pathogenic fungus.”
According to the team, Potteromyces asteroxylicola is likely related to the fungus phylum Ascomycota in the subkingdom Dikarya.
“Although other fungal parasites have been found in Rhynie Chert before, this is the first case of one causing disease in a plant,” Dr. Strullu-Derrien said.
“What’s more, Potteromyces asteroxylicola can provide a valuable point from which to date the evolution of different fungus groups, such as Ascomycota, the largest fungal phylum.”
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C. Strullu-Derrien et al. 2023. A fungal plant pathogen discovered in the Devonian Rhynie Chert. Nat Commun 14, 7932; doi: 10.1038/s41467-023-43276-1
