Deep in the forests of Yunnan, in southwestern China, a fungus rising from the soil in thick, fleshy columns has been given a formal name and a family of its own. Its discoverers call it Dianjunus rex, the king, and the title fits a body that can stand half a meter tall. Its genes and its shape pulled against each other, and the scientists resolved the tension by drawing a new branch on the tree of life, one whose roots reach back to the world that followed the great extinction of about 65 million years ago.
Giant Chinese Fungus Dianjunus rex Reaches 50 cm and 2.2 kg, Belongs to a 65-Million-Year-Old Lineage
Rex, Latin for king, for a fungus half a meter tall
Mark
Why does a big mushroom-like thing in Yunnan merit a new family?
Mimi
Because the DNA and the body told different stories. Genetically it sits next to Graphostromataceae, but it looks quite different, so the authors proposed Dianjunaceae.
Mark
And the 65-million-year figure?
Mimi
It's the estimated origin, early Paleocene, just after the Cretaceous–Paleogene extinction. They used genome data from 66 fungal samples.
Luke
Worth saying that's an estimate. The paper's own range is 50 to 80 million years ago, and it depends on calibration from earlier divergence-time estimates.
Mark
What about the size?
Mimi
Stromata reach 20 to 50 cm including the buried stalk, typically 250 to 600 grams. The 2.2 kg one was a single bilobed specimen.
Luke
So 2.2 kg is the top of the record, not the norm.
Mark
And the missing pectin-lyase genes?
Mimi
D. rex has zero or one, versus 7 to 19 in close relatives, and it has fewer carbohydrate-active enzyme genes overall.
Luke
The authors say this may help explain its growth. That's a hypothesis. The reporting doesn't show how those genes would produce a giant fruiting body.
Mark
So what's next?
Mimi
Testing that idea with more genomic and ecological study.
Le Pouls
- A fungus rising to half a meter, unlike any relative the researchers had catalogued, has forced a rethinking of its family tree.
- Its physical form and its genetic kin pointed in different directions, leaving the taxonomists with an unresolved mismatch.
- A new family, Dianjunaceae, was proposed to hold it, with a genome-scale dating that places its origin in the early Paleocene.
- Its strikingly few pectin-lyase genes offer a tentative explanation for its growth, a hypothesis still waiting for genomic and ecological tests.
Deep in the forests of Yunnan, in southwestern China, a fungus rising from the soil in thick, fleshy columns has been given a formal name and a family of its own. Its discoverers call it Dianjunus rex, the king, and the title fits a body that can stand half a meter tall. Its genes and its shape pulled against each other, and the scientists resolved the tension by drawing a new branch on the tree of life, one whose roots reach back to the world that followed the great extinction of about 65 million years ago.
In the forests of Yunnan Province, researchers have gathered a fungus that pushes up from the ground in thick, fleshy columns, some of them half a meter tall. They have now formally described it as Dianjunus rex, a name drawn from the Latin for king, and published the findings in Frontiers in Fungal Biology along with a new family created to house it.
The specimens came from three sites: tropical rainforest in Xishuangbanna and temperate coniferous forests near Kunming and Lufeng. Its upright structures vary from cylindrical to palm-shaped, and most weigh between 250 and 600 grams. The largest specimen weighed 2.2 kilograms.
The team combined close physical study with genetic sequencing across four genetic regions. Every analysis placed the fungus in its own lineage, close to the family Graphostromataceae, yet its form differed sharply from that family. That contradiction led them to propose Dianjunaceae, with Dianjunus as its only genus.
Their dating suggests the lineage began around 65 million years ago, just after the extinction that wiped out roughly three-quarters of plant and animal species. The estimate rests on genomes from 66 samples.
Comparing three strains, the researchers found the fungus carried far fewer carbohydrate-active enzyme genes than its relatives, and almost no pectin-lyase genes, which help break down plant cell walls. The team suggests this may help explain its unusual growth, though that remains a proposal to be tested by further study.
In the forests of Yunnan Province, in southwestern China, researchers have collected a fungus that rises from the ground in thick, fleshy columns, some of them half a meter tall. The organism, now formally named Dianjunus rex, has been described in a paper in Frontiers in Fungal Biology, along with a new family built to hold it.
The specimens came from fungal diversity surveys in three places: the tropical rainforest of Xishuangbanna Dai Autonomous Prefecture, and temperate coniferous forests in Kunming and Lufeng. The fungus produces upright structures called stromata, and these vary in shape from cylindrical and spindle-like to palm-shaped. Total height, counting the buried stalk, runs from 20 to 50 centimetres. The fertile part above ground measures 10 to 20 centimetres high and 7 to 10 centimetres across, occasionally reaching 15 centimetres in width.
Most stromata weigh between 250 and 600 grams. The largest specimen in the study, a bilobed one, weighed 2.2 kilograms. The species name, rex, is the Latin word for king, chosen for the fungus's size and majestic appearance.
To pin down what it was, the team combined close examination of its physical features with genetic sequencing and genome-scale analysis. They looked at four genetic regions, known as ITS, LSU, RPB2 and TUB2, and compared them with other fungi in the order Xylariales. Every analysis placed Dianjunus rex in its own lineage, closely related to the family Graphostromataceae. Yet its physical characteristics differed markedly from that family's. That mismatch led the researchers to propose a new family, Dianjunaceae, with Dianjunus as its new genus.
The dating reaches far back. The researchers estimate that Dianjunaceae originated around 65 million years ago, in the early Paleocene, shortly after the Cretaceous–Paleogene extinction event, which wiped out an estimated 75 percent of plant and animal species. The study gives a wider divergence range of 50 to 80 million years ago. The estimate rests on genome-scale data from 66 fungal samples, calibrated with established divergence-time estimates. The phylogenomic analyses consistently supported the fungus as a distinct lineage related to Graphostromataceae.
The team also compared the genomes of three Dianjunus rex strains, focusing on enzymes that process carbohydrates. Across the three samples, the fungus carried 219 to 224 carbohydrate-active enzyme genes, substantially fewer than reported for several relatives, including Xylaria, Daldinia and Hypoxylon. Genes for pectin lyases, which help break down pectin in plant cell walls, were nearly absent: zero or one in D. rex, with none in one strain, against 7 to 19 in closely related Xylariales. Glycosyltransferases, which mainly help build fungal cell walls, made up about 25.9 to 26.0 percent of its enzyme repertoire.
The researchers propose that these genomic features may help explain the fungus's unusual growth. That remains a proposal rather than a demonstrated mechanism, and further genomic and ecological work would be needed to test it.
Citations marquantes
The researchers propose that the fungus's genomic features may help explain its unusual growth.— Study authors, Frontiers in Fungal Biology (paraphrased)
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