Kunming Institute of Botany Team Describes a Giant Fungus: Dianjunus rex
A research team led from the Kunming Institute of Botany, Chinese Academy of Sciences, has formally described a fungus from Yunnan Province, China, that produces upright fruiting structures up to 50 cm high. The study, by Jing Song and colleagues in Frontiers in Fungal Biology (2026), names the organism Dianjunus rex. It proposes the species as the type of a new genus and a new family, Dianjunaceae, within the order Xylariales. The authors report that its stromata, the dense fungal tissue carrying the spore-bearing structures, are the largest documented in the Ascomycota.
Where Dianjunus rex Was Found
Specimens were collected in August and September 2024 and in July 2025 at three sites: Damaidi Village near Kunming, Yipinglang Town in Lufeng and Mengla County in Xishuangbanna, a tropical rainforest area. The fungus arises from the roots of dying host plants, and the type specimen was associated with roots of Quercus variabilis. Voucher specimens are held at the Kunming Institute of Botany fungarium (HKAS).
The authors describe fleshy stromata 20 to 50 cm in total height, whitish when young and dark yellow at maturity, with a powdery-fibrous surface. Tropical collections were larger than subtropical ones, and fresh stromata dehydrate rapidly once detached.
How the Placement Was Made
The taxonomic case combines morphology with molecular data. A four-gene phylogeny (ITS, LSU, RPB2 and TUB2) covering 202 strains placed five collections in a single clade, sister to the family Graphostromataceae, with maximum-likelihood and Bayesian support of 100% and 1.00. The team also sequenced genomes and transcriptomes from three stromata. Assemblies ranged from 30.48 to 32.01 Mb, and at least 95.96% of single-copy BUSCO genes, a standard completeness check, were identified.
Two genome-scale analyses across 66 Pezizomycotina samples, one using 302 single-copy orthologs and a coalescent-based alternative using 345, both resolved Dianjunus as sister to Graphostromataceae. Distinguishing features include an S-shaped germ slit in the ascospores and a nodulisporium-like asexual stage with periconiella-like branching. The authors also compared the fungus with Squamotubera le-ratii, known only from a short 1903 description with a holotype no longer available, and concluded that the two differ in size, form and spore features.
A Date Close to the K-Pg Extinction
Molecular dating, calibrated with divergence times from TimeTree, places the origin of Dianjunaceae at about 65 million years ago, within an interval of 50 to 80 million years. The authors note that this coincides with the period after the Cretaceous-Paleogene extinction, when an estimated 75% of plant and animal species were lost. They suggest the lineage may reflect an adaptive radiation, or the use of newly available niches as forests recovered, but they frame this as a possibility, not a finding. The interval is wide, which limits how tightly the timing can be tied to the event. It also adds to a wider body of work on fungal evolution.
A Streamlined Enzyme Toolkit
For the Fungi sector, the genome is the more notable result. The authors say Xylariales are known for secondary metabolites and for enzymes that degrade plant polymers, which makes them of interest to biotechnology and natural product discovery. D. rex, however, carries 220, 224 and 219 carbohydrate-active enzyme (CAZyme) genes in its three sequenced strains. That compares with 535 to 635 in Xylaria, 458 to 496 in Daldinia and 423 to 577 in Hypoxylon. Pectin lyase genes number zero or one, against 7 to 19 in close relatives. Glycosyltransferases, which the authors link to cell wall construction, make up about 26% of the total.
The authors read this as a reduced capacity to degrade pectin, consistent with genomic signatures of latent endophytes, which live inside healthy plant tissue. Because fruiting bodies appeared only after host death, they propose a working hypothesis of a shift from endophyte to decomposer. They suggest that low enzyme maintenance costs might help channel carbon into the large stromata. The paper reports no bioactivity, metabolite or enzyme-assay data for D. rex, so any commercial relevance remains untested.
Limitations and Open Questions
Several points need care. The abstract gives individual stromata weights of up to 2.2 kg, while the formal description lists 250 to 600 g, and the text does not reconcile the two. The paper also cites a Kenyan Engleromyces goetzei specimen of about 30 cm diameter and roughly 3.2 kg, and calls that species the largest reported in Xylariales to date. Readers should therefore treat the "largest" claim as the authors' own.
The lifestyle explanation rests on genomic patterns and has not been tested experimentally. The authors describe Yunnan as underexplored: over 6,000 fungal species are documented there, while total richness may exceed 100,000. That gap echoes how little is known about fungal diversity globally.
