Scientists have poured decades and billions of dollars into reading the genomes of animals and crops. Fungi mostly got left behind.
The kingdom tends to earn attention only when it spoils bread or colonizes someone’s toes. That is a strange blind spot, given everything fungi have already handed us.
Fungi built modern medicine
Penicillin came from a mold. Statins, the cholesterol drugs taken by millions, trace back to fungal chemistry too.
“This neglect is kind of remarkable considering how fungi have shaped modern medicine,” said Xue Gao, a chemical and biomolecular engineer at the University of Pennsylvania.
“From the serendipitous discovery of penicillin to cholesterol-lowering statins, we owe many recent breakthroughs in longevity to fungal chemistry. But despite this, the vast majority of the fungal kingdom remains a black box.”
Why lab molds go quiet
Part of the trouble sits inside the fungus itself. In the wild, molds switch on gene pathways that build chemical weapons to fight off bacteria.
Move that same fungus into a clean laboratory dish, and those pathways fall silent. Nothing is attacking it, so it stops making the very compounds researchers hope to find.
Reaching those hidden pathways means rewriting the genes that keep them locked down. That has been the frustrating part for years.
“To turn those silent pathways back on, we needed a powerful way to precisely manipulate fungal genome, such as editing their master regulatory genes, but traditional tools weren’t up to the task,” Gao said.
CRISPR-Cas9 has been the famous name in gene editing for over a decade. In thread-like molds, though, it behaves more like a sledgehammer than a scalpel.
It cuts clean through both strands of DNA, and the cell repairs the damage sloppily. The result is a scatter of unintended insertions and deletions that can wreck a careful experiment.
A newer approach called prime editing sidesteps those double breaks altogether. It rewrites the genetic code one letter at a time, with much finer control.
Until now, nobody had made prime editing work in filamentous fungi. Gao and her team at Penn built a version that does, and they named it fPE7max.
Two problems, two fixes
Getting there meant solving two stubborn problems. The first was fragile instructions.
Prime editing relies on a guide made of RNA that tells the tool where to go and what to write. When the edit gets large, that guide grows long, and long guides tend to shred before the work is done.
The team’s answer was a protein called fLa. It wraps around the delicate RNA and shields it, so the tool can handle big insertions and deletions that would break lesser systems.
An early version borrowed this protein from humans, and it flopped inside fungal cells. Switching to a fungus’s own version of the protein made all the difference.
The second problem was the fungus fighting the edit. Its natural repair machinery treats each new change as an error and reverses it.
So the researchers added a second protein that mutes that repair system for a short window.
With both fixes working together, fPE7max hit editing accuracy approaching 90 percent, and stayed reliable across many genes and several species.
Removing fungal gene brakes
Then came the elegant part of the work. The team aimed the tool at a master regulator gene called laeA.
This single gene controls sprawling networks of chemical production. Flip it, and dozens of downstream pathways respond.
Sitting just upstream of laeA are tiny genetic sequences that act like a brake on it.
Rather than tampering with laeA directly, the researchers used fPE7max to snip out that brake with pinpoint accuracy.
Freed from the brake, laeA ramped up. Dormant clusters of genes came alive, and unfamiliar compounds began appearing in fungi that had never made them in the lab.
The same trick worked in molds spread far apart on the fungal family tree. That range suggests the method could travel widely across the kingdom.
Hidden fungal molecules discovered
The payoff was substantial.
“We isolated 18 distinct complex molecules, eight of which possessed chemical structures entirely new to science,” said Chunxiao Sun, a postdoctoral researcher in the Gao Lab.
“Of these uncovered molecules, three exhibited promising anti-cancer properties. These molecules can serve as lead compounds for disease treatment, providing a vital new pipeline for drug discovery,” Sun said.
Several of the fresh finds belonged to a chemical family called pyranonigrins. A few carried building blocks never before seen stitched into that core structure.
Three that attack cancer cells
The team first tested the new compounds against common bacteria and yeast. None of them did much there.
Against human cancer cells, the picture changed sharply. One molecule showed selective toxicity toward breast, liver, and leukemia cancer cells, while leaving other cells largely alone.
Tiny structural details turned out to matter enormously. A single sulfur-containing side chain appeared to decide whether a molecule could kill cancer cells or do nothing.
Remove that one feature, and the activity vanished. That kind of clue helps chemists understand what makes a compound work, and how they might sharpen it.
Where this goes next
The finding points to a far larger reserve waiting in plain sight. More than 90 percent of fungal gene clusters remain uncharacterized, which means an enormous store of chemistry sits unexamined.
“It’s a compelling proof-of-concept demonstrating that the next generation of life-saving therapeutics might already exist in nature,” Gao said.
The team now wants to point fPE7max at many more fungal species.
The plan is to retire the old treasure-hunt method, combing through wild fungi in hope of a lucky find, and replace it with something systematic and repeatable.
For a long-overlooked branch of biology, that is a genuine turn. The black box is finally beginning to open.
The study is published in the journal Nature Biotechnology.
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