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Here’s what you’ll learn when you read this story:
- Some fungi, particularly species in the order Mucorales, can change from one form to another by changing what genes they express.
- Mucor lusitanicus will take the form of yeast in anaerobic environments, but change to a mycelial form in aerobic environments.
- Knowing which genes are responsible for the transformations could help with developing antifungal treatments, and may have other pharmaceutical and industrial applications.
Some organisms have the almost-paranormal ability to take one form and then switch to another. Known as dimorphism, this trick is common in the fictional worlds of werewolves and shapeshifters, but thanks to a certain fungus, it’s also happening in real life.
Many species of Mucorales fungi can transform themselves from a yeast to a mycelium and back. While yeasts are unicellular and reproduce asexually, mycelial fungi are multicellular, have many filaments (or hyphae), and can self-replicate through either sexual or asexual reproduction. How exactly the genes of these fungi allow them to morph, depending on the environment, and then morph back within a single genome was unknown until now. Curious to find out, a team of researchers observed several Mucorales species such as Mucor lusitanicus. It turned out that hundreds of gene families in these fungal species underwent convergent evolution.
Though not related to each other, groups of genes that undergo convergent evolution develop similar features. So do entire organisms. Both birds and bats evolved powered flight, despite bats being mammals. While different Mucorales gene families carry out their own functions, their paralogs, or genes whose ancestral form split into two distinct types, have convergent adaptations that make it possible to transform into yeast or mycelia depending on the environment. The researchers also discovered two previously unknown genes that control the expression of dimorphic gene families. Mutant forms of M. lusitanicus that were missing these genes were unable to switch forms.
“The genomes of dimorphic Mucorales have undergone substantial adaptation to the dimorphic process,” they said in a study recently published in Nature Communications. “This adaptation is also reflected in the pronounced differences between the yeast and mycelial forms, as well as in the unique dimorphic characteristics of these organisms, including the independence of the two morphotypes and the reversible transitions between them.”
During the morphological transition from yeast to mycelium or vice versa, paralogs in M. lusitanicus and other dimorphic fungi will work together to coordinate their expression so that the characteristics of that particular form show up at the same time. M. lusitanicus is a yeast powered by fermentative metabolism in anaerobic environments. In general, yeasts thrive in high carbon dioxide and glucose levels, while mycelia need oxygen. When exposed to an aerobic environment, M. lusitanicus will turn into a mycelium that uses an oxidative metabolism, sprouting hyphae that further differentiate into more complex structures. Similarly, other Mucorales species can cause the potentially fatal fungal infection mucormycosis in oxygen-rich environments.
Understanding the genes that change the morphology of Mucorales fungi can potentially inform more effective antifungal treatments. Immunocompromised individuals such as organ transplant recipients or people with conditions such as diabetes, leukemia, or lymphoma are especially susceptible to mucormycosis, but only if the fungus is able to take its mycelial form. Pathogenic fungi have an advantage in the body of another organism because they are fueled by an abundance of nutrients and can easily invade tissues with their hyphae. However, there is one signaling pathway that can turn them into yeast—even in aerobic conditions. If used against them in the right way, the pathway could obliterate the infection.
Understanding dimorphism in fungi can be an asset in many applications. Engineering fungi to stay in one form or the other makes it possible to take advantage of specific abilities, such as yeasts being used for industrial fermentation. Fungi can also be genetically optimized for metabolite production. Fungal metabolites can be used in antioxidant supplements, pharmaceuticals (penicillin can vouch for that), dyes, and industrial enzymes. They also have properties that could do everything from slowing down aging to fighting cancer.
“[Our] findings illuminate the evolutionary strategies underlying dimorphism in Mucorales, providing a foundation for future studies on its impact on fungal physiology, pathogenicity, and phylogeny,” the researchers said. “The insights gained from this research also provide a critical foundation for understanding virulence in Mucorales.”
Elizabeth Rayne is a creature who writes. Her work has appeared in Popular Mechanics, Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.
