Dimorphic fungi; Source: Mycology on line

Creatures that can change from one form to another ?

Yes,  Nature, too, has its shapeshifters, such as dimorphic fungi.

Dimorphic organisms possess the remarkable genome capacity to alternate genetic information between two distinct life forms. In dimorphic Mucorales, lineages can reversibly transition between yeast and mycelium as a function of environmental stimuli. 

While scientists have known for some time that they can reversibly transition between yeast and mycelium forms, a paper recently published in the journal Nature Communications explains how.

Some fungi, such as members of the Mucorales order, can live as yeasts, tiny single-celled organisms, or as mycelium, multicellular branching filaments. Triggers for the morphological switch include oxygen levels and glucose concentrations.  How can a single genome encode two different body plans and could switch between them?

To find out, scientists grew the fungus (Mucor lusitanicus) under oxygen-rich conditions to promote mycelial growth, and under low-oxygen, high-carbon-dioxide conditions to induce the yeast form. Once the fungus had changed shape, the team collected samples and examined the active genetic instructions, specifically the RNA, to see which were being used in each form.

The team found that instead of using the same genes for both forms, the fungus uses paralogs. These are closely related genes that share a common ancestor and arise when a gene is duplicated within a single genome.

In total, they found 490 dimorphic gene families. Although each twin pair has similar functions, there is a specific version for yeast and one for mycelium. For example, a gene responsible for iron absorption in the yeast form has a nearly identical counterpart that performs the same function in the mycelium form.

They are organized in a very elegant way in the genome. The scientists discovered that two related genes are positioned back to back on the DNA and share a bidirectional promoter. These regulate gene expression and so act like control switches. It means the promoters can easily turn one off and the other on without getting them mixed up.

At the heart of the operation, according to the researchers, are two master regulator genes, dkl and dfl. When the team deleted them, the fungus could no longer control its switches and lost its ability to change shape.

The findings identify an evolutionary mechanism that integrates and optimizes the genetic information required for two distinct life forms within a single organism.

These findings identify an evolutionary mechanism that integrates and optimizes the genetic information required for two distinct life forms within a single organism.

One of the most exciting aspects of this research is the potential for new antifungal treatments. Knowing how a fungus switches to its invasive mycelial form gives scientists a clear target to stop the transformation and therefore the spread of fungal infections.

Ghizlane Tahiri et al, Coordinated gene family evolution shapes the genome of dimorphic Mucorales, Nature Communications (2026). DOI: 10.1038/s41467-026-68866-7