Japanese Scientists Uncover Genetic Mechanisms of Multicellularity

Researchers at Nagoya University in Japan have unveiled critical genetic mechanisms that enable certain organisms to transition between single-celled and multicellular forms. This discovery, published in the journal Nature, sheds light on the evolutionary processes that may have shaped complex life forms such as animals and plants from their simpler, single-celled ancestors.

The study, led by Professor Gohta Goshima at the university’s Sugashima Marine Biological Laboratory, focuses on the black marine yeast Hortaea werneckii. The researchers found that when nutrients are plentiful, these yeast cells multiply and form multicellular structures. Conversely, when nutrient resources diminish, the cells revert to a solitary existence, allowing them to disperse and search for new sources of sustenance. This adaptability could provide a significant survival advantage in the ever-changing conditions of ocean environments.

To investigate the genetic basis behind this remarkable switching ability, the team isolated mutants of H. werneckii that had lost the capacity to alternate between forms. Through their analysis, they identified ten key genes responsible for this process. Notably, the deletion of a particular gene resulted in the yeast becoming fixed in either a unicellular or multicellular state. However, by also deleting a different gene, the yeast regained its switching capability, indicating multiple genetic pathways can facilitate this flexibility.

Professor Goshima noted, “We found that a protein called Myb1 acts as a master switch controlling the change between cellular states. When Myb1 levels are high, cells bud and separate; however, when this protein is degraded in nutrient-rich conditions, cells form multicellular structures.” This discovery highlights the evolutionary significance of gene recycling, as some of the identified genes were previously understood to aid in spore formation in fungi but were adapted by H. werneckii for its unique cellular transitions.

The research team also identified strains of H. werneckii that favor multicellularity, all of which were found on the surfaces of marine animals such as sponges and corals. These environments are rich in nutrients, primarily due to the presence of symbiotic bacteria. The researchers proposed that forming multicellular bodies allows the yeast to anchor itself in these nutrient-rich locales, preventing it from being washed away by ocean currents.

Laboratory experiments supported this hypothesis; when unicellular and multicellular strains were subjected to simulated water flow, the multicellular clusters remained attached, while the single cells were dislodged.

The study not only examined the genetic mechanisms in H. werneckii but also extended its findings to related yeast species. It revealed that these species exhibit varied evolutionary adaptations regarding their switching capabilities. For instance, in the closely related yeast Neodothiora pruni, while many genes function similarly, the role of Myb1 is unique to H. werneckii, indicating that closely related species may evolve different genetic solutions for similar biological behaviors.

Looking ahead, Professor Goshima aims to explore what drives this evolutionary diversity and how simple multicellular forms might evolve into more complex structures. He stated, “What we achieved was controlling unicellularity and simple multicellularity, but the next obvious step is whether simple multicellularity becomes more complex multicellularity.” The ability to easily alter or restore cellular flexibility through single mutations suggests that transitions between unicellular and multicellular states may have repeatedly occurred in evolutionary history.

As a result, H. werneckii has emerged as a significant research tool for scientists investigating the evolution of multicellular life. Professor Goshima emphasized that the organism’s switching capability may represent a crucial evolutionary stepping stone leading to the development of permanently multicellular organisms.

The study was published in March 2026 by the authors Kurita et al., and can be accessed through Nature at doi: 10.1038/s41586-025-09881-4.