A recent study published in The EMBO Journal reveals significant insights into the evolutionary origins of the cytoskeleton, a crucial component of eukaryotic cells. Conducted by researchers at the Indian Institute of Science (IISc), the study explores how the cytoskeleton may have evolved from simpler structures found in ancient microbes. This research addresses fundamental questions about how life transitioned from basic microbial cells to the complex organisms we see today, including animals, plants, and fungi.
The cytoskeleton serves as the internal scaffold of modern cells, maintaining their shape, facilitating movement, organizing internal components, and controlling cell division. In complex organisms, this network consists of various protein filaments, including actin and microtubules. These proteins form sophisticated molecular machines that are essential for cellular function. However, the origins of these proteins can be traced back to microbial ancestors, particularly the Asgard archaea, which are considered the closest living relatives of all eukaryotes.
The researchers focused on a specific Asgard species, Odinarchaeota yellowstonii, named after the Norse god Odin and isolated from Yellowstone National Park in the United States. They examined two proteins, FtsZ1 and FtsZ2, which are ancient relatives of tubulin and serve as building blocks for microtubules in contemporary eukaryotic cells. Through biochemical analysis and cryo-electron microscopy, the team discovered that these two proteins exhibit distinct behaviors.
OdinFtsZ1 forms curved single filaments, reminiscent of the rings produced by FtsZ during bacterial cell division. In contrast, OdinFtsZ2 assembles into stacked spiral rings, resembling primitive microtubule-like structures. Notably, the proteins anchor themselves to the cell membrane in unique ways—one directly through a helical tail and the other via an adaptor protein. This indicates an early form of functional specialization among structural proteins, which may have foreshadowed the complexity seen in modern cytoskeletons.
The findings suggest that the complex nature of the modern cytoskeleton may have emerged through processes such as gene duplication, specialization, and cooperative interactions among filament systems. The evidence indicates that this diversification process may have already begun in Asgard archaea. The research highlights a pivotal moment where simple filaments evolved into multifunctional networks, paving the way for the intricate inner frameworks of eukaryotic cells.
The research team is now focused on culturing Asgard archaea in laboratory settings, which will allow for direct cell biology experiments. Observing these proteins in living cells could yield unprecedented insights into the functioning of early cytoskeletal systems and their role in the emergence of complex life forms.
“We believe that these proteins preserve a snapshot of an ancient transition,” stated Saravanan Palani, Assistant Professor in the Department of Biochemistry at IISc and the study’s corresponding author. “They connect the threads of history between the simplest microbial filaments and the dynamic scaffolds that sustain all higher organisms.”
As the scientific community continues to unravel the mysteries of cellular evolution, this study stands as a significant contribution to understanding the origins and development of one of life’s fundamental structures.
