IISc discovers ancient proteins revealing how cells evolved complexity

The question of how life went from simple to complex has haunted biology for decades. Bacteria and archaea are relatively straightforward—minimal internal structures, streamlined machinery. Eukaryotes, by contrast, are baroque: compartments within compartments, elaborate systems for holding their shape, intricate choreography for cell division. The gap between the two seems almost unbridgeable. Yet somewhere in the deep past, one crossed into the other.

Scientists hunting for clues have turned to an unusual group of microbes called Asgard archaea. These organisms are thought to be the closest living relatives of eukaryotes, and their genetic blueprints read like a bridge between two worlds. In them, researchers hope to find the first sketches of complexity—the moment when life began experimenting with the machinery that would eventually build animals, plants, and fungi.

A team at the Indian Institute of Science has now identified a crucial piece of that machinery. They were studying Odinarchaeota, one member of the Asgard family, and found something unexpected: not one but two versions of a gene called FtsZ, along with a gene that resembles tubulin. In most microbes, you get one FtsZ. Having two is rare, and having both alongside a tubulin-like gene suggested something more complex was at work.

The researchers set out to understand what these proteins actually do. Using phylogenetic analysis, biochemical testing, and cryo-electron microscopy, they watched how each FtsZ protein behaved when exposed to energy molecules like GTP. They tested whether the proteins could bind to artificial membranes. What emerged was a portrait of specialization. The first protein, OdinFtsZ1, assembled into straight filaments much like the FtsZ found in bacteria, and it could attach directly to cell membranes on its own. The second, OdinFtsZ2, did something stranger—it formed spiral, ring-like structures and needed a helper protein to latch onto membranes. When both were present together, they interacted with each other, suggesting they might work in concert inside living cells.

This division of labor is the key insight. Rather than relying on a single, multipurpose protein, Odinarchaeota had evolved two versions that could split the work between them. One handled the straightforward structural job; the other took on a more specialized role. Combined with the tubulin-like protein also present in these cells, the picture that emerges is of an organism experimenting with multiple strategies for building and maintaining its skeleton—the cytoskeleton that gives cells their shape and enables them to divide.

Saravanan Palani, who led the project, described the finding as a rare window into a turning point in evolution. "These proteins give us a snapshot of a moment when life began building the dynamic skeleton that supports all higher organisms today," he told The Hindu. The work was published in The EMBO Journal and represents the kind of molecular archaeology that can only happen when you have access to organisms that seem to have paused at a crucial moment in the story of life.

What comes next is equally important. Palani's team plans to cultivate Asgard microbes in the laboratory and observe these proteins in action within living cells. If they succeed, they will have achieved something remarkable: a real-time view of one of evolution's most consequential leaps, the moment when simple cells began to build the machinery of complexity.