Cambridge researchers have identified a minimal toolkit of genes that controls how plants grow, revealing a biological system that has remained virtually unchanged for over 450 million years.
By studying the liverwort Marchantia polymorpha, a team from the Haseloff group in the Department of Plant Sciences has provided a new framework for understanding the evolution of land plants, potentially unlocking new ways to engineer crop growth.
While modern crop species have evolved complex systems involving over 30 different cyclin proteins – the molecular engines that drive cell division – the study shows that liverwort uses a simple relay of just three cyclins to drive cells through each division phase.
The research indicates that the simple toolkit found in Marchantia is not a reduced or stripped-down version of a more complex system but is likely to represent something close to the system the first land plants used over 450 million years ago.
The research was published in the journal 'The Plant Cell' on 9 April 2026.
The minimal engine of life
To understand how this minimal system works in practice, the team used advanced single-cell sequencing and live imaging to track cyclin activity in dividing cells.
All dividing cells, from yeast to humans to plants, progress through a series of proteins called cyclins that drive the transitions between phases: G1, S – when DNA is copied; G2; and mitosis – when the cell divides.
The team found that three specific proteins – MpCYCD;1, MpCYCA, and MpCYCB;1 – act as a relay team, with each one taking charge of a different phase of the cell division process.
This ‘one-cyclin-per-phase’ model matches classic textbook predictions for how cells divide across various life forms but has never been seen so clearly in a plant.
Dr Facundo Romani, Research Associate at Cambridge University and co-lead author of the study, said: “Every time a plant cell divides, it relies on proteins called cyclins to move through the different stages of division. From yeast to animals, and algae this system of proteins is highly conserved.
“In crop species, there are over 30 cyclins, many with overlapping roles, which has made it difficult to work out what each one actually does.
“Non-seed plants – liverworts, mosses, hornworts – generally have single copies of the core cell cycle genes. The question was how this system can operate with minimal components because that is likely to be the ancestral configuration.”
Accelerators and brakes
To prove these proteins were truly in control, the team performed functional experiments to manipulate the cell cycle. They found that artificially activating the entry cyclin, MpCYCD;1, was sufficient to push dormant cells back into active division. This confirmed its role as the system’s primary ‘accelerator’.
The study also highlighted the importance of timing. When the researchers forced the later-acting cyclins (MpCYCA or MpCYCB;1) to remain active beyond their natural window, the cells simply stopped dividing. This demonstrates that the timely degradation of these proteins is just as vital as their activation for the cycle to complete successfully.
The team also investigated the ‘brakes’ of the system – inhibitors known as KIP-related and WEE regulators. When these regulators were enhanced, they caused a total arrest of plant growth.
"These results tell us that both the accelerators and the brakes of cell division are deeply conserved," says Dr Romani. "The basic logic of how plants speed up or slow down proliferation has been in place for hundreds of millions of years".
Future impact: from evolution to engineering
By establishing this framework in Marchantia, the researchers hope to provide a foundation not only for understanding how cell division evolved across the plant kingdom, but also for synthetic biology approaches to engineering plant growth.
Professor Jim Haseloff, Head of the Synthetic Biology for Engineering Plant Growth group at the Department of Plant Sciences, Cambridge said: “This work opens new possibilities for engineering cell proliferation. The study brings together a simple, stripped-down experimental system and a map of the minimal components required to regulate cell division. It provides a practical testbed for bottom-up reprogramming of organogenesis in plants.”
Reference: Romani, F., Bonter, I. et al: ‘A simple cell-cycle control system in Marchantia polymorpha provides a framework for understanding plant cell proliferation.’ The Plant Cell, April 2026. DOI: 10.1093/plcell/koag103
Image: Schematic model of the simple cell-cycle control system in Marchantia. Credit: Facundo Romani