Researchers have found that a multi-protein molecular switch used by modern plants to determine cell fate originated in the earliest land plants nearly half a billion years ago. The study shows how this system was repurposed over millennia, allowing plants to adapt to life on land.
While scientists already knew that this regulatory mechanism – the MBW complex – controlled traits like petal colour and root hairs in modern flowering plants, this research indicates it was already functional by the time they split from liverworts early in land plant evolution.
Professor Beverley Glover, Head of the Evolution and Development group at the Department of Plant Sciences, Cambridge, and senior author of the paper said: “What excites me most about this work is that it feels like looking through a special telescope that shows us what was happening when plants first made the transition onto land about 470 million years ago – we have the opportunity to understand what tools those early plants had to specify different cell types, and how those tools then diversified over time.”
Dr Thea Kongsted, lead author of the paper who completed her PhD in the Glover lab and is now a Postdoctoral Fellow at the Gregor Mendel Institute of Molecular Plant Biology in Vienna, said: "Our findings help solve an evolutionary puzzle – while nearly all plants make red pigments, they do so through many different chemical pathways. By understanding how pigmentation may have functioned in their common ancestor, we can begin to piece together why so many different pathways have evolved.
“We found that even though the pigments themselves differ, their production is triggered by the same genetic mechanism across different species. Beyond this, we were surprised to find that these pigment regulators had been repurposed for new pathways in liverworts in a remarkably similar way to how they were repurposed in flowering plants.”
While other ancient genetic mechanisms are made of 'siblings' from the same protein family, the MBW complex represents the first known example of a regulatory team made of three completely different protein families that has remained intact across such a vast evolutionary timescale.
The study was published in the journal Current Biology on 8 May 2026.
Uncovering the origins of plant diversity
The MBW complex is a 3-protein unit that governs the gene expression behind much of the cell diversity in flowering plants (angiosperms). From colour pigments in petals to protective leaf hairs and the precise spacing of root hairs, almost every specialised cell type on a plant’s surface is managed by this complex.
Within the complex, ‘W’ is thought to act as a scaffold that enables ‘M’ and ‘B’ to bind together. Once linked, the ‘M’ and ‘B’ factors activate a suite of downstream genes that define a cell’s specialised features. Because plants carry many different versions of ‘M’, the specific 'M' that occupies the complex determines the cell's fate.
To find out whether the MBW complex was a recent innovation or an ancient ancestral trait, the research team isolated the ‘M’, ‘B’, and ‘W’ genes from the liverwort Marchantia polymorpha. They found that the proteins in liverworts assemble into the same 3-part framework used by flowering plants.
Liverworts are a part of the bryophyte lineage – the branch of plant life that split from the group leading to angiosperms at the very base of the plant family tree. Finding the MBW complex here suggests that this regulatory machinery is ancestral to all land plants and remains a foundational toolkit across the plant kingdom.
From sunscreen to chemical defences: repurposing for survival
The two different ‘M’ genes in liverworts control different cell fates.
One gene controls red pigments called auronidins, which protect the plant from infection and UV light. Evidence suggests that producing these sunscreen-like pigments was the original role of the MBW complex, allowing plants to endure the sun's rays – a critical adaptation for surviving life on land.
The other ‘M’ gene is responsible for building oil bodies – tiny sacs unique to liverworts that store toxic chemicals to deter animals from eating the plant. It is likely that this second ‘M’ is a mutation of the original pigment-regulating gene, duplicated and modified for this new function.
Crucially, when the researchers used CRISPR to knock out the ‘B’ gene, the plants lost both their red colour and their protective oil bodies. This indicates that the ‘M’ genes don’t work alone; they are dependent on the MBW molecular framework to function.
Furthermore, the duplication of these 'M' proteins in liverworts happened independently from the duplications seen in flowering plants. This reveals that the MBW complex has been 're-tasked' to regulate new specialised cell types repeatedly throughout plant evolution.
A replicated blueprint across time
This study shows that nature is remarkably efficient. Rather than inventing entirely new systems, it often duplicates and tweaks specific parts of an ancient, proven machine to meet new environmental challenges.
The findings suggest that much of the diversity of traits we see in the plants around us today is the result of evolution repeatedly 'copying and pasting' this ancient toolkit. This reveals a replicated blueprint for survival: by tweaking specific ‘M’ factors, plants have successfully innovated across hundreds of millions of years.
Engineering the next generation of plants
While this research contributes to solving an evolutionary puzzle, it also provides a roadmap for modern industry and agriculture. Understanding how plant cell types have been modified by evolution may help scientists design strategies to modify cell fate in crops and optimise the production of pigments, drugs and food industry products.
By learning to toggle the specialist ‘M’ genes, we can move away from unpredictable genetic changes and toward surgical-level modifications of plant traits.
This knowledge could help transform plants into precision bio-factories capable of mass-producing high-value medicinal proteins or lipids. Perhaps most urgently, the work could contribute to efforts to future-proof agriculture against a changing climate. By manipulating the density of pest-protective leaf hairs or nutrient-absorbing root hairs, for example, scientists can help adapt crops to a rapidly changing environment.
In the end, the study reminds us that the staggering diversity of the modern world is the result of millions of years of clever recycling. Perhaps this can provide a functional blueprint for engineering the next generation of plants.
Funding: The work was supported by the UKRI Natural Environment Research Council and the Biotechnology and Biological Sciences Research Council.
Reference: Kongsted, T. E., et al. ‘Replicated repurposing of an ancestral transcriptional complex in land plants.’ Current Biology, May 2026. DOI: 10.1016/j.cub.2026.04.031.
Image: From ancient sunscreen to modern petals: the same genetic engine at work. Left: Gemmae cups and gemmae on a Liverwort (Marchantia polymorpha). Credit: Ed Reschke (Getty Images). Right: A bee gathers pollen from a red flower. Credit: Audrey Abryutin (Getty Images).