In an unexpected fusion of fieldwork and laboratory science, researchers at the John Innes Centre have uncovered compelling evidence of ancient and conserved mechanisms behind how plants fall ill — findings that could shape the future of crop disease management and deepen our understanding of plant immunity.
The study, published this week in Current Biology, demonstrates how non-flowering plants — thought to have diverged from flowering plants over 500 million years ago — can still fall prey to the same core pathogens that infect modern crops. The research offers rare evolutionary insight into plant-microbe interactions, while also reaffirming the importance of direct observation in nature.
A Walk on the Wild Side
Led by Dr Phil Carella, a group of plant scientists ventured beyond the glassy walls of their laboratories at Norwich Research Park to examine nature’s own experiments — wild patches of Marchantia polymorpha, a liverwort that often grows in damp cracks in pavements or under shaded rocks.
Typically used in controlled lab experiments, Marchantia is a simple, non-flowering plant with a compact genome, making it an ideal model for plant biology. However, its natural environment had rarely been examined for real-world disease interactions.
READ MORE: Australian Space Tourist Returns to Earth After Historic Polar Orbit
“We work with lab-grown versions of these non-flowering species in our experiments, often infecting them with pathogens from flowering plants,” said Dr Carella. “Our colleagues would often ask us: ‘Do they naturally get infected, too?’ So we decided to go outside and check it out. Then some interesting things started to happen.”
From Pavement Cracks to the Laboratory
The research team, led in the field and lab by Kayla Robinson, a skilled laboratory technician and the study’s first author, surveyed areas near their base at the John Innes Centre in search of diseased Marchantia. They collected samples displaying signs of illness — lesions, discoloration, or decay — and returned to the lab to isolate microbes present in the infected tissue.
What they found was striking: 40 strains of Pseudomonas bacteria, some pathogenic, others not. Among them was Pseudomonas viridiflava, a known pathogen of flowering plants — but never before identified in non-flowering liverworts.
“This was the first time we saw such a well-known flowering plant pathogen infecting a non-flowering plant like Marchantia,” said Robinson. “It raised immediate questions about how this could happen — and what it meant for our understanding of plant disease.”
A Shared Mechanism Across 500 Million Years
To confirm the bacteria’s virulence, the researchers re-infected lab-grown Marchantia with isolated strains, observing clear signs of infection. They then used genetic sequencing to uncover the pathogen’s playbook — the genetic machinery it used to infiltrate the plant.
Genomic analysis identified five effector genes — molecular tools that pathogens use to hijack plant cells. Two of these effectors were shared across all pathogenic strains, suggesting a common and deeply conserved method of infection.
The surprise came when these same bacterial strains were used to infect a well-known flowering model plant, Nicotiana benthamiana. The pathogen behaved similarly, using the same core effectors to breach plant defenses, regardless of the host’s evolutionary background.
“Our study shows there is a shared, ancient mechanism for causing disease in very distantly related plants,” said Dr Carella. “Some of the bacteria we study can have up to thirty effectors, but here, we’ve identified a pathogen with just five — yet it’s capable of infecting both flowering and non-flowering plants. That’s remarkable.”
This streamlined infection strategy, using a minimal set of tools, suggests that the pathogen targets ancient and essential immune pathways that have been conserved across hundreds of millions of years.
Why Marchantia Matters
Marchantia polymorpha may not be as familiar as wheat, corn, or soybeans — but its simplicity and genetic tractability make it an increasingly valuable model for studying plant immunity.
“One of the advantages of Marchantia is that it’s haploid — it has only one copy of its genome instead of two,” explained Dr Carella. “That makes it faster and easier to identify the genetic basis of immune responses, and because these mechanisms are shared with flowering plants, what we learn from Marchantia can apply broadly — including to agriculture.”
Additionally, Marchantia is easier to grow, maintain, and experiment with than more complex flowering models, offering researchers a streamlined platform for testing pathogen resistance, gene function, and even potential treatments.
Implications for Agriculture and Beyond
Understanding the minimal requirements for a pathogen to infect a plant has practical consequences. As plant pathogens become more resistant to conventional control measures, identifying their most fundamental tools — the core effectors that enable infection — could help scientists develop broad-spectrum disease resistance in crops.
“If these effectors are essential to a pathogen’s ability to infect a plant, they become high-value targets for new resistance strategies,” said Dr Carella. “This could mean editing plant genomes to block those effectors, or designing treatments that disrupt their function.”
At a time when climate change and global food demand are increasing pressure on agriculture, the ability to predict and prevent pathogen spread across species is more valuable than ever.
A Technicians’ Triumph
Dr Carella was quick to highlight the often-overlooked role of skilled technical staff in scientific breakthroughs. In this study, Kayla Robinson’s design, execution, and troubleshooting of both field and lab experiments were critical to its success.
“Having someone with the experience and expertise to carefully assess, plan, and adapt experiments is imperative,” he said. “It’s just one of the reasons the John Innes Centre has signed on to the Technician Commitment, recognising the essential contributions of our technical workforce.”
Fieldwork Sparks Fresh Thinking
The study is also a reminder that, sometimes, scientific progress comes from stepping outside of the lab.
“This started as a side project,” said Robinson. “We just wanted to know whether our lab models reflected what happens in nature. What we found ended up reshaping how we think about plant-pathogen interactions on a fundamental level.”
Indeed, what began as a curiosity-driven walk in the wilds of a research park has blossomed into a discovery with implications stretching from the molecular heart of plant immunity to the front lines of global agriculture.
