Plant immune memory opens a new route for crop breeding

By Rebecca Stone

A University of Sheffield-led study in Nature Communications found that part of an immune memory created in rice by the XVE molecular tool was transmitted to offspring, pointing to a breeding route beyond selection for DNA-sequence differences.

That rice result remains early evidence rather than a released or validated breeding product. Professor Jurriaan Ton and Dr Adam Hannan Parker led the study, which identified mechanisms that allow plants to maintain and reset immune memory. The breeding opportunity is a way to generate useful variation in how existing genes are regulated.

Ton said: “Our collaboration with researchers at the Okinawa Institute of Science and Technology (OIST) in Japan is revealing promising results in rice, suggesting the epigenetic memory by XVE in rice is not completely reset between generations, with part of it transmitted to offspring.”

How do plants remember infection?

Plants lack the specialized immune cells found in animals, but an earlier infection can prime their defenses to respond faster and more forcefully to a later attack. This response can remain as epigenetic memory, a retained pattern of gene regulation that does not alter the underlying DNA sequence.

Earlier work from Ton’s laboratory found that plants store part of this memory by removing chemical tags attached to DNA. Those tags influence gene expression, meaning the degree to which genes are switched on or off, without rewriting the sequence itself.

The new team used a molecular tool called XVE to activate the enzyme REPRESSOR OF SILENCING 1 (ROS1) more precisely than infection does. The researchers described the experimental step as “plant vaccination” and used it to examine how immune memory develops, how long it lasts and how it is erased.

How does the method protect the genome?

Activating ROS1 creates a second problem. Removing DNA tags can release genetic elements that plants normally keep silent, potentially weakening genome stability, or the integrity of the plant’s genetic material.

Dr Adam Hannan Parker said: “Too much ROS1 activity carries a potential risk. It can release silenced transposons, or ‘jumping genes,’ which move within the genome and cause mutations. These elements are particularly abundant in pericentromeres, the regions surrounding the constricted centres of chromosomes.”

After ROS1-triggered activation, plants temporarily redirected the machinery that silences DNA away from defense genes and toward chromosome regions rich in transposons. That arrangement kept the jumping genes suppressed while defense genes on chromosome arms retained their epigenetic memory.

What does the rice result mean for breeders?

Conventional crop breeding mainly selects for differences in DNA sequence. XVE could instead alter the distribution of DNA methylation, generating epigenetic variation that changes how existing genes are regulated.

The Sheffield team is refining XVE to deliver a stronger “epigenetic shock,” meaning a more powerful change in gene regulation. The aim is to generate useful variation that remains stable across generations, after which breeders could screen plants for beneficial traits.

What could the approach deliver besides disease resistance?

The researchers see potential targets in tolerance to three non-biological environmental stresses: drought, heat and salinity. The method could also generate variation in crop-quality traits, including the nutritional value of vegetables and compounds with potential health benefits.

Researchers must still establish whether useful changes can be generated reliably and inherited. If they can, epigenetic memory could give breeders an additional source of variation for improving crop resilience and quality.

What changes for growers?

For growers, the immediate significance is limited to the breeding pipeline. The published findings include no commercial cultivar, field trial, planting timetable, policy provision, input-cost estimate, basis forecast or farm-margin calculation.

Accordingly, the study cannot yet support claims of lower disease losses, lower input bills or higher net returns. Its economic case would require reliable inheritance and recovery of beneficial traits, the uncertainties the Sheffield team still has to resolve.

The research now turns on whether a stronger XVE treatment can produce stable, useful epigenetic variation across generations without compromising genome stability; until then, the work remains a research-stage breeding tool rather than a farm-ready input.