University of Warwick researchers have uncovered a rapid, jasmonate-driven early immune response in plants, made visible using a breakthrough live-imaging tool.
Published in Nature Plants, the study shows that plants activate systemic immune defences far sooner than scientists have believed for decades — through an early signalling mechanism that has largely been overlooked.
Unlike animals, plants cannot move away from threats or rely on specialised immune cells and antibodies. Instead, every plant cell must be capable of detecting and responding to attack from pathogens such as viruses, bacteria and fungi, as well as insect pests. When infection occurs, plants launch defences at the point of attack, but they can also trigger immune protection in distant, uninfected tissues to safeguard the rest of the organism. This whole-plant protection is known as Systemic Acquired Resistance (SAR).
For decades, SAR has been thought to depend primarily on the signalling molecule salicylic acid, supported by N-hydroxypipecolic acid, to build and sustain long-lasting immunity. These molecules are produced after infection and gradually accumulate in uninfected tissues over time, according to a press release.
The Warwick team has now shown that before this salicylic acid-based defence becomes established, plants activate a much faster communication system. Within just a few hours, a wave of jasmonate-dependent immune signals spreads through the plant, triggering early SAR well in advance of classical indicators of systemic immune activation.
“What we show here is that whole-plant immunity is activated much faster than we ever realised,” said Professor Murray Grant, Elizabeth Creak Chair in Food Security at the University of Warwick and senior author of the study. “Classic salicylic acid–based SAR is still vital, but our work reveals a new early-warning system powered by jasmonates — hormones previously thought to suppress salicylic acid based immune response.
“Whereas salicylic acid accumulation can take more than 24 hours, the jasmonate-dependent signal appeared within three to four hours of infection, moving rapidly through the plant’s epidermal and vascular tissues to the uninfected leaves. It is a fundamental shift in our understanding of how plant immunity works.”
Watching Immunity Spread in Real Time
To reveal this previously hidden early phase of SAR, the researchers developed a new jasmonate-linked reporter system, JISS1:LUC, which acts as a molecular tracker for early immune activation. Using this tool, they were able to visualise immune signals travelling from infected leaves into uninfected leaves in real time.
This early signalling phase has gone undetected until now because most conventional methods capture immune activity only once systemic defences are already established. Traditional approaches typically measure classical SAR markers or salicylic acid itself — well after the jasmonate-driven signals have already emerged.
The results point to a multi-phase SAR strategy.
“Jasmonates sound the alarm,” explained Dr Erin Stroud, Research Fellow in the School of Life Sciences at Warwick and joint first author. “They coordinate a fast, mobile immune signal, alerting the entire plant that trouble is coming. Classic signalling compounds such as salicylic acid and N-hydroxypipecolic acid then strengthen and stabilises these defences to ensure long-lasting protection.”
This study showed that even in plants unable to produce or perceive salicylic acid, the early wave of signalling still occurred — but SAR disappeared when jasmonate biosynthesis was disrupted. Plants lacking jasmonate signalling were still able to mount normal local immune responses at the site of infection, but they failed to protect distant leaves, leaving them vulnerable to secondary infections.
New Possibilities for Crop Protection
Unexpectedly, the team also found that jasmonate signalling is required to support plant-wide electrical signalling — a system previously associated mainly with wound and herbivore responses.
“These electrical signals are similar to those elicited by herbivory and require functional jasmonate signalling to allow this rapid long-distance communication,” said Dr Emily Breeze, Assistant Professor at Warwick and joint first author. “Our JISS1:LUC reporter system is an excellent tool for visualising early jasmonate-based SAR initiation in real time, within hours of local attack, which gives us a unique method to explore how plants integrate hormones, calcium fluxes and bioelectricity signals to ultimately protect themselves against invaders.”
The finding that jasmonate and electrical signalling are both activated during early systemic immunity opens new opportunities to engineer crops that respond to infection more rapidly. Faster immune activation could help limit disease spread and reduce yield losses, particularly in situations where pathogens move quickly through crops or where plants face multiple disease threats at the same time.
“This work not only reshapes our understanding of systemic plant immunity but understanding common SAR signalling mechanisms gives us a unique lead to design strategies for bioengineering defence systems that provide broad spectrum, rather than pathogen specific crop resistance,” Grant said.
“Specifically, activation of systemic immunity via conditional activation of early jasmonate signalling could provide a novel approach to mitigate crop losses to devastating diseases such as rusts, blights and mildews without the needs for environmentally damaging chemical control.”
