Amazing stuff!
"Plants mobilize their immune defenses far earlier than scientists have believed for decades—and through a previously overlooked early signaling mechanism—according to a new study ...
When attacked, plants quickly initiate defense responses at the site of challenge, but they can also activate immune responses in distant, not yet infected tissues to protect the rest of the plant, a process known as Systemic Acquired Resistance (SAR).
For decades, SAR has been understood to rely on the signaling molecule salicylic acid—supported by N-hydroxypipecolic acid—to execute and maintain long-lasting immune protection throughout the plant. These molecules are synthesized following infection and gradually accumulate in distant uninfected tissues.
The ... team now shows that before this salicylic acid-centered defense is established, plants deploy a much faster communication system: a wave of jasmonate-dependent immune signals that spreads through the plant within just a few hours, initiating SAR well before classical measures of activated SAR. ..."
"... To uncover this hidden early SAR phase, the researchers developed a novel jasmonate-linked SAR reporter, JISS1:LUC, which functions as a molecular tracker for this early immune activation. This tool allowed them to visualise immune signals moving out of infected leaves and across into uninfected leaves in real time.
This very early signalling phase has remained hidden until now because most traditional approaches detect immune responses during or after systemic defences are fully established, measuring classical molecular markers or SA itself, well after these jasmonate-driven signals are developed.
The results point to a multi-phase SAR strategy. “Jasmonates sound the alarm,” ... “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 occurred — but SAR disappeared when jasmonate biosynthesis was disrupted. Those plants lacking jasmonate signalling mounted normal local immune responses to infection, but failed to protect distant leaves, making them vulnerable to secondary infections. ..."
From the abstract:
"Successful recognition of pathogen effectors by plant disease resistance proteins, or effector-triggered immunity (ETI), contains the invading pathogen through localized hypersensitive cell death. ETI also activates long-range signalling to establish broad-spectrum systemic acquired resistance (SAR).
Here we describe a sensitive luciferase (LUC) reporter that captures the spatial–temporal dynamics of SAR signal generation, propagation and establishment in systemic responding leaves following ETI.
JASMONATE-INDUCED SYSTEMIC SIGNAL 1 (JISS1) encodes an endoplasmic-reticulum-localized protein of unknown function. JISS1::LUC captured very early ETI-elicited SAR signalling, which surprisingly was not affected by classical SAR mutants but was dependent on calcium and was also wound responsive.
Both jasmonate biosynthesis and perception mutants abolished JISS1::LUC signalling and SAR to Pseudomonas syringae.
Furthermore, we discovered that ETI initiated jasmonate-dependent systemic surface electrical potentials. These surface potentials were dependent on both glutamate receptors and JISS1, despite neither JISS1 loss-of-function nor glutamate receptor mutants altering SAR to Pseudomonas syringae.
We thus demonstrate that jasmonate signalling, usually associated with antagonism of defence against biotrophs, is crucial to the rapid initiation and establishment of SAR systemic defence responses (including the activation of systemic surface potentials) and that JISS1::LUC serves as a reporter to further dissect these pathways."
New study overturns long-held model of how plants coordinate immune responses (original news release) "University of Warwick researchers discover rapid, jasmonate-driven, early immune response in plants using breakthrough live-imaging tool."
Rapid local and systemic jasmonate signalling drives the initiation and establishment of plant systemic immunity (open access)
Fig. 1: JISS1 expression is induced systemically by ETI. [Looks like fireworks to me]
Fig. 2: JISS1::LUC is activated by the jasmonate signalling pathway but not classical SAR elicitors.
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