Amazing stuff!
"... One way that plants protect themselves against pathogens is with a response system called systemic acquired resistance (SAR), in which cells in infected tissues signal to cells further away to protect themselves. Researchers knew that plant cells used molecules like salicylic acid to communicate these instructions, but the early signaling mechanisms and factors involved in initiating this response remained a mystery.
Now, researchers ... demonstrated that hormones called jasmonates, metabolites associated with wound signaling, trigger early warnings after infection and are vital to SAR. ...
“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,” ...
To further explore the role of jasmonates in SAR as part of the present study, the team created a reporter by fusing a gene that’s expressed early in SAR to luciferase.
Using this reporter, the team confirmed that this gene is expressed three hours after they infected leaves with a plant pathogen. They observed that expression of this same gene turns on in nearby leaves four hours after the infection of the first leaf, supporting its early role in systemic responses. ..."
"Plants mobilise their immune defences far earlier than scientists have believed for decades—and through a previously overlooked early signalling mechanism ..."
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."
Fig. 5: Systemic electric signal propagation is a general feature of ETI activation.
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