Systemic acquired resistance (SAR), initiated by a plant upon recognition of microbial effectors, involves generation of a mobile signal at the primary infection site, which translocates to and activates defense responses in distal tissues via unknown mechanism(s). We find that an acyl carrier protein, ACP4, is required to perceive the mobile SAR signal in distal tissues of Arabidopsis. Although acp4 plants generated the mobile signal, they failed to induce the systemic immunity response. Defective SAR in acp4 plants was not due to impairment in salicylic acid (SA)-, methyl SA-, or jasmonic acid-mediated plant hormone signaling pathways but was associated with the impaired cuticle of acp4 leaves. Other cuticle-impairing genetic mutations or physical removal of the cuticle also compromised SAR. This cuticular requirement was relevant only during mobile signal generation and its translocation to distal tissues. Collectively, these data suggest an active role for the plant cuticle in SAR-related molecular signaling.
|Number of pages||15|
|Journal||Cell Host and Microbe|
|State||Published - Feb 19 2009|
Bibliographical noteFunding Information:
We thank John Johnson for help with gas chromatography, Larry Rice for help with SEM, Mary Gail Engle for help with TEM, Claire Venard for help with thick sectioning, Rae-Dong Jeong for quantification of R gene levels, and Thomas Muse and Lev Orlov for help with fatty acid extractions and genotyping. We also thank Mike Pollard for cutin monomer spectra and useful advice, John Browse for lacs2 and lacs9 seeds, and Walter Grassmann for Pseudomonas syringae strain containing AvrRPS4. We thank Kansas Lipidomics Research Center Analytical Laboratory and its support from National Science Foundation's EPSCoR program, under grant number EPS-0236913 with matching support from the State of Kansas through Kansas Technology Enterprise Corporation and Kansas State University. This work was supported by grants from NSF (MCB#0421914), USDA-NRI (2004-03287), and KSEF (419-RDE-004, 04RDE-006, 820-RDE-007).
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