The plant cuticle regulates apoplastic transport of salicylic acid during systemic acquired resistance

Gah Hyun Lim, Huazhen Liu, Keshun Yu, Ruiying Liu, M. B. Shine, Jessica Fernandez, Tessa Burch-Smith, Justin K. Mobley, Nicholas McLetchie, Aardra Kachroo, Pradeep Kachroo

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The plant cuticle is often considered a passive barrier from the environment. We show that the cuticle regulates active transport of the defense hormone salicylic acid (SA). SA, an important regulator of systemic acquired resistance (SAR), is preferentially transported from pathogen-infected to uninfected parts via the apoplast. Apoplastic accumulation of SA, which precedes its accumulation in the cytosol, is driven by the pH gradient and deprotonation of SA. In cuticle-defective mutants, increased transpiration and reduced water potential preferentially routes SA to cuticle wax rather than to the apoplast. This results in defective long-distance transport of SA, which in turn impairs distal accumulation of the SAR-inducer pipecolic acid. High humidity reduces transpiration to restore systemic SA transport and, thereby, SAR in cuticle-defective mutants. Together, our results demonstrate that long-distance mobility of SA is essential for SAR and that partitioning of SA between the symplast and cuticle is regulated by transpiration.

Original languageEnglish
Article numbereaaz0478
JournalScience advances
Issue number19
StatePublished - May 2020

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