Roles of Plant Hormones in Plant Resistance and Susceptibility to Pathogens
Plants and animals trigger an innate immune response upon perception of pathogen-associated molecular patterns (PAMPs) such as flagellin. In Arabidopsis, flagellin perception elevates resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), although the molecular mechanisms involved remain elusive. A flagellin-derived peptide transiently enhances the accumulation of a plant microRNA that directs degradation of mRNA for TIR1, an F-box auxin receptor. The resulting repression of auxin signaling effectively restricts Pst DC3000 growth, implicating this previously unsuspected miRNA-mediated switch in bacterial disease resistance. These data suggest that elevation of auxin levels constitute a bacterial pathogenicity strategy that is suppressed during the innate immune response to PAMPs. In a separate work, we showed that DELLA proteins, which are normally associated with gibberellin responses, play a role in the balance between salicylic acid and jasmonic acid–mediated defense signaling pathways. DELLA loss-of-function mutants show reduced growth inhibition in response to flg22, enhanced susceptibility to necrotrophic pathogens, and enhanced resistance to Pst DC3000.
KeywordsSalicylic Acid Transgenic Line Tobacco Mosaic Virus Auxin Signaling DELLA Protein
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