A Feedback Regulatory Loop between G3P and Lipid Transfer Proteins DIR1 and AZI1 Mediates Azelaic-Acid-Induced Systemic Immunity

• Published in: Cell reports (Cambridge) 2013-04, Vol.3 (4), p.1266-1278
• Main Authors: Yu, Keshun, Soares, Juliana Moreira, Mandal, Mihir Kumar, Wang, Caixia, Chanda, Bidisha, Gifford, Andrew N., Fowler, Joanna S., Navarre, Duroy, Kachroo, Aardra, Kachroo, Pradeep
• Format: Article
• Language: English
• Subjects: Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Dicarboxylic Acids - metabolism; Dicarboxylic Acids - pharmacology; Disease Resistance - drug effects; Fatty Acids, Unsaturated - metabolism; Mutation; Phosphoric Monoester Hydrolases - metabolism; Phosphoric Monoester Hydrolases - pharmacology; Plants, Genetically Modified - metabolism; Signal Transduction; Transcription, Genetic
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2013.03.030

Systemic acquired resistance (SAR), a highly desirable form of plant defense, provides broad-spectrum immunity against diverse pathogens. The recent identification of seemingly unrelated chemical inducers of SAR warrants an investigation of their mutual interrelationships. We show that SAR induced by the dicarboxylic acid azelaic acid (AA) requires the phosphorylated sugar derivative glycerol-3-phosphate (G3P). Pathogen inoculation induced the release of free unsaturated fatty acids (FAs) and thereby triggered AA accumulation, because these FAs serve as precursors for AA. AA accumulation in turn increased the levels of G3P, which is required for AA-conferred SAR. The lipid transfer proteins DIR1 and AZI1, both of which are required for G3P- and AA-induced SAR, were essential for G3P accumulation. Conversely, reduced G3P resulted in decreased AZI1 and DIR1 transcription. Our results demonstrate that an intricate feedback regulatory loop among G3P, DIR1, and AZI1 regulates SAR and that AA functions upstream of G3P in this pathway. [Display omitted] •Systemic acquired resistance is associated with release of free fatty acids•Unsaturated fatty acids undergo cleavage at carbon 9 to form azelaic acid•Azelaic acid functions upstream of the SAR inducer glycerol-3-phosphate•Glycerol-3-phosphate is required for the stability of lipid transfer proteins The recent identification of several seemingly chemically unrelated mobile inducers suggests that independently functioning diverse signals might regulate systemic acquired resistance (SAR) in plants. Kachroo and colleagues now provide genetic, biochemical, and molecular evidence in support of a linear pathway connecting azelaic acid and glycerol-3-phosphate (G3P), as well as a cyclic feedback regulatory loop between G3P and the lipid transfer proteins DIR1 and AZI1, in the induction of SAR.