Azelaic acid-induced priming in Arabidopsis systemic acquired resistance

CECCHINI NM; GREENBERG JT

Congreso; Gordon Research Conferences - Plant Molecular Biology; 2012

Priming of defense responses could be a major mechanism behind the immunological ?memory? observed during plant systemic acquired resistance (SAR). A lipidic signal, azelaic acid (AZA) was identified as a key mobile priming factor. AZA treatment induces the essential SAR-component AZI1. The product of this gene is related to lipid transfer proteins suggesting that AZA, or an AZA-derivative, could be bound and translocated by AZI1. To discern the role of AZI1 in AZA-conferred priming we analyzed two key aspects: how AZI1 affects AZA movement and AZI1 subcellular locations.Using phloem uploading assays we analyzed the 14C-AZA uptake in azi1-1. The azi1-1 mutant showed a significant decrease in uptake compared to wild-type plants. Moreover, in a preliminary radiotracer experiment azi1-1 moved less 14C-AZA from source to sink leaves.Localization studies using confocal microscopy showed AZI1-GFP in vesicles, plasma membrane and cell wall/apoplast. Western blot analysis of subcellular fractions was in agreement with confocal localization. Interestingly, at higher expression levels AZI1 was found surrounding and inside chloroplast, and in contact sites between ER/chloroplasts. These sites are proposed as places were lipids exchange occurs. Taken together these results suggest the attractive idea that AZI1 affects the movement of a key signal such as AZA.This work was supported by a grant to JTG from the NSF and U. S. Department of Energy, Office of Biological and Environmental Research