Lipid transfer proteins and azelaic acid-conferred systemic priming in Arabidopsis. / Conferencista invitado

CECCHINI NM; SCHLÄPPI MR; GIFFORD AN; GREENBERG JT

Buenos Aires

Simposio; 32nd New Phytologist Symposium.; 2013

Priming of defence 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 mobile priming factor. The products of two essential SAR-components, AZI1 and DIR1, are related to lipid transfer proteins (LTPs), suggesting that AZA could be translocated by these LTPs. To discern the possible roles of AZI1/DIR1 during AZA-priming, we analysed their subcellular locations, possible interaction, and if they affected AZA systemic movement. Localization and fractionation studies showed AZI1-GFP in vesicles-like structures, the ER, plasma membrane, and cell wall, whereas DIR1-GFP localized mainly to the ER and apoplast. Remarkably, AZI1 was also found in chloroplasts, enriched in contact sites between ER/chloroplasts. These sites are proposed as key places were lipid exchange occurs. Moreover, tissues co-expressing AZI1-GFP/DIR1-RFP showed co-localization to the ER. In agreement with the microscopy data, co-immunoprecipitation studies revealed interactions between AZI1 and DIR1 as well with other members of these LTPs-related protein families. Using 14C-AZA radiotracer and uploading assays, we found that AZI1, but not DIR1, is implicated in AZA movement from source to sink leaves as well as in its local uptake. The results suggest the existence of a LTPs complex(s) acting in different steps/places during SAR establishment, probably moving a lipidic signal(s), such as AZA, intracellularly as well as over long distance to the systemic tissues.This work was supported by a grant to JTG from the NSF and U.S. Department of Energy, Office of Biological and Environmental Research