PHB3 interacts with ICS1 and is involved in the SA-mediated defense response of Arabidopsis thaliana   
A. SEGUEL (1), J. Jelenska (2), A. Herrera (1), J. Greenberg (2), L. Holuigue (1) (1) Pontificia Universidad Católica de Chile, Chile; (2) The University of Chicago, U.S.A.

SA acid (SA) is a phytohormone widely known for its role on the regulation of the plant defense. It accumulates during a variety of biotic and abiotic stress conditions, such as pathogen infections and UV-C light exposure, among others. In Arabidopsis thaliana, the main source of SA under such conditions is a chloroplastic pathway, called ICS, in which Isochorismate synthase 1 (ICS1) is, so far, the enzyme known to be involved. However it is known that in some bacteria ICS1 forms a complex in order to produce SA. Therefore, we hypothesized that ICS1 could work in a similar way in plants. To test this possibility, we performed immunoprecipitation of ICS1 and used mass spectrometry to identify ICS1-interacting proteins. In this analysis, we found a large number of peptides from a protein family that was previously described as mitochondria-localized, called Prohibitins (PHBs). Here we report that PHB3  localizes to chloroplasts, similar to ICS1. We evaluated the phb3-3 mutant plant under UV-C treatments and Pseudomonas syringae DC3000 (Pst) infections. In both conditions SA levels in mutant plants are reduced compared with WT and levels of the SA-regulated PR1 protein are decreased. The phb3-3 mutant plant also shows higher susceptibility to some P. syringae strains. This evidence suggests that PHB3 is involved in the regulation of the accumulation and possibly also the response mediated by SA in Arabidopsis thaliana.    

Abstract Number: P16-469
Session Type: Poster