A new chloroplast targeting mechanism revealed by systemic defense-associated lipid transfer proteins
N. CECCHINI (1), C. Hu (2), E. Agbo (2), K. Zodrow (2), D. Speed (2), S. Roychoudhry (2), J. Greenberg (2) (1) Molecular Genetics and Cell Biology - The University of Chicago, U.S.A.; (2) Molecular Genetics and Cell Biology, The University of Chicago, U.S.A.

Priming is a major mechanism behind the immunological “memory” observed during plant systemic defenses against pathogens. The mobile signal azelaic acid (AZA) together with the lipid transfer protein (LTP)-like AZI1 are important components for priming establishment. AZI1 is needed for the systemic movement and uptake of AZA in Arabidopsis plants. Localization studies indicate that a pool of AZI1 exists near the site of AZA production, in the chloroplast outer envelope. However, AZI1 does not possess a classical chloroplastic transit peptide that can explain its localization. Here, we show that this LTP-like and several members of the AZI1 family use an undescribed N-terminal signature that allows the chloroplast targeting. We will present evidence that cytoskeleton integrity, protein kinases and specific features of the AZI1 N-terminus mediate AZI1-plastid targeting. Interestingly, in Arabidopsis ~0.3 % of the coded proteins display a similar N-terminal signature. The study of some of them corroborate their chloroplast localization although their localization patterns are not predicted by standard algorithms. Therefore, our results suggest the existence of a novel mode of plastid targeting and trafficking possible related to defense responses.

Abstract Number: P18-662
Session Type: Poster