A new plastid targeting mechanism revealed by the systemic defense-associated lipid transfer protein AZI1 / Conferencista invitado

CECCHINI, NICOLAS M; ROYCHOUDHRY, SURUCHI; HU, CIARA; AGBO, E; SPEED, DEQUANTARIUS J; STEFFES, KEVIN; TAMBE, ARJUN; ZODROW, KRISTIN; KONSTANTINOFF, KATERINA; JUNG, HO WON; GREENBERG, JEAN T

Conferencia; XII Reunión de Biología Vegetal. Chilean Society of Plant Biologists.; 2017

Chilean Society of Plant Biologists.

Right subcelular localization of defense factors is essential for the plant immune system. The mobile signal azelaic acid (AZA) together with the lipid transfer protein (LTP)-like AZI1 are key components for systemic resistance and the priming or immunological ?memory? establishment. AZI1 allows 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 associated to defense and specific features of the AZI1 N-terminus mediate AZI1-plastid targeting. Interestingly, ~0.3 % of the Arabidopsis coded proteins display a similar N-terminal signature. The study of some of them corroborate their plastid localization although their organelle targeting is not predicted by standard algorithms. Moreover, because we observed that AZI1 play a role and localizes to root plastids, this signal may also be functioning in underground tissues. Taken together, our results suggest the existence of a novel mode of plastid targeting/trafficking possible related to defense responses.