The Arabidopsis oligopeptidases TOP1 and TOP2 are salicylic acid targets that modulate SA-mediated signaling and the immune response.

The Plant journal : for cell and molecular biology

PubMedID: 24004003

Moreau M, Westlake T, Zampogna G, Popescu G, Tian M, Noutsos C, Popescu S. The Arabidopsis oligopeptidases TOP1 and TOP2 are salicylic acid targets that modulate SA-mediated signaling and the immune response. Plant J. 2013;.
Salicylic acid (SA) is a plant small phenolic molecule with hormonal properties and an essential component of the immune response. SA exerts its functions by interacting with protein targets; however, the specific cellular components modulated by SA and critical for immune signal transduction are largely unknown. To uncover cellular activities targeted by SA, we screened the interaction space of SA with a large fraction of the Arabidopsis proteome using protein microarrays. We demonstrate that thimet oligopeptidases constitute a class of SA binding enzymes. Biochemical evidence demonstrates that SA interacts with TOPs and inhibits their peptidase activities to different degrees both in vitro and in plant extracts. Functional characterization of mutants with altered TOPs expression indicates that TOP1 and TOP2 mediate SA-dependent signaling and are necessary for the immune response to avirulent pathogens. Our results support a model whereby TOP1 and TOP2 act in separate pathways to modulate SA-mediated cellular processes. This article is protected by copyright. All rights reserved.