CONICET | Buscador de Institutos y Recursos Humanos

Jasmonates (JA), a group of lipid-derived hormones, play a central role controlling inducible defenses in plants thus having a profound impact on plant interaction with the biotic environment. In a basal state, JA responses are repressed by JASMONATE-ZIM DOMAIN (JAZ) proteins through the interaction with bHLH-type transcription factors such as MYC2. Accumulation of JA-Ile, the bioactive hormone, promotes degradation of JAZ proteins unleashing JA-inducible responses. JA-Ile brings together the two parts of the receptor complex: the JAZ proteins and the F-box protein CORONATINE INSENSITIVE 1 (COI1). All JAZ proteins shared a conserved protein domain known as Jas required for both JAZ degradation and JAZ binding to the transcription factor MYC2. JAZ proteins undergo alternative splicing on the Jas domain generating isoforms with increased resistance to JA-induced degradation. Here, we show that JA-desensitization mechanism of plant tissues is partially mediated by Jas-domain truncated isoforms. We studied the JAZ10 gene because: 1) jaz10 mutant shows a JA-hypersensitive phenotype in root length inhibition assays, and 2) JAZ10.4 is the only splice variant lacking the whole Jas domain in Arabidopsis. We found that JAZ10 encodes for a cryptic MYC2 binding domain located in the N-terminal region. Complementation studies showed that the expression of JAZ10.4 under the control from the native JAZ10 promoter is sufficient to attenuate JA responses of the jaz10 mutant. In addition, inmunoblot analysis showed in vivo accumulation of the JA-resistant JAZ10.4 isoform in the presence of exogenous JA. Taken all together, these results support the existence of a negative feedback to dampen deleterious effects of over-activating JA responses in plant cells. The negative feedback mechanism dependent on the extent of JAZ-gene expression and alternative splicing provides an exceptional plasticity to the defense response limiting collateral impact on other plant responses.