Unwinding JAZ7 – enigma to harmony

JASMONATE ZIM-DOMAIN (JAZ) proteins are primary transcriptional repressors in the jasmonate (JA) signal-ing pathway that regulate a broad range of JA-dependent responses. A mechanistic mode of action is well established , but what are the biological roles of individual JAZs, and how do they contribute to the specification of JA signaling outputs? Two recent articles in Journal of Experimental Botany reveal roles of JAZ7 in regulating dark-induced senescence and susceptibility to fungal pathogens. Jasmonates (JAs) regulate a broad range of processes, from growth and development to biotic and abiotic stress responses. JASMONATE ZIM-DOMAIN (JAZ) proteins are key regulators in controlling JA signaling outputs. Since the discovery of JAZs in 2007, over 100 research articles have been published on the characterization of JAZ functions, genomic or transcriptomic analyses of JAZs, or the identification of downstream transcription factors in the JA signaling pathway through yeast two-hybrid screens using JAZs as bait (reviewed in Pauwels and Goossens, 2011; Shyu and Brutnell, 2015). Biochemical and molecular functions of JAZ proteins have been extensively studied, but surprisingly little is known about the biological role of JAZs and how they contribute to specific JA signaling outputs. JAZs were identified in 2007 as the missing link between the F-box protein CORONATINE INSENSITIVE 1 (COI1) and the transcription factor MYC2, which mediates JA responses proteins function as transcriptional repressors that repress gene expression by bridging co-repressors NOVEL INTERACTOR OF JAZ (NINJA)/TOPLESS and transcription factors to repress JA-responsive gene expression. Upon accumulation of bioactive JA, JAZs form a co-receptor complex with COI1 to perceive JA. This interaction leads to ubiquitination and degradation of JAZ proteins, resulting in activation of JAZ-interacting transcription factors and JA-responsive gene expression (reviewed in Pauwels and Goossens, 2011). Among the 13 JAZ proteins in Arabidopsis, JAZ7 is one of the more enigmatic members of the family. Unlike most JAZs, JAZ7 does not form homo or heterodimers with other JAZ members , and interacts with very few transcription factors, namely Lines are drawn based on phenotypes reported in loss-of-function, overexpres-sion, or dominant-negative lines of the JAZ proteins indicated. JAZX represents JAZs other than those specified; dashed lines indicate speculative interactions. permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.