A single JAZ repressor controls the jasmonate pathway in Marchantia polymorpha (Molecular Plant) ($)

Previously, Monte et al. showed that the liverwort Marchantia polymorpha perceives the jasmonate pathway precursor dn-OPDA instead of the well known JA-Ile phytohormone of vascular plants. Now, Monte and colleagues focus on the MpJAZ, downstream of the signal transduction pathway. MpJAZ is the sole ortholog in Marchantia to the 13 JAZ genes of Arabidopsis. In this paper, the authors studied the conservation of each relevant feature for JAZ genes in Marchantia. They found that while subcellular localization, protein-protein interactions, degradation by COI, and gene induction in response to wounding and OPDA are similar to vascular plants, but alternative splicing mechanism presents significant differences. The authors also showed that the knockout mutant mpjaz-1 presents a severe developmental abnormality, consistent with observations in Arabidopsis JAZ multiple mutants, and transcriptional changes demonstrating that the regulation of defense and secondary metabolism is conserved and dependent on COI1. This paper highlights the versatility of this model system to overcome genetic redundancy and provide new insights on transcription factor functional evolution. MpJAZ could resemble the “ancestral” state features of JAZ regulation and domain architecture, helping to understand how the entire family diversified and acquired new regulatory elements during evolution of vascular plants. (Summary by Facundo Romani) 10.1016/j.molp.2018.12.017