Conserved function of mediator in regulating nuclear hormone receptor activation between plants and animals

Perception of the plant hormone jasmonoyl-isoleucine (JA-Ile) involves the formation of a co-receptor complex between COI1, the F-box subunit of a SCF-type E3 ubiquitin ligase, and its substrates, a group of jasmonate ZIM-domain (JAZ) transcriptional repressors. In recent studies, we show that MED25, a subunit of the Arabidopsis Mediator, physically and functionally interacts with COI1 and the master transcription factor MYC2 on MYC2 target promoters. Here we provide evidence that MED25 also physically interacts with a subset of JAZ proteins. Therefore, in term of their interaction with Mediator, the JA-Ile co-receptor complex SCF(COI1)-JAZs together with the master transcription factor MYC2 resembles the nuclear hormone receptor system of metazoans. In addition, we show that the plant MED25 and its animal counterpart also cooperates with similar epigenetic regulators in distinct signaling pathways. Our study reveals a scenario that plants and animals have evolved distinct, yet largely similar, mechanism for nuclear hormone receptor activation at the level of transcriptional regulation.