Arabidopsis ECAP Is a New Adaptor Protein that Connects JAZ Repressors with the TPR2 Co-repressor to Suppress Jasmonate-Responsive Anthocyanin Accumulation

Suppression mechanisms mediated by transcriptional repressors commonly exist in diverse phytohormone signaling pathways.In Arabidopsis thaliana,JASMONATE-ZIM DOMAIN(JAZ)proteins are transcriptional repressors that function as negative regulators of diverse JA responses.Novel Interactor of JAZ(NINJA)is an adaptor protein connecting JAZs with the co-repressor,TOPLESS(TPL),to mediate gene repression in JA-dependent root growth inhibition and defense pathways.However,whether NINJA or other adaptor proteins are employed in other JA-responsive biological processes remains to be elucidated.In the present study,we demonstrate that a previously uncharacterized protein,ECAP(EAR motif-Containing Adaptor Protein),directly interacts with JAZ6 and JAZ8 and enhances their transcriptional repression activities.We provide evidence that ECAP is a novel adaptor protein for JAZ6/8 recruitment of the transcriptional co-repressor,TOPLESS-RELATED 2(TPR2),into a transcriptional repressor complex that represses the WD-repeat/bHLH/MYB complex,an important transcriptional activator in the JA-dependent anthocyanin biosynthesis pathway.Our findings,together with previous reports,reveal that specific adaptor proteins play a critical role in distinct JA responses by pairing different JAZs(which possess overlapping but also specific functions)with the general co-repressors,TPL and TPRs.