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.

由转录阻遏物介导的抑制机制通常存在于多种植物激素信号传导途径中。在拟南芥中JASMONATE-ZIM DOMAIN（JAZ）蛋白是转录阻遏物，可作为多种JA反应的负调节剂。JAZ的新型相互作用子（NINJA）是将JAZ与共抑制子TOPLESS（TPL）连接的衔接蛋白，可在JA依赖的根生长抑制和防御途径中介导基因抑制。然而，是否需要在其他JA反应生物过程中使用NINJA或其他衔接蛋白。在本研究中，我们证明了以前未表征的蛋白质ECAP（包含EAR基序的衔接子蛋白质）直接与JAZ6和JAZ8相互作用，并增强了它们的转录抑制活性。我们提供的证据表明ECAP是转录共抑制子TOPLESS-RELATED 2（TPR2）的JAZ6 / 8募集的新型衔接子蛋白，进入转录阻遏物复合物，该复合物可抑制WD重复/ bHLH / MYB复合物，这是JA依赖的花色苷生物合成途径中的重要转录激活因子。我们的发现以及以前的报道表明，特定的衔接子蛋白通过将不同的JAZ（具有重叠但也具有特定功能）与一般的共抑制子，TPL和TPR配对在不同的JA反应中发挥关键作用。