NLRs derepress MED10b- and MED7-mediated repression of jasmonate-dependent transcription to activate immunity

Abstract

Plant intracellular nucleotide-binding domain, leucine-rich repeat-containing receptors (NLRs) activate a robust immune response upon detection of pathogen effectors. How NLRs induce downstream immune defense genes remains poorly understood. The Mediator complex plays a central role in transducing signals from gene-specific transcription factors to the transcription machinery for gene transcription/activation. In this study, we demonstrate that MED10b and MED7 of the Mediator complex mediate jasmonate-dependent transcription repression, and coiled-coil NLRs (CNLs) in <i>Solanaceae</i> modulate MED10b/MED7 to activate immunity. Using the tomato CNL <i>Sw-5b</i>, which confers resistance to <i>tospovirus</i>, as a model, we found that the CC domain of Sw-5b directly interacts with MED10b. Knockout/down of <i>MED10b</i> and other subunits including <i>MED7</i> of the middle module of Mediator activates plant defense against <i>tospovirus</i>. MED10b was found to directly interact with MED7, and MED7 directly interacts with JAZ proteins, which function as transcriptional repressors of jasmonic acid (JA) signaling. MED10b-MED7-JAZ together can strongly repress the expression of JA-responsive genes. The activated Sw-5b CC interferes with the interaction between MED10b and MED7, leading to the activation of JA-dependent defense signaling against <i>tospovirus</i>. Furthermore, we found that CC domains of various other CNLs including helper NLR NRCs from <i>Solanaceae</i> modulate MED10b/MED7 to activate defense against different pathogens. Together, our findings reveal that MED10b/MED7 serve as a previously unknown repressor of jasmonate-dependent transcription repression and are modulated by diverse CNLs in <i>Solanaceae</i> to activate the JA-specific defense pathways.