Changes in gene expression driven by stress are fully characterized, however, the components that regulate H2O2-dependent gene expression remain largely enigmatic. The Mediator complex bridge specific transcription factors with the RNA Pol II machinery and converges different signals before channeling instructions to initiate gene transcription. Although well studied, a specific function of any of the Mediator subunits in regulating oxidative stress responses or H2O2-triggered gene expression was not yet known. Our work show that the Arabidopsis MED8 confers tolerance to stress. We demonstrate that MED8 mainly function as a repressor of H2O2-induced gene expression, negatively regulating pathways that are dependent on stress hormones such as salicylic acid and jasmonic acid. We believe that MED8 achieve its role by interacting with other components that are not necessarily required for transcription such as NOT2, a key regulator of microRNA biogenesis. Our next challenge is to comprehensively profile the Mediator interactome and to shed light on its redox regulation.
