Extended Data Figure 9: A model for Mediator-dependent growth inhibition in Arabidopsis ref8 mutants.

Mutation or disruption of REF8 leads to direct alterations in the composition of the cell wall and other metabolic changes due to the loss of C3′H activity. Information on these changes is relayed to the nucleus by an at present unknown signalling pathway or sensor, resulting in massive changes in gene expression (represented by green and red transcripts in the model). Some of these transcriptional changes are directly dependent on MED5 (centre, illustrated as a direct MED5–transcription-factor interaction), whereas others are independent of MED5 (left) or are indirectly affected by MED5 (right), such as genes controlled by transcription factors that are themselves MED5-dependent targets. Ultimately, changes in the transcription of direct and/or indirect targets of MED5 result in inhibition of growth, sterility and indirect effects on cell wall architecture, all of which can be rescued by disruption of MED5.