DELLA Proteins Recruit the Mediator Complex Subunit MED15 to Co-activate Transcription in Land Plants

Data for the manuscript

Jorge Hernández-García*1,2, Antonio Serrano-Mislata1, María Lozano-Quiles1, Cristina Úrbez1, María A Nohales1, Noel Blanco-Touriñán1, Huadong Peng3,4, Rodrigo Ledesma-Amaro3,4, Miguel A Blázquez*1.

1Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-Universitat Politècnica de València, Valencia, Spain
2Laboratory of Biochemistry, Wageningen University, Stippeneng 4, 6703 WE Wageningen, The Netherlands
3Imperial College Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.
4Department of Bioengineering, Imperial College London, London SW7 2AZ, UK.
*Corresponding authors: Jorge Hernández-García, Miguel A Blázquez.
Email: [e-mail], [e-mail]

Abstract

DELLA proteins are negative regulators of the gibberellin response pathway in angiosperms, acting as central hubs that interact with hundreds of transcription factors and regulators to modulate their activities. While the mechanism of transcription factor sequestration by DELLAs to prevent DNA binding to downstream targets has been extensively documented, the mechanism that allows them to act as co-activators remains to be understood. Here, we demonstrate that DELLAs directly recruit the Mediator complex to specific loci in Arabidopsis, facilitating transcription. This recruitment involves DELLA amino-terminal domain and the conserved MED15 KIX domain. Accordingly, partial loss of MED15 function mainly disrupted processes known to rely on DELLA co-activation capacity; including cytokinin-dependent regulation of meristem function and skotomorphogenic response, gibberellin metabolism feedback, and flavonol production. We have also found that the single DELLA protein in the liverwort Marchantia polymorpha is capable of recruiting MpMED15 subunits, contributing to transcriptional co-activation. The conservation of Mediator-dependent transcriptional co-activation by DELLA between Arabidopsis and Marchantia implies that this mechanism is intrinsic to the emergence of DELLA in the last common ancestor of land plants.