Specific functions for Mediator complex subunits from different modules in the transcriptional response of Arabidopsis thaliana to abiotic stress

Tim Crawford,Nóra Lehotai,Jeanette Blomberg,Fazeelat Karamat,Matilda Rentoft,Stefan Björklund,Åsa Strand

doi:10.1038/s41598-020-61758-w

Abstract

Adverse environmental conditions are detrimental to plant growth and development. Acclimation to abiotic stress conditions involves activation of signaling pathways which often results in changes in gene expression via networks of transcription factors (TFs). Mediator is a highly conserved co-regulator complex and an essential component of the transcriptional machinery in eukaryotes. Some Mediator subunits have been implicated in stress-responsive signaling pathways; however, much remains unknown regarding the role of plant Mediator in abiotic stress responses. Here, we use RNA-seq to analyze the transcriptional response of Arabidopsis thaliana to heat, cold and salt stress conditions. We identify a set of common abiotic stress regulons and describe the sequential and combinatorial nature of TFs involved in their transcriptional regulation. Furthermore, we identify stress-specific roles for the Mediator subunits MED9, MED16, MED18 and CDK8, and putative TFs connecting them to different stress signaling pathways. Our data also indicate different modes of action for subunits or modules of Mediator at the same gene loci, including a co-repressor function for MED16 prior to stress. These results illuminate a poorly understood but important player in the transcriptional response of plants to abiotic stress and identify target genes and mechanisms as a prelude to further biochemical characterization.

Highlights

Adverse environmental conditions are detrimental to plant growth and development
Previous reports indicated flowering-time phenotypes in med[16], med[18] and cdk[837–39], so we grew our plants in soil or a hydroponic system to mature rosette stage under non-inductive short-day conditions in order to avoid effects caused by differences in flowering time between different lines
We observed no major differences in development, the mutants generally appeared smaller: cdk[8] and especially med[18] displayed reduced rosette diameter and biomass, while med[9], med[18] and especially med[16] accumulated less total chlorophyll than Col-0 (Supplemental Fig. S2A–D)

Summary

Introduction

Adverse environmental conditions are detrimental to plant growth and development. Acclimation to abiotic stress conditions involves activation of signaling pathways which often results in changes in gene expression via networks of transcription factors (TFs). Our data indicate different modes of action for subunits or modules of Mediator at the same gene loci, including a co-repressor function for MED16 prior to stress These results illuminate a poorly understood but important player in the transcriptional response of plants to abiotic stress and identify target genes and mechanisms as a prelude to further biochemical characterization. Plants have evolved complex signaling transduction pathways to perceive and respond to environmental changes These are initiated from multiple sites within the cell and terminate in the nucleus, influencing gene expression via networks of transcription factors (TFs), allowing plants to regulate their energy expenditure and growth as they mount an adaptive response to the stress[2,3]. There are four plant-specific subunits (MED34-MED37) which have so far not been assigned to any module, MED36 was recently confirmed as a middle module subunit[22]

Methods

Results

Conclusion