Mediator: A key regulator of plant development

Abstract

Mediator is a multiprotein complex that regulates transcription at the level of RNA pol II assembly, as well as through regulation of chromatin architecture, RNA processing and recruitment of epigenetic marks. Though its modular structure is conserved in eukaryotes, its subunit composition has diverged during evolution and varies in response to environmental and tissue-specific inputs, suggesting different functions for each subunit and/or Mediator conformation. In animals, Mediator has been implicated in the control of differentiation and morphogenesis through modulation of numerous signaling pathways. In plants, studies have revealed roles for Mediator in regulation of cell division, cell fate and organogenesis, as well as developmental timing and hormone responses. We begin this review with an overview of biochemical mechanisms of yeast and animal Mediator that are likely to be conserved in all eukaryotes, as well as a brief discussion of the role of Mediator in animal development. We then present a comprehensive review of studies of the role of Mediator in plant development. Finally, we point to important questions for future research on the role of Mediator as a master coordinator of development.

Transcriptome Analysis of Four Arabidopsis thaliana Mediator Tail Mutants Reveals Overlapping and Unique Functions in Gene Regulation

“…As such, it is somewhat remarkable that, under favorable growth conditions, Arabidopsis is largely robust to perturbation of many Mediator complex subunits. Unlike mice, in which all MED knockouts tested have proved to be embryonic lethal, many of the single Arabidopsis MED mutants studied to date grow well enough in controlled environments that they are fertile (Yin and Wang 2014; Buendía-Monreal and Gillmor 2016). This makes Arabidopsis uniquely suited to studying the effects of disruption of the complex in a developing, multicellular eukaryote.…”

Regulation of flowering time by SPL10/MED25 module in Arabidopsis

“…Further studies showed that MED25 regulates flowering in cooperation with the photoperiod pathway (Iñigo et al ., ; Liu et al ., ). Other than med25 , several mediator subunit mutants also show a late‐flowering phenotype: med8 , med12 , med13 , med15 , med16 , med17 , med18 and med20a (Buendia‐Monreal & Gillmor, ). In addition, three mediator subunits are involved in age‐regulated flowering time; for instance, MED12 and MED13 repress the expression of miR156 , and MED18 interacts with SPL15 to initiate transcription of flowering‐related genes (Gillmor et al ., ; Hyun et al ., ).…”

Developmental role of the tomato Mediator complex subunit MED18 in pollen ontogeny

“…Depending on the species, MEDIATOR is a large multimeric protein comprising 25–34 subunits (Allen and Taatjes, ; Samanta and Thakur, ), which are organized in four modules: head, middle, tail and CDK/Cycline (Chadick and Asturias, ; Conaway et al ., ). Each subunit seems to be a specific regulator for defined gene sets related to different functions involved in gene transcription mediated by RNA Polymerase II, including transcription, initiation and elongation, as well as RNA processing, chromatin spatial conformation and enhancer–promoter interaction (Buendía‐Monreal and Gillmor, ).…”