Interaction map of Arabidopsis Mediator complex expounding its topology

Abstract

Understanding of mechanistic details of Mediator functioning in plants is impeded as the knowledge of subunit organization and structure is lacking. In this study, an interaction map of Arabidopsis Mediator complex was analyzed to understand the arrangement of the subunits in the core part of the complex. Combining this interaction map with homology-based modeling, probable structural topology of core part of the Arabidopsis Mediator complex was deduced. Though the overall topology of the complex was similar to that of yeast, several differences were observed. Many interactions discovered in this study are not yet reported in other systems. AtMed14 and AtMed17 emerged as the key component providing important scaffold for the whole complex. AtMed6 and AtMed10 were found to be important for linking head with middle and middle with tail, respectively. Some Mediator subunits were found to form homodimers and some were found to possess transactivation property. Subcellular localization suggested that many of the Mediator subunits might have functions beyond the process of transcription. Overall, this study reveals role of individual subunits in the organization of the core complex, which can be an important resource for understanding the molecular mechanism of functioning of Mediator complex and its subunits in plants.

The Important Function of Mediator Complex in Controlling the Developmental Transitions in Plants

“…The full-length of AtMED9, AtMED21 and AtMED25 possesses transactivation property, whereas parts of AtMED4 and AtMED10 display transactivation property [18]. In yeast, MED2, MED3 and MED15 can activate the reporter genes, while AtMED2 and AtMED3 have no transactivation ability in Arabidopsis [18]. Therefore, we speculate that the specialized function of the mediator complex in different eukaryotes might be caused by the differences in the interaction map of Mediator subunits.…”

“…Moreover, MED14 and MED26 in Arabidopsis are the part of the middle module ( Figure 1B). AtMED14 and AtMED17 are found as the master component of the whole Mediator complex [18]. AtMED6 links the head module with the middle module, and AtMED10 connects the middle with the tail [18].…”

“…AtMED14 and AtMED17 are found as the master component of the whole Mediator complex [18]. AtMED6 links the head module with the middle module, and AtMED10 connects the middle with the tail [18]. However, the yeast MED14 is the main linker to connects the head, middle and tail modules [11].…”

“…Moreover, AtMED6, AtMED17, AtMED10, AtMED19, AtMED15, and AtMED4 form homodimers as an initial step to control the Mediator function in the plant cell. The full-length of AtMED9, AtMED21 and AtMED25 possesses transactivation property, whereas parts of AtMED4 and AtMED10 display transactivation property [18]. In yeast, MED2, MED3 and MED15 can activate the reporter genes, while AtMED2 and AtMED3 have no transactivation ability in Arabidopsis [18].…”

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

“…Our results suggest that WRKYs are involved in this process, consistent with reported interactions with CDK8 61 and that overexpression of WRKYs results in increased cold tolerance 62 . AtMED9 was recently shown to interact with MED4, MED21 and MED31 in planta and to display transactivation activity in yeast 63 . Combined with our results identifying a connection between MED9 and WRKYs, these data provide the first descriptions of MED9 function in plants.…”