The Arabidopsis thaliana Med25 mediator subunit integrates environmental cues to control plant development

Abstract

Development in plants is controlled by abiotic environmental cues such as day length, light quality, temperature, drought, and salinity. These signals are sensed by a variety of systems and transmitted by different signal transduction pathways. Ultimately, these pathways are integrated to control expression of specific target genes, which encode proteins that regulate development and differentiation. The molecular mechanisms for such integration have remained elusive. We here show that a linear 130-aminoacids-long sequence in the Med25 subunit of the Arabidopsis thaliana Mediator is a common target for the drought response element binding protein 2A, zinc finger homeodomain 1, and Myb-like transcription factors which are involved in different stress response pathways. In addition, our results show that Med25 together with drought response element binding protein 2A also function in repression of PhyB-mediated light signaling and thus integrate signals from different regulatory pathways.

The Arabidopsis Mediator subunit MED16 regulates iron homeostasis by associating with EIN3/EIL1 through subunit MED25

“…B€ ackstr€ om et al (2007) proposed that Mediator recruits and works with species-specific transcription factors through either newly evolved subunits or subunits with one conserved Mediator-interacting domain and one species-specific regulator-interacting domain. This proposal is supported by recent research that the ACID domain of MED25 interacts with many transcription factors in Arabidopsis (Elfving et al, 2011;Ou et al, 2011;Zhu et al, 2011;C ßevik et al, 2012) and our results that MED25 interacts with YID1/MED16 through its conserved N-terminal vWF-A domain. We noticed, however, that neither YID1/MED16 nor MED25 was induced by iron deficiency ( Figure S6), which raised the question of how the Mediator complex was assembled under iron-deficient conditions.…”

“…That MED25 interacts with YID1/MED16 in vivo suggests that MED25 is probably a tail subunit. The interaction of MED25 with different transcription factors regulates multiple physiological processes (Elfving et al, 2011;Ou et al, 2011;Chen et al, 2012), because tail subunits usually interact with transcription factors through conformational changes (Casamassimi and Napoli, 2007;Toth-Petroczy et al, 2008;Meyer and Fu, 2012). The N-terminal vWF-A domain of MED25 was conserved among metazoans, Arabidopsis and other plant species.…”

Arabidopsis GROWTH-REGULATING FACTOR7 Functions as a Transcriptional Repressor of Abscisic Acid– and Osmotic Stress–Responsive Genes, Including DREB2A

“…Subsequent research on DREB2A-INTERACTING PROTEIN1 and DRIP2 revealed their roles in the rapid degradation of DREB2A through 26S proteasome-dependent proteolysis under nonstress conditions (Qin et al, 2008). Recently, reports on Arabidopsis MEDIATOR25, a newly described DREB2A-interacting cofactor protein, suggested another method of regulation of DREB2A activation (Elfving et al, 2011;Blumberg et al, 2012).…”

Covalent and Non-Covalent Associations Mediate MED28 Homo- Oligomerization

“…Since then, genomic analyses allowed identifying genes coding for subunits of Mediator complex in other plant species such as rice [11]. In plants, individual mediator subunits have been implicated in development and stress responses [12][13][14][15]. Attention has recently been given to a possible redox regulation of the Mediator complex.…”

“…The link between Mediator and redox regulation has been primarily proposed from reports on the involvement of Mediator complex subunits in plant immunity and root hair differentiation [16,17]. MED25, the most studied Mediator subunit, plays important roles in flowering time and light signaling [12,18], organ growth [19], jasmonic acid and (JA) and abscisic acid (ABA) signaling [19,20], abiotic stress [13], and root hair development [16]. In these processes, reactive oxygen species (ROS) have an important role and therefore MED25 might be regulated by or relay the changes in redox homeostasis [16].…”