Mediator subunit 17 regulates light and darkness responses in Arabidopsis plants

Abstract

Mediator 17 (MED17) is part of the head of the Mediator complex, which regulates transcription initiation indifferent eukaryotic organisms, including plants. We have previously characterized MED17 roles in Arabidopsisplants exposed to UV-B radiation, revealing its involvement in various aspects of the DNA damage response afterexposure. med17 mutant plants showed altered HY5 expression, which encodes a transcription factor with acentral role in photomorphogenesis. Our results demonstrate that med17 mutants show altered photomorphogenicresponses and also to darkness, when compared to WT plants, and these differences could be due to alteredexpression of genes encoding key regulators of light and darkness signaling pathways, such as HY5, COP1 andPIF3. Moreover, med17 mutants exhibit transcriptome changes similar to those previously reported in plantsexposed to red and blue light, as well as those previously described for photoreceptor mutants. Interestingly,med17 and hy5 mutants show a similar set of differentially expressed genes compared to WT plants, whichsuggests that both proteins may participate in a common light and dark-induced signaling pathways. Together,our data provides evidence that MED17 is an important regulator of the light and darkness responses inArabidopsis.