PIF4/HEMERA-mediated daytime thermosensory growth requires the Mediator subunit MED14

ABSTRACT: Warm ambient temperatures do not trigger stress responses in plants but stimulate the growth of specific organs. The basic helix-loop-helix transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) plays a central role in regulating thermomorphogenetic hypocotyl elongation in various plant species, including the model dicotyledonous plant Arabidopsis thaliana. Although it is well known that PIF4 promotes plant thermosensory growth by activating key genes involved in the biosynthesis and signaling of the phytohormone auxin, the detailed molecular mechanism of such transcriptional activation is still not clear. Our previous studies demonstrated that HEMERA (HMR), a transcription co-activator of PIF4, promotes the thermo-induced expression of PIF4 target genes through the nine-amino-acid transactivation domain (9aaTAD) in its carboxy-terminus. In this report, we investigate the role of the Mediator complex in the PIF4/HMR-mediated thermoresponsive gene expression. Through the characterization of various mutants of the Mediator complex, a tail subunit named MED14 is identified as an essential factor for thermomorphogenetic hypocotyl growth. MED14 is required for the thermal induction of key PIF4 target genes but has a marginal effect on the levels of PIF4 and HMR. Further transcriptomic analyses confirm that the expression of numerous PIF4/HMR-dependent, auxin-related genes requires MED14 at a warm temperature. Moreover, PIF4 and HMR physically interact with MED14 and both are indispensable for the association of MED14 with the promoters of these thermoresponsive genes. Together, these results unveil an important thermomorphogenetic mechanism, in which PIF4 and its coactivator HMR recruit the Mediator complex to activate auxin-related growth-promoting genes when plants sense moderate increases in ambient temperature.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE196969 | GEO | 2022/09/26

REPOSITORIES: GEO