MEDIATOR SUBUNIT17 integrates jasmonate and auxin signaling pathways to regulate thermomorphogenesis

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Authors	AGRAWAL Rekha SHARMA Mohan DWIVEDI Nidhi MAJI Sourobh THAKUR Pallabi JUNAID Alim FAJKUS Jiří LAXMI Ashverya THAKUR Jitendra K.
Year of publication	2022
Type	Article in Periodical
Magazine / Source	Plant Physiology
MU Faculty or unit	Central European Institute of Technology
Citation
Web	https://academic.oup.com/plphys/article/189/4/2259/6585885
Doi	http://dx.doi.org/10.1093/plphys/kiac220
Keywords	TRANSCRIPTIONAL REGULATION; HISTONE MODIFICATIONS; PLANT MEDIATOR; SALICYLIC-ACID; ARABIDOPSIS; COMPLEX; PHYTOCHROME; BHLH; MYC2; EXPRESSION
Description	Plant adjustment to environmental changes involves complex crosstalk between extrinsic and intrinsic cues. In the past two decades, extensive research has elucidated the key roles of PHYTOCHROME-INTERACTING FACTOR4 (PIF4) and the phytohormone auxin in thermomorphogenesis. In this study, we identified a previously unexplored role of jasmonate (JA) signaling components, the Mediator complex, and their integration with auxin signaling during thermomorphogenesis in Arabidopsis (Arabidopsis thaliana). Warm temperature induces expression of JA signaling genes including MYC2, but, surprisingly, this transcriptional activation is not JA dependent. Warm temperature also promotes accumulation of the JA signaling receptor CORONATINE INSENSITIVE1 (COI1) and degradation of the JA signaling repressor JASMONATE-ZIM-DOMAIN PROTEIN9, which probably leads to de-repression of MYC2, enabling it to contribute to the expression of MEDIATOR SUBUNIT17 (MED17). In response to warm temperature, MED17 occupies the promoters of thermosensory genes including PIF4, YUCCA8 (YUC8), INDOLE-3-ACETIC ACID INDUCIBLE19 (IAA19), and IAA29. Moreover, MED17 facilitates enrichment of H3K4me3 on the promoters of PIF4, YUC8, IAA19, and IAA29 genes. Interestingly, both occupancy of MED17 and enrichment of H3K4me3 on these thermomorphogenesis-related promoters are dependent on PIF4 (or PIFs). Altered accumulation of COI1 under warm temperature in the med17 mutant suggests the possibility of a feedback mechanism. Overall, this study reveals the role of the Mediator complex as an integrator of JA and auxin signaling pathways during thermomorphogenesis.
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