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Plant J. 2019 Nov 21. doi: 10.1111/tpj.14618. [Epub ahead of print]

The JA-pathway MYC transcription factors regulate photomorphogenic responses by targeting HY5 gene expression.

Author information

1
Department of Plant Molecular Genetics, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049, Madrid, Spain.
2
Genomics Unit, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049, Madrid, Spain.
3
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, 92037.
4
Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, CA, 92037.
5
Centre for AgriBioscience, Department of Animal, Plant and Soil Science, School of Life Science, La Trobe University, Bundoora, VIC, 3086, Australia.

Abstract

Jasmonates are key regulators of the balance between defense and growth in plants. However, the molecular mechanisms by which activation of defense reduces growth are not yet fully understood. Here, we analyze the role of MYC transcription factors (TFs) and jasmonic acid (JA) in photomorphogenic growth. We found that multiple myc mutants share light-associated phenotypes with mutants of the phytochrome B photoreceptor, such as delayed seed germination in the dark and long hypocotyl growth. Over-expression of MYC2 in a phyB background partially suppressed its long hypocotyl phenotype. Transcriptomic analysis of multiple myc mutants confirmed that MYCs are required for full expression of red (R) light regulated genes, including the master regulator HY5. ChIP-Seq analyses revealed that MYC2 and MYC3 bind directly to the promoter of HY5 and that HY5 gene expression and protein levels are compromised in multiple myc mutants. Altogether, our results pinpoint MYCs as photomorphogenic TFs that control phytochrome responses by activating HY5 expression. This has important implications in understanding the trade-off between growth and defense since the same TFs that activate defense responses are photomorphogenic growth regulators.

KEYWORDS:

Arabidopsis; HY5; Jasmonate; Light signalling; MYC; defense; trade-off

PMID:
31755159
DOI:
10.1111/tpj.14618

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