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Proc Natl Acad Sci U S A. 2017 Feb 14;114(7):1720-1725. doi: 10.1073/pnas.1616938114. Epub 2017 Jan 30.

Structural insights into alternative splicing-mediated desensitization of jasmonate signaling.

Zhang F1,2,3,4,5, Ke J3,4, Zhang L2,6, Chen R2, Sugimoto K2, Howe GA2,7,8, Xu HE3,9, Zhou M10, He SY11,6,8,12, Melcher K13.

Author information

1
College of Plant Protection, Nanjing Agricultural University, 210095, Nanjing, Jiangsu Province, China.
2
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824.
3
Laboratory of Structural Sciences, Van Andel Research Institute, Grand Rapids, MI 49503.
4
Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, MI 49503.
5
State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.
6
Department of Plant Biology, Michigan State University, East Lansing, MI 48824.
7
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824.
8
Plant Resilience Institute, Michigan State University, East Lansing, MI 48824.
9
Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
10
College of Plant Protection, Nanjing Agricultural University, 210095, Nanjing, Jiangsu Province, China; mgzhou@njau.edu.cn hes@msu.edu karsten.melcher@vai.org.
11
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824; mgzhou@njau.edu.cn hes@msu.edu karsten.melcher@vai.org.
12
Howard Hughes Medical Institute, Michigan State University, East Lansing, MI 48824.
13
Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, MI 49503; mgzhou@njau.edu.cn hes@msu.edu karsten.melcher@vai.org.

Abstract

Jasmonate ZIM-domain (JAZ) transcriptional repressors play a key role in regulating jasmonate (JA) signaling in plants. Below a threshold concentration of jasmonoyl isoleucine (JA-Ile), the active form of JA, the C-terminal Jas motif of JAZ proteins binds MYC transcription factors to repress JA signaling. With increasing JA-Ile concentration, the Jas motif binds to JA-Ile and the COI1 subunit of the SCFCOI1 E3 ligase, which mediates ubiquitination and proteasomal degradation of JAZ repressors, resulting in derepression of MYC transcription factors. JA signaling subsequently becomes desensitized, in part by feedback induction of JAZ splice variants that lack the C-terminal Jas motif but include an N-terminal cryptic MYC-interaction domain (CMID). The CMID sequence is dissimilar to the Jas motif and is incapable of recruiting SCFCOI1, allowing CMID-containing JAZ splice variants to accumulate in the presence of JA and to re-repress MYC transcription factors as an integral part of reestablishing signal homeostasis. The mechanism by which the CMID represses MYC transcription factors remains elusive. Here we describe the crystal structure of the MYC3-CMIDJAZ10 complex. In contrast to the Jas motif, which forms a single continuous helix when bound to MYC3, the CMID adopts a loop-helix-loop-helix architecture with modular interactions with both the Jas-binding groove and the backside of the Jas-interaction domain of MYC3. This clamp-like interaction allows the CMID to bind MYC3 tightly and block access of MED25 (a subunit of the Mediator coactivator complex) to the MYC3 transcriptional activation domain, shedding light on the enigmatic mechanism by which JAZ splice variants desensitize JA signaling.

KEYWORDS:

plant defense; plant hormone; plant insect; plant pathogen; signaling

PMID:
28137867
PMCID:
PMC5320967
DOI:
10.1073/pnas.1616938114
[Indexed for MEDLINE]
Free PMC Article

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