---
OA_type: closed access
_id: '21255'
abstract:
- lang: eng
  text: As an important plant hormone to regulate growth and development, auxin has
    been investigated for more than a century. It had been clearly demonstrated and
    well-accepted that the intracellular auxin receptors, TIR1/AFBs, are F-box proteins
    mediating transcriptional auxin signaling by their E3 ubiquitin ligase activity,
    which targets and sends for degradation the Aux/IAA transcriptional repressors.
    The recent discovery of adenylate cyclase (AC) and guanylate cyclase (GC) activities
    for TIR1/AFBs open entirely new perspectives on how auxin signaling can operate.
    This chapter traces back the history of how canonical transcriptional auxin signaling
    was established and introduces the discovery of the TIR1/AFBs-mediated nontranscriptional
    signaling branch. Finally, the current understanding and open questions of how
    TIR1/AFBs’ AC and GC activities contribute to the transcriptional and nontranscriptional
    auxin signaling are discussed, highlighting the possibility that cyclic adenosine
    monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) act as second messengers
    in auxin signal transduction.
alternative_title:
- Foundations and Frontiers in Enzymology
article_processing_charge: No
author:
- first_name: Linlin
  full_name: Qi, Linlin
  last_name: Qi
- first_name: Jiří
  full_name: Friml, Jiří
  id: 4159519E-F248-11E8-B48F-1D18A9856A87
  last_name: Friml
  orcid: 0000-0002-8302-7596
citation:
  ama: 'Qi L, Friml J. Nucleotidyl cyclase activities of TIR1/AFB auxin receptors:
    new insights into the mechanism of auxin signaling. In: Irving H, Gehring C, Wong
    A, eds. <i>Cryptic Enzymes and Moonlighting Proteins</i>. Elsevier; 2025:299-322.
    doi:<a href="https://doi.org/10.1016/b978-0-443-15719-6.00015-5">10.1016/b978-0-443-15719-6.00015-5</a>'
  apa: 'Qi, L., &#38; Friml, J. (2025). Nucleotidyl cyclase activities of TIR1/AFB
    auxin receptors: new insights into the mechanism of auxin signaling. In H. Irving,
    C. Gehring, &#38; A. Wong (Eds.), <i>Cryptic Enzymes and Moonlighting Proteins</i>
    (pp. 299–322). Elsevier. <a href="https://doi.org/10.1016/b978-0-443-15719-6.00015-5">https://doi.org/10.1016/b978-0-443-15719-6.00015-5</a>'
  chicago: 'Qi, Linlin, and Jiří Friml. “Nucleotidyl Cyclase Activities of TIR1/AFB
    Auxin Receptors: New Insights into the Mechanism of Auxin Signaling.” In <i>Cryptic
    Enzymes and Moonlighting Proteins</i>, edited by Helen Irving, Chris Gehring,
    and Aloysius Wong, 299–322. Elsevier, 2025. <a href="https://doi.org/10.1016/b978-0-443-15719-6.00015-5">https://doi.org/10.1016/b978-0-443-15719-6.00015-5</a>.'
  ieee: 'L. Qi and J. Friml, “Nucleotidyl cyclase activities of TIR1/AFB auxin receptors:
    new insights into the mechanism of auxin signaling,” in <i>Cryptic Enzymes and
    Moonlighting Proteins</i>, H. Irving, C. Gehring, and A. Wong, Eds. Elsevier,
    2025, pp. 299–322.'
  ista: 'Qi L, Friml J. 2025.Nucleotidyl cyclase activities of TIR1/AFB auxin receptors:
    new insights into the mechanism of auxin signaling. In: Cryptic Enzymes and Moonlighting
    Proteins. Foundations and Frontiers in Enzymology, , 299–322.'
  mla: 'Qi, Linlin, and Jiří Friml. “Nucleotidyl Cyclase Activities of TIR1/AFB Auxin
    Receptors: New Insights into the Mechanism of Auxin Signaling.” <i>Cryptic Enzymes
    and Moonlighting Proteins</i>, edited by Helen Irving et al., Elsevier, 2025,
    pp. 299–322, doi:<a href="https://doi.org/10.1016/b978-0-443-15719-6.00015-5">10.1016/b978-0-443-15719-6.00015-5</a>.'
  short: L. Qi, J. Friml, in:, H. Irving, C. Gehring, A. Wong (Eds.), Cryptic Enzymes
    and Moonlighting Proteins, Elsevier, 2025, pp. 299–322.
date_created: 2026-02-16T15:53:52Z
date_published: 2025-05-02T00:00:00Z
date_updated: 2026-02-17T13:28:38Z
day: '02'
department:
- _id: JiFr
doi: 10.1016/b978-0-443-15719-6.00015-5
editor:
- first_name: Helen
  full_name: Irving, Helen
  last_name: Irving
- first_name: Chris
  full_name: Gehring, Chris
  last_name: Gehring
- first_name: Aloysius
  full_name: Wong, Aloysius
  last_name: Wong
language:
- iso: eng
month: '05'
oa_version: None
page: 299-322
publication: Cryptic Enzymes and Moonlighting Proteins
publication_identifier:
  isbn:
  - '9780443157196'
publication_status: published
publisher: Elsevier
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Nucleotidyl cyclase activities of TIR1/AFB auxin receptors: new insights into
  the mechanism of auxin signaling'
type: book_chapter
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2025'
...