The AFB4 auxin receptor is a negative regulator of auxin signaling in seedlings

Katie Greenham, Aaron Santner, Cristina Castillejo, Sutton Mooney, Ilkka Sairanen, Karin Ljung, Mark Estelle

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


The plant hormone auxin is perceived by a family of F box proteins called the TIR1/auxin-signaling F box proteins (AFBs). Phylogenetic studies reveal that these proteins fall into four clades in flowering plants called TIR1, AFB2, AFB4, and AFB6 [1]. Genetic studies indicate that members of the TIR1 and AFB2 groups act as positive regulators of auxin signaling [1, 2]. In this report, we demonstrate a unique role for the AFB4 clade. Both AFB4 and AFB5 function as auxin receptors based on in vitro assays. However, unlike other members of the family, loss of AFB4 results in a range of growth defects that are consistent with auxin hypersensitivity, including increased hypocotyl and petiole elongation and increased numbers of lateral roots. Indeed, qRT-PCR experiments show that afb4-2 is hypersensitive to indole-3-acetic acid (IAA) in the hypocotyl, indicating that AFB4 is a negative regulator of auxin response. Furthermore, we show that AFB4 has a particularly important role in the response of seedlings to elevated temperature. Finally, we provide evidence that the AFB4 clade is the major target of the picloram family of auxinic herbicides. These results reveal a previously unknown aspect of auxin receptor function.

Original languageEnglish (US)
Pages (from-to)520-525
Number of pages6
JournalCurrent Biology
Issue number6
StatePublished - Mar 22 2011
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by grants to M.E. from the US Department of Energy (De-FG02-02ER15312) and National Institutes of Health (GM43644) and to K.L. from the Swedish Governmental Agency for Innovation Systems (VINNOVA) and the Swedish Research Council (VR).


Dive into the research topics of 'The AFB4 auxin receptor is a negative regulator of auxin signaling in seedlings'. Together they form a unique fingerprint.

Cite this