The F-box Protein KIB1 Mediates Brassinosteroid-Induced Inactivation and Degradation of GSK3-like Kinases in Arabidopsis

Jia-Ying Zhu, Yuyao Li, Dong-Mei Cao, Hongjuan Yang, Eunkyoo Oh, Yang Bi, Shengwei Zhu, Zhi-Yong Wang*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

101 Citations (Scopus)

Abstract

The glycogen synthase kinase-3 (GSK3) family kinases are central cellular regulators highly conserved in all eukaryotes. In Arabidopsis, the GSK3-like kinase BIN2 phosphorylates a range of proteins to control broad developmental processes, and BIN2 is degraded through unknown mechanism upon receptor kinase-mediated brassinosteroid (BR) signaling. Here we identify KIB1 as an F-box E3 ubiquitin ligase that promotes the degradation of BIN2 while blocking its substrate access. Loss-of-function mutations of KIB1 and its homologs abolished BR-induced BIN2 degradation and caused severe BR-insensitive phenotypes. KIB1 directly interacted with BIN2 in a BR-dependent manner and promoted BIN2 ubiquitination in vitro. Expression of an F-box-truncated KIB1 caused BIN2 accumulation but dephosphorylation of its substrate BZR1 and activation of BR responses because KIB1 blocked BIN2 binding to BZR1. Our study demonstrates that KIB1 plays an essential role in BR signaling by inhibiting BIN2 through dual mechanisms of blocking substrate access and promoting degradation.

Original languageEnglish
Pages (from-to)648-657
Number of pages10
JournalMolecular Cell
Volume66
Issue number5
Early online date1 Jun 2017
DOIs
Publication statusPublished - Jun 2017

Scopus Subject Areas

  • Molecular Biology
  • Cell Biology

User-Defined Keywords

  • brassinosteroid
  • E3 ubiquitin ligase
  • F-box protein
  • GSK3
  • BIN2
  • Arabidopsis
  • steroid hormone
  • proteasome
  • GSK3 degradation
  • ubiquitination

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