Present address: Centre for Bioenergy and Climate Change, Plant and Invertebrate Ecology Department, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK.
Degradation of the auxin response factor ARF1
Article first published online: 15 DEC 2007
© 2008 The Authors
The Plant Journal
Volume 54, Issue 1, pages 118–128, April 2008
How to Cite
Salmon, J., Ramos, J. and Callis, J. (2008), Degradation of the auxin response factor ARF1. The Plant Journal, 54: 118–128. doi: 10.1111/j.1365-313X.2007.03396.x
- Issue published online: 15 DEC 2007
- Article first published online: 15 DEC 2007
- Received 3 October 2007; revised 5 December 2007; accepted 10 December 2007.
Auxin-mediated gene expression is largely controlled through a family of DNA-binding proteins known as auxin response factors (ARF). Previous studies on the role of proteolytic regulation in auxin signaling have focused on degradation of their interacting partner, the Aux/IAA proteins. Aux/IAA family members with domain II sequences are rapidly degraded, show auxin-enhanced degradation rates, and interact with the related F-box proteins TIR1 and AFB1-3, which indicates that they are ubiquitylated by a CUL1-dependent E3 ligase. To date, limited data have been generated regarding degradation of ARFs. Here, we focus on the degradation rate of one ARF family member, Arabidopsis thaliana ARF1, and find that the half-lives of N-terminally HA-tagged ARF1 and C-terminally luciferase-tagged ARF1 are both approximately 3–4 h. This half-life appears to be conferred by a component of the middle region (MR), and degradation of the luciferase fusion with the MR is more rapid when the fusion includes an additional nuclear localization signal. ARF1 degradation is proteasome-dependent and rates are not altered in a CUL1 mutant background, suggesting that this ARF is targeted for proteasomal degradation via an alternative set of machinery to that used for Aux/IAA degradation. Consistent with this, exogenous indole acetic acid does not affect the degradation of ARF1. Given increasing evidence that the relative ratio of Aux/IAAs to ARFs rather than the absolute quantity within the cell appears to be the mode through which auxin signaling is modulated, this half-life is likely to be biologically relevant.