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Degradation of Aux/IAA proteins is essential for normal auxin signalling

Worley, C.K., Zenser, N., Ramos, J., Rouse, D., Leyser, O., Theologis, A. and Callis, J. (2000) Degradation of Aux/IAA proteins is essential for normal auxin signalling. The Plant Journal, 21 (6). pp. 553-562. ISSN 0960-7412

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Abstract

The growth substance auxin mediates many cellular processes, including division, elongation and differentiation. PSIAA6 is a member of the Aux/IAA family of short-lived putative transcriptional regulators that share four conserved domains and whose mRNAs are rapidly induced in the presence of auxin. Here PSIAA6 was shown to serve as a dominant transferable degradation signal when present as a translational fusion with firefly luciferase (LUC), with an in vivo half-life of 13.5 min in transgenic Arabidopsis seedlings. In a transient assay system in tobacco protoplasts using steady-state differences as an indirect measure of protein half-life, LUC fusions with full-length PSIAA6 and IAA1, an Aux/IAA protein from Arabidopsis, resulted in protein accumulations that were 3.5 and 1.0%, respectively, of that with LUC alone. An N-terminal region spanning conserved domain II of PSIAA6 containing amino acids 18–73 was shown to contain the necessary cis-acting element to confer low protein accumulation onto LUC, while a fusion protein with PSIAA6 amino acids 71–179 had only a slight effect. Single amino acid substitutions of PSIAA6 in conserved domain II, equivalent to those found in two alleles of axr3, a gene that encodes Aux/IAA protein IAA17, resulted in a greater than 50-fold increase in protein accumulation. Thus, the same mutations resulting in an altered auxin response phenotype increase Aux/IAA protein accumulation, providing a direct link between these two processes. In support of this model, transgenic plants engineered to over-express IAA17 have an axr3-like phenotype. Together, these data suggest that rapid degradation of Aux/IAA proteins is necessary for a normal auxin response.

Item Type: Article
Copyright, Publisher and Additional Information: Open access copy available from the journal web site.
Institution: The University of York
Academic Units: The University of York > Biology (York)
Depositing User: Open Access From Journal
Date Deposited: 22 Dec 2008 14:45
Last Modified: 22 Dec 2008 14:45
Published Version: http://dx.doi.org/10.1046/j.1365-313x.2000.00703.x
Status: Published
Publisher: Wiley-Blackwell
Refereed: Yes
Identification Number: 10.1046/j.1365-313x.2000.00703.x
URI: http://eprints.whiterose.ac.uk/id/eprint/5112

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