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Abstract Detail


Hormone Biology

Santner, Aaron [1], Mooney, Sutton [2], Prigge, Michael [2], Estelle, Mark [2].

Auxin Signaling F-Box 4 (AFB4) is essential for hypocotyl elongation in Arabidopsis.

Auxin signaling involves ubiquitin-mediated degradation of the Aux/IAA proteins promoted by the SCFTIR1 E3. The Arabidopsis genome encodes 5 proteins that are closely related to TIR1 called AUXIN SIGNALING F-BOX (AFB) proteins. So far three of these, AFB1-AFB3 have been characterized and function similarly to TIR1. A phylogenetically distinct group of F-box proteins within this family is comprised of AFB4 (At4g24390) and AFB5 (At5g49980). To investigate the function of AFB4 in planta, a mutant line has been obtained in which the AFB4 protein-coding region is disrupted by T-DNA insertion. The afb4 mutants display a number of growth phenotypes that are more severe than any of the tir1, afb1, afb2, afb3, and afb5 mutant phenotypes. Mature afb4 plants are dwarf and have a proliferation of secondary inflorescences. Light-grown afb4 seedlings have small tightly curled cotyledons and true leaves that display polarity defects. Regardless of the light environment, afb4 hypocotyls are shorter than wild type and fail to elongate when challenged with exogenous auxins or GA3 at concentrations known to stimulate hypocotyl elongation. However, this apparent lack of response to exogenous auxin does not appear to result from reduced auxin response. Rather, afb4 seedlings are hypersensitive to auxin treatments suggesting that AFB4 may act antagonistically to the other auxin receptors. Indeed, double mutant analyses indicate that TIR1, AFB1, and AFB2 act antagonistically to AFB4 in controlling hypocotyl length.


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1 - Indiana University, Biology, 915 East Third Street, Bloomington, Indiana, 47405, USA
2 - Indiana University, Biology

Keywords:
auxin
F-box proteins
hypocotyl elongation.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P35031
Abstract ID:924


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