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Abstract Detail


Tropisms

Pedmale, Ullas [1], Liscum, Mannie [2].

Structure and functional analysis of NPH3 - a regulator of phototropism in Arabidopsis.

Genetic studies have identified a number of genes encoding proteins functioning in the signal-response system(s) mediating phototropism in Arabidopsis thaliana. One such gene NPH3 encodes a novel protein that is absolutely required for phototropic signaling and interacts with the dominant photoreceptor mediating phototropism, phot1. Yet, little is known about how phot1 mediates phototropic signaling through NPH3. We have taken a multi-faceted approach to understand the biochemical function(s) of NPH3. First, we demonstrate that NPH3 is a phosphorylated protein in the dark and is rapidly dephosphorylated upon blue-light (BL) irradiation. This light dependent posttranslational state is also dark-reversible. BL-dependent dephosphorylation of NPH3 and phototropic response of the hypocotyl are both abrogated by use of type1/2A protein phosphatase (PP1/PP2A)-specific inhibitors. Thus, it appears that dephosphorylation of NPH3 is necessary for progression of phot1-dependent phototropic signaling. Genetic evidence indicate that phot1 is necessary for dephosphorylation of NPH3. We hypothesize that photoactived phot1 regulates the activity of the phosphatase which in turn catalyzes the dephosphorylation reaction on NPH3. Given the prior association of NPH3 with Cullin 3, it is reasonable to predict that the phosphorylation state of NPH3 regulates the activity of an E3 ubiquitin ligase that contains NPH3 and CUL3. Second, employing modified yeast genetic screening called yeast-three-hybrid technique to identify potential signal transducers or modifiers of phototropic response. Third, we are attempting to produce sufficient quantities of highly purified NPH3 for crystallization and subsequent 3-D structure studies. In the end, the structure-function studies described here are aimed at the identification additional members of the phot1-NPH3 signaling complex and will provide important insights into the biochemical function(s) of NPH3.


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1 - University of Missouri-Columbia, Div. of Biological Sciences and Bond Life Sciences Center, 302 Life Sciences Center, Columbia, MO, 65211, USA
2 - University of Missouri-Columbia, Biological Sciences and Bond Life Sciences Center

Keywords:
NPH3
Phot1
phototropism
Phosphorylation
Signaling.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P32014
Abstract ID:2295


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