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postdoc position

Tai-ping Sun tps at acpub.duke.edu
Sat Jan 24 18:14:32 EST 2004

Postdoctoral Position in the Dept. of Biology, Duke University:
A postdoctoral position (funded by NSF) is available immediately to 
study "Regulation of Gibberellin Signaling in Arabidopsis."

Regulation of Gibberellin Signaling in Arabidopsis:

Bioactive gibberellins (GAs) are plant growth regulators, which 
control such diverse processes as germination, stem elongation, and 
flower and fruit development.  The RGA gene encodes a negative 
regulator of GA response in Arabidopsis.   Several structural 
features in the RGA protein suggest that it may be a transcriptional 
regulator.  In support of this, we showed that a green fluorescent 
protein (GFP)-RGA fusion protein is localized to the nucleus in 
transgenic Arabidopsis plants.  Confocal microscopy and immunoblot 
analyses demonstrated that GA activates its signaling pathway by 
causing the degradation of the RGA protein, and the DELLA motif near 
the N terminus of RGA is required for GA-induced degradation of this 
protein.  The ubiquitin-proteasome pathway is likely to play a role 
in RGA degradation. SLEEPY1 (SLY1), an activator of GA signaling, is 
an F-box protein.  RGA protein accumulates to a high level in the 
sly1 mutant, suggesting that RGA is a target of the SCFSLY1 complex 
(an ubiquitin E3 ligase).    Using biochemical and genetic 
approaches, we are currently investigating the mechanism by which GA 
regulates the stability of RGA.  We are also using microarray 
analysis to identify the downstream targets of RGA.

Related publications:

Silverstone et al. (2001) Repressing a repressor: gibberellin-induced 
rapid reduction of the RGA protein in Arabidopsis.  Plant Cell 13, 

Dill and Sun (2001) Synergistic derepression of gibberellin signaling 
by removing RGA and GAI function in Arabidopsis thaliana.  Genetics 
159, 777-785.

Dill et al. (2001) The DELLA motif is essential for 
gibberellin-induced degradation of RGA.  Proc. Natl. Acad. Sci. USA. 
98, 14162-14167.

Olszewski et al. (2002) Gibberellin signaling: Biosynthesis, 
catabolism and response pathways.  Plant Cell Supplement, S61-S80.

McGinnis et al. (2003) The Arabidopsis SLEEPY1 (SLY1) gene encodes a 
putative F-box subunit of an SCF E3 ubiquitin ligase. Plant Cell. 15, 

A background in protein chemistry, genetics, molecular biology or 
plant development is desirable.  If you are interested in applying, 
please send (by e-mail) a curriculum vitae and names, e-mail 
addresses, and phone numbers of three references to:

Tai-ping Sun
e-mail address: tps at duke.edu

Tai-ping Sun
Associate Professor
Department of Biology
LSRC B327, Box 91000
Duke University
Durham, NC 27708-1000

e-mail: tps at acpub.duke.edu
TEL: (919)-613-8166
FAX: (919)-613-8177

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