Poster: Hormones

Abs # 645: The Arabidopsis nuclear pore complex modulates activity of the AXR1 dependent auxin response

Presenter:	Parry, Geraint J, gparry@indiana.edu
Authors	Parry, Geraint J (A)   Ward, Sally  (B)   Cernac, Alex  (C)   Estelle, Mark  (A)
Affiliations:	(A): Indiana University, Bloomington (B): University of York, UK (C): Michigan State University, East Lansing

The sar1 and sar3 mutants were isolated during a screen to identify suppressors of the auxin resistant mutant axr1 (Cernac et al, 1997). The AXR1 protein plays a crucial role in the control of SCF E3 ubiquitin ligase activity that facilitates the degradation of Aux/IAA proteins. Both the sar1axr1 and sar3axr1 double mutants exhibit a more wildtype response to a variety of auxin mediated developmental effects such as root elongation, lateral root formation and apical dominance. Neither sar1 or sar3 mutants have altered auxin responses but they exhibit a reduction in root elongation and an early bolting phenotype. sar1sar3 double mutant plants show severely retarded growth and are sterile. Molecular characterisation has revealed that both SAR1 and SAR3 are related to the mammalian nucleoporins NUP160 and NUP96 respectively. Work in mammalian cell lines has demonstrated that these proteins lie within the nuclear pore and interact in a protein complex (Vasu and Forbes, 2001). This first insight into the function of the Arabidopsis nuclear pore is indicative of a relationship between the nuclear pore and activity of the SCF complex. Ongoing work aims to decipher the precise mechanism by which SAR1 and SAR3 modulate RUB1 modification of Cullin, SCF function and the auxin response. Cernac et al (1997), Development 124, 1583. Vasu and Forbes (2001), Curr. Op. Cell Biol. 13, 363