Poster: Hormones

Abs # 572: IAA amidohydrolase homologs differ in expression and enzyme activity

Presenter:	Campanella, James J., campanellj@mail.montclair.edu
Authors	Campanella, James J. (A)   Ludwig-Mueller, Jutta  (B)   Bakllamaja, Vinela  (A)   Cartier, Ania  (A)   Sharma, Will  (A)
Affiliations:	(A): Montclair State University, Montclair, NJ 07043 (B): Institut fuer Botanik, Technische Universitaet Dresden, Dresden, Germany

We have isolated and characterized a homolog (sILR1) of the Arabidopsis thaliana IAA amidohydrolase ILR1 from Arabidopsis suecica. This study examines the enzymatic characterization of sILR1, as well as spatial and temporal expression of ILR1 and sILR1. The sILR1 protein can utilize IAA-Alanine and IAA-Glycine as substrates, respectively, 7-fold and 2-fold more effectively than ILR1. Additionally, sILR1 can not cleave IAA-Phenylalanine or IAA-Leucine as substrates, as ILR1 can. ILR1 and sILR1 share a pH optima of 8.0 in Tris buffer. Based on the calculated Km, sILR1 has a higher affinity for IAA-Alanine than ILR1. The sILR1 transcript is first detectable at day 4 after germination and rises to a steady state level up to day 15. In A. thaliana, expression of ILR1 begins with a burst at day 1 and decreases over 15 days to a low, but steady state level. A study of tissue expression shows that both sILR1 and ILR1 are highly expressed in roots, although ILR1 appears more highly expressed in hypocotyls, flowers, and basal leaves.