Poster: Hormone synthesis & metabolism

Abs # 463: Auxin amino acid conjugate hydrolases in Medicago truncatula

Presenter:	Campanella, James J, james.campanella@montclair.edu
Authors	Campanella, James J (A)   Wexler, Shiri  (A)   Ludwig-Müller, Jutta  (B)
Affiliations:	(A): Montclair State University, Dept. of Biology and Molecular Biology (B): Technische Universitaet Dresden, Institut fuer Botanik

Both vascular and non-vascular plants regulate auxin balance through interactions among de novo synthesis, degradation, efflux, influx, and conjugate synthesis/hydrolysis. An interspecific knowledge of the regulation and character of these pathways and their interactions is key to delineating auxin influences on plant growth and development. We are using molecular genetic approaches to isolate and characterize the regulation of auxin conjugate hydrolysis (especially Indole-3-acetic acid (IAA) amide conjugates) in Medicago truncatula (barrel clover). We have chosen to examine these pathways in Medicago because it is a major model legume system for host-symbiote interactions where there is evidence that mycorrhizal formation may be regulated by auxins. Because M. truncatula forms symbiotic root nodules, unlike Arabidopsis, this approach is particularly important in investigating genes specific to microbial colonization and nodule development in legumes. In the Medicago genome, we have distinguished seven putative, uncharacterized, IAA amidohydrolases that are most closely homologous to the IAR3 gene of the ILR1-like family in Arabidopsis thaliana. Five of those hydrolases appear to be full-length open reading frames capable of expressing a protein while two appear to be pseudogenes. We have been able to clone and isolate four of the full-length genes (MtIAR32, MtIAR33, MtIAR34 and MtIAR35) and are presently in the process of characterizing them. MtIAR32 has already been characterized for enzymatic activity and appears to use IAA-Alanine, IAA-Glycine and IAA-Phenylalanine as well as IBA-Alanine (indole-3-butyric acid) as substrates.We are still in the process of characterizing the other amidohydrolases for enzymatic activity.