Poster: Hormone synthesis & metabolism

Abs # 467: Expression and functional analyses of a novel auxin amidohydrolase from wheat

Presenter:	Campanella, James J., james.campanella@montclair.edu
Authors	Campanella, James J. (A)   Ludwig-Müller, Jutta  (B)   Magnus, Volker  (C)   Olajide, Adebanke F. (A)
Affiliations:	(A): Montclair State University, Dept. of Biology and Molecular Biology (B): Technische Universitaet Dresden, Institut fuer Botanik (C): Rudjer Boskovic Institute, Zagreb, Croatia

We have started to investigate how the ILR1-like indole acetic acid amidohydrolase family of genes has functionally evolved and diverged in the monocotyledonous species wheat (Triticum aestivum). We have isolated and cloned from wheat an ortholog for the Arabidopsis IAR3 auxin amidohydrolase which was called TaIAR3. TaIAR3 has no substrate specificity for any indole acetic acid (IAA) conjugates tested, unlike its ortholog IAR3. Instead, TaIAR3 has low specificity for the ester conjugates IAA-glucose and IAA-inositol and high specificity for the conjugates of indole-3-butyric acid (IBA-Alanine and IBA-Glycine) and indole-3-propionic-acid (IPA-Alanine). TaIAR3 has no substrate specificity for the methyl esters of the two IBA conjugates. IBA and IBA-Alanine were detected in wheat tissues where the conjugate may serve as a natural substrate for this enzyme. Endogenous IPA and IPA conjugates were not detected in seedlings. Additionally, crude protein extracts of wheat seedlings possess auxin amidohydrolase activity. Temporal expression studies of TaIAR3 indicate that the transcript is initially expressed at day 1 after germination. Expression down-regulates through days 2, 5, 10, 15 and 20. Spatial expression studies found similar levels of expression throughout the wheat tissues examined.