Conjugation of Indole-3-Acetic Acid to Proteins and Peptides

Indole-3-acetic acid is found in plants in both free and conjugated form. One of the less well-studied forms of conjugated IAA are a unique class of proteins where IAA is a prosthetic group attached directly to the protein structure. An increasing body of evidence suggests that regulation of protein stability is important to auxin function, thus making these modified proteins of particular interest. The first gene for a protein covalently modified by IAA was recently cloned from bean and found to be related to proteins present in several other plant species, including the model plant Arabadopsis. Four lines of study will further characterize these proteins in plants.

1) Experiments will define, on the molecular level, the expression, regulation and function of the bean 35 kDa protein.

2) Previous studies which focused on bean will be extended, starting with cloning the respective genes, to related proteins from species more amenable to genetic manipulation, such as Arabadopsis and Medicago.

3) IAA-protein gene expression will be analyzed at the tissue and subcellular level using reporter genes and immunological techniques.

4) The attachment of IAA to the proteins will be analyzed using complex liquid chromatography mass spectrometry methods that will allow rapid identification of this class of modified proteins.

These studies should provide the biochemical, tissue and molecular information necessary to further understand the possible roles of this unique class of modified proteins in relation to phytohormone regulation.