Biochemical and genetic studies of a number of higher plants have shown that the normal pathway for the production of indole-3-acetic acid (IAA) in seedlings is directly from indole by a tryptophan-independent pathway. In contrast, a tryptophan dependent pathway for IAA biosynthesis has been shown to be operative in the first hours after a wounding stress. These studies demonstrated that wounding alters in a transient way the route of IAA biosynthesis. It is unknown which tryptophan-dependent pathway is activated by wounding or if the IAA produced following wounding has a discrete role that differentiates it form the IAA produced under normal growth conditions.
Thus, the objectives of this project are:
- Determine the effect of wounding on tryptophan-independent and different tryptophan-dependent pathways using stable isotope rapid kinetic labeling methods, gene expression analysis and enzyme protein quantification methods.
- Determine if stresses other than wounding alter the pathways used for IAA biosynthesis in normal and mutant plants.
- Determine, by specific labeling patterns, if the IAA that enters the polar transport system has a specific metabolic origin that differentiates it from the bulk of the IAA in the tissue under normal, wounding, and stress conditions.