Abstract
Formation and degradation of IAA-amino acid conjugates (IAA-aa) play an important role in IAA homeostasis. GH3, an early auxin inducible gene, was reported recently to encode the proteins that catalyzed the adenylation of IAA. We found that GH3 catalyzed the formation of IAA-aa from IAA and amino acids in the presence of ATP, indicating that GH3 was IAA-aa synthetase. Hence the inhibition of GH3 would be a key to understand the mechanism of IAA homeostasis. However, due to the presence of multiple synthetic pathways catalyzed by several GH3s, a genetic approach such as a gene knockout would encounter difficulty. We therefore synthesized a specific inhibitor of IAA-aa synthetase on the basis of its proposed catalytic mechanism. This chemical approach is expected to inhibit all the GH3s involved in IAA-aa synthesis, and the inhibitor is expected to serve as a highly effective tool to study IAA homeostasis.
