Present address: Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
Indole-3-glycerol phosphate, a branchpoint of indole-3-acetic acid biosynthesis from the tryptophan biosynthetic pathway in Arabidopsis thaliana
Article first published online: 25 DEC 2001
The Plant Journal
Volume 24, Issue 3, pages 327–334, November 2000
How to Cite
Ouyang, J., Shao, X. and Li, J. (2000), Indole-3-glycerol phosphate, a branchpoint of indole-3-acetic acid biosynthesis from the tryptophan biosynthetic pathway in Arabidopsis thaliana. The Plant Journal, 24: 327–334. doi: 10.1046/j.1365-313x.2000.00883.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 7 July 2000; accepted 15 August 2000.
- antisense RNA;
- IAA biosynthesis;
- indole-3-glycerol phosphate;
- Arabidopsis thaliana.
The phytohormone indole-3-acetic acid (IAA) plays a vital role in plant growth and development as a regulator of numerous biological processes. Its biosynthetic pathways have been studied for decades. Recent genetic and in vitro labeling evidence indicates that IAA in Arabidopsis thaliana and other plants is primarily synthesized from a precursor that is an intermediate in the tryptophan (Trp) biosynthetic pathway. To determine which intermediate(s) acts as the possible branchpoint for the Trp-independent IAA biosynthesis in plants, we took an in vivo approach by generating antisense indole-3-glycerol phosphate synthase (IGS) RNA transgenic plants and using available Arabidopsis Trp biosynthetic pathway mutants trp2-1 and trp3-1. Antisense transgenic plants display some auxin deficient-like phenotypes including small rosettes and reduced fertility. Protein gel blot analysis indicated that IGS expression was greatly reduced in the antisense lines. Quantitative analyses of IAA and Trp content in antisense IGS transgenic plants and Trp biosynthetic mutants revealed striking differences. Compared with wild-type plants, the Trp content in all the transgenic and mutant plants decreased significantly. However, total IAA levels were significantly decreased in antisense IGS transgenic plants, but remarkably increased in trp3-1 and trp2-1 plants. These results suggest that indole-3-glycerol phosphate (IGP) in the Arabidopsis Trp biosynthetic pathway serves as a branchpoint compound in the Trp-independent IAA de novo biosynthetic pathway.