Journal
GENETICS
Volume 180, Issue 1, Pages 237-251Publisher
GENETICS SOCIETY AMERICA
DOI: 10.1534/genetics.108.090399
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Funding
- University of Missouri at St. Louis
- University Of Missouri Research Board
- National Science Foundation (NSF) [IBN-0315596, MCB-0745122]
- Robert A. Welch Foundation [CA 309]
- Rice-Houston Alliance [NSF HRD-0450363]
- National Institutes of Health (NIH) [F31-GM081911, F31-GM066373]
- American Society of Plant Biologists
- Houston Livestock Show and Rodeo Fellowship
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [F31GM066373, F31GM081911] Funding Source: NIH RePORTER
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Genetic evidence suggests that indole-3-butyric acid (IBA) is converted to the active auxin indole-3-acetic acid (IAA) by removal of two side-chain methlene units in a process similar to fatty acid beta-oxidation. Previous studies implicate peroxisomes as the site of IBA metabolism, although the enzymes that act in this process are still being identifed. Here, we describe two IBA-response mutants, ibr1 and ibr10. Like the previously described ibr3 mutant, which disrupts a putative peroxisomal acyl-CoA oxidase/dehydrogenase, ibr1 and ibr10 display normal IAA reponses and defective IBA reponses. These defects include reduced root elongation inhibition, decreased lateral root initiation, and reduced IBA-responsive gene expression. Howerer, peroxisomal energy-generating patways necessary during early seediing development are unaffected in the mutants. Positional cloning of the genes reponsible for the mutant defects reveals that IBR1 encodes a member of the short-chain dehydrogenase/reductase family and that IBR10 resembles enoly-CoA hydratases/isomerases. Both enzymes contain C-terminal peroxisomal-targeting signals, consisent with IBA metabolism occuring in peroxisomes. We present a model in which IBR3, IBR10, and IBR1 may act sequentially in peroxisomal IBA beta-oxidation to IAA.
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