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Plant Cell. 1999 Mar;11(3):365-76.

IAR3 encodes an auxin conjugate hydrolase from Arabidopsis.

Author information

  • 1Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA.

Abstract

Amide-linked conjugates of indole-3-acetic acid (IAA) are putative storage or inactivation forms of the growth hormone auxin. Here, we describe the Arabidopsis iar3 mutant that displays reduced sensitivity to IAA-Ala. IAR3 is a member of a family of Arabidopsis genes related to the previously isolated ILR1 gene, which encodes an IAA-amino acid hydrolase selective for IAA-Leu and IAA-Phe. IAR3 and the very similar ILL5 gene are closely linked on chromosome 1 and comprise a subfamily of the six Arabidopsis IAA-conjugate hydrolases. The purified IAR3 enzyme hydrolyzes IAA-Ala in vitro. iar 3 ilr1 double mutants are more resistant than either single mutant to IAA-amino acid conjugates, and plants overexpressing IAR3 or ILR1 are more sensitive than is the wild type to certain IAA-amino acid conjugates, reflecting the overlapping substrate specificities of the corresponding enzymes. The IAR3 gene is expressed most strongly in roots, stems, and flowers, suggesting roles for IAA-conjugate hydrolysis in those tissues.

PMID:
10072397
[PubMed - indexed for MEDLINE]
PMCID:
PMC144182
Free PMC Article
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