A gain-of-function mutation in IAA16 confers reduced responses to auxin and abscisic acid and impedes plant growth and fertility
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Auxin regulates many aspects of plant development, in part, through degradation of the Aux/IAA family of transcriptional repressors. Consequently, stabilizing mutations in several Aux/IAA proteins confer reduced auxin responsiveness. However, of the 29 apparent Aux/IAA proteins in Arabidopsis thaliana, fewer than half have roles established through mutant analysis. We identified iaa16-1, a dominant gain-of-function mutation in IAA16 (At3g04730), in a novel screen for reduced root responsiveness to abscisic acid. The iaa16-1 mutation also confers dramatically reduced auxin responses in a variety of assays, markedly restricts growth of adult plants, and abolishes fertility when homozygous. We compared iaa16-1 phenotypes with those of dominant mutants defective in the closely related IAA7/AXR2, IAA14/SLR, and IAA17/AXR3, along with the more distantly related IAA28, and found overlapping but distinct patterns of developmental defects. The identification and characterization of iaa16-1 provides a fuller understanding of the IAA7/IAA14/IAA16/IAA17 clade of Aux/IAA proteins and the diverse roles of these repressors in hormone response and plant development.
KeywordsAuxin signaling Abscisic acid Aux/IAA gain of function IAA16
We thank Luise Rogg for introgressing the iaa28-1 mutation into the Col-0 accession, Mark Estelle for axr2-1 and axr3-1, Hidehiro Fukaki for slr-1, and Lauren Gunther, David Korasick, and Julie Thole for critical comments on the manuscript. This research was supported by the National Institutes of Health (R00 GM089987-03 to L.C.S.), the National Science Foundation (MCB-0745122 to BB), and the Robert A. Welch Foundation (C-1309 to BB).
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