Abstract
Under unfavorable environmental conditions, the stress phytohormone ABA inhibits the developmental transition from an embryo in a dry seed into a young seedling. We developed a genetic screen to isolate Arabidopsis thaliana mutants whose early seedling development is resistant to ABA. Here, we report the identification of a recessive mutation in AUXIN RESISTANT1 (AUX1), encoding a cellular auxin influx carrier. Although auxin is a major morphogenesis hormone in plants, little is known about ABA-auxin interactions during early seedling growth. We show that aux1 and pin2 mutants are insensitive to ABA-dependent repression of embryonic axis (hypocotyl and radicle) elongation. Genetic and physiological experiments show that this involves auxin transport to the embryonic axis elongation zone, where ABA enhances the activity of an auxin-responsive promoter. We propose that ABA represses embryonic axis elongation by potentiating auxin signaling in its elongation zone. This involves repression of the AUXIN INDUCIBLE (Aux/IAA) gene AXR2/IAA7, encoding a key component of ABA- and auxin-dependent responses during postgerminative growth.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Abscisic Acid / pharmacology*
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Arabidopsis / drug effects*
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Arabidopsis / embryology
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Arabidopsis / genetics
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Arabidopsis / metabolism*
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism
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Arabidopsis Proteins / physiology
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Blotting, Northern
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Blotting, Western
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Chromatography, High Pressure Liquid
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Gene Expression Regulation, Plant / drug effects
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Gene Expression Regulation, Plant / genetics
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Gene Expression Regulation, Plant / physiology
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Germination / drug effects
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Germination / genetics
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Germination / physiology*
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Indoleacetic Acids / metabolism*
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Microscopy, Fluorescence
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Plant Growth Regulators / metabolism*
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Plants, Genetically Modified / drug effects
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Plants, Genetically Modified / embryology
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Plants, Genetically Modified / genetics
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Plants, Genetically Modified / metabolism
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Seedlings / drug effects
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Seedlings / embryology
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Seedlings / genetics
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Seedlings / metabolism
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Seeds / drug effects
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Seeds / embryology
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Seeds / genetics
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Seeds / metabolism
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Signal Transduction / physiology
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Spectrometry, Mass, Electrospray Ionization
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Tandem Mass Spectrometry
Substances
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Arabidopsis Proteins
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Indoleacetic Acids
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Plant Growth Regulators
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Abscisic Acid