Abstract
Light and the phytohormone abscisic acid (ABA) regulate overlapping processes in plants, such as seed germination and seedling development. However, the molecular mechanism underlying the interaction between light and ABA signaling is largely unknown. Here, we show that FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED IMPAIRED RESPONSE1 (FAR1), two key positive transcription factors in the phytochrome A pathway, directly bind to the promoter of ABA-Insensitive5 and activate its expression in Arabidopsis (Arabidopsis thaliana). Disruption of FHY3 and/or FAR1 reduces the sensitivity to ABA-mediated inhibition of seed germination, seedling development, and primary root growth. The seed germination of the fhy3 mutant is also less sensitive to salt and osmotic stress than that of the wild type. Constitutive expression of ABA-Insensitive5 restores the seed germination response of fhy3. Furthermore, the expression of several ABA-responsive genes is decreased in the fhy3 and/or far1 mutants during seed imbibition. Consistently, FHY3 and FAR1 transcripts are up-regulated by ABA and abiotic stresses. Moreover, the fhy3 and far1 mutants have wider stomata, lose water faster, and are more sensitive to drought than the wild type. These findings demonstrate that FHY3 and FAR1 are positive regulators of ABA signaling and provide insight into the integration of light and ABA signaling, a process that may allow plants to better adapt to environmental stresses.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Abscisic Acid / metabolism*
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Abscisic Acid / pharmacology
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Adaptation, Physiological / drug effects
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Adaptation, Physiological / genetics
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Adaptation, Physiological / radiation effects
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Arabidopsis / drug effects
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Arabidopsis / genetics
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Arabidopsis / metabolism*
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Arabidopsis / radiation effects
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Basic-Leucine Zipper Transcription Factors / genetics
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Basic-Leucine Zipper Transcription Factors / metabolism
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Droughts
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Gene Expression Regulation, Plant / drug effects
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Gene Expression Regulation, Plant / radiation effects
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Gene Knockout Techniques
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Germination / drug effects
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Germination / genetics
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Light*
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Mutation / genetics
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Nuclear Proteins / metabolism*
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Osmotic Pressure / drug effects
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Osmotic Pressure / radiation effects
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Phenotype
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Phytochrome / metabolism*
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Plant Roots / drug effects
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Plant Roots / genetics
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Plant Roots / growth & development
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Plant Roots / radiation effects
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Plant Stomata / drug effects
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Plant Stomata / physiology
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Salinity
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Seeds / drug effects
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Seeds / growth & development
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Signal Transduction / radiation effects*
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Stress, Physiological / drug effects
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Stress, Physiological / genetics
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Stress, Physiological / radiation effects
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Transcription Factors / metabolism*
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Up-Regulation / drug effects
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Up-Regulation / genetics
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Up-Regulation / radiation effects
Substances
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ABI5 protein, Arabidopsis
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Arabidopsis Proteins
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Basic-Leucine Zipper Transcription Factors
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FAR1 protein, Arabidopsis
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FHY3 protein, Arabidopsis
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Nuclear Proteins
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Transcription Factors
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Phytochrome
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Abscisic Acid