ABA induction of miR159 controls transcript levels of two MYB factors during Arabidopsis seed germination

• Published in: The Plant journal : for cell and molecular biology 2007-02, Vol.49 (4), p.592-606
• Main Authors: Reyes, José L, Chua, Nam-Hai
• Format: Article
• Language: English
• Subjects: ABA signaling; ABI3; Abscisic Acid - pharmacology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Base Sequence; Biological and medical sciences; Blotting, Northern; Botany; Cloning, Molecular; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Dose-Response Relationship, Drug; Drought; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Developmental - drug effects; Gene Expression Regulation, Plant - drug effects; Germination - drug effects; Germination - genetics; Germination and dormancy; microRNA; MicroRNAs - genetics; MicroRNAs - metabolism; miR159; Models, Biological; Models, Molecular; Molecular and cellular biology; Molecular genetics; Mutation; MYB factors; Plant Growth Regulators - pharmacology; Plant physiology and development; Plant reproduction; Plants, Genetically Modified - genetics; Seeds - drug effects; Seeds - genetics; Seeds - metabolism; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription. Transcription factor. Splicing. Rna processing
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2006.02980.x

Upon seed imbibition, abscisic acid (ABA) levels decrease to allow embryos to germinate and develop into seedlings. However, under abiotic stress conditions, ABA levels remain high, and growth and development are arrested. Several transcription factors, including abscisic acid-insensitive (ABI)3 and ABI5, are known to control this developmental checkpoint. Here, we show that, in germinating Arabidopsis thaliana seeds, ABA induces the accumulation of microRNA 159 (miR159) in an ABI3-dependent fashion, and miRNA159 mediates cleavage of MYB101 and MYB33 transcripts in vitro and in vivo. The two MYB transcription factors function as positive regulators of ABA responses, as null mutants of myb33 and myb101 show hyposensitivity to the hormone. Consistent with this, miR159 over-expression suppresses MYB33 and MYB101 transcript levels and renders plants hyposensitive to ABA, whereas transgenic plants over-expressing cleavage-resistant forms of MYB33 and MYB101 are hypersensitive, as are plants over-expressing the Turnip mosaic virus (TuMV) P1/HC-Pro viral protein that is known to inhibit miRNA function. Our results suggest that ABA-induced accumulation of miR159 is a homeostatic mechanism to direct MYB33 and MYB101 transcript degradation to desensitize hormone signaling during seedling stress responses.