Gibberellin Modulates Anther Development in Rice via the Transcriptional Regulation of GAMYB

• Published in: The Plant cell Vol. 21; no. 5; pp. 1453 - 1472
• Main Authors: Aya, Koichiro, Ueguchi-Tanaka, Miyako, Kondo, Maki, Hamada, Kazuki, Yano, Kentaro, Nishimura, Mikio, Matsuoka, Makoto
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01.05.2009
• Subjects: 3-Oxoacyl-(Acyl-Carrier-Protein) Reductase; Alcohol Oxidoreductases - genetics; Alcohol Oxidoreductases - metabolism; Anthers; Binding Sites; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Developmental biology; Flowers - growth & development; Flowers - metabolism; Gene Expression Profiling; Gene expression regulation; Gene Expression Regulation, Plant - drug effects; Genes; Gibberellins; Gibberellins - pharmacology; Gibberellins - physiology; Microspores; Mutagenesis, Site-Directed; Mutants; Mutation; Oligonucleotide Array Sequence Analysis; Oryza - drug effects; Oryza - genetics; Oryza - growth & development; Oryza - metabolism; Phenotype; Plant cells; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Proteins - physiology; Plants; Pollen; Promoter Regions, Genetic; Protein Interaction Mapping; Rice; Signal Transduction; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription Factors - physiology; Transcription, Genetic
• DOI: 10.1105/tpc.108.062935
• ISSN: 1040-4651

Gibberellins (GAs) play important roles in regulating reproductive development, especially anther development. Our previous studies revealed that the MYB transcriptional factor GAMYB, an important component of GA signaling in cereal aleurone cells, is also important for anther development. Here, we examined the physiological functions of GA during anther development through phenotypic analyses of rice (Oryza sativa) GA-deficient, GA-insensitive, and gamyb mutants. The mutants exhibited common defects in programmed cell death (PCD) of tapetal cells and formation of exine and Ubisch bodies. Microarray analysis using anther RNAs of these mutants revealed that rice GAMYB is involved in almost all instances of GA-regulated gene expression in anthers. Among the GA-regulated genes, we focused on two lipid metabolic genes, a cytochrome P450 hydroxylase CYP703A3 and β-ketoacyl reductase, both of which might be involved in providing a substrate for exine and Ubisch body. GAMYB specifically interacted with GAMYB binding motifs in the promoter regions in vitro, and mutation of these motifs in promoter-β-glucuronidase (GUS) transformants caused reduced GUS expression in anthers. Furthermore, a knockout mutant for CYP703A3 showed gamyb-like defects in exine and Ubisch body formation. Together, these results suggest that GA regulates exine formation and the PCD of tapetal cells and that direct activation of CYP703A3 by GAMYB is key to exine formation.