title: Loss-of-function mutations of the rice GAMYB gene impair alpha-amylase expression in aleurone and flower development.
abstract: GAMYB was first isolated as a positive transcriptional regulator of gibberellin (GA)-dependent alpha-amylase expression in barley aleurone cells, and its molecular and biochemical properties have been well characterized. However, the role of GAMYB elsewhere in the plant is not well understood. To investigate the molecular function of GAMYB outside of the aleurone cells, we isolated loss-of-function mutants from a panel of rice mutants produced by the insertion of a retrotransposon, Tos17. Through PCR screening using primers for rice GAMYB (OsGAMYB) and Tos17, we isolated three independent mutant alleles that contained Tos17 inserted in the exon region. No alpha-amylase expression in the endosperm was induced in these mutants in response to GA treatment, indicating that the Tos17 insertion had knocked out OsGAMYB function. We found no significant defects in the growth and development of the mutants at the vegetative stage. After the phase transition to the reproductive stage, however, shortened internodes and defects in floral organ development, especially a defect in pollen development, were observed. On the other hand, no difference was detected in flowering time. High-level OsGAMYB expression was detected in the aleurone cells, inflorescence shoot apical region, stamen primordia, and tapetum cells of the anther, but only low-level expression occurred in organs at the vegetative stage or in the elongating stem. These results demonstrate that, in addition to its role in the induction of alpha-amylase in aleurone, OsGAMYB also is important for floral organ development and essential for pollen development.
authors.affiliation: BioScience Center, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kaneko
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Inukai
authors.forename: Miyako
authors.initials: M
authors.lastname: Ueguchi-Tanaka
authors.forename: Hironori
authors.initials: H
authors.lastname: Itoh
authors.forename: Takeshi
authors.initials: T
authors.lastname: Izawa
authors.forename: Yuhko
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Tsukaho
authors.initials: T
authors.lastname: Hattori
authors.forename: Akio
authors.initials: A
authors.lastname: Miyao
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Hirochika
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Ashikari
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D004251:DNA Transposable Elements / Q000235:genetics / Q000502:physiology; D004790:Enzyme Induction; D035264:Flowers / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005875:Gibberellins / Q000494:pharmacology; D016254:Mutagenesis, Insertional / Q000379:methods; D009154:Mutation; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D000516:alpha-Amylases / Q000235:genetics* / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D005875:Gibberellins; C106119:OsGAmyb protein, Oryza sativa; D010940:Plant Proteins; D014157:Transcription Factors; D000516:alpha-Amylases