The gibberellin signaling pathway is regulated by the appearance and disappearance of SLENDER RICE1 in nuclei.
The slender rice1 mutant (slr1) shows a constitutive gibberellin (GA) response phenotype. To investigate the mode of action of SLR1, we generated transgenic rice expressing a fusion protein consisting of SLR1 and green fluorescent protein (SLR1-GFP) and analyzed the phenotype of the transformants and the subcellular localization of GFP in vivo. SLR1-GFP worked in nuclei to repress the GA signaling pathway; its overproduction caused a dwarf phenotype. Application of GA(3) to SLR1-GFP overproducers induced GA actions such as shoot elongation, downregulation of GA 20-oxidase expression, and upregulation of SLR1 expression linked with the disappearance of the nuclear SLR1-GFP protein. We also performed domain analyses of SLR1 using transgenic plants overproducing different kinds of truncated SLR1 proteins. The analyses revealed that the SLR1 protein can be divided into four parts: a GA signal perception domain located at the N terminus, a regulatory domain for its repression activity, a dimer formation domain essential for signal perception and repression activity, and a repression domain at the C terminus. We conclude that GA signal transduction is regulated by the appearance or disappearance of the nuclear SLR1 protein, which is controlled by the upstream GA signal.
Itoh
Hironori
H
BioScience Center, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Ueguchi-Tanaka
Miyako
M
Sato
Yutaka
Y
Ashikari
Motoyuki
M
Matsuoka
Makoto
M
D029681:Arabidopsis Proteins; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005875:Gibberellins / Q000494:pharmacology*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D019913:Nuclear Localization Signals / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D010641:Phenotype; D010937:Plant Growth Regulators / Q000494:pharmacology*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018514:Plant Structures / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C076705:SLR1 protein, Brassica; D049452:Green Fluorescent Proteins