The Arabidopsis dwarf mutant shi exhibits reduced gibberellin responses conferred by overexpression of a new putative zinc finger protein.
shi (for short internodes), a semidominant dwarfing mutation of Arabidopsis caused by a transposon insertion, confers a phenotype typical of mutants defective in the biosynthesis of gibberellin (GA). However, the application of GA does not correct the dwarf phenotype of shi plants, suggesting that shi is defective in the perception of or in the response to GA. In agreement with this observation, the level of active GAs was elevated in shi plants, which is the result expected when feedback control of GA biosynthesis is reduced. Cloning of the SHI gene revealed that in shi, the transposon is inserted into the untranslated leader so that a cauliflower mosaic virus 35S promoter in the transposon reads out toward the SHI open reading frame. This result, together with mRNA analysis, suggests that the phenotype of the shi mutant is a result of overexpression of the SHI open reading frame. The predicted amino acid sequence of SHI has acidic and glutamine-rich stretches and shows sequence similarity over a putative zinc finger region to three presumptive Arabidopsis proteins. This suggests that SHI may act as a negative regulator of GA responses through transcriptional control.
Fridborg
I
I
Department of Physiological Botany, Uppsala University, Villavägen 6, S-752 36 Uppsala, Sweden.
Kuusk
S
S
Moritz
T
T
Sundberg
E
E
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D017796:Caulimovirus / Q000235:genetics; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D005246:Feedback; D005875:Gibberellins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D016335:Zinc Fingers
D029681:Arabidopsis Proteins; D004251:DNA Transposable Elements; D005875:Gibberellins; D012333:RNA, Messenger; D014157:Transcription Factors; C120562:short internodes protein, Arabidopsis