1. A new role for the Arabidopsis AP2 transcription factor, LEAFY PETIOLE, in gibberellin-induced germination is revealed by the misexpression of a homologous gene, SOB2/DRN-LIKE.
- Author
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Ward JM, Smith AM, Shah PK, Galanti SE, Yi H, Demianski AJ, van der Graaff E, Keller B, and Neff MM
- Subjects
- Amino Acid Sequence, Arabidopsis anatomy & histology, Arabidopsis metabolism, Arabidopsis Proteins genetics, Darkness, Germination physiology, Light, Molecular Sequence Data, Mutation, Oligonucleotides, Antisense, Phenotype, Seedlings anatomy & histology, Seedlings physiology, Seeds physiology, Sequence Alignment, Signal Transduction physiology, Transcription Factors genetics, Arabidopsis genetics, Arabidopsis Proteins metabolism, Gene Expression Regulation, Plant, Germination drug effects, Gibberellins pharmacology, Plant Growth Regulators pharmacology, Transcription Factors metabolism
- Abstract
Gibberellic acid (GA) promotes germination, stem/hypocotyl elongation, and leaf expansion during seedling development. Using activation-tagging mutagenesis, we identified a mutation, sob2-D (for suppressor of phytochromeB-4 [phyB-4]#2 dominant), which suppresses the long-hypocotyl phenotype of a phyB missense allele, phyB-4. This mutant phenotype is caused by the overexpression of an APETALA2 transcription factor, SOB2, also called DRN-like. SOB2/DRN-like transcript is not detectable in wild-type seedling or adult tissues via RT-PCR analysis, suggesting that SOB2/DRN-like may not be involved in seedling development under normal conditions. Adult sob2-D phyB-4 plants have curled leaves and club-like siliques, resembling plants that overexpress a closely related gene, LEAFY PETIOLE (LEP). Hypocotyls of a LEP-null allele, lep-1, are shorter in the light and dark, suggesting LEP involvement in seedling development. This aberrant hypocotyl phenotype is due at least in part to a delay in germination. In addition, lep-1 is less responsive to GA and more sensitive to the GA biosynthesis inhibitor paclobutrazol, indicating that LEP is a positive regulator of GA-induced germination. RT-PCR shows that LEP transcript accumulates in wild-type seeds during imbibition and germination, and the transcript levels of REPRESSOR OF ga1-3-LIKE2 (RGL2), a negative regulator of GA signaling during germination, is unaffected in lep-1. These results suggest LEP is a positive regulator of GA-induced germination acting independently of RGL2. An alternative model places LEP downstream of RGL2 in the GA-signaling cascade.
- Published
- 2006
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