title: CHOTTO1, a putative double APETALA2 repeat transcription factor, is involved in abscisic acid-mediated repression of gibberellin biosynthesis during seed germination in Arabidopsis.
abstract: The phytohormones abscisic acid (ABA) and gibberellins (GAs) are the primary signals that regulate seed dormancy and germination. In this study, we investigated the role of a double APETALA2 repeat transcription factor, CHOTTO1 (CHO1), in seed dormancy, germination, and phytohormone metabolism of Arabidopsis (Arabidopsis thaliana). Wild-type seeds were dormant when freshly harvested seeds were sown, and these seeds were released from dormancy after a particular period of dry storage (after-ripening). The cho1 mutant seeds germinated easily even in a shorter period of storage than wild-type seeds. The cho1 mutants showed reduced responsiveness to ABA, whereas transgenic plants constitutively expressing CHO1 (p35SCHO1) showed an opposite phenotype. Notably, after-ripening reduced the ABA responsiveness of the wild type, cho1 mutants, and p35SCHO1 lines. Hormone profiling demonstrated that after-ripening treatment decreased the levels of ABA and salicylic acid and increased GA(4), jasmonic acid, and isopentenyl adenine when wild-type seeds were imbibed. Expression analysis showed that the transcript levels of genes for ABA and GA metabolism were altered in the wild type by after-ripening. Hormone profiling and expression analyses indicate that cho1 seeds, with a short period of storage, resembled fully after-ripened wild-type seeds. Genetic analysis showed that the cho1 mutation partially restored delayed seed germination and reduced GA biosynthesis activity in the ABA-overaccumulating cyp707a2-1 mutant background but did not restore seed germination in the GA-deficient ga1-3 mutant background. These results indicate that CHO1 acts downstream of ABA to repress GA biosynthesis during seed germination.
authors: RIKEN Plant Science Center, Yokohama, Kanagawa 230-0045, Japan.
authors: Ryoichi
authors: R
authors: Yano
authors: Yuri
authors: Y
authors: Kanno
authors: Yusuke
authors: Y
authors: Jikumaru
authors: Kazumi
authors: K
authors: Nakabayashi
authors: Yuji
authors: Y
authors: Kamiya
authors: Eiji
authors: E
authors: Nambara
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D024202:Electrophoretic Mobility Shift Assay; D018506:Gene Expression Regulation, Plant; D018525:Germination; D005875:Gibberellins / Q000096:biosynthesis*; D005966:Glucuronidase / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry*; D010937:Plant Growth Regulators / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D012639:Seeds / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C099055:AINTEGUMENTA protein, Arabidopsis; C499534:APETALA2 protein, Arabidopsis; D029681:Arabidopsis Proteins; C545451:CHO1 protein, Arabidopsis; D005875:Gibberellins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D014157:Transcription Factors; D000040:Abscisic Acid; D005966:Glucuronidase