title: The rice GERMINATION DEFECTIVE 1, encoding a B3 domain transcriptional repressor, regulates seed germination and seedling development by integrating GA and carbohydrate metabolism.
abstract: It has been shown that seed development is regulated by a network of transcription factors in Arabidopsis including LEC1 (LEAFY COTYLEDON1), L1L (LEC1-like) and the B3 domain factors LEC2, FUS3 (FUSCA3) and ABI3 (ABA-INSENSITIVE3); however, molecular and genetic regulation of seed development in cereals is poorly understood. To understand seed development and seed germination in cereals, a large-scale screen was performed using our T-DNA mutant population, and a mutant germination-defective1 (gd1) was identified. In addition to the severe germination defect, the gd1 mutant also shows a dwarf phenotype and abnormal flower development. Molecular and biochemical analyses revealed that GD1 encodes a B3 domain-containing transcription factor with repression activity. Consistent with the dwarf phenotype of gd1, expression of the gibberelic acid (GA) inactivation gene OsGA2ox3 is increased dramatically, accompanied by reduced expression of GA biosynthetic genes including OsGA20ox1, OsGA20ox2 and OsGA3ox2 in gd1, resulting in a decreased endogenous GA₄ level. Exogenous application of GA not only induced GD1 expression, but also partially rescued the dwarf phenotype of gd1. Furthermore, GD1 binds to the promoter of OsLFL1, a LEC2/FUS3-like gene of rice, via an RY element, leading to significant up-regulation of OsLFL1 and a large subset of seed maturation genes in the gd1 mutant. Plants over-expressing OsLFL1 partly mimic the gd1 mutant. In addition, expression of GD1 was induced under sugar treatment, and the contents of starch and soluble sugar are altered in the gd1 mutant. These data indicate that GD1 participates directly or indirectly in regulating GA and carbohydrate homeostasis, and further regulates rice seed germination and seedling development.
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research-Beijing, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Guo
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Hou
authors.forename: Jun
authors.initials: J
authors.lastname: Fang
authors.forename: Piwei
authors.initials: P
authors.lastname: Wei
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Mingluan
authors.initials: M
authors.lastname: Chen
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Feng
authors.forename: Chengcai
authors.initials: C
authors.lastname: Chu
mesh_terms: D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004269:DNA, Bacterial; D035264:Flowers / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics*; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000187:drug effects / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D005875:Gibberellins; D010940:Plant Proteins; D012097:Repressor Proteins; C036483:T-DNA; D014157:Transcription Factors; C007842:gibberellic acid
keywords: B3 domain transcription factor; EAR motif; germination-defective1; gibberellin; rice; seed germination