The RY/Sph element mediates transcriptional repression of maturation genes from late maturation to early seedling growth.
In orthodox seeds, the transcriptional activator ABI3 regulates two major stages in embryo maturation: a mid-maturation (MAT) stage leading to accumulation of storage compounds, and a late maturation (LEA) stage leading to quiescence and desiccation tolerance. Our aim was to elucidate mechanisms for transcriptional shutdown of MAT genes during late maturation, to better understand phase transition between MAT and LEA stages. Using transgenic and transient approaches in Nicotiana, we examined activities of two ABI3-dependent reporter genes driven by multimeric RY and abscisic acid response elements (ABREs) from a Brassica napus napin gene, termed RY and ABRE, where the RY reporter requires ABI3 DNA binding. Expression of RY peaks during mid-maturation and drops during late maturation, mimicking the MAT gene program, and in Arabidopsis thaliana RY elements are over-represented in MAT, but not in LEA, genes. The ABI3 transactivation of RY is inhibited by staurosporine, by a PP2C phosphatase, and by a repressor of maturation genes, VAL1/HSI2. The RY element mediates repression of MAT genes, and we propose that transcriptional shutdown of the MAT program during late maturation involves inhibition of ABI3 DNA binding by dephosphorylation. Later, during seedling growth, VAL1/HSI2 family repressors silence MAT genes by binding RY elements.
Guerriero
Gea
G
KTH Biotechnology, Swedish Center of Biomimetic Fiber Engineering, AlbaNova, SE-106 91, Stockholm, Sweden.
Martin
Nathalie
N
Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, SE-751 23, Uppsala; Sweden.
Golovko
Anna
A
Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, SE-751 23, Uppsala; Sweden.
Sundström
Jens F
JF
Department of Plant Biology and Forest Genetics, SLU, Box 7080, SE-750 07, Uppsala, Sweden.
Rask
Lars
L
Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, SE-751 23, Uppsala; Sweden.
Ezcurra
Ines
I
KTH Biotechnology, Swedish Center of Biomimetic Fiber Engineering, AlbaNova, SE-106 91, Stockholm, Sweden.
D017360:Arabidopsis / Q000235:genetics; D001483:Base Sequence; D029688:Brassica napus / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D008954:Models, Biological; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D030821:Plants, Genetically Modified; D000071636:Protein Phosphatase 2C; D036226:Seedlings / Q000235:genetics* / Q000254:growth & development*; D012639:Seeds / Q000196:embryology* / Q000235:genetics*; D019311:Staurosporine / Q000494:pharmacology; D014026:Nicotiana / Q000196:embryology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects
D018744:DNA, Plant; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D019311:Staurosporine