RESUMO
Plants produce new appendages reiteratively from groups of stem cells called shoot apical meristems. LEAFY (LFY) and APETALA1 (AP1) are pivotal for the switch to the reproductive phase, where instead of leaves the shoot apical meristem produces flowers. Use of steroid-inducible activation of LFY demonstrated that early expression of AP1 is a result of transcriptional induction by LFY. This AP1 induction is independent of protein synthesis and occurs specifically in the tissues and at the developmental stage in which floral fate is assumed. Later expression of AP1 appears to be only indirectly affected by LFY.
Assuntos
Proteínas de Arabidopsis , Arabidopsis/genética , Proteínas de Homeodomínio/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transativadores/metabolismo , Fatores de Transcrição , Ativação Transcricional , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Dexametasona/farmacologia , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Homeodomínio/metabolismo , Hibridização in Situ Fluorescente , Proteínas de Domínio MADS , Meristema/genética , Meristema/metabolismo , Mutação , Proteínas de Plantas/biossíntese , Estruturas Vegetais/genética , Estruturas Vegetais/crescimento & desenvolvimento , Estruturas Vegetais/metabolismo , Regiões Promotoras Genéticas , RNA de Plantas/genética , RNA de Plantas/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Transativadores/genética , Transformação GenéticaRESUMO
The floral homeotic gene APETALA3 (AP3) is required for stamen and petal development in Arabidopsis. The previously described ap3-1 allele is temperature sensitive and carries a missense mutation near a 5' splice site. The missense mutation lies within a domain of the AP3 protein that is thought to be important for protein-protein interactions, which suggests that temperature sensitivity of ap3-1 could reflect an unstable interaction with cofactors. Here, we show instead that the ap3-1 mutation causes a temperature-dependent splicing defect and that temperature sensitivity is not a property of the protein products of ap3-1 but of RNA processing, possibly because of unstable base pairing between the transcript and small nuclear RNAs. The unexpected defect of the ap3-1 mutant offers unique opportunities for genetic and molecular studies of splice site recognition in plants.
Assuntos
Proteínas de Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Genes de Plantas , Proteínas de Domínio MADS , Splicing de RNA/genética , Processamento Alternativo/genética , Sequência de Aminoácidos , Arabidopsis/crescimento & desenvolvimento , Sequência de Bases , Primers do DNA/genética , DNA de Plantas/genética , Genes Homeobox , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Íntrons , Dados de Sequência Molecular , Mutação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Processamento Pós-Transcricional do RNA/genética , RNA de Plantas/genética , RNA de Plantas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , TemperaturaRESUMO
To understand how homeotic genes affect morphogenesis and differentiation, their target genes must be identified. In Arabidopsis flowers, the homeotic protein heterodimer APETALA3/PISTILLATA is necessary for petal and stamen formation. Here, AP3/PI function was put under posttranslational control to analyze its immediate effect on the floral mRNA population, with indirect effects blocked by cycloheximide. Using differential display, a target gene of AP3/PI was identified (NAP:NAC-LIKE, ACTIVATED BY AP3/PI), which is homologous to genes required for meristem establishment and separation of floral organs. The expression pattern of NAP and the phenotypes caused by its misexpression suggest that it functions in the transition between growth by cell division and cell expansion in stamens and petals.
Assuntos
Proteínas de Arabidopsis , Arabidopsis/genética , Genes Homeobox/genética , Genes Homeobox/fisiologia , Genes de Plantas/genética , Proteínas de Domínio MADS , Meristema/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Mapeamento Cromossômico , Expressão Gênica/genética , Genes de Plantas/fisiologia , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/fisiologia , Meristema/química , Dados de Sequência Molecular , Proteínas de Plantas/fisiologia , RNA Mensageiro/análise , RNA Mensageiro/genética , RNA Mensageiro/fisiologia , Receptores de Glucocorticoides/fisiologia , Homologia de Sequência de Aminoácidos , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Ativação Transcricional/genética , Ativação Transcricional/fisiologiaRESUMO
The promoter of the bean PAL2 gene (encoding phenylalanine ammonia-lyase; EC 4.3.1.5) is a model for studies of tissue-restricted gene expression in plants. Petal epidermis is one of the tissues in which this promoter is activated in tobacco. Previous work suggested that a major factor establishing the pattern of PAL2 expression in tobacco petals is the tissue distribution of a protein closely related to Myb305, which is a Myb-like transcriptional activator from snapdragon. In the present work, we show that Myb305 expression in tobacco leaves causes ectopic activation of the PAL2 promoter. To achieve Myb305 expression in planta, a viral expression vector was used. This approach combines the utility of transient assays with the possibility of direct biochemical detection of the introduced factor and may have wider application for studying the function of plant transcription factors.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica de Plantas , Vetores Genéticos/genética , Proteínas de Plantas/metabolismo , Potexvirus/genética , Proteínas Proto-Oncogênicas c-myb , Fatores de Transcrição/metabolismo , Sequência de Bases , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/genética , Genes Reporter , Dados de Sequência Molecular , Fenilalanina Amônia-Liase/biossíntese , Fenilalanina Amônia-Liase/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/biossíntese , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Plantas Tóxicas , Regiões Promotoras Genéticas/genética , Distribuição Tecidual , Nicotiana/genética , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genéticaRESUMO
Synthesis of flavonoid pigments in flowers requires the co-ordinated expression of genes encoding enzymes in th phenylpropanoid biosynthetic pathway. Some cis-elements involved in the transcriptional control of these genes have been defined. We report binding of petal-specific activities from tobacco and Antirrhinum majus (snapdragon) to an element conserved in promoters of phenylpropanoid biosynthetic genes and implicated in expression in flowers. These binding activities were inhibited by antibodies raised against Myb305, a flower-specific Myb protein previously cloned from Antirrhinum by sequence homology. Myb305 bound to the same element and formed a DNA-protein complex with the same mobility as the Antirrhinum petal protein in electrophoretic mobility shift experiments. Myb305 activated expression from its binding site in yeast and in tobacco protoplasts. In protoplasts, activation also required a G-box-like element, suggesting co-operation with other elements and factors. The results strongly suggest a role for Myb305-related proteins in the activation of phenylpropanoid biosynthetic genes in flowers. This is consistent with the genetically demonstrated role of plant Myb proteins in the regulation of genes involved in flavonoid synthesis.
