RESUMEN
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.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis/genética , Proteínas de Homeodominio/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transactivadores/metabolismo , Factores de Transcripción , Activación Transcripcional , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Dexametasona/farmacología , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Proteínas de Homeodominio/metabolismo , Hibridación Fluorescente in Situ , Proteínas de Dominio MADS , Meristema/genética , Meristema/metabolismo , Mutación , Proteínas de Plantas/biosíntesis , Estructuras de las Plantas/genética , Estructuras de las Plantas/crecimiento & desarrollo , Estructuras de las Plantas/metabolismo , Regiones Promotoras Genéticas , ARN de Planta/genética , ARN de Planta/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Transactivadores/genética , Transformación GenéticaRESUMEN
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.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Genes de Plantas , Proteínas de Dominio MADS , Empalme del ARN/genética , Empalme Alternativo/genética , Secuencia de Aminoácidos , Arabidopsis/crecimiento & desarrollo , Secuencia de Bases , Cartilla de ADN/genética , ADN de Plantas/genética , Genes Homeobox , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Intrones , Datos de Secuencia Molecular , Mutación , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Procesamiento Postranscripcional del ARN/genética , ARN de Planta/genética , ARN de Planta/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , TemperaturaRESUMEN
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.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis/genética , Genes Homeobox/genética , Genes Homeobox/fisiología , Genes de Plantas/genética , Proteínas de Dominio MADS , Meristema/genética , Proteínas de Plantas/genética , Secuencia de Aminoácidos , Secuencia de Bases , Mapeo Cromosómico , Expresión Génica/genética , Genes de Plantas/fisiología , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/fisiología , Meristema/química , Datos de Secuencia Molecular , Proteínas de Plantas/fisiología , ARN Mensajero/análisis , ARN Mensajero/genética , ARN Mensajero/fisiología , Receptores de Glucocorticoides/fisiología , Homología de Secuencia de Aminoácido , Factores de Transcripción/genética , Factores de Transcripción/fisiología , Activación Transcripcional/genética , Activación Transcripcional/fisiologíaRESUMEN
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.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Regulación de la Expresión Génica de las Plantas , Vectores Genéticos/genética , Proteínas de Plantas/metabolismo , Potexvirus/genética , Proteínas Proto-Oncogénicas c-myb , Factores de Transcripción/metabolismo , Secuencia de Bases , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/genética , Genes Reporteros , Datos de Secuencia Molecular , Fenilanina Amoníaco-Liasa/biosíntesis , Fenilanina Amoníaco-Liasa/genética , Hojas de la Planta/metabolismo , Proteínas de Plantas/biosíntesis , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente , Plantas Tóxicas , Regiones Promotoras Genéticas/genética , Distribución Tisular , Nicotiana/genética , Factores de Transcripción/biosíntesis , Factores de Transcripción/genéticaRESUMEN
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.