RESUMEN
The promoter of the Arabidopsis thaliana L. AtEm1 gene encoding a late embryogenesis abundant protein was fused to the beta-glucuronidase reporter gene and introduced into Brassica napus. The promoter is highly active in the vascular tissues of embryo and pollen grains and also active in petals, sepals, caulinar leaves, and carpels.
Asunto(s)
Arabidopsis/genética , Brassica/genética , Regulación de la Expresión Génica de las Plantas , Proteínas de Plantas/genética , Arabidopsis/embriología , Fusión Artificial Génica , Transporte Biológico/genética , Genes de Plantas , Genes Reporteros , Glucuronidasa/genética , Estructuras de las Plantas/genética , Plantas Modificadas Genéticamente , Polen/genética , Regiones Promotoras Genéticas , Semillas/genéticaRESUMEN
The gene coding for a new class of proteins rich in glycine and proline (GPRP) was cloned in Arabidopsis thaliana. In the protein sequence, five amino acids - glycine, proline, alanine, tyrosine and histidine - account for 79.4% of the total composition. The protein has two different glycine-rich domains interrupted by a hydrophobic segment having a high probability of helix formation. The protein synthesized in vitro interacts with microsomes possibly through the hydrophobic domain. The gene in Arabidopsis has two introns, one in the coding region and the other one in the 5' non-coding region. The later one is 778 bp long. Homologous sequences are found in carrot, tomato and tobacco. GPRP mRNA is found in the different organs of the plant analyzed except in mature seeds and anthers, and mostly in epidermal and vascular tissues. Possible hypotheses about the function of GPRP are discussed.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis/genética , Genes de Plantas , Proteínas de Plantas/genética , Secuencia de Aminoácidos , Arabidopsis/metabolismo , Secuencia de Bases , Membrana Celular/metabolismo , Clonación Molecular , ADN Complementario , ADN de Plantas , Biblioteca de Genes , Genoma de Planta , Glicina , Datos de Secuencia Molecular , Proteínas de Plantas/química , Proteínas de Plantas/clasificación , Proteínas de Plantas/metabolismo , ProlinaRESUMEN
The distribution of ribosomal transcripts in the plant nucleolus has been studied by non-isotopic in situ hybridization in ultrathin Lowicryl K4M sections and by high-resolution autoradiography after labelling with tritiated uridine. In parallel, cytochemical techniques were applied to localize RNA on different plant nucleolar components of Allium cepa L. root meristematic cells and Capsicum annuum L. pollen grains. For RNA/RNA in situ hybridization, several biotinylated single-stranded ribosomal RNA probes were used for mapping different fragments of the 18 S and the 25 S rRNA gene transcribed regions. Ribosomal RNAs (from pre-rRNAs to mature 18 and 25 S RNAs) were found in the nucleolus, in the dense fibrillar (DFC) and granular components (GC). Hybridization signal was found at the periphery of some fibrillar centres (FCs) with probes recognizing both 18 and 25 S rRNA sequences. A quantitative study was performed to analyze the significance of this labelling. Incorporation of tritiated uridine into roots was carried out and, later, after a long time-exposure, autoradiography revealed the presence of newly synthesized RNA mainly in the DFC and at the periphery of the FCs. The presence of RNA in these areas was also confirmed by the cytochemical techniques used in this study. Taken together, these data favour the hypothesis that transcription can begin at the periphery of the FCs, although we cannot exclude the possibility that the DFC plays a role in this process.
Asunto(s)
Nucléolo Celular/ultraestructura , ARN Mensajero/ultraestructura , ARN Ribosómico/ultraestructura , Verduras/ultraestructura , Allium/ultraestructura , Arabidopsis/genética , Autorradiografía , Capsicum/ultraestructura , ADN Ribosómico/genética , Histocitoquímica/métodos , Hibridación in Situ , Plantas Medicinales , Sondas ARN , ARN Mensajero/genética , ARN Mensajero/aislamiento & purificación , ARN Ribosómico/genética , ARN Ribosómico/aislamiento & purificación , ARN Ribosómico 18S/genética , ARN Ribosómico 18S/aislamiento & purificación , ARN Ribosómico 18S/ultraestructura , Transcripción Genética , Verduras/genéticaRESUMEN
The organization of methylated rDNA repeats of radish and pea is described and it is shown that methylated repeats and non-methylated repeats are interspersed one with another. Methylated arrays are not much longer than 100 kb, or about 10 repeat units in length.
Asunto(s)
ADN Ribosómico/genética , Fabaceae/genética , Plantas Medicinales , Plantas/genética , Secuencias Repetitivas de Ácidos Nucleicos , ADN Ribosómico/aislamiento & purificación , Metilación , Peso Molecular , Hibridación de Ácido Nucleico , Especificidad de la EspecieRESUMEN
Precursors for radish storage proteins were identified by immunoprecipitation of cell-free protein-synthesis products. The 12S globulin polypeptides (21,000-33,000 Mr) are made from four larger precursors (47,500-60,000 Mr) and the 1.7 S albumin polypeptides (7,000-12,000 Mr) are synthesized as eight products of Mr about 20,000. From a cDNA library, several clones have been identified, using heterologous cDNA probes for rapeseed cruciferin and napin, and two of them (pAE10 and pBA3) used to hybrid-select the corresponding mRNA. The napin cDNA clone selects all translation products immunoprecipitated by anti-napin antibodies whereas the cruciferin clone selects only one polypeptide among the four recognized by 12S antibodies. The 12S globulin and the 1.7S albumin message sizes were estimated to be 1950 and 800 nucleotides respectively. Experiments carried out with mRNA populations from different maturation stages suggest a sequential gene expression for the two major storage protein families. In addition two napin subfamilies can be distinguished by their expression pattern. In dry seed, napin mRNA is not detectable and the amount of cruciferin mRNA decreased considerably so that it no longer represents a major fraction of dry seed mRNA.