RESUMEN

Grafting is an ancient method that has been intensively used for the clonal propagation of vegetables and woody trees. Despite its importance in agriculture the physiological and molecular mechanisms underlying phenotypic changes of plants following grafting are still poorly understood. In the present study, we analyse the populations of small RNAs in homo and heterografts and take advantage of the sequence differences in the genomes of heterograft partners to analyse the possible exchange of small RNAs. We demonstrate that the type of grafting per se dramatically influences the small RNA populations independently of genotypes but also show genotype specific effects. In addition, we demonstrate that bilateral exchanges of small RNAs, mainly short interfering RNAs, may occur in heterograft with the preferential transfer of small RNAs from the scion to the rootstock. Altogether, the results suggest that small RNAs may have an important role in the phenotype modifications observed in heterografts.

RESUMEN

The Enhancer of Zeste Polycomb group proteins, which are encoded by a small gene family in Arabidopsis thaliana, participate to the control of plant development. In the tomato (Solanum lycopersicum), these proteins are encoded by three genes (SlEZ1, SlEZ2 and SlEZ3) that display specific expression profiles. Using a gene specific RNAi strategy, we demonstrate that repression of SlEZ2 correlates with a general reduction of H3K27me3 levels, indicating that SlEZ2 is part of an active PRC2 complex. Reduction of SlEZ2 gene expression impacts the vegetative development of tomato plants, consistent with SlEZ2 having retained at least some of the functions of the Arabidopsis CURLY LEAF (CLF) protein. Notwithstanding, we observed significant differences between transgenic SlEZ2 RNAi tomato plants and Arabidopsis clf mutants. First, we found that reduced SlEZ2 expression has dramatic effects on tomato fruit development and ripening, functions not described in Arabidopsis for the CLF protein. In addition, repression of SlEZ2 has no significant effect on the flowering time or the control of flower organ identity, in contrast to the Arabidopsis clf mutation. Taken together, our results are consistent with a diversification of the function of CLF orthologues in plants, and indicate that although partly conserved amongst plants, the function of EZ proteins need to be newly investigated for non-model plants because they might have been recruited to specific developmental processes.

Asunto(s)

Regulación de la Expresión Génica de las Plantas/fisiología , Proteínas de Plantas/metabolismo , Solanum lycopersicum/crecimiento & desarrollo , Solanum lycopersicum/metabolismo , Regulación hacia Abajo , Evolución Molecular , Flores/crecimiento & desarrollo , Flores/metabolismo , Frutas/crecimiento & desarrollo , Frutas/metabolismo , Solanum lycopersicum/genética , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Proteínas de Plantas/genética , Tallos de la Planta/crecimiento & desarrollo , Tallos de la Planta/metabolismo , Interferencia de ARN

RESUMEN

The Enhancer of Zeste (E(z)) Polycomb group (PcG) proteins, which are encoded by a small gene family in Arabidopsis thaliana, have been shown to participate to the control of flowering and seed development. For the time being, little is known about the function of these proteins in other plants. In tomato E(z) proteins are encoded by at least two genes namely SlEZ1 and SlEZ2 while a third gene, SlEZ3, is likely to encode a truncated non-functional protein. The analysis of the corresponding mRNA demonstrates that these two genes are differentially regulated during plant and fruit development. We also show that SlEZ1 and SlEZ2 are targeted to the nuclei. These results together with protein sequence analysis makes it likely that both proteins are functional E(z) proteins. The characterisation of SlEZ1 RNAi lines suggests that although there might be some functional redundancy between SlEZ1 and SlEZ2 in most plant organs, the former protein is likely to play specific function in flower development.

Asunto(s)

Flores/crecimiento & desarrollo , Regulación de la Expresión Génica de las Plantas/fisiología , Proteínas de Plantas/metabolismo , Solanum lycopersicum/genética , Solanum lycopersicum/metabolismo , Transporte Activo de Núcleo Celular , Secuencia de Aminoácidos , Clonación Molecular , Flores/genética , Flores/metabolismo , Frutas/metabolismo , Genoma de Planta , Datos de Secuencia Molecular , Filogenia , Hojas de la Planta/metabolismo , Proteínas de Plantas/clasificación , Proteínas de Plantas/genética , Isoformas de Proteínas , Interferencia de ARN , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Tiempo

RESUMEN

Ductal carcinoma in situ is defined as breast cancer confined to the ducts of the breast without evidence of penetration of the basement membrane. Local treatment quality represents one of the most prognostic factors as half of recurrences are invasive diseases. The main goal of adjuvant radiotherapy after conservative surgery is to decrease local recurrences and to permit breast conservation with low treatment-induced sequelae. Several randomized trials have established the impact of 50 Gy to the whole breast in terms of local control. Nevertheless, no randomized trial is still available concerning the role of the boost in this disease. In this review, we present updated results of the literature and we detail the French multicentric randomized trial evaluating the impact of a 16 Gy boost after 50 Gy delivered to the whole breast in 25 fractions and 33 days. This protocol will start inclusions in October 2008.

Asunto(s)

Neoplasias de la Mama/radioterapia , Carcinoma Intraductal no Infiltrante/radioterapia , Neoplasias de la Mama/patología , Carcinoma Intraductal no Infiltrante/patología , Femenino , Humanos , Estudios Multicéntricos como Asunto , Necrosis , Invasividad Neoplásica , Recurrencia Local de Neoplasia/epidemiología , Pronóstico , Dosificación Radioterapéutica , Ensayos Clínicos Controlados Aleatorios como Asunto

RESUMEN

Tomato fruit cells are characterized by a strong increase in nuclear ploidy during fruit development. Average ploidy levels increased to similar levels (above 50C) in two distinct fruit tissues, pericarp and locular tissue. However, ploidy profiles differed significantly between these two tissues suggesting a tissue-specific control of endoreduplication in tomato fruit. To determine possible relationships between endoreduplication and epigenetic mechanisms, the methylation status of genomic DNA from pericarp and locular tissue of tomato fruit was analysed. Pericarp genomic DNA was characterized by an increase of CG and/or CNG methylation at the 5S and 18S rDNA loci and at gyspsy-like retrotransposon sequences during fruit growth. A sharp decrease of the global DNA methylation level together with a reduction of methylation at the rDNA loci was also observed in pericarp during fruit ripening. Inversely, no major variation of DNA methylation either global or locus-specific, was observed in locular tissue. Thus, tissue-specific variations of DNA methylation are unlikely to be triggered by the induction of endoreduplication in fruit tissues, but may reflect tissue-specific ploidy profiles. Expression analysis of eight putative tomato DNA methyltransferases encoding genes showed that one chromomethylase (CMT) and two rearranged methyltransferases (DRMs) are preferentially expressed in the pericarp during fruit growth and could be involved in the locus-specific increase of methylation observed at this developmental phase in the pericarp.

Asunto(s)

Metilación de ADN , Frutas/crecimiento & desarrollo , Frutas/genética , Duplicación de Gen , Solanum lycopersicum/crecimiento & desarrollo , Solanum lycopersicum/genética , Citosina/metabolismo , ADN (Citosina-5-)-Metiltransferasas/genética , ADN (Citosina-5-)-Metiltransferasas/metabolismo , Flores/enzimología , Flores/genética , Frutas/citología , Frutas/enzimología , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Solanum lycopersicum/citología , Solanum lycopersicum/enzimología , Especificidad de Órganos , Ploidias , Secuencias Repetitivas de Ácidos Nucleicos/genética

Asunto(s)

Crianza de Animales Domésticos , Vestuario , Países en Desarrollo , Ovinos , Factores Socioeconómicos , Lana , Crianza de Animales Domésticos/economía , Crianza de Animales Domésticos/educación , Crianza de Animales Domésticos/historia , Crianza de Animales Domésticos/legislación & jurisprudencia , Animales , Vestuario/economía , Vestuario/historia , Vestuario/psicología , Comercio/economía , Comercio/educación , Comercio/historia , Comercio/legislación & jurisprudencia , Países en Desarrollo/economía , Países en Desarrollo/historia , Francia/etnología , Historia del Siglo XIX , Industrias/economía , Industrias/educación , Industrias/historia , Industrias/legislación & jurisprudencia , Salud Rural/historia , Población Rural/historia , Industria Textil/economía , Industria Textil/educación , Industria Textil/historia , Industria Textil/legislación & jurisprudencia , Lana/economía , Lana/historia

RESUMEN

We have isolated a protein, mature RRFHCP, from chloroplasts of spinach (Spinacia oleracea L.) that shows 46% sequence identity and 66% sequence homology with ribosome recycling factor (RRF) of Escherichia coli. RRF recycles ribosomes through disassembly of the posttermination complex. From the cDNA analysis and from the amino-terminal sequencing of the isolated protein, the mature RRFHCP was deduced to have a Mr of 21,838 with 193 aa. It lacks the 78-aa chloroplast targeting sequence encoded by the RRFHCP cDNA sequence. The RRFHCP synthesized in vitro was imported into isolated chloroplasts with simultaneous conversion to the mature RRFHCP. Transcription of the gene coding for RRFHCP was not dependent on light, yet it was limited mostly to photosynthetic tissues in which only one transcript size was detected. Mature RRFHCP exerted a bactericidal effect on E. coli carrying temperature-sensitive RRF at the permissive temperature whereas wild-type E. coli was not affected.

Asunto(s)

Cloroplastos/química , Escherichia coli/metabolismo , Proteínas de Plantas/genética , Proteínas/metabolismo , Ribosomas/metabolismo , Spinacia oleracea/metabolismo , Secuencia de Aminoácidos , Antibacterianos/metabolismo , Secuencia de Bases , Clonación Molecular , Luz , Datos de Secuencia Molecular , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Proteínas/genética , ARN Mensajero/metabolismo , Proteínas Recombinantes/genética , Proteínas Ribosómicas , Homología de Secuencia de Aminoácido , Temperatura

RESUMEN

In this paper, we briefly review RRF (ribosome recycling factor, previously called ribosome releasing factor) (for recent reviews covering historical background see (1, 2)).

Asunto(s)

Antiinfecciosos/farmacología , Proteínas Bacterianas/metabolismo , Biosíntesis de Proteínas , Proteínas , Ribosomas/metabolismo , Secuencia de Aminoácidos , Proteínas Ribosómicas , Terminología como Asunto

RESUMEN

Using antibodies raised against E37, one of the major polypeptides of the inner membrane from the chloroplast envelope, it has been demonstrated that a single immunologically related polypeptide was present in total protein extracts from various higher plants (monocots and dicots), in photosynthetic and non-photosynthetic tissues from young spinach plantlets, as well as in the cytoplasmic membrane from the cyanobacteria Synechococcus. This ubiquitous distribution of E37 strongly suggests that this protein plays an envelope-specific function common to all types of plastids. Comparison of tobacco and spinach E37 amino acid sequences deduced from the corresponding cDNA demonstrates that consensus motifs for S-adenosyl methionine-dependent methyltransferases are located in both sequences. This hypothesis was confirmed using a biochemical approach. It was demonstrated that E37, together with two minor spinach chloroplast envelope polypeptides of 32 and 39 kDa, can be specifically photolabeled with [3H]-S-adenosyl methionine upon UV-irradiation. Identification of E37 as a photolabeled polypeptide was established by immunoprecipitation. Furthermore, photolabeling of the three envelope polypeptides was specifically inhibited by very low concentration of S-adenosyl homocysteine, thus providing evidence for the presence within these proteins of S-adenosyl methionine- and S-adenosyl homocysteine-binding sites that were closely associated. Taken as a whole these results strongly suggest that E37 is an ubiquitous plastid envelope protein that probably has an S-adenosyl methionine-dependent methyltransferase activity. The 32 and 39 kDa envelope polypeptides probably have a similar methyltransferase activity.

Asunto(s)

Metiltransferasas/química , Proteínas de Plantas/química , Plastidios/química , Secuencia de Aminoácidos , Western Blotting , Proteínas de Cloroplastos , Datos de Secuencia Molecular , Alineación de Secuencia

RESUMEN

A cDNA coding for the outer membrane protein E24 of spinach chloroplast envelope has been obtained by screening an expression library of spinach cDNA with polyclonal antibodies. Analysis of the protein sequence and comparison with the thermolysin susceptibility of E24 in the chloroplast in situ suggest that E24 is a transmembrane protein and show that its NH2 terminal end is located on the cytosolic side of chloroplasts.

Asunto(s)

Cloroplastos/genética , Proteínas de la Membrana/química , Proteínas de Plantas/química , Spinacia oleracea/genética , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , ADN Complementario/genética , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Proteínas de Plantas/genética