RESUMEN
Despite having very similar initial pools of stored mRNAs and proteins in the dry state, mature Arabidopsis seeds can either proceed toward radicle protrusion or stay in a dormant state upon imbibition. Dormancy breaking, a prerequisite to germination completion, can be induced by different treatments though the underlying mechanisms remain elusive. Thus, we investigated the consequence of such treatments on the seed proteome. Two unrelated dormancy-releasing treatments were applied to dormant seeds, namely, cold stratification and exogenous nitrates, in combination with differential proteomic tools to highlight the specificities of the imbibed dormant state. The results reveal that both treatments lead to highly similar proteome adjustments. In the imbibed dormant state, enzymes involved in reserve mobilization are less accumulated and it appears that several energetically costly processes associated to seed germination and preparation for subsequent seedling establishment are repressed. Our data suggest that dormancy maintenance is associated to an abscisic-acid-dependent recapitulation of the late maturation program resulting in a higher potential to cope with environmental stresses. The comparison of the present results with previously published -omic data sets reinforces and extends the assumption that post-transcriptional, translational, and post-translational regulations are determinant for seed germination.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/embriología , Frío , Nitratos/metabolismo , Proteoma , Semillas/metabolismo , Arabidopsis/metabolismo , Electroforesis en Gel Bidimensional , Germinación , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , TranscriptomaRESUMEN
The seed is the dispersal unit of plants and must survive the vagaries of the environment. It is the object of intense genetic and genomic studies because processes related to seed quality affect crop yield and the seed itself provides food for humans and animals. Presently, the general aim of postgenomics analyses is to understand the complex biochemical and molecular processes underlying seed quality, longevity, dormancy, and vigor. Due to advances in functional genomics, the recent past years have seen a tremendous progress in our understanding of several aspects of seed development and germination. Here, we describe the proteomics protocols (from protein extraction to mass spectrometry) that can be used to investigate several aspects of seed physiology, including germination and its hormonal regulation, dormancy release, and seed longevity. These techniques can be applied to the study of both model plants (such as Arabidopsis) and crops.
Asunto(s)
Arabidopsis/crecimiento & desarrollo , Germinación/genética , Latencia en las Plantas/genética , Proteómica , Semillas/crecimiento & desarrollo , Ácido Abscísico/genética , Ácido Abscísico/metabolismo , Ácido Abscísico/fisiología , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulación de la Expresión Génica de las Plantas , Germinación/fisiología , Espectrometría de Masas , Latencia en las Plantas/fisiología , Reguladores del Crecimiento de las Plantas/genética , Reguladores del Crecimiento de las Plantas/metabolismo , Procesamiento Proteico-Postraduccional , Semillas/genéticaRESUMEN
Seeds play a fundamental role in colonization of the environment by spermatophytes, and seeds harvested from crops are the main food source for human beings. Knowledge of seed biology is therefore important for both fundamental and applied issues. This review on seed biology illustrates the important progress made in the field of Arabidopsis seed research over the last decade. Access to 'omics' tools, including the inventory of genes deduced from sequencing of the Arabidopsis genome, has speeded up the analysis of biological functions operating in seeds. This review covers the following processes: seed and seed coat development, seed reserve accumulation, seed dormancy and seed germination. We present new insights in these various fields and describe ongoing biotechnology approaches to improve seed characteristics in crops.
Asunto(s)
Arabidopsis/genética , Genómica , Semillas/crecimiento & desarrollo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Biotecnología/tendencias , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genoma de Planta , Germinación , Reguladores del Crecimiento de las Plantas/metabolismo , Proteínas de Almacenamiento de Semillas/metabolismo , Semillas/genética , Semillas/metabolismoRESUMEN
Aging and death are universal to living systems. In temperate climate latitudes the mature seeds of higher plants are exposed to aging and have developed resistance mechanisms allowing survival and plant propagation. In addition to the physicochemical properties of the seed that confer stress resistance, the protein metabolism contributes importantly to longevity mechanisms. Recently, genetic studies have demonstrated the occurrence of the Protein L-isoaspartyl methyltransferase repair enzyme in controlling age-related protein damages and seed survival. These protective mechanisms by protein repair are widespread in all kingdoms, so that the use of seeds as models to study these controlling processes offers the prospect of understanding longevity mechanisms better.
Asunto(s)
Semillas/crecimiento & desarrollo , Desecación , Regulación de la Expresión Génica de las Plantas , Genoma de Planta , Germinación/genética , Estrés Oxidativo , Proteínas de Plantas/genética , Proteínas de Plantas/fisiología , Plantas Modificadas Genéticamente , Preservación Biológica , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/genética , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/fisiología , Semillas/genética , Semillas/ultraestructuraRESUMEN
Temozolomide is an effective alkylating agent that is increasingly used for the treatment of pediatric brain tumors. Secondary, or treatment-related, myelodysplasia is a life-threatening complication of alkylating chemotherapy and has been reported in children with brain tumors after treatments other than temozolomide. We describe for the first time a case of temozolomide-related myelodysplasia in a child.
Asunto(s)
Antineoplásicos Alquilantes/efectos adversos , Neoplasias Encefálicas/complicaciones , Dacarbazina/análogos & derivados , Síndromes Mielodisplásicos/inducido químicamente , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/radioterapia , Niño , Terapia Combinada , Irradiación Craneana , Dacarbazina/efectos adversos , Resultado Fatal , Humanos , Masculino , Síndromes Mielodisplásicos/genética , Síndromes Mielodisplásicos/patología , TemozolomidaRESUMEN
The formation of abnormal amino acid residues is a major source of spontaneous age-related protein damage in cells. The protein l-isoaspartyl methyltransferase (PIMT) combats protein misfolding resulting from l-isoaspartyl formation by catalyzing the conversion of abnormal l-isoaspartyl residues to their normal l-aspartyl forms. In this way, the PIMT repair enzyme system contributes to longevity and survival in bacterial and animal kingdoms. Despite the discovery of PIMT activity in plants two decades ago, the role of this enzyme during plant stress adaptation and in seed longevity remains undefined. In this work, we have isolated Arabidopsis thaliana lines exhibiting altered expression of PIMT1, one of the two genes encoding the PIMT enzyme in Arabidopsis. PIMT1 overaccumulation reduced the accumulation of l-isoaspartyl residues in seed proteins and increased both seed longevity and germination vigor. Conversely, reduced PIMT1 accumulation was associated with an increase in the accumulation of l-isoaspartyl residues in the proteome of freshly harvested dry mature seeds, thus leading to heightened sensitivity to aging treatments and loss of seed vigor under stressful germination conditions. These data implicate PIMT1 as a major endogenous factor that limits abnormal l-isoaspartyl accumulation in seed proteins, thereby improving seed traits such as longevity and vigor. The PIMT repair pathway likely works in concert with other anti-aging pathways to actively eliminate deleterious protein products, thus enabling successful seedling establishment and strengthening plant proliferation in natural environments.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Germinación/genética , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/metabolismo , Semillas/enzimología , Arabidopsis/genética , Proteínas de Arabidopsis/genética , ADN Bacteriano/genética , Regulación de la Expresión Génica de las Plantas , Ácido Isoaspártico/metabolismo , Mutagénesis Insercional , Mutación , Plantas Modificadas Genéticamente/enzimología , Plantas Modificadas Genéticamente/genética , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/genética , ARN de Planta/genética , Semillas/genéticaRESUMEN
CONTEXT: GH deficiency (GHD) associated with central precocious puberty (CPP) has been widely reported in cases of arachnoid cyst, septo-optic dysplasia, brain tumors, or after cerebral radiation therapy. However, idiopathic GHD associated with CPP has been reported in only one isolated case. OBJECTIVE: To evaluate the occurrence and clinical features of the association of nonacquired GHD and CPP. DESIGN AND SETTING: This was a retrospective multicenter study. PATIENTS AND METHODS: The study population was identified through a French nationwide multicenter network (about 3000 patients). We reviewed the medical records of all subjects diagnosed with nonacquired GHD and CPP, with or without developmental abnormalities of the hypothalamic-pituitary axis on cerebral magnetic resonance imaging (MRI), and without any known associated anomaly. RESULTS: We identified four patients with either isolated GHD (n=1) or multiple anterior pituitary hormone deficiencies (n=3). Clinical signs of CPP occurred at 6.4 +/- 2.3 years in boys and 7.5 +/- 0.5 years in girls, and GnRH analog therapy was started at 4.2 +/- 1.6 years after the initiation of recombinant human GH treatment. Cerebral MRI demonstrated ectopic neurohypophysis associated with anterior pituitary hypoplasia in three out of the four patients. The morphology and position of the anterior pituitary and neurohypophysis were normal in one patient who displayed a persistence of the craniopharyngeal canal. CONCLUSIONS: CPP is very rare in patients with nonacquired GHD and is mostly associated with developmental defects in the hypothalamic-pituitary area. Whether molecular mechanisms governing development and activation of the hypothalamic-pituitary axis share dependent factors remains to be explored.
Asunto(s)
Discapacidades del Desarrollo/complicaciones , Hormona de Crecimiento Humana/deficiencia , Sistema Hipotálamo-Hipofisario/crecimiento & desarrollo , Pubertad Precoz/complicaciones , Enfermedades Raras , Distribución por Edad , Encéfalo/patología , Niño , Preescolar , Coristoma/complicaciones , Coristoma/diagnóstico , Discapacidades del Desarrollo/diagnóstico , Discapacidades del Desarrollo/epidemiología , Femenino , Humanos , Enfermedades Hipotalámicas/complicaciones , Enfermedades Hipotalámicas/diagnóstico , Imagen por Resonancia Magnética , Masculino , Eminencia Media , Neurohipófisis , Hormonas Adenohipofisarias/deficiencia , Pubertad Precoz/fisiopatología , Estudios Retrospectivos , Silla Turca/anomalías , Silla Turca/patologíaRESUMEN
The mechanisms controlling seed dormancy in Arabidopsis (Arabidopsis thaliana) have been characterized by proteomics using the dormant (D) accession Cvi originating from the Cape Verde Islands. Comparative studies carried out with freshly harvested dormant and after-ripened non-dormant (ND) seeds revealed a specific differential accumulation of 32 proteins. The data suggested that proteins associated with metabolic functions potentially involved in germination can accumulate during after-ripening in the dry state leading to dormancy release. Exogenous application of abscisic acid (ABA) to ND seeds strongly impeded their germination, which physiologically mimicked the behavior of D imbibed seeds. This application resulted in an alteration of the accumulation pattern of 71 proteins. There was a strong down-accumulation of a major part (90%) of these proteins, which were involved mainly in energetic and protein metabolisms. This feature suggested that exogenous ABA triggers proteolytic mechanisms in imbibed seeds. An analysis of de novo protein synthesis by two-dimensional gel electrophoresis in the presence of [(35)S]-methionine disclosed that exogenous ABA does not impede protein biosynthesis during imbibition. Furthermore, imbibed D seeds proved competent for de novo protein synthesis, demonstrating that impediment of protein translation was not the cause of the observed block of seed germination. However, the two-dimensional protein profiles were markedly different from those obtained with the ND seeds imbibed in ABA. Altogether, the data showed that the mechanisms blocking germination of the ND seeds by ABA application are different from those preventing germination of the D seeds imbibed in basal medium.
Asunto(s)
Ácido Abscísico/farmacología , Arabidopsis/metabolismo , Reguladores del Crecimiento de las Plantas/farmacología , Proteómica , Semillas/fisiología , Arabidopsis/embriología , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Electroforesis en Gel Bidimensional , Regulación de la Expresión Génica de las Plantas , Germinación/efectos de los fármacos , Germinación/fisiología , Semillas/metabolismo , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
Seed dormancy in Nicotiana plumbaginifolia is characterized by an abscisic acid accumulation linked to a pronounced germination delay. Dormancy can be released by 1 year after-ripening treatment. Using a cDNA-amplified fragment length polymorphism (cDNA-AFLP) approach we compared the gene expression patterns of dormant and after-ripened seeds, air-dry or during one day imbibition and analyzed 15,000 cDNA fragments. Among them 1020 were found to be differentially regulated by dormancy. Of 412 sequenced cDNA fragments, 83 were assigned to a known function by search similarities to public databases. The functional categories of the identified dormancy maintenance and breaking responsive genes, give evidence that after-ripening turns in the air-dry seed to a new developmental program that modulates, at the RNA level, components of translational control, signaling networks, transcriptional control and regulated proteolysis.
Asunto(s)
Perfilación de la Expresión Génica/métodos , Nicotiana/genética , Biosíntesis de Proteínas/genética , Semillas/genética , Transducción de Señal/genética , Northern Blotting , ADN Complementario/química , ADN Complementario/genética , Regulación del Desarrollo de la Expresión Génica/genética , Regulación de la Expresión Génica de las Plantas/genética , Germinación/genética , Datos de Secuencia Molecular , Técnicas de Amplificación de Ácido Nucleico/métodos , Reproducibilidad de los Resultados , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Semillas/crecimiento & desarrollo , Análisis de Secuencia de ADNRESUMEN
Mature seeds of the Cape Verde Islands (Cvi) ecotype of Arabidopsis thaliana (L.) Heynh. show a very marked dormancy. Dormant (D) seeds completely fail to germinate in conditions that are favourable for germination whereas non-dormant (ND) seeds germinate easily. Cvi seed dormancy is alleviated by after-ripening, stratification, and also by nitrate or fluridone treatment. Addition of gibberellins to D seeds does not suppress dormancy efficiently, suggesting that gibberellins are not directly involved in the breaking of dormancy. Dormancy expression of Cvi seeds is strongly dependent on temperature: D seeds do not germinate at warm temperatures (20-27 degrees C) but do so easily at a low temperature (13 degrees C) or when a fluridone treatment is given to D seeds sown at high temperature. To investigate the role of abscisic acid (ABA) in dormancy release and maintenance, we measured the ABA content in both ND and D seeds imbibed using various dormancy-breaking conditions. It was found that dry D seeds contained higher amounts of ABA than dry ND after-ripened seeds. During early imbibition in standard conditions, there was a decrease in ABA content in both seeds, the rate of which was slower in D seeds. Three days after sowing, the ABA content in D seeds increased specifically and then remained at a high level. When imbibed with fluridone, nitrate or stratified, the ABA content of D seeds decreased and reached a level very near to that of ND seeds. In contrast, gibberellic acid (GA3) treatment caused a transient increase in ABA content. When D seeds were sown at low optimal temperature their ABA content also decreased to the level observed in ND seeds. The present study indicates that Cvi D and ND seeds can be easily distinguished by their ability to synthesize ABA following imbibition. Treatments used here to break dormancy reduced the ABA level in imbibed D seeds to the level observed in ND seeds, with the exception of GA3 treatment, which was active in promoting germination only when ABA synthesis was inhibited.
Asunto(s)
Ácido Abscísico/metabolismo , Arabidopsis/metabolismo , África Occidental , Arabidopsis/efectos de los fármacos , Arabidopsis/crecimiento & desarrollo , Germinación , Giberelinas/farmacología , Modelos Biológicos , Nitratos/farmacología , Piridonas/farmacología , Semillas/efectos de los fármacos , Semillas/crecimiento & desarrollo , Semillas/metabolismo , TemperaturaRESUMEN
A recent proteomic analysis of germinating Arabidopsis thaliana seeds demonstrates the effectiveness of functional genomics for investigating the complexity of developmental regulatory networks, such as the development of the embryo into a young plant.