RESUMEN

All living organisms rely on nutrients to sustain cell metabolism and energy production, which in turn need to be adjusted based on available resources. The evolutionarily conserved target of rapamycin (TOR) protein kinase is a central regulatory hub that connects environmental information about the quantity and quality of nutrients to developmental and metabolic processes in order to maintain cellular homeostasis. TOR is activated by both nitrogen and carbon metabolites and promotes energy-consuming processes such as cell division, mRNA translation, and anabolism in times of abundance while repressing nutrient remobilization through autophagy. In animals and yeasts, TOR acts antagonistically to the starvation-induced AMP-activated kinase (AMPK)/sucrose nonfermenting 1 (Snf1) kinase, called Snf1-related kinase 1 (SnRK1) in plants. This review summarizes the immense knowledge on the relationship between TOR signaling and nutrients in nonphotosynthetic organisms and presents recent findings in plants that illuminate the crucial role of this pathway in conveying nutrient-derived signals and regulating many aspects of metabolism and growth.

Asunto(s)

Carbono/metabolismo , Nitrógeno/metabolismo , Plantas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Autofagia , Desarrollo de la Planta , Transducción de Señal

RESUMEN

The Target of Rapamycin (TOR) kinase regulates essential processes in plant growth and development by modulation of metabolism and translation in response to environmental signals. In this study, we show that abscisic acid (ABA) metabolism is also regulated by the TOR kinase. Indeed ABA hormone level strongly decreases in Lst8-1 and Raptor3g mutant lines as well as in wild-type (WT) Arabidopsis plants treated with AZD-8055, a TOR inhibitor. However the growth and germination of these lines are more sensitive to exogenous ABA. The diminished ABA hormone accumulation is correlated with lower transcript levels of ZEP, NCED3 and AAO3 biosynthetic enzymes, and higher transcript amount of the CYP707A2 gene encoding a key-enzyme in abscisic acid catabolism. These results suggest that the TOR signaling pathway is implicated in the regulation of ABA accumulation in Arabidopsis.

Asunto(s)

Ácido Abscísico/biosíntesis , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Genes de Plantas , Mutación , Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/antagonistas & inhibidores , Proteínas de Arabidopsis/fisiología , Fosfatidilinositol 3-Quinasas , Inhibidores de las Quinasa Fosfoinosítidos-3 , Transducción de Señal

RESUMEN

Although the eukaryotic TOR (target of rapamycin) kinase signalling pathway has emerged as a key player for integrating nutrient-, energy- and stress-related cues with growth and metabolic outputs, relatively little is known of how this ancient regulatory mechanism has been adapted in higher plants. Drawing comparisons with the substantial knowledge base around TOR kinase signalling in fungal and animal systems, functional aspects of this pathway in plants are reviewed. Both conserved and divergent elements are discussed in relation to unique aspects associated with an autotrophic mode of nutrition and adaptive strategies for multicellular development exhibited by plants.

Asunto(s)

Células Vegetales/enzimología , Plantas/enzimología , Transducción de Señal/fisiología , Serina-Treonina Quinasas TOR/metabolismo , Animales , Ciclo Celular/fisiología , Metabolismo Energético/fisiología , Células Vegetales/química , Plantas/química , Serina-Treonina Quinasas TOR/química

RESUMEN

Recent work on hormone mediated regulation of the SAM is reviewed, emphasizing how combinations of genetic, molecular and modelling approaches have refined models based on classic experimental and physiological work. Special emphasis is given to newly described mechanisms that modulate the responsiveness of specific tissues to hormones and their potential to direct position dependent determination processes.

Asunto(s)

Meristema/fisiología , Reguladores del Crecimiento de las Plantas/fisiología , Fenómenos Fisiológicos de las Plantas , Brotes de la Planta/fisiología , División Celular , Citocininas/fisiología , Giberelinas/fisiología , Homeostasis , Ácidos Indolacéticos/metabolismo , Desarrollo de la Planta , Brotes de la Planta/citología , Brotes de la Planta/crecimiento & desarrollo , Sistemas de Mensajero Secundario/fisiología , Transducción de Señal

RESUMEN

Chrysin, a passion flower extract, may be beneficial because of its potential to attenuate surgical suppression of natural killer (NK) cell activity. We divided 37 male Sprague-Dawley rats into 3 treatment groups: (1) rats undergoing abdominal surgery and administered isoflurane and a 5% solution of dimethyl sulfoxide in saline (vehicle), (2) rats undergoing abdominal surgery and administered isoflurane and chrysin solubilized in 5% dimethyl sulfoxide, and (3) rats not undergoing surgery but administered isoflurane and chrysin. Natural killer cell activity was measured before and 24 hours after the experiment. Analysis of covariance, with preoperative NK cell activity as the covariate, was used to compare differences in NK cell activity among groups. The Scheffe procedure was used to make post hoc comparisons. Analysis revealed a significant difference (P = .006) such that group 2 had significantly less NK cell suppression compared with groups 1 and 3. These findings suggest that chrysin may attenuate surgical suppression of NK cell activity, thereby minimizing metastatic spread of cancer.

Asunto(s)

Flavonoides , Agonistas del GABA , Tolerancia Inmunológica , Células Asesinas Naturales , Laparotomía/efectos adversos , Fitoterapia/métodos , Administración por Inhalación , Análisis de Varianza , Anestésicos por Inhalación/administración & dosificación , Animales , Dimetilsulfóxido/administración & dosificación , Modelos Animales de Enfermedad , Evaluación Preclínica de Medicamentos , Flavonoides/administración & dosificación , Flavonoides/inmunología , Flavonoides/farmacología , Agonistas del GABA/administración & dosificación , Agonistas del GABA/inmunología , Agonistas del GABA/farmacología , Tolerancia Inmunológica/efectos de los fármacos , Tolerancia Inmunológica/fisiología , Isoflurano/administración & dosificación , Células Asesinas Naturales/efectos de los fármacos , Células Asesinas Naturales/inmunología , Recuento de Linfocitos , Masculino , Passiflora , Extractos Vegetales/administración & dosificación , Extractos Vegetales/inmunología , Extractos Vegetales/farmacología , Ratas , Ratas Sprague-Dawley , Solventes/administración & dosificación , Factores de Tiempo

Asunto(s)

Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Tipificación del Cuerpo , Ácidos Indolacéticos/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Transporte Biológico , Simulación por Computador , Raíces de Plantas/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo

RESUMEN

The essential nature of meristematic tissues is addressed with reference to conceptual frameworks that have been developed to explain the behaviour of animal stem cells. Comparisons are made between different types of plant meristems with the objective of highlighting common themes that might illuminate underlying mechanisms. A more in depth comparison of the root and shoot apical meristems is made which suggests a common mechanism for maintaining stem cells. The relevance of organogenesis to stem cell maintenance is discussed, along with the nature of underlying mechanisms which help ensure that stem cell production is balanced with the depletion of cells through differentiation. Mechanisms that integrate stem cell behaviour in the whole plant are considered, with a focus on the roles of auxin and cytokinin. The review concludes with a brief discussion of epigenetic mechanisms that act to stabilise and maintain stem cell populations.

Asunto(s)

Meristema/metabolismo , Transducción de Señal/fisiología , Células Madre/metabolismo , Diferenciación Celular , Epigénesis Genética , Regulación de la Expresión Génica de las Plantas , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/fisiología , Meristema/citología , Modelos Biológicos , Reguladores del Crecimiento de las Plantas/fisiología , Proteínas de Plantas/genética , Proteínas de Plantas/fisiología , Células Madre/citología , Factores de Transcripción/genética , Factores de Transcripción/fisiología

RESUMEN

In higher plants, leaves initiate in constant spatial and temporal patterns. Although the pattern of leaf initiation is a key element of plant shoot architecture, little is known about how the time interval between initiation events, termed plastochron, is regulated. Here, we present a detailed analysis of plastochron2 (pla2), a rice (Oryza sativa) mutant that exhibits shortened plastochron and precocious maturation of leaves during the vegetative phase and ectopic shoot formation during the reproductive phase. The corresponding PLA2 gene is revealed to be an orthologue of terminal ear1, a maize (Zea mays) gene that encodes a MEI2-like RNA binding protein. PLA2 is expressed predominantly in young leaf primordia. We show that PLA2 normally acts to retard the rate of leaf maturation but does so independently of PLA1, which encodes a member of the P450 family. Based on these analyses, we propose a model in which plastochron is determined by signals from immature leaves that act non-cell-autonomously in the shoot apical meristem to inhibit the initiation of new leaves.

Asunto(s)

Oryza/crecimiento & desarrollo , Proteínas de Plantas/fisiología , Proteínas de Unión al ARN/fisiología , Secuencia de Aminoácidos , Clonación Molecular , Genes de Plantas , Meristema/metabolismo , Modelos Biológicos , Datos de Secuencia Molecular , Mutación , Oryza/anatomía & histología , Oryza/metabolismo , Fenotipo , Filogenia , Hojas de la Planta/anatomía & histología , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Tallos de la Planta/anatomía & histología , Tallos de la Planta/crecimiento & desarrollo , Tallos de la Planta/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Reproducción , Homología de Secuencia de Aminoácido

RESUMEN

Animal models of osteomyelitis traditionally have been characterized by inherent weaknesses related to animal size, differences in clinical findings compared with humans, aggressive behavior, high complication rate, and high cost. In this experiment, a model of tibial osteomyelitis was established in 28 goats with a very low complication rate and a consistent clinical, radiographic, and histologic disease course. The infecting Staphylococcus aureus organism was isolated in all but five of 28 animals (82%), in which there was no growth of bacteria at 24 and 72 hours. All five of these specimens had histologic evidence of osteomyelitis. Twenty-seven of the 28 animals (96%) had radiographic and histologic evidence of osteomyelitis. Clinical progression of the disease was observed by draining wounds, a postoperative limp that subsided in all goats, and varied periods of anorexia despite an average increase in body weight. There were no complications or mortalities related to the establishment of the animal model. This large animal model will provide a practical method of studying osteomyelitis and comparing treatment protocols.

Asunto(s)

Modelos Animales de Enfermedad , Cabras , Osteomielitis/patología , Infecciones Estafilocócicas/patología , Staphylococcus aureus/patogenicidad , Animales , Temperatura Corporal , Enfermedad Crónica , Femenino , Masculino , Osteomielitis/diagnóstico por imagen , Osteomielitis/microbiología , Radiografía , Infecciones Estafilocócicas/complicaciones , Infecciones Estafilocócicas/diagnóstico por imagen , Tibia/microbiología , Tibia/patología

RESUMEN

BACKGROUND: Flowering plant development is wholly reliant on growth from meristems, which contain totipotent cells that give rise to all post-embryonic organs in the plant. Plants are uniquely able to alter their development throughout their lifespan through the generation of new organs in response to external signals. To identify genes that regulate meristem-based growth, we considered homologues of Raptor proteins, which regulate cell growth in response to nutrients in yeast and metazoans as part of a signaling complex with the target of rapamycin (TOR) kinase. RESULTS: We identified AtRaptor1A and AtRaptor1B, two loci predicted to encode Raptor proteins in Arabidopsis. Disruption of AtRaptor1B yields plants with a wide range of developmental defects: roots are thick and grow slowly, leaf initiation and bolting are delayed and the shoot inflorescence shows reduced apical dominance. AtRaptor1A AtRaptor1B double mutants show normal embryonic development but are unable to maintain post-embryonic meristem-driven growth. AtRaptor transcripts accumulate in dividing and expanding cells and tissues. CONCLUSION: The data implicate the TOR signaling pathway, a major regulator of cell growth in yeast and metazoans, in the maintenance of growth from the shoot apical meristem in plants. These results provide insights into the ways in which TOR/Raptor signaling has been adapted to regulate plant growth and development, and indicate that in plants, as in other eukaryotes, there is some Raptor-independent TOR activity.

Asunto(s)

Proteínas de Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/genética , Isoformas de Proteínas/genética , Semillas/crecimiento & desarrollo , Semillas/genética , Arabidopsis/embriología , Proteínas de Ciclo Celular/genética , Mutación , Fosfatidilinositol 3-Quinasas/genética , Isoformas de Proteínas/fisiología , Semillas/embriología

RESUMEN

A predominantly plant-based family of genes encoding RNA binding proteins is defined by the presence of a highly conserved RNA binding motif first described in the mei2 gene of the fission yeast Schizosaccharomyces pombe. In silico analyses reveal nine mei2 -like genes in Arabidopsis thaliana and six in Oryza sativa. These predicted genes group into four distinct clades, based on overall sequence similarity and subfamily-specific sequence elements. In situ analysis show that Arabidopsis genes from one of these clades, TEL1 and TEL2, are specifically expressed in central zone of the shoot apical meristem and the quiescent center of the root apical meristem, suggesting that they may somehow function to maintain indeterminacy in these tissues. By contrast, members of two sister clades, AML1 through AML5, are expressed more broadly, a trend that was confirmed by Q-PCR analysis. mei2 -like transcripts with similar sequences showed similar expression patterns, suggesting functional redundancy within the four clades. Phenotypic analyses of lines that contain T-DNA insertions to individual mei2 -like genes reveal no obvious phenotypes, further suggesting redundant activities for these gene products.

Asunto(s)

Proteínas de Plantas/genética , Plantas/genética , Proteínas de Unión al ARN/genética , Empalme Alternativo , Secuencias de Aminoácidos/genética , Secuencia de Aminoácidos , Arabidopsis/embriología , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Secuencia Conservada/genética , ADN Complementario/química , ADN Complementario/genética , ADN de Plantas/química , ADN de Plantas/genética , Duplicación de Gen , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes de Plantas/genética , Variación Genética , Hibridación in Situ , Datos de Secuencia Molecular , Oryza/genética , Filogenia , Alineación de Secuencia , Análisis de Secuencia de ADN , Eliminación de Secuencia , Homología de Secuencia de Aminoácido

RESUMEN

The Schizosaccharomyces pombe Mei2 gene encodes an RNA recognition motif (RRM) protein that stimulates meiosis upon binding a specific non-coding RNA and subsequent accumulation in a "mei2-dot" in the nucleus. We present here the first systematic characterization of the family of proteins with characteristic Mei2-like amino acid sequences. Mei2-like proteins are an ancient eukaryotic protein family with three identifiable RRMs. The C-terminal RRM (RRM3) is unique to Mei2-like proteins and is the most highly conserved of the three RRMs. RRM3 also contains conserved sequence elements at its C-terminus not found in other RRM domains. Single copy Mei2-like genes are present in some fungi, in alveolates such as Paramecium and in the early branching eukaryote Entamoeba histolytica, while plants contain small families of Mei2-like genes. While the C-terminal RRM is highly conserved between plants and fungi, indicating conservation of molecular mechanisms, plant Mei2-like genes have changed biological context to regulate various aspects of developmental pattern formation.

Asunto(s)

Proteínas de Unión al ARN/genética , Proteínas de Schizosaccharomyces pombe/genética , Schizosaccharomyces/genética , Secuencia de Aminoácidos , Datos de Secuencia Molecular , Filogenia , Conformación Proteica , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/clasificación , Proteínas de Unión al ARN/fisiología , Proteínas de Schizosaccharomyces pombe/química , Proteínas de Schizosaccharomyces pombe/clasificación , Proteínas de Schizosaccharomyces pombe/fisiología , Homología de Secuencia de Aminoácido

RESUMEN

Although roots and shoots exhibit profound differences in their pattern of organogenesis, both apices share the capacity for indeterminate growth. Ongoing molecular and genetic analyses have revealed relatively little overlap between the genes that regulate organogenesis in the root and shoot apices. In the shoot, an ensemble of transcription factors lays the foundations for the leaf, in which indeterminacy is exchanged for more limited and polarized growth. Class-I KNOX genes are downregulated in the anlagen of the leaf early in its establishment, but are maintained in other regions of the shoot apex. This persistent expression of KNOX genes may serve to prevent the precocious determination of apical initial derivatives, and thus may allow the production of a large number of pluripotent cells from a relatively small number of stem cells. Greater commonality between roots and shoots is seen in mechanisms that underlie histogenesis and radial-patterning processes. Recent work suggests that undetermined stem cells in both the root and the shoot may be maintained by related mechanisms, which feature regulation of WUSCHEL-like organizer activities by feedback mechanisms that involve receptor-like kinases.

Asunto(s)

Meristema/citología , Meristema/fisiología , Regulación de la Expresión Génica de las Plantas/genética , Meristema/genética , Células Vegetales , Fenómenos Fisiológicos de las Plantas , Raíces de Plantas/citología , Raíces de Plantas/fisiología , Brotes de la Planta/citología , Brotes de la Planta/fisiología

RESUMEN

We have characterized the tomato (Lycopersicon esculentum Mill.) MADS box gene TM29 that shared a high amino acid sequence homology to the Arabidopsis SEP1, 2, and 3 (SEPALLATA1, 2, and 3) genes. TM29 showed similar expression profiles to SEP1, with accumulation of mRNA in the primordia of all four whorls of floral organs. In addition, TM29 mRNA was detected in inflorescence and vegetative meristems. To understand TM29 function, we produced transgenic tomato plants in which TM29 expression was down-regulated by either cosuppression or antisense techniques. These transgenic plants produced aberrant flowers with morphogenetic alterations in the organs of the inner three whorls. Petals and stamens were green rather than yellow, suggesting a partial conversion to a sepalloid identity. Stamens and ovaries were infertile, with the later developing into parthenocarpic fruit. Ectopic shoots with partially developed leaves and secondary flowers emerged from the fruit. These shoots resembled the primary transgenic flowers and continued to produce parthenocarpic fruit and additional ectopic shoots. Based on the temporal and spatial expression pattern and transgenic phenotypes, we propose that TM29 functions in floral organ development, fruit development, and maintenance of floral meristem identity in tomato.

Asunto(s)

Flores/crecimiento & desarrollo , Frutas/crecimiento & desarrollo , Proteínas de Homeodominio/genética , Solanum lycopersicum/crecimiento & desarrollo , Factores de Transcripción/genética , Secuencia de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulación hacia Abajo/genética , Flores/genética , Flores/ultraestructura , Frutas/genética , Frutas/ultraestructura , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas de Homeodominio/metabolismo , Solanum lycopersicum/genética , Solanum lycopersicum/ultraestructura , Proteínas de Dominio MADS/genética , Proteínas de Dominio MADS/metabolismo , Microscopía Electrónica de Rastreo , Datos de Secuencia Molecular , Familia de Multigenes/genética , Familia de Multigenes/fisiología , Fenotipo , Filogenia , Brotes de la Planta/genética , Brotes de la Planta/crecimiento & desarrollo , Brotes de la Planta/ultraestructura , Plantas Modificadas Genéticamente , Homología de Secuencia de Aminoácido , Factores de Transcripción/metabolismo