RESUMEN
Raspberry fruits were harvested at five developmental stages, from green to red ripe, and the changes in cell wall composition, pectin and hemicellulose solubilization, and depolymerization were analyzed. Fruit softening at intermediate stages of ripening was associated with increased pectin solubilization, which occurred without depolymerization. Arabinose was found to be the most abundant noncellulosic neutral sugar in the cell wall and showed dramatic solubilization late in ripening. No changes in pectin molecular size were observed even at the 100% red stage. Subsequently, as fruit became fully ripe a dramatic depolymerization occurred. In contrast, the hemicellulosic fractions showed no significant changes in content or polymer size during ripening. The paper discusses the sequence of events leading to cell wall disassembly in raspberry fruit.
Asunto(s)
Pared Celular/ultraestructura , Frutas/ultraestructura , Rosaceae/ultraestructura , Pared Celular/química , Frutas/crecimiento & desarrollo , Pectinas/análisis , Pectinas/química , Polímeros/química , Polisacáridos/análisis , Polisacáridos/química , Solubilidad , Factores de TiempoRESUMEN
Large-scale, single pass sequencing and parallel gene expression analysis using DNA microarrays were employed for the comprehensive investigation of ripening in strawberry fruit. A total of 1701 cDNA clones (comprising 1100 strawberry ESTs and 601 unsequenced cDNAs) obtained from a strawberry (Fragariaxananassa) ripe fruit cDNA library were displayed on microarrays, and used for monitoring concurrent gene expression in receptacle and achene tissues. Analysis of expression ratios identified 66 out of the 259 (25%) achene-related clones and 80 out of 182 (44%) receptacle-related clones with more than a 4-fold difference in expression between the two tissue types. Half of the achene-associated genes putatively encode proteins with unknown function, and a large number of the remainder were proteins predicted to form part of the signal and regulation cascades related to achene maturation and acquisition of stress and desiccation tolerance. These included phosphatases, protein kinases, 14-3-3 proteins, transcription factors, and others. In the receptacle, key processes and novel genes that could be associated with ripening were identified. Genes putatively encoding proteins related to stress, the cell wall, DNA/RNA/protein, and primary metabolism were highly represented. Apart from providing a global observation on gene expression programmes and metabolic pathways in the developing strawberry, this study has made available a large database and unique information for gene discovery, promoter selection and markers for molecular breeding approaches.
Asunto(s)
Perfilación de la Expresión Génica/métodos , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Estructuras de las Plantas/genética , Rosaceae/genética , Ácido Abscísico/fisiología , Adaptación Fisiológica/genética , Transporte Biológico/genética , Pared Celular/genética , Pared Celular/metabolismo , Clonación Molecular , ADN Complementario/química , ADN Complementario/genética , Bases de Datos Factuales , Etilenos/metabolismo , Etiquetas de Secuencia Expresada , Ácidos Grasos/metabolismo , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Microscopía Electrónica de Rastreo , Estrés Oxidativo , Pigmentos Biológicos/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Estructuras de las Plantas/crecimiento & desarrollo , Estructuras de las Plantas/ultraestructura , ARN de Planta/genética , ARN de Planta/metabolismo , Rosaceae/crecimiento & desarrollo , Rosaceae/ultraestructura , Transducción de Señal/genéticaRESUMEN
Detergent extracts of microsomal fractions from suspension cultured cells of Rubus fruticosus (blackberry) were tested for their ability to synthesize in vitro sizable quantities of cellulose from UDP-glucose. Both Brij 58 and taurocholate were effective and yielded a substantial percentage of cellulose microfibrils together with (1-->3)-beta-d-glucan (callose). The taurocholate extracts, which did not require the addition of Mg(2+), were the most efficient, yielding roughly 20% of cellulose. This cellulose was characterized after callose removal by methylation analysis, electron microscopy, and electron and x-ray synchrotron diffractions; its resistance toward the acid Updegraff reagent was also evaluated. The cellulose microfibrils synthesized in vitro had the same diameter as the endogenous microfibrils isolated from primary cell walls. Both polymers diffracted as cellulose IV(I), a disorganized form of cellulose I. Besides these similarities, the in vitro microfibrils had a higher perfection and crystallinity as well as a better resistance toward the Updegraff reagent. These differences can be attributed to the mode of synthesis of the in vitro microfibrils that are able to grow independently in a neighbor-free environment, as opposed to the cellulose in the parent cell walls where new microfibrils have to interweave with the already laid polymers, with the result of a number of structural defects.