Estudio de la composiciĆ³n y estructura de la pared celular de los frutos de Fragaria chiloensis y Fragaria x ananassa cv Camarosa
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2012
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es
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Universidad AndrƩs Bello
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Un aspecto importante en el estudio del desarrollo y la maduraciĆ³n de las frutas, se relaciona con cambios en su textura, que conducen al ablandamiento de la fruta. Desde un punto comercial, es muy importante, especialmente para los frutos que se sabe que tienen una corta vida de postcosecha, como es el caso de las frutillas. Aunque algunos artĆculos indican que la presiĆ³n hidrostĆ”tica y la deshidrataciĆ³n pueden tener una influencia sobre el fenĆ³meno de ablandamiento, otro aspecto importante a considerar es la degradaciĆ³n o cambios en la arquitectura de la pared celular, que desempeƱa un papel importante en la firmeza de la fruta. Dos especies de frutillas, Fragaria chiloensis (Fc) y Fragaria x ananassa cv. Camarosa (Fa), han mostrado diferencias en la firmeza de sus receptĆ”culos, en perĆodos similares de desarrollo. Propusimos un anĆ”lisis general de la composiciĆ³n y estructura de la pared celular de Fragaria chiloensis y Fragaria x ananassa cv Camarosa, en cinco etapas de desarrollo de los frutos de un fruto inmaduro (E1, E2 y E3) a uno maduro (E4) y sobre-maduros (E5). La pared celular se compone de proteĆnas, polĆmeros de hidratos de carbono, iones inorgĆ”nicos y compuestos fenĆ³licos, que demostraron ser modificados durante el desarrollo de diferentes frutos y su maduraciĆ³n. En la degradaciĆ³n de la pared celular de Fc y Fa, al igual que en otras frutas como tomate, melĆ³n, manzana, durazno y uvas, las pectinas se muestran como uno de los polisacĆ”ridos principales involucrados en el cambio en la textura durante la maduraciĆ³n de la fruta. Donde la solubilizaciĆ³n de las pectinas serĆa el proceso que mas contribuirĆa al ablandamiento de la pulpa, sin descartar la participaciĆ³n de las hemicelulosas en el proceso de desmontaje de la pared celular. Los resultados indican que ramnogalacturonan I (RGI) es el polisacĆ”rido que mayormente mostrĆ³ cambios durante el desarrollo y la maduraciĆ³n de Fc y Fa. AdemĆ”s, se observaron diferencias significativas en el importe de la galactosa, entre ambas especies de frutillas, asĆ como una mayor actividad de galactosidasa, lo que puede indicar diferencias en los polĆmeros pĆ©cticos como galactanos, los cuales correlacionan con las diferencias de firmeza entre Fc y Fa. Resultados de la inmunofluorescencia nos muestran in situ la distribuciĆ³n espacial de epĆtopes de la pared celular, que coincide con los datos de contenido de azĆŗcares obtenidos anteriormente. Por otra parte, experimentos de proteĆ³mica muestran diferencias en el contenido de proteĆnas presentes en ambas especies, en diferentes etapas de desarrollo, donde 276 proteĆnas fueron diferencialmente acumuladas. Donde 56 de ellas fueron secuenciadas y muestran diferencias entre Fc y Fa, en proteĆnas asociadas a proteĆnas de almacenamiento, biosĆntesis de flavonoides, relacionadas a propiedades organolĆ©pticas, proteĆnas involucradas en maduraciĆ³n, metabolismo de carbohidratos, proteĆnas de estrĆ©s y de sĆntesis de metionina. Sin embargo, no se encontraron secuencias de proteĆnas de pared celular que expliquen las diferencias en la firmeza entre Fc y Fa, aunque la proporciĆ³n de proteĆnas secuenciadas refleja solo cerca del 20% del las proteĆnas diferencialmente acumuladas, restando aĆŗn proteĆnas que pudieran identificarse.
An important aspect in the study of development and maturation of fruits is related to changes in texture, leading to softening of the fruit. From a commercial point, it is very important, especially for fruits that are known to have a short postharvest life, as is the case of strawberries. Although some articles indicate that the hydrostatic pressure and dehydration can have an influence on the phenomenon of softening, another important aspect to consider is the degradation or changes in cell wall architecture, which plays an important role in fruit firmness. Two species of strawberry, Fragaria chiloensis (Fc) and Fragaria x ananassa cv. Camarosa (Fa), have shown differences in the strength of their receptacles, in similar periods of development. We proposed a general analysis of the composition and structure of the cell wall of Fragaria chiloensis and Fragaria x ananassa cv Camarosa, at five stages of fruit development from immature fruit (E1, E2 and E3) to a mature (E4) and overripe (E5). The cell wall is composed of protein, carbohydrate polymers, inorganic ions and phenolic compounds, which were shown to be modified during different fruit development and ripening. In the cell wall degradation of Fc and Fa, like in other fruits such as tomato, melon, apple, peach and grapes, pectins are shown as one of the major polysaccharides involved in the change in texture during fruit ripening. The solubilization of pectin would be the process that contributes the most to the softening of the pulp, without discarding the involvement of the hemicelluloses in the process of disassembly of the cell wall. The results indicate that ramnogalacturonan I (RGI) is the polysaccharide that mainly showed changes during development and maturation of Fc and Fa. Additionally, we observed significant differences in the amount of the cell wall monosaccharide galactose between both investigated species of strawberries, as well as increased galactosidase activity, which may indicate differences in pectic polymers as galactans, which correlate with differences in firmness between Fc and Fa. Immunofluorescence results show in situ the spatial distribution of cell wall epitopes, which coincides with the sugar content data previously obtained. Moreover, proteomics experiments show differences in the protein present in both species at different stages of development, where 276 proteins were differentially accumulated. Where 56 of them were sequenced and show differences between Fc and Fa, proteins associated with storage proteins, biosynthesis of flavonoids, related to organoleptic properties, proteins involved in maturation, carbohydrate metabolism, stress proteins and synthesis of methionine. However, we did not found protein sequences of cell wall to explain the differences in firmness between Fc and Fa, although the protein sequence reflects only about 20% of the differentially accumulated proteins, but remained proteins that could still be identified.
An important aspect in the study of development and maturation of fruits is related to changes in texture, leading to softening of the fruit. From a commercial point, it is very important, especially for fruits that are known to have a short postharvest life, as is the case of strawberries. Although some articles indicate that the hydrostatic pressure and dehydration can have an influence on the phenomenon of softening, another important aspect to consider is the degradation or changes in cell wall architecture, which plays an important role in fruit firmness. Two species of strawberry, Fragaria chiloensis (Fc) and Fragaria x ananassa cv. Camarosa (Fa), have shown differences in the strength of their receptacles, in similar periods of development. We proposed a general analysis of the composition and structure of the cell wall of Fragaria chiloensis and Fragaria x ananassa cv Camarosa, at five stages of fruit development from immature fruit (E1, E2 and E3) to a mature (E4) and overripe (E5). The cell wall is composed of protein, carbohydrate polymers, inorganic ions and phenolic compounds, which were shown to be modified during different fruit development and ripening. In the cell wall degradation of Fc and Fa, like in other fruits such as tomato, melon, apple, peach and grapes, pectins are shown as one of the major polysaccharides involved in the change in texture during fruit ripening. The solubilization of pectin would be the process that contributes the most to the softening of the pulp, without discarding the involvement of the hemicelluloses in the process of disassembly of the cell wall. The results indicate that ramnogalacturonan I (RGI) is the polysaccharide that mainly showed changes during development and maturation of Fc and Fa. Additionally, we observed significant differences in the amount of the cell wall monosaccharide galactose between both investigated species of strawberries, as well as increased galactosidase activity, which may indicate differences in pectic polymers as galactans, which correlate with differences in firmness between Fc and Fa. Immunofluorescence results show in situ the spatial distribution of cell wall epitopes, which coincides with the sugar content data previously obtained. Moreover, proteomics experiments show differences in the protein present in both species at different stages of development, where 276 proteins were differentially accumulated. Where 56 of them were sequenced and show differences between Fc and Fa, proteins associated with storage proteins, biosynthesis of flavonoids, related to organoleptic properties, proteins involved in maturation, carbohydrate metabolism, stress proteins and synthesis of methionine. However, we did not found protein sequences of cell wall to explain the differences in firmness between Fc and Fa, although the protein sequence reflects only about 20% of the differentially accumulated proteins, but remained proteins that could still be identified.
Notas
Tesis (Doctor en BiotecnologĆa)
Palabras clave
Frutos - Pared Celular, Frutillas