Estudio de la participación de genes claves de la biosíntesis de lípidos en el desarrollo de desórdenes fisiológicos en palta cv. Hass
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Fecha
2010
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Profesor/a Guía
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Idioma
es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
El almacenamiento refrigerado es ampliamente utilizado para extender la vida de
frutas y hortalizas después de la cosecha. La reducción de la temperatura disminuye el
metabolismo celular y retrasa la senescencia y maduración de los frutos. Los frutos
subtropicales, como la palta (Persea americana), son menos tolerantes a las bajas temperatura
que los frutos templados, Jo que resulta en el desarrollo de desórdenes fisiológicos. Por lo
tanto, el objetivo principal de este trabajo fue estudiar el mecanismo que conduce al desarrollo
de pardeamiento interno (PI) en palta Hass. PI fue estudiado teniendo en cuenta la época de
cosecha (cosecha temprana v/s tardía), temperatura de almacenamiento ( 5 o C v/s O o C), y la
inhibición del etileno (1-metilciclopropeno ). En general se observó una mayor incidencia de
PI en frutos cosechados tardíamente los cuales fueron almacenados a O o C. De este estudió se
relacionó la generación de PI a dos pasos enzimáticos relacionados con el metabolismo de
lípidos, es decir, las enzimas acetil CoA carboxilasa (ACCase) y estearoil ACP desaturasa.
Respecto a ACCase, dos subunidades se identificaron y caracterizaron: i) biotina carboxilasa
(BC) y ii) proteína transportadora de carboxil biotina (BCCP). Los transcritos de largo
completos de las dos subunidades mostraron dominios altamente conservados entre
secuencias pertenecientes a otras especies de plantas. Ambos genes mostraron un patrón de
expresión relacionadas con el desarrollo del PI, donde PamACCase BC y PamACCase BCCP
tuvieron una disminución en frutas que desarrollaron PI, correspondiente a paltas de una
cosecha tardía almacenadas a O o C. La expresión de PamSAD tuvo una respuesta diferente a
Jos genes ya mencionados la cual estuvo suprimida en frutos con síntomas de PI. En relación
con la inhibición de etileno, sólo PamACCase BCCP y PamSAD mostraron cambios en su
expresión en fruta tratada con 1-metilciclopropeno, lo que indicaría que el etileno podría
regular la expresión génica. Por lo tanto, los genes estudiados en este trabajo podrían ser parte
de un importante mecanismo para explicar el desarrollo diferencial de PI en palta Hass.
Refrigerated storage is widely used to extend the life offruit and vegetables after harvest. The reduction of temperature decreases the cellular metabolism and delay fruit senescence and ripening. Subtropical fruit such as avocado (Persea americana), are less tolerant to the reduction on temperature than temperate fruit, resulting in the development of physiological disorders. Therefore, the main objective ofthis work was to study the underlying mechanism leading to the development of interna! browning (lB) in Hass avocado. lB was studied considering harvest time (early vs. late harvest), storage temperature (5°C vs. Ü0 C), and ethylene inhibition (1-methylcyclopropene). In general we observed a higher incidence ofiB in late harvested fruit and in the one stored under 0°C. From this study we could relate the generation ofiB toa two enzymatic steps related to lipid metabolism, i.e. the enzymes Acetyl CoA Carboxylase (ACCase) and Stearoyl ACP desaturase. Regarding ACCase, two subunits were identified and characterized: i) Biotin carboxylase (BC) and ii) Biotin carboxyl carrier protein(BCCP). Full length ofthe two subunits showed highly conserved domains among the sequences belonging to other plant species. Both genes showed an expression pattern related to the development ofiB, where PamACCase BC and PamACCase BCCP hada decrease in fruit with lB development, corresponding to avocados from a late harvest or stored under Ü°C. PamSAD expression had a different response to the genes already mentioned remaining suppressed in fruit with lB symptoms. Relative to ethylene inhibition, only PamACCase BCCP and PamSAD showed changes in their expression on fruit applied with 1-methylcyclopropene, which would indicate that ethylene could be regulating gene expression. Therefore, it seems that the genes studied in this work could be part of a major mechanism to explain the differential development ofiB on Hass avocado.
Refrigerated storage is widely used to extend the life offruit and vegetables after harvest. The reduction of temperature decreases the cellular metabolism and delay fruit senescence and ripening. Subtropical fruit such as avocado (Persea americana), are less tolerant to the reduction on temperature than temperate fruit, resulting in the development of physiological disorders. Therefore, the main objective ofthis work was to study the underlying mechanism leading to the development of interna! browning (lB) in Hass avocado. lB was studied considering harvest time (early vs. late harvest), storage temperature (5°C vs. Ü0 C), and ethylene inhibition (1-methylcyclopropene). In general we observed a higher incidence ofiB in late harvested fruit and in the one stored under 0°C. From this study we could relate the generation ofiB toa two enzymatic steps related to lipid metabolism, i.e. the enzymes Acetyl CoA Carboxylase (ACCase) and Stearoyl ACP desaturase. Regarding ACCase, two subunits were identified and characterized: i) Biotin carboxylase (BC) and ii) Biotin carboxyl carrier protein(BCCP). Full length ofthe two subunits showed highly conserved domains among the sequences belonging to other plant species. Both genes showed an expression pattern related to the development ofiB, where PamACCase BC and PamACCase BCCP hada decrease in fruit with lB development, corresponding to avocados from a late harvest or stored under Ü°C. PamSAD expression had a different response to the genes already mentioned remaining suppressed in fruit with lB symptoms. Relative to ethylene inhibition, only PamACCase BCCP and PamSAD showed changes in their expression on fruit applied with 1-methylcyclopropene, which would indicate that ethylene could be regulating gene expression. Therefore, it seems that the genes studied in this work could be part of a major mechanism to explain the differential development ofiB on Hass avocado.
Notas
Tesis (Magister en Biotecnología)
Palabras clave
Paltas - Almacenamiento, Paltas - Tecnología de Postcosecha, Pardeamiento Interno, ACCase BC, ACCase BCCP, SAD, 1-MCP