CaracterizaciĆ³n de los principales genes y metabolitos responsables del aumento de la acidez durante la maduraciĆ³n de la chirimoya (annona cherimola mill.)
Cargando...
Archivos
Fecha
2017
Autores
Tejerina Pardo, Luis Eugenio
Profesor/a GuĆa
Facultad/escuela
Idioma
es
TĆtulo de la revista
ISSN de la revista
TĆtulo del volumen
Editor
Universidad AndrƩs Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
La chirimoya (Annona cherimola Mill.) es un fruto climatĆ©rico, subtropical del gĆ©nero Annonaceae. Madura rĆ”pidamente entre 6 a 7 dĆas, tiempo en el cual el fruto se ablanda, el almidĆ³n se reduce a azĆŗcares mĆ”s simples y a diferencia de otros frutos la acidez aumenta para dar su sabor caracterĆstico.
Al igual que en otros frutos climatĆ©ricos, la producciĆ³n de los Ć”cidos orgĆ”nicos puede ser modulada por la acciĆ³n de la hormona etileno. En manzana y plĆ”tano se ha descrito que en la maduraciĆ³n es etileno-dependiente, mientras que en otros frutos, como en melĆ³n o tomate es etileno-independiente. Sin embargo, no se ha descrito ninguna relaciĆ³n entre la acciĆ³n del etileno, la acumulaciĆ³n de los Ć”cidos orgĆ”nicos en la chirimoya ni su regulaciĆ³n a nivel bioquĆmico ni molecular.
Por esto en esta Tesis, se analizĆ³ el comportamiento del metabolismo de los Ć”cidos orgĆ”nicos a nivel de transcritos, mediante el estudio de los cambios en los principales genes involucrados en su sĆntesis y degradaciĆ³n; a nivel proteico, con el estudio de la actividad en las enzimas claves de este metabolismo; y a nivel de metabolitos, mediante el estudio en la acumulaciĆ³n de los Ć”cidos orgĆ”nicos preponderantes (mĆ”lico y cĆtrico) durante la maduraciĆ³n de la variedad āConcha Lisaā, en respuesta a la inhibiciĆ³n de la acciĆ³n del etileno.
De los 9 genes relacionados a este metabolismo identificados en chirimoya en este trabajo, se observĆ³ un aumento en la expresiĆ³n de dos genes de sĆntesis, el que codifica para la malato deshidrogenasa dependiente de NAD (cyNAD-MDH) y el de la citrato sintasa (mCS), aumento que se correlacionarĆa con el incremento medido para cada Ć”cido, lo que nos indicarĆa que estos genes serĆan claves para explicar el aumento de la acidez durante la maduraciĆ³n de la chirimoya. Por otra parte, nuestros resultados indican que el etileno no estarĆa regulando la acidez titulable de la chirimoya, pero si la acumulaciĆ³n de los Ć”cidos mĆ”lico y cĆtrico. A su vez, el etileno estarĆa regulando los genes involucrados en la degradaciĆ³n del Ć”cido mĆ”lico y cĆtrico; NADP-ME, ACON, ATP-CS y PEPC, y el de sĆntesis de Ć”cido mĆ”lico gNAD-MDH, en los cuales se ve alterada su transcripciĆ³n durante la maduraciĆ³n, como tambiĆ©n en los genes principales relacionados a la sĆntesis de ambos Ć”cidos (cyNAD-MDH y mCS) al compararse los tratamientos con Etileno y 1-MCP.
Flavor is a major quality attribute in fruit formed by a mixture of volatile compounds, sugar and acid levels, typical of each fruit. Cherimoya (Annona cherimola Mill.) is a climacteric subtropical fruit which shows an acidity increase during ripening in contrast to most fruits. The hypothesis of this study is: āEthylene regulates organic acids metabolism in cherimoya, causing a transcript increase of genes encoding PEPC and NAD-MDH enzymes and a transcript decrease of NADP-ME and ACON, resulting in malic and citric acid accumulationā. For this, āConcha Lisaā variety cherimoyas were harvested and stored at 20Ā°C under ethylene, 1-MCP and control conditions. To characterize the ripening process, ethylene production, respiration rate, flesh firmness, soluble solids and titratable acidity were determined and HPLC analysis was conducted for malic and citric acid quantitation. Additionally, expression of genes encoding key enzymes involved in the synthesis and degradation of these metabolites was determined by real-time PCR and activity assays were performed to observe the activity of these enzymes. Results show that all the measured ripening parameters were delayed by 1-MCP and the ethylene regulates the accumulation of malic and citric acid but not the titratable acidity. In addition, we achieve nine genes related to the organic acid metabolism, cyNAD-MDH and mCS are related directly at the increase of malic and citric acid respectively, and ethylene is related in the regulation of this genes together at the genes related to the degradation of this acids, specifically NADP-ME, gNAD-MDH, ACON, ATP-CS and PEP-C. For this and literature reviews, we postulate that the accumulation of this organic acids is for storage and the synthesis in cherimola fruit.
Flavor is a major quality attribute in fruit formed by a mixture of volatile compounds, sugar and acid levels, typical of each fruit. Cherimoya (Annona cherimola Mill.) is a climacteric subtropical fruit which shows an acidity increase during ripening in contrast to most fruits. The hypothesis of this study is: āEthylene regulates organic acids metabolism in cherimoya, causing a transcript increase of genes encoding PEPC and NAD-MDH enzymes and a transcript decrease of NADP-ME and ACON, resulting in malic and citric acid accumulationā. For this, āConcha Lisaā variety cherimoyas were harvested and stored at 20Ā°C under ethylene, 1-MCP and control conditions. To characterize the ripening process, ethylene production, respiration rate, flesh firmness, soluble solids and titratable acidity were determined and HPLC analysis was conducted for malic and citric acid quantitation. Additionally, expression of genes encoding key enzymes involved in the synthesis and degradation of these metabolites was determined by real-time PCR and activity assays were performed to observe the activity of these enzymes. Results show that all the measured ripening parameters were delayed by 1-MCP and the ethylene regulates the accumulation of malic and citric acid but not the titratable acidity. In addition, we achieve nine genes related to the organic acid metabolism, cyNAD-MDH and mCS are related directly at the increase of malic and citric acid respectively, and ethylene is related in the regulation of this genes together at the genes related to the degradation of this acids, specifically NADP-ME, gNAD-MDH, ACON, ATP-CS and PEP-C. For this and literature reviews, we postulate that the accumulation of this organic acids is for storage and the synthesis in cherimola fruit.
Notas
Tesis (Magister en BiotecnologĆa)
Palabras clave
Chirimoyas, Calidad, MaduraciĆ³n