TY  - SER
AU  - MCKERSIE, B.D.
AU  - THOMPSON, J.E.
TI  - In vitro simulation of cytoplasmic membrane senescence in cotyledons
AV  - 7972 
KW  - Phaseolus vulgaris
KW  - Enzymes
KW  - Cotyledons
KW  - Proteins
KW  - Germination
KW  - ATP
KW  - Timing
KW  - PLANT AGE
KW  - Plant tissues
KW  - Frijol
KW  - Beans
KW  - Journal articles
KW  - Artículos en revistas
KW  - Electronic documents
KW  - Documentos electrónicos
KW  - Journal article
N2  - La perdida de actividad microsomatica de NADH -citocromo c reductasa (EC 1.6.99.3) en los cotiledones, puede ser simulada en un sitema in vitro, en el cual se tratan con fracciones de citosol (sobrenadantes microsomaticos) microsomas aislados de tejidos de 2 dias de edad. Se sabe que la actividad de esta enzima se hace presente durante la germinacion de Phaseolus vulgaris y se piensa que refleja el avance de la senescencia de la membrana citoplasmatica. Al tratar microsomas durante 4 horas con fracciones de citosol provinientes de tejidos de 1 -2 dias, la inactivacion de la enzima es relativamente baja, pero aumenta en aproximadamente 68 por ciento al tratarlos con una fraccion equivalente proveniente de cotiledones de 3 dias de edad. Este modelo temporal es consistente con la disminucion observada in situ en la NADH-citocromo c reductasa detectable entre el segundo y el cuarto dia despues de la germinacion. Las fracciones de citosol preparadas a partir de tejidos mas viejos, incluyendo las recolectadas 9 dias despues de la germinacion en el momento en que los cotiledones comenzaban a desprenderse ocasionaron tambien una inactivacion extensiva in vitro. El grado de inactivacion del sistema in vitro mostro ser proporcional a la concentracion del citosol presente en la mezcla de incubacion, y tambien aumento con el tiempo para concentraciones dadas de citosol. Mas aun, la tasa de inactivacion in vitro fue aproximadamente 18 veces mayor que la que se presento in situ. Estos datos indican que la senescencia de la membrana citoplasmatica en los cotiledones es en parte regulada por uno o mas factores extrinsecos en el citosol, los cuales son retenidos in situ y liberados gradualmente durante la germinacion a medida que la senescencia se hace mas notoria. (RA-CIAT); The loss of microsomal NADH-cytochrome c reductase activity (EC 1.6.99.3) in cotyledons, known to accompany germination of Phaseolus vulgaris and thought to reflect the progress of cytoplasmis membrane senescence, can be simulated in an in vitro system in which isolated microsomes from 2-day-old tissue are treated with cytosol fractions (microsomal supernatants). Inactivation of the enzyme is comparatively low when the microsomes are treated for 4 h with cytosol fractions from 1- and 2-day-old tissue but increases to about 68 percent upon treatment with a corresponding fraction from 3-day-old cotyledons. This temporal pattern is consistent with the pronounced in situ decline in NADH- cytochrome c reductase detectable between the 2nd and 4th days of germination. Extensive in vitro inactivation was also effected by cytosol fractions prepared from older tissue, including that harvested after 9 days of germination, by which time the cotyledons were beginning to abscise. The degree of inactivation in the in vitro system proved to be proportional to the concentration of cytosol present in the incubation mixture and also increased with time at fixed cytosol concentrations. Moreover, the rate of in vitro inactivation was some 18-fold greater than that occurring in situ. The data were interpreted as indicating that cytoplasmic membrane senescence in cotyledons is, in part, mediated by one or more factors in the cytosol, extrinsic agects which are sequestered in situ and released gradually during germination as the pressures of senescence become more intense. (AS)
UR  - http://www.plantphysiol.org/cgi/reprint/56/4/518
ER  -