INVESTIGADORES
CIVELLO Pedro Marcos
artículos
Título:
Modification of expansin protein abundance in tomato fruit alters softening and cell wall polymer metabolism during ripening.
Autor/es:
DA BRUMMELL,; MH HARPSTER,; PEDRO MARCOS CIVELLO; BENNETT AB; P DUNSMUIR,
Revista:
PLANT CELL
Editorial:
American Society of Plant Physiologists
Referencias:
Año: 1999 vol. 11 p. 1 - 1
ISSN:
1040-4651
Resumen:
The role of the ripening-specific expansin Exp1 protein in fruit
softening and cell wall metabolism was investigated by suppression and
overexpression of Exp1 in transgenic tomato plants. Fruit in which Exp1
protein accumulation was suppressed to 3% that of wild-type levels were firmer
than controls throughout ripening. Suppression of Exp1 protein also substantially
inhibited polyuronide depolymerization late in ripening but did not prevent the
breakdown of structurally important hemicelluloses, a major contributor to
softening. In contrast, fruit overexpressing high levels of recombinant Exp1
protein were much softer than controls, even in mature green fruit before
ripening commenced. This softening was correlated with the precocious and
extensive depolymerization of structural hemicelluloses, whereas polyuronide
depolymerization was not altered. These data are consistent with there being at
least three components to fruit softening and textural changes. One component
is a relaxation of the wall directly mediated by Exp1, which indirectly limits
part of a second component due to polyuronide depolymerization late in
ripening, perhaps by controlling access of a pectinase to its substrate. The
third component is caused by depolymerization of hemicelluloses, which occurs independently
of or requires only very small amounts of Exp1 protein.