These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Modification of expansin protein abundance in tomato fruit alters softening and cell wall polymer metabolism during ripening.
    Author: Brummell DA, Harpster MH, Civello PM, Palys JM, Bennett AB, Dunsmuir P.
    Journal: Plant Cell; 1999 Nov; 11(11):2203-16. PubMed ID: 10559444.
    Abstract:
    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.
    [Abstract] [Full Text] [Related] [New Search]