ABSTRACT
Fruits and vegetables contribute to human diet due to their nutritional value. Their production requires understanding of molecular mechanisms regulating fruit ripening. Fruit ripening is a developmental programme comprising biochemical and physiological changes. Several molecular events are activated such as pectin solubilisation and depolymerisation and a decrease in cell turgor pressure and water loss due to transpiration. Enzymes such as pectate lyase (PL), endo-polygalacturonases (endo-PG), pectin methylesterases (PMEs) either cleave or modify pectin constituents altering the length, width and degree of branching of pectin chains during ripening. Silencing of a tomato endo-PG is the first transgenic fruit with desirable softening traits in the market, while suppression of PL expression resulted in delay of fruit softening without affecting ripening. Recently, the role of arabinogalactan proteins (AGPs) extensins and prolyl-4-hydroxylases were investigated in relation to fruit ripening regulation. The presence of AGPs in the fruit pericarp tissue and the alterations in their spatio-temporal distribution during ripening stages indicate involvement in this developmental programme. The use of tools determining structural changes in cell wall pectins in relation to the production of transgenic lines with altered expression of cell wall–acting enzymes will provide significant information on mechanistic details on the role of cell wall glycoproteins.
