Low oxygen environment effect on the tomato cell wall composition during the fruit ripening process

Abstract

Abstract Background Oxygen concentration is a key characteristic of the fruit storage environment determining shelf life and fruit quality. The aim of the work was to identify cell wall components that are related to the response to low oxygen conditions in fruit and to determine the effects of such conditions on the ripening process. Tomato (Solanum lycopersicum) fruits at different stages of the ripening process were stored in an anoxic and hypoxic environment, at 0% and 5% oxygen concentrations, respectively. We used comprehensive and comparative methods: from microscopic immunolabelling and estimation of enzymatic activities to detailed molecular approaches. Changes in the composition of extensin, arabinogalactan proteins, rhamnogalacturonan-I, low methyl-esterified homogalacturonan, and high methyl-esterified homogalacturonan were analysed. Results The results indicate alterations in fruits stored in the low oxygen environment, i.e. changes in fruit morphology, protein content, distribution of low methyl-esterified homogalacturonan, secretion of callose, modified activities of β-1,3-glucanase, endo-β-1,4-glucanase, and guaiacol peroxidase (GPX), and numerous disruptions in the cell wall structure at the molecular level. Conclusions In-depth molecular analyses showed that low oxygen stress immediately affected the cell wall composition. This may be considered a way of cell wall remodelling as a response to unfavourable conditions. Taken together, our results confirm that the 5% oxygen concentration slows down the ripening process and 0% oxygen accelerates the changes taking place during ripening. Thus, the observed molecular reset occurring in tomato cell walls in hypoxic and anoxic conditions emerges to be a result of regulatory and protective mechanisms modulating ripening processes.