Browsing by Subject "Zellwandmodifizierende Proteine"

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Sortenspezifische Veränderung der Fruchtfleischfestigkeit bei Apfel während der Lagerung unter Berücksichtigung des Signalmoleküls Ethylen
(2019) Zimmermann, Telse; Wünsche, Jens Norbert
Ripening of apples is initialized by ethylene, a ripening hormone, and the start of ripening is marked by an increase of ethylene production. During ripening fruit firmness is one of the changing processes and it is one of the major quality parameters for consumer and trade. After harvest the decline of apple fruit firmness consist of three distinct phase, in which the first phase, where no significant firmness reduce is observed, is the main part. The length of the first phase is different between the cultivars, so rapid softening cultivars have a short and cultivars, which obtain firmness over long time, have a long first phase. Application of ethylene will shorten this phase depending on the ethylene sensivity of the cultivars. The decline of fruit firmness is affected by changes in the cell wall. The aim of this study is to investigate this cultivar specific firmness decline by measuring gene expression of cell wall modifying enzymes and the activity of the cell wall modifying enzyme β galactosidase (GAL), and to find out the reason for the ethylene sensivity of the cultivars by recording ethylene production, gene expression and activity of ethylene biosynthesis enzymes also gene expression of the ethylene receptors and ethylene signal transduction proteins. To reach that goals three cultivars with different firmness and ethylene production are used and stored up to 4 month in a cool storage with 10 °C. The used cultivars are ‘Pinova’, which maintain firmness, ‘Elstar’ and ‘Golden Delicious’, which soften rapidly. ‘Pinova’ and ‘Elstar’ have a low ethylene production compared to ‘Golden Delicious’. Additional the ripening process is influenced by an inhibiting action of 1 Methylcyclopropen (1 MCP) and a promoting effect of ethylene. The main results are that correlation between ethylene production and fruit firmness persist just in softening cultivars although there are no difference between ‘Elstar’ and ‘Pinova’ in gene expression of ethylene biosynthesis enzymes. Also there are no differences between them in gene expression of ethylene receptors and ethylene signal transduction proteins while ‘Elstar’ shows an ethylene sensivity in contrast to ‘Pinova’. By comparison of the literature it is hypothesized that the amount of the ethylene receptors ERS1 and ERS2 is related to fruit firmness and the ethylene receptor ETR2 could be the sensor of ethylene sensivity. Furthermore the results about the changes/shifting of the cell wall refer to a difference between the cultivars in the gene expression of MdPG, MdAF, MdXTH2 und MdXYL with higher values for ‘Elstar’, but neither the expected inhibition of 1 MCP nor the promotion of ethylene in this genes happened. The activity of GAL shows indeed a cultivar specific pattern but it doesn´t correlate to fruit firmness. Also for other cell wall modifying enzyme activity or cell wall content exist no reference for a relationship to fruit firmness. So it is hypothesized that the interlinkage of the single cell wall components causes the fruit firmness on the one hand and limits the substrate availability of the respective cell wall modifying enzyme on the other hand.