Expression of two endo-1,4-β-glucanase genes during fruit ripening and softening of two pear varieties

Abstract

Endo-1,4-β-glucanase (EG) is involved in the metabolism of plant cell wall, and plays important roles in the growth and development of plants. EG is closely associated with cell elongation, fruit ripening, and tissue abscission. Here, two EG genes were cloned from Pyrus bretschneideri Rehd. cv. Chili, and their expression patterns were analyzed in fruit of Pyrus bretschneideri Rehd. cv. Chili and fruit of Pyrus pyrifolia Rehd. cv. Whangkeumbae. The two pear varieties showed different softening behaviors, 'Chili' maintained a stable firmness during the storage time, while the firmness of 'Whangkeumbae' decreased during the storage. The functions of two EG genes were discussed in the ripening and softening processes. During the 0°C storage period of 'Chili' pears, PbEG3 and PbEG4 expression levels both showed a downward trend. The expression levels of both the genes were high during the early harvest period (0 days), and declined rapidly thereafter. Treatment with 1-methylcyclopropene (1-MCP) inhibited PbEG3 expression, but had no significant effect on PbEG4. During the 0°C storage period of 'Whangkeumbae' pears, the expression of PbEG3 first increased, peaked at the 60 th day of storage, declining gradually thereafter until 120 d of storage. In contrast, PbEG4 gene expression displayed decreasing trend at first and increased thereafter. The different expression patterns of the PbEG3 and PbEG4 genes in 'Chili' pears and 'Whangkeumbae' pears showed that PbEG3 might be involved in ripening and softening, and the expression of the two genes are different in different cultivars.