Cloning of cDNAs encoding cell-wall hydrolases from pear (Pyrus communis) fruit and their involvement in fruit softening and development of melting texture

Abstract

'La France' pear (Pyrus communis L.) fruit stored at 1°C for 1 month (short-term storage) before transfer to 20°C softened and developed a melting texture during ripening, whereas fruit stored for 5 months (long-term storage) before transfer to 20°C softened but did not develop a melting texture. To clarify the mechanisms involved in fruit softening and textural changes, the cDNAs encoding cell-wall hydrolases were isolated by RT-PCR, and their expression and localization were investigated in 'La France' pears. Genes encoding three polygalacturonases (PG; EC 3.2.1.15), four pectin methylesterases (PME; EC 3.1.1.11), one α-arabinofuranosidase (ARF; EC 3.2.1.55), three β-galactosidases (GAL; EC 3.2.1.23), and two endo-1,4-β-d-glucanases (Cel; EC 3.2.1.4) were isolated. Among these 13 isolated genes, PcPG1 was the only gene for which the mRNA expression levels increased in both the short- and long-term stored fruits. This suggested that PcPG1 is involved in fruit softening rather than in the development of the melting texture. In contrast, the expression levels of PcPG3, PcPME1, PcPME2, PcPME3, PcGAL1, PcGAL2, and PcCel2 increased during ripening only in the short-term stored fruit. These genes might thus be involved in the development of the melting texture. Copyright © Physiologia Plantarum 2006.