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.

Identification of European and Asian pears using EST-SSRs from Pyrus

“…Presence of PYC-007 in two locations in the pear genome was confirmed by mapping to linkage groups 9 and 17 of an M27 9 M116 apple population (Felicidad Fernández-Fernández, personal communication). The dinucleotide motif in PYC-001 was found in the 3 0 UTR of the polygalacturonase PC-PG2, one of three PG enzymes isolated from pear (Sekine et al 2006). The forward primer of PYC-001 was designed from the coding region that is usually conserved in the three pear genes.…”

Temporal and spatial expression of polygalacturonase gene family members reveals divergent regulation during fleshy fruit ripening and abscission in the monocot species oil palm

“…By contrast, PGs involved in fleshy fruit ripening, such as the tomato (TFPG), grape (VvPG1), apple (MdPG1), kiwi (CkPGA3) and pear (PcPG1) are also found within this clade [23,25-27,36,43,44,48,50,51]. In addition, only the melon PG (CmPG3) that has an expression profile related to ripening is found in the same subclade as the dry fruit dehiscence and abscission PGs, while the other two melon PGs (CmPG1 and CmPG2) associated with organ abscission and ripening are in the same subclade as EgPG4 [19].…”

β-Galactosidase and α-L-Arabinofuranosidase in Cell Wall Modification Related with Fruit Development and Softening

“…At least seven β-galactosidase genes are expressed during development and ripening of tomato fruit (Smith and Gross, 2000). A family of β-galactosidase was also reported in strawberry (Trainotti et al, 2001), Japanese pear (Tateishi et al, 2001b(Tateishi et al, , 2005b, avocado (Tateishi et al, 2002(Tateishi et al, , 2007, pear (Pyrus communis) (Mwaniki et al, 2005(Mwaniki et al, , 2007Sekine et al, 2006), and grape (Vitis vinifera) (Nunan et al, 2001). Some gene expressions overlapped.…”

“…Itai et al (2003) reported that family 51 α-L-arabinofuranosidase cloned from tomato fruit were expressed during fruit development and declined during ripening. Sekine et al (2006) reported that family 51 α-L-arabinofuranosidase cloned from pear fruit was expressed constitutively during fruit storage. From only expression analysis of family 51 α-L-arabinofuranosidase, it seems to contribute less to fruit softening, but its detailed role in physiological metabolism remains unclear.…”