TY - JOUR
T1 - European, Chinese and Japanese pear fruits exhibit differential softening characteristics during ripening
AU - Hiwasa, Kyoko
AU - Nakano, Ryohei
AU - Hashimoto, Akiko
AU - Matsuzaki, Mikio
AU - Murayama, Hideki
AU - Inaba, Akitsugu
AU - Kubo, Yasutaka
N1 - Funding Information:
The authors thank Dr Francis M Mathooko (Jomo Kenyatta University of Agriculture and Technology, Kenya) and Dr Willis O Owino (Graduate School of Natural Science and Technology in Okayama University, Japan) for their helpful advice and critical reading of this manuscript. This work was supported in part by Grants-in-Aid for Scientific Research (grant no. 11660032 to YK and 14360023 to AI), JSPS Research Fellowships for Young Scientists (grant no. 6509 to KH) from the Japanese Society for the Promotion of Science, the Sasakawa Scientific Research Grant from the Japan Society (to KH), and Okayama University COE program ‘Establishment of Plant Health Science’ (to YK).
PY - 2004/10
Y1 - 2004/10
N2 - Softening characteristics were investigated in three types of pear fruit, namely, European pear 'La France', Chinese pear 'Yali', and Japanese pear 'Nijisseiki'. 'La France' fruit softened dramatically and developed a melting texture during ripening, while 'Yali' fruit with and without propylene treatment showed no change in flesh firmness and texture during ripening. Non-treated 'Nijisseiki' did not show a detectable decrease in flesh firmness, whereas continuous propylene treatment caused a gradual decrease in firmness resulting in a mealy texture. In 'La France', the analysis of cell wall polysaccharides revealed distinct solubilization and depolymerization of pectin and hemicellulose during fruit softening. In 'Nijisseiki', propylene treatment led to the solubilization and depolymerization of pectic polysaccharides to a limited extent, but not of hemicellulose. In 'Yali', hemicellulose polysaccharides were depolymerized during ripening, but there was hardly any change in pectic polysaccharides except in the water-soluble fraction. PC-PG1 and PC-PG2, two polygalacturonase (PG) genes, were expressed in 'La France' fruit during ripening, while only PC-PG2 was expressed in 'Nijisseiki' and neither PC-PG1 or PC-PG2 was expressed in 'Yali'. The expression pattern of PC-XET1 was constitutive during ripening in all three pear types. PG activity measured by the reducing sugar assay increased in all three pears during ripening. However, viscometric measurements showed that the levels of endo-PG activity were high in 'La France', low in 'Nijisseiki', and undetectable in 'Yali' fruits. These results suggest that, in pears, cell wall degradation is correlated with a decrease in firmness during ripening and the modification of both pectin and hemicellulose are essential for the development of a melting texture. Furthermore, the data suggest that different softening behaviours during ripening among the three pear fruits may be caused by different endo-PG activity and different expression of PG genes.
AB - Softening characteristics were investigated in three types of pear fruit, namely, European pear 'La France', Chinese pear 'Yali', and Japanese pear 'Nijisseiki'. 'La France' fruit softened dramatically and developed a melting texture during ripening, while 'Yali' fruit with and without propylene treatment showed no change in flesh firmness and texture during ripening. Non-treated 'Nijisseiki' did not show a detectable decrease in flesh firmness, whereas continuous propylene treatment caused a gradual decrease in firmness resulting in a mealy texture. In 'La France', the analysis of cell wall polysaccharides revealed distinct solubilization and depolymerization of pectin and hemicellulose during fruit softening. In 'Nijisseiki', propylene treatment led to the solubilization and depolymerization of pectic polysaccharides to a limited extent, but not of hemicellulose. In 'Yali', hemicellulose polysaccharides were depolymerized during ripening, but there was hardly any change in pectic polysaccharides except in the water-soluble fraction. PC-PG1 and PC-PG2, two polygalacturonase (PG) genes, were expressed in 'La France' fruit during ripening, while only PC-PG2 was expressed in 'Nijisseiki' and neither PC-PG1 or PC-PG2 was expressed in 'Yali'. The expression pattern of PC-XET1 was constitutive during ripening in all three pear types. PG activity measured by the reducing sugar assay increased in all three pears during ripening. However, viscometric measurements showed that the levels of endo-PG activity were high in 'La France', low in 'Nijisseiki', and undetectable in 'Yali' fruits. These results suggest that, in pears, cell wall degradation is correlated with a decrease in firmness during ripening and the modification of both pectin and hemicellulose are essential for the development of a melting texture. Furthermore, the data suggest that different softening behaviours during ripening among the three pear fruits may be caused by different endo-PG activity and different expression of PG genes.
KW - Cell wall modification
KW - Enzyme activity
KW - Fruit softening
KW - Gene expression
KW - Pear fruit
KW - Polygalacturonase
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U2 - 10.1093/jxb/erh250
DO - 10.1093/jxb/erh250
M3 - Article
C2 - 15333646
AN - SCOPUS:5144225281
VL - 55
SP - 2281
EP - 2290
JO - Journal of Experimental Botany
JF - Journal of Experimental Botany
SN - 0022-0957
IS - 406
ER -