European, Chinese and Japanese pear fruits exhibit differential softening characteristics during ripening
European, Chinese and Japanese pear fruits exhibit differential softening characteristics during ripening
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DOI：
10.1093/jxb/erh250
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发表时间：
2004-10-01
影响因子：
6.9
通讯作者：
Kubo, Y
中科院分区：
文献类型：
--
作者：
Hiwasa, K;Nakano, R;Kubo, Y
以欧洲梨‘La France’、中国梨‘Yali’和日本梨‘Nijisseiki’为试材，研究了3种梨果实的软化特性。'法国'果实软化显着，并在成熟过程中开发了一个融化的质地，而'鸭梨'果实与丙烯处理和不处理，在成熟过程中果肉硬度和质地没有变化。未处理的'Nijisseiki'没有表现出可检测到的果肉硬度降低，而连续丙烯处理导致硬度逐渐降低，导致粉状质地。在'La France'中，细胞壁多糖的分析揭示了在果实软化过程中果胶和半纤维素的明显溶解和解聚。在‘二次成’中，丙烯处理导致果胶多糖在有限程度上的溶解和解聚，但半纤维素没有。鸭梨果实成熟过程中，半纤维素多糖发生解聚，而果胶多糖除水溶性组分外几乎没有变化。多聚半乳糖醛酸酶（PG）基因PC-PG 1和PC-PG 2在'La France'果实成熟过程中表达，而PC-PG 2在'Nijisseiki'中表达，而PC-PG 1和PC-PG 2在'Yali'中均不表达。在所有三种梨类型中，PC-XET 1的表达模式在成熟过程中都是组成型的。PG活性测定的还原糖含量增加，在所有三个梨成熟过程中。然而，粘度测量结果表明，内PG活性水平高，在'法国'，低，在'二精'，和检测不到的'鸭梨'水果。这些结果表明，在梨，细胞壁降解与成熟过程中的硬度下降和果胶和半纤维素的修改是必不可少的熔融质地的发展。此外，这些数据表明，不同的软化行为之间的梨果实成熟可能是由不同的内源PG活性和PG基因的不同表达。
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.