苹果果实质地软化过程中碳水化合物代谢及其关键酶基因表达的变化

Carbohydrate Metabolism and the Key Gene Expression in Apple During Fruit Texture Softening

以耐贮的富士苹果和不耐贮的金冠苹果果实为试材,研究果实发育和采后软化过程中糖和淀粉含量及其代谢相关酶活性变化,并分析其关键酶基因表达的变化。结果表明,淀粉含量和淀粉酶(AM)活性与果实硬度变化显著相关,且在富士和金冠果实间差异显著。随果实软化,金冠果实AM活性显著升高,而富士果实维持在较低水平,与金冠果实淀粉含量下降而富士淀粉含量低且稳定的变化规律相吻合;MdAM基因在金冠贮藏期的表达量迅速增加,显著高于富士。苹果果实蔗糖、果糖和葡萄糖含量均与成熟期果实硬度变化显著相关,贮藏期金冠果实蔗糖含量与硬度变化显著负相关,且SPS活性与硬度下降显著负相关,MdSPS基因大量表达,与此期SPS活性升高及蔗糖积累相一致。由此认为,淀粉降解参与了苹果果实软化,并与果实耐贮性关系密切,而且SPS在苹果果实蔗糖代谢和果实软化中起着重要作用,也与果实贮藏品质存在一定的相关性。

The fruits of‘Fuji'and‘Golden Delicious' apple were taken as materials to investigate the changes of the soluble sugars and starch contents and metabolism-related enzymes activities,and analyzed the expression level of the Md SPS and Md AM genes during fruit development and softening. The results indicated that the changes of starch content and amylase(AM)activity had significant correlation with firmness loss and show significant differences between‘Fuji'and‘Golden Delicious' fruits. AM activity significantly increased in‘Golden Delicious' with fruit softening,while it remained a relatively low activity in‘Fuji'fruit. These phenomena were consistent with the decrease of starch content in‘Golden Delicious' and the low content of starch in‘Fuji'fruit. In addition,the expression level of Md AM gene increased rapidly in‘Golden Delicious' fruit during storage,being compared to that in‘Fuji'fruit. We also found that the changes of sucrose,fructose and glucose content were significantly correlated with the loss of fruit firmness during maturity,which excepted that the changes of sucrose content in‘Golden Delicious' fruit showed significantly negative correlation with fruit softening during storage. Sucrose Phosphate Synthase(SPS)activity was significantly correlated with firmness in‘Golden Delicious',being accompanied with its higher expression level of Md SPS gene. Taken together,we concluded that starch degradation involved in fruit softening and had a close correlation with fruit storability,and SPS may play more important roles in sucrose metabolism during fruit softening in apple fruits and was also correlated with fruit storable characteristics.