Identification and Expression Analysis of Polygalacturonase Family Members during Peach Fruit Softening.

Polygalacturonase (PG) is an important hydrolytic enzyme involved in pectin degradation during fruit softening. However, the roles of family members in fruit softening remain unclear. We identified 45 genes in the peach genome which are clustered into six subclasses. consist of four to nine exons and three to eight introns, and the exon/intron structure is basically conserved in all but subclass E. Only 16 genes were expressed in ripening fruit, and their expression profiles were analyzed during storage in two peach cultivars with different softening characteristics. Eight (, -, -, -, -, -, -, and -) in fast-softening "Qian Jian Bai" (QJB) fruit and three (, -, and -) in slow-softening "Qin Wang" (QW) fruit exhibited softening-associated patterns; which also were affected by ethylene treatment. Our results suggest that the different softening characters in QW and QJB fruit is related to the amount of members. While keeping relatively lower levels during QW fruit softening, the expression of six (, -, -, -, -, and -) rapidly induced by ethylene. , - and - may not be involved in softening of peach fruit.