Abstract：Abstract Kiwifruit (Actinidia chinensis) has high nutritional value and hygienical function, but softing will effect its commercial quality seriously during storage. Polygalacturonase (PG) is closely related to fruit softing which involve in degrading pectin. To explore the molecular regulation mechanism of fruit softening, the Mi liang 1 hao kiwifruit was used to study the differences of firmness, titratable acid, soluble solids and vitamin C that stored in room temperature, low temperature and treated by abscisic acid (ABA), the bioinformatics and expression patterns of polygalacturonase gene (AcPG) were also analyzed respectively. The results showed that the firmness and content of titratable acid were decreased during storage when soluble solids and vitamin C were increased reciprocally, and ABA might promote the process of kiwifruit softening, but low temperature would inhibit it. AcPG (GenBank No. KY 129958 ) was cloned with an open reading frame of 1 545 bp, which encoded 514 amino acids. Bioinformatics analysis showed that AcPG was unstable protein, had signal peptide, transmembrane structure, polygalacturonase conserved domain and phosphorylation site, and AcPG kept low homology with other species. According to qRT-PCR results, the expression of AcPG was downregulated when fruit softening during storage in room and low temperature, however, AcPG would response induction of ABA. These results indicated that cryopreservation was propitious to storage of kiwifruit, and AcPG involved in regulation of its softening. This study provides a theoretical basis for further research of fruit softing in kiwifruit by using molecular biology technology.
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