Abstract: In the present study, the relationships between browning development and peroxidase (POD) gene expression in both core and flesh tissues of ‘Yali’ pears subjected to different cooling methods (rapid cooling or slow cooling), as well as those collected at different harvest dates (early, mid and late) were investigated using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). The results showed that the expression level of POD gene in pear core with slow cooling treatment was higher than that in rapidly cooled fruits at the same harvest time, indicating that POD gene was closely related to the browning of pear core. Additionally, the POD activity was the highest in mid harvested pears, followed by early harvested pears, and late harvested pears had the lowest POD activity, which suggested that maturity played an important role in ‘Yali’ pear browning. Also, the prokaryotic expression of POD gene (cDNA) in ‘Yali’ pears was investigated. A prokaryotic expression vector (pET-32a-pbPOD) for POD gene cDNA was established, and then induced successfully to be expressed in E. coli BL21(DE3). This study may provide a foundation for studying the mechanism of the browning of ‘Yali’ pears.

Key words: ‘Yali’ pear, browning, POD gene, prokaryotic expression, maturity, cooling rate