关键词: 木奈, 多酚氧化酶, 序列分析, 基因表达, 机械损伤

Abstract:   Polyphenol oxidase（PPO）has been regarded to be a critical enzyme in food technology. A new clone，named PsPPO2，was separated from cDNA library prepared from mature leaf of the Prunus salicina Lindl. var. cordata J. Y. Zhang et al. The deduced amino acid sequences shared 81% and 80% identity with the PPO from Hebei Yali pear and Fuji apple and shared 55% and 56% identity with the PPO gene from P. salicina leaf and fruit which previous isolated，respectively. RT-PCR showed that three PPO gene displayed unique patterns of expression in developmental specific manner in leaf and fruit tissue. In the process of leaf development，the PsPPO2 mRNA was detectable at all stages. In contrast，PsPPO1 and  PsPPO3 were expressed in young tissue. PsPPO2 and PsPPO3 expression are higher at the early stages of fruit development，then dramatically reduced as the fruit ripened. The PsPPO1 mRNA was detectable only at the browning fruit. Upon wounding，PsPPO1 was significantly induced in mature fruit，whereas the level of PsPPO2 and PsPPO3 were not affected by mechanical damage.

Key words: Prunus salicina, polyphenol oxidase, sequence analysis, gene expression, mechanical damage