采后龙眼果肉自溶过程中PME基因的表达分析

Expression Analysis of Pectin Methylesterase Genes in Postharvest Longan Fruit during Aril Breakdown

采用RT-PCR和RACE-PCR相结合的方法,研究了果胶甲酯酶基因(PME)表达与采后龙眼(Dimocarpus longan Lour.)果肉自溶的关系。从龙眼果实中分离得到3个包含3′非翻译区的PME基因片段,分别命名为DlPME1、DlPME2和DlPME3,其推导的氨基酸序列与多种植物的PME蛋白有较高的同源性。采用半定量RT-PCR的方法分析了常温(22℃)和低温(4℃)贮藏下的龙眼果肉自溶过程中3个PME基因的表达特征,结果表明:常温贮藏下,果肉自溶过程中DlPME1的表达逐渐减弱,DlPME2和DlPME3的表达先增高后降低;低温贮藏下,果肉自溶过程中DlPME1和DlPME3的表达先增强后降低,而DlPME2的表达持续减弱。这些表明,龙眼果实PME基因在常温和低温下的果肉自溶中可能具有不同的响应机制,常温下可能与DlPME2和DlPME3的表达有关,而低温下可能与DlPME1和DlPME3的表达有关。

The relationship between pectin pethylesterase （PME） genes expression and aril breakdown of longan （Dimocarpus longan Lour.）fruit was studied by using RT PCR and RACE PCR methods. Three PME cDNA fragments containing 3＇UTR （untranslate region）, named as DIPME1, DIPME2 and DIPME3, respectively, were cloned from longan fruits. The deduced amino acid sequences of the three DlPMEs genes shared high homology with those of other plants. Moreover, their expression profiles were studied by using semiquantitative RT PCR during aril breakdown of 10ngan fruits. When stored at room temperature, the expression of DIPME1 gradually weakened during aril breakdown of longan fruits, while DIPME3 and DIPME2 transcripts increased progressively and then decreased. However, accumulations of DIPME1 and DlPME3 transcripts enhanced firstly, then decreased stored at low temperature （4℃）, and DIPME2 transcript continuously decreased. These suggested that the expression patterns of DIPMEs were different during aril breakdown of longan fruits, DIPME2 and DlPME3 might be involved in the aril breakdown of longan fruits stored at room temperature, while DIPME1 and DIPME3 did at low temperature.