两种砂梨果实香气成分分析及其相关基因PpAAT的克隆与表达分析

Analysis on Aromatic Constituents from Two P. pyrifalia Cultivars and the Cloning and Expression of the relevant PpAAT Gene

梨(Pyrus spp)是深受国内外消费者喜爱的水果,果实香气是果实品质的重要指标,也是吸引消费者和增强市场竞争力的主要因素之一。本文以砂梨品种‘二十世纪’及其芽变品种‘金二十世纪’为试材,研究了其果实不同发育时期香气成分的差异,克隆获得了梨果实香气成分合成相关的醇酰基转移酶基因(PpAAT),分析了该基因在梨果实不同发育时期及不同部位中的时空表达规律,结果表明:‘二十世纪’绿熟期、商熟期和完熟期果实的主要香气成分均为己醛,‘金二十世纪’绿熟期果实的主要香气成分同样是己醛,但商熟期果实中己酸乙酯的含量迅速增加,成为主要香气成分,完熟期时含量进一步增加,高含量的酯类化合物可能是‘金二十世纪’具有浓郁香气的主要原因;随着果实的成熟,PpAAT基因在‘金二十世纪’果皮中的表达量呈逐渐下降的趋势,绿熟期表达量最高,商熟期表达量开始降低,完熟期表达量非常弱;PpAAT在果肉中的表达量呈先升高后降低的趋势,在商熟期果肉中表达量最高,绿熟期果肉中次之,完熟期果肉中的表达量最低。总体上,PpAAT基因在商熟期的表达量高于绿熟期和完熟期,在果皮中的表达量高于果肉。

Pyrus spp is a very popular fruit in the world. Fruit aroma is an important index of fruit quality, it is also a main factor of attracting consumers and strengthening market competitiveness. In this paper, the volatile compounds of the fruit of P. pyrifalia‘Er shi shi ji’ and P. pyrifalia‘Jin er shi shi ji’ in different developmental stages (green stage, commercial stage and ripe stage) were studied by GC-MS. Then the full sequence of alcohol acyltransferase (PpAAT) gene which related to the biosynthesis of aromatic compounds in pear were cloned by RACE method, and the expression patterns of PpAAT gene in different developmental stages and different organs of pear fruits were analyzed by RT-PCR. The results showed that hexanal was the main aromatic compounds of‘Er shi shi ji’ in 3 different mature stages of fruit, so the green stage of‘Jin er shi shi ji’, but ethyl caproate became the main aromatic compounds of ‘Jin er shi shi ji’ in commercial stage, and its amount further increased in the full ripe stage. The high amounts of esters may be the main reason for the rich aroma of‘Jin er shi shi ji’;We also found that the expression level of PpAAT gene gradually declined along with fruit riping in pear pericarp of‘Jin er shi shi ji’, which reached the highest level in the green stage, and started to drop from the commercial stage, then dropped rapidly at ripe stage. The expression level of PpAAT gene in pear sarcocarp firstly increased from green stage to commercial stage, and then dropped rapidly in ripe stage. As a whole, the expression level of PpAAT gene in commercial stage was higher than which in the other two stages, and it was also higher in the pericarp than in the sarcocarp.