不同砂梨果实中糖酸含量及代谢相关基因表达分析

The contents of sugars and acids, and the expression analysis of metabolism-associated genes in fruit of Pyrus pyrifolia

【目的】探讨糖酸含量对梨果实口感的影响,并找出砂梨果实发育过程中可能的糖酸代谢关键基因。【方法】使用高效液相色谱仪对4个不同类型的砂梨果实中主要糖酸含量进行分析,从梨基因组注释数据中检索并分离获得糖酸代谢密切相关的基因家族,并使用‘雪青’梨转录组数据对这些基因家族在果实不同发育时期进行表达分析。【结果】‘翠冠’梨中糖含量高,‘1-8-34’梨酸含量高。口感偏酸的‘新酥’梨和‘1-8-34’果实中的总糖含量与口感偏甜的‘金二十世纪’梨差异不显著。研究共分离获得糖酸代谢密切相关的10个基因家族共44成员,其中23个成员在不同果实发育时期发生表达。2个蔗糖磷酸合成酶(SPS1和SPS2)、1个磷酸烯醇式丙酮酸羧化酶(PEPC3)和2个苹果酸脱氢酶(MDH3和MDH4)在梨果实成熟期均表现出较高表达量。【结论】梨果实口感酸的主要原因是果肉中酸含量高。SPS1,SPS2,PEPC3,MDH3和MDH4在梨果实糖酸合成中起关键作用。

【Objective】The contents of sugars and acids in fruit are important characters to evaluate the quality of pear.Sugars and acids not only affect the taste of fruit,but also are the intermediate products in many metabolic pathways,which participate in the regulation of various metabolic activities in plants.The aim of this study is to evaluate the taste of pear fruit based on the contents of sugars and acids,and to find putative key regulatory genes in the metabolism of sugars and acids.【Methods】The contents of sugars and acids in the fruits of four Pyrus cultivars(‘Cuiguan’‘Gold Nijiss Qiki’‘Xinsu’and‘1-8-34’)were analyzed with high performance liquid chromatography.Genes related to sugar and acid metabolism were isolated from the genome data of‘Suli’pear,and their expressions were revealed by RNA-seq data of‘Xueqing’pear【.Results】The content of total sugars in‘Cuiguan’(107 g·L-1)was higher than that in the other cultivars,and the content of total acids in‘1-8-34’(5.88 g·L-1)was higher than that in the others.In this study,the content of sugars in‘Xinsu’,‘1-8-34’(acid tasting)and‘Gold Nijiss Qiki’(sweet tasting)was similar.The fruits of‘Xinsu’and‘1-8-34’were dominant by citric acid,and those of‘Cuiguan’and‘Gold Nijiss Qiki’by malic acid.Ten gene families including forty-four members related to the metabolism of sugars and acids were isolated from genome data,of which twenty-three members were detected to be expressed in fruit.Five members of sucrose phosphate synthase(SPS),four members of malic dehydrogenase(MDH),three members of malic enzyme(ME)and three members of phosphate dehydrogenase(PEPC)were analyzed,and the results showed that these 3 enzymes played important roles in sugar metabolism and acid metabolism during the development of pear fruit.The expression of SPS1 and SPS2 were up-regulated from the stage of fruit cell division to fruit mature period,but the expressions of SPS3,SPS4 and SPS5 were up-regulated during the cell division phase,and then down regulated.Three malic enzymes and two malic dehydrogenases(MDH3 and MDH4)showed higher expression in all stages.Among the three phosphoenolpyruvate carboxylases,the expression of PEPC3 was stable in the fruit development.While PEPC1 and PEPC2 were highly expressed at day 0 and day 7,and decreased thereafter,suggesting that these two members may not participate acid accumulation in maturation period.【Conclusion】Sugar and acid levels strongly affects fruit flavors.SPS1,SPS2,PEPC3,MDH3 and MDH4 play important roles in the metabolism of sugars and acids in the fruit of pear.