不同酸度欧李果实有机酸积累特性与相关代谢酶活性分析

Analysis of Organic Acid Accumulation Characteristics and Organic Acid-Metabolizing Enzyme Activities of Chinese Dwarf Cherry(Cerasus humilis Bunge) Fruit

【目的】比较不同欧李品种果实中主要有机酸积累特性及相关酶活性。【方法】以6年生欧李品种‘农大3号’和‘农大4号’为材料,采用超高效液相色谱(UPLC)检测果实发育过程中总酸、苹果酸和柠檬酸含量,并测定苹果酸和柠檬酸相关酶活性。【结果】两个品种果实中苹果酸和柠檬酸主要在果实发育后期积累,品种间积累速率存在较大差异。果实发育前期NADP-苹果酸酶(NADP-ME)活性较高,NAD-苹果酸脱氢酶(NAD-MDH)活性和磷酸烯醇式丙酮酸羧化酶(PEPC)活性相对较低,使苹果酸仅少量积累;果实发育后期NADP-ME活性迅速下降,而NAD-MDH活性和PEPC活性开始上升,促进了苹果酸大量积累;果实成熟时NADP-ME活性突然升高,而NAD-MDH活性和PEPC活性开始下降,促使苹果酸降解。果实成熟前(花后18-19周)‘农大4号’NAD-MDH活性显著高于‘农大3号’、而NADP-ME活性低于‘农大3号’,导致成熟时前者苹果酸含量高于后者。花后17-19周‘农大3号’柠檬酸合成酶(CS)活性高于‘农大4号’,成熟时柠檬酸含量也高于后者。【结论】果实发育后期是苹果酸和柠檬酸积累的关键时期,苹果酸的积累差异主要由NAD-MDH活性和NADP-ME活性协同变化引起,柠檬酸积累差异主要受CS活性变化影响。

【Objective】 The accumulation characteristics of main organic acid and activities of acid-related enzymes between two cultivars of Chinese dwarf cherry with different acidities were compared. 【Method】 Using the method of ultra performance liquid chromatograph （UPLC）, the contents of total organic acids, malic acid and citric acid, as well as the activities of organic acid-metabolizing enzymes were analyzed during the fruit development of 6-year-old Chinese dwarf cherry ‘Nongda 3’ and ‘Nongda 4’. 【Result】Malic acid and citric acid of these two varieties accumulated mainly in the late period of fruit development, but their accumulation rates were quite different. Because of the high NADP-ME activity and the low NAD-MDH and PEPC activities, there was only a small amount of malic acid accumulation in the early period of fruit development. During the late period, NADP-ME activity decreased rapidly and NAD-MDH activity and PEPC activity began increasing, which promoted a massive accumulation of malic acid. The sudden increase of NADP-ME activity and the decline of NAD-MDH activity and PEPC activity caused the degradation of mailc acid at the ripening stage. Before the ripening stage（18-19 weeks after anthesis）, NAD-MDH activity of ‘Nongda 4’ was higher than the activity of ‘Nongda 3’ , while NADP-ME activity of ‘Nongda 4’ was lower. As a result, the content of malic acid of ‘Nongda 4’ was higher than the content of ‘Nongda 3’. The content of citric acid of ‘Nongda 3’ was higher （17-19 weeks after anthesis） because its CS activity was higher at the ripening stage.【Conclusion】The late period of fruit development is a critical period for the accumulation of malic acid and citric acid. The difference in malic acid accumulation is mainly caused by the coordination change of NAD-MDH activity and NADP-ME activity, while the difference in the accumulation of citric acid is mainly affected by the change of CS activity.