单 位：
贵州省果树工程技术研究中心;贵州大学农学院
关键词：
李果实;有机酸;苹果酸;磷酸烯醇式丙酮酸羧化酶;NADP-苹果酸酶;NAD-苹果酸脱氢酶;高效液相色谱
摘 要：
【目的】明确‘蜂糖李’果实有机酸组成与含量特点,揭示其发育过程中有机酸含量的变化规律及其与苹果酸代谢相关酶的关系,阐明有机酸积累的关键时期和关键酶。【方法】以‘蜂糖李’及对照‘四月李’为材料,采用高效液相色谱法(high performance liquid chromatograph,HPLC)分析测试李果实发育过程中有机酸组分及含量,并测定苹果酸代谢相关酶的活性。【结果】利用高效液相色谱分析李果实中有机酸组分及含量,发现‘蜂糖李’果实成熟时总酸含量(ω,后同)为5.94 mg·g-1,包括苹果酸、酒石酸、柠檬酸、草酸、莽草酸和琥珀酸6种,其中以苹果酸含量最高(占总酸含量的88%),‘四月李’果实中有机酸组分与‘蜂糖李’一致,均属于苹果酸型。2个李品种果实中总酸含量的差异主要是由苹果酸含量的差异所致。通过分析李果实发育过程中有机酸含量的变化,发现‘蜂糖李’果实中苹果酸含量大量积累的关键时期在果实发育前期,整体呈先增加后降低的趋势,草酸、酒石酸含量逐渐降低,而柠檬酸含量逐渐升高。与‘四月李’相比,‘蜂糖李’果实中苹果酸、草酸、酒石酸及总酸含量的变化趋势与之一致,且苹果酸及总酸含量在整个过程中均显著低于‘四月李’,而柠檬酸含量的变化趋势与之相反。最后通过分析苹果酸含量与相关代谢酶活性之间的相关性,表明‘蜂糖李’果实中苹果酸在果实发育前期大量积累主要是该时期磷酸烯醇式丙酮酸羧化酶(PEPC)活性增强促进了苹果酸的大量合成以及NADP-苹果酸酶(NADP-ME)活性降低减少苹果酸的分解,与NAD-苹果酸脱氢酶(NAD-MDH)关系不大,而‘四月李’苹果酸积累的关键酶是NAD-MDH。在果实发育后期,‘蜂糖李’及‘四月李’NADP-ME活性迅速升高,前者PEPC活性减弱,后者NAD-MDH活性下降,使得2者果实中苹果酸的降解大于合成而呈降低趋势。【结论】‘蜂糖李’是以苹果酸为主要有机酸的低酸型李品种,其果实中苹果酸积累的关键时期为果实发育前期,苹果酸含量的变化由PEPC和NADP-ME协同调控,而对照‘四月李’由NAD-MDH和NADP-ME起主要的调控作用。
译 名：
Changes in organic acids content during‘Fengtang'plum(Prunus salicina) fruit development in relation to malic acid metabolism related enzymes
作 者：
WANG Xiaohong;CHEN Hong;DONG Xiaoqing;College of Agriculture, Guizhou University;Guizhou Fruits Engineering Technology Research Centre;
关键词：
Plum(Prunus salicina) fruit;;Organic acids;;Malic acid;;PEPC;;NADP-ME;;NAD-MDH;;HPLC
摘 要：
【Objective】In order to understand the mechanisms regulating acidity in plum fruit, the composition and contents of organic acids in‘Fengtang'plum(Prunus salicina‘Fengtang') fruit were determined, and the changes in organic acids content during the fruit development and their relationships with the activities of enzymes associated with malic acid metabolism were analyzed. The critical period and key enzymes of organic acid accumulation were elucidated.【Methods】‘Fengtang'and‘Siyue'fruits were used as experimental material. The composition and contents of organic acids in plum fruitsduring the development were analyzed by high performance liquid chromatography(HPLC) and the activities of enzymes related with malic acid metabolism were determined by spectrophotometer. The correlations between the changes in malic acid content and the activities of malic acid metabolism enzymes were analyzed in this study.【Results】The total acid content was 5.94 mg· g~(-1) at maturity in‘Fengtang',including 6 organic acids, malic acid, tartaric acid, citric acid, oxalic acid, shikimic acid and succinic acid. Among them, malic acid was the dominant acid accounting for 88% of the total acid content.‘Siyue'fruit had the same composition of organic acids. Both cultivars belong to the malic acid type. During the growth and development of plum, the content of malic acid increased first and decreased at the late phase. The malic acid content in‘Fengtang'reduced to a minimum when the fruit was ripe, and was always significantly lower than‘Siyue'. The content of oxalic acid and tartaric acid gradually decreased with the growth and development of fruit, and the amplitude was small at the ripening period,but the content of citric acid gradually increased. The changes in total acid content and malic acid content in the fruit of‘Siyue'were similar to those of‘Fengtang'. The difference in total acid content in the two cultivars was mainly due to the difference in malic acid content. The changes in malic acid content were closely related to the changes in NAD-malate dehydrogenase(NAD-MDH), NADP-malosterase(NADP-ME) and phosphoenolpyruvate carboxylase(PEPC) activities. The activity of NADMDH in‘Fengtang'and‘Siyue'had a significant difference. The activity of NAD-MDH in the‘Fengtang'fruit fluctuated within the range of 82.24~(-1)69.12 U· mg~(-1). NAD-MDH activity in‘Siyue'showed an M pattern and was higher than that in‘Fengtang'. There was a significant positive correlation between malic acid content and NAD-MDH activity in the two cultivars with a correlation coefficient of0.97** and 0.95**, respectively. The change pattern of the activity of NADP-ME in‘Fengtang'was similar to that‘Siyue', increasing during young fruit enlargement period and decreasing during maturation. However, the activity of NADP-ME in the fruit of‘Fengtang'was always significantly lower than that of‘Siyue'. The activity of NADP-ME was significantly negatively correlated with malic acid content with a correlation coefficient of-0.86--0.87, respectively. The change in PEPC activity in the fruit‘Fengtang'exhibited an M pattern. Except for the fruit ripening period, the enzyme activity was always significantly higher in‘Fengtang'. The activity of PEPC in‘Siyue'fruit changed smoothly during the whole fruit development period. There was a significant positive correlation between the activity of PEPC and the content of malic acid in‘Fengtang'and‘Siyue'with a coefficient of 0.75* and 0.73*,respectively. The early stage of fruit development was the critical period of malic acid accumulation in‘Fengtang', when enhanced activity of PEPC promoted the synthesis of malic acid and the decreased activity of NADP-ME reduced the decomposition of malic acid, while NAD-MDH had little effect.However the key enzyme for accumulation of malic acid in‘Siyue'was NAD-MDH. At the later stage of fruit development, the activity of NADP-ME increased rapidly in both cultivars, while the activity of PEPC in‘Fengtang'was weakened and the NAD-MDH in‘Siyue'activity decreased. As a result, the degradation of malic acid was greater than synthesis and the content of malic acid became lower in the both cultivars.【Conclusion】‘Fengtang'is a low-acid plum variety, in which malic acid is the main organic acid. The critical period of malic acid accumulation is the early stages of fruit development. The change in malic acid content is coordinated by PEPC and NADP-ME. However, in‘Siyue'malic acid content is mainly controlled by NAD-MDH and NADP-ME.
