外源γ-氨基丁酸对蛇龙珠葡萄果实糖酸代谢的影响

Effects of exogenous γ-aminobutyric acid spray on sugar and acid metabolism in Cabernet Gernischet grape berries

【目的】探讨外源γ-氨基丁酸(GABA)对葡萄果实糖酸积累及代谢的影响。【方法】以蛇龙珠葡萄为试材,于开花期、坐果期、膨大期和转色期分别用5 mmol·L^(-1)(T1)、10 mmol·L^(-1)(T2)、15 mmol·L^(-1)(T3)、20 mmol·L^(-1)(T4)的GABA溶液进行叶面喷施,以喷施蒸馏水作为对照(CK),研究其对葡萄果实发育过程中糖、酸组分含量以及相关代谢酶活性的影响。【结果】叶面喷施GABA溶液能显著提高葡萄果实可溶性糖含量,T2处理显著提高蔗糖、葡萄糖和果糖含量,蔗糖合成酶合成方向(Su Sy-s)、蔗糖磷酸合成酶(SPS)、酸性转化酶(AI)及中性转化酶(NI)活性均显著提高。GABA处理均能显著提高谷氨酸脱羧酶(GAD)活性和果实GABA含量。适宜浓度GABA处理能显著提高葡萄果实草酸、酒石酸、富马酸、柠檬酸、α-酮戊二酸、苹果酸含量,酸代谢相关酶活性均显著提高。GABA与NI、柠檬酸呈极显著正相关,与SPS、草酸、线粒体乌头酸酶(Mit-ACO)呈显著正相关。【结论】外源GABA通过提高蔗糖合成相关酶、转化酶活性和有机酸代谢酶活性,提高了葡萄果实葡萄糖、果糖、苹果酸、酒石酸等有机酸含量,进而改善了葡萄风味品质。

【Objective】Sugars and organic acids are metabolites that affect fruit quality,and together with volatile substances,determine the flavor quality of fruit.Appropriate sugar and acid content of wine grapes determine the flavor and quality of the wine.At present,the accumulation of sugar and organic acids in grapes is mainly improved through the regulation and cultivation measures of environmental factors such as temperature,light,water and soil.The main sugars are glucose and fructose,and the organic acids are mainly tartaric acid and malic acid,and also contain a small amount of succinic acid,oxalic acid and citric acid in grape berries.The synthesis and accumulation of sugars and organic acids are mainly regulated by sucrose metabolism-related enzymes and tricarboxylic acid cycle-related enzymes in berries.γ-aminobutyric acid(GABA)is a growth regulator widely present in plants,which can affect the accumulation of organic acids through the tricarboxylic acid cycle.In this study,the wine grape Cabernet Gernischet was used as the test material,and the grapevines were treated with different concentrations of GABA at each growth stage to determine the sugar and acid components,sugar and acid metabolism,and GABA synthesis-related enzyme activities.The purpose was to investigate the effect of GABA on the ripening process of grape berries,and provide a theoretical basis for improving quality and yield in agricultural production.【Methods】The foliar spray with 5 mmol·L^(-1)(T1), 10 mmol·L^(-1) (T2), 15 mmol·L^(-1) (T3), and 20 mmol·L^(-1) (T4) GABA solution were carried out atthe flowering stage, berry setting stage, expansion stage and veraison stage, and the distilled waterspray served as the control (CK). The contents of GABA, total soluble sugar, glucose, fructose, sucrose,oxalic acid, tartaric acid, shikimic acid, fumaropimaric acid, citrate acid, α-ketoglutaric acid, malate andglutamic acid as well as the activities of decarboxylase, sucrose metabolism-related enzymes and organicacid metabolism-related enzymes were determined.【Results】(1) The foliar spraying with GABA solutionsignificantly increased the soluble sugar content in grape berries. The appropriate concentrationof GABA treatment significantly increased the sucrose, glucose and fructose contents, and the activitiesof sucrose synthase synthesis (SuSy-s), sucrose phosphate synthase (SPS), acid invertase (AI), and neutralinvertase (NI) significantly increased in grape berries, among which, the contents of total solublesugar, sucrose, glucose and fructose with T2 treatment at the mature stage were 0.09, 0.63, 0.33 and0.48 times more than those with CK, respectively. (2) The different concentrations of GABA significantlyenhanced glutamate decarboxylase (GAD) activity and GABA content, among which, the GABA contentwith T3 treatment was 2.93 times more than that with CK at the maturity stage. (3) The appropriateconcentration of GABA treatment can significantly increase the contents of oxalic acid, tartaric acid, fumaropimaricacid, citrate acid, α-ketoglutaric acid and malate in grape berries. Among them, oxalic acid,tartaric acid, fumaropimaric acid, citrate acid, α-ketoglutaric acid and malate contents with T2 treatmentat the mature stage were 1.21, 1.08, 0.49, 2.26, 3.41 and 1.11 times more than that with CK, respectively.The activity of citrate acid synthase (CS), aconitic acid enzyme (ACO), isocitrate dehydrogenase(NAD-IDH), phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (NAD-MDH) andmalate enzyme (NADP-ME) significantly increased with T2 treatment. (4) The correlation analysis indicatedthat GABA had an extremely significant positive correlation with NI activity and citric acid contents,and had a positive correlation with SPS, oxalic acid and Mit-ACO. The sucrose content had avery significant positive correlation with soluble sugar, glucose, fructose contents and SuSy-s activity,and an extremely significant negative correlation with SuSy-c and NI activities. In addition, the glucoseand fructose contents were significantly and positively correlated with soluble sugar, sucrose contentsand SuSy-s activity, negatively correlated with SuSy-c and NI activities, and significantly and negativelycorrelated with AI activity. The tartaric acid content was extremely positively correlated with oxalicacid, fumaropimaric acid contents and ME activity, and significantly and positively correlated with citrateacid content and MDH activity. The malate content was extremely positively correlated with GADactivity, shikimic acid content, MDH and PEPC activities, significantly and positively correlated withMit-ACO activity, and significantly and negatively correlated with CS, IDH and ME activities.【Conclusion】Exogenous GABA promoted the sucrose accumulation by increasing the activities of SuSy-s andSPS and inhibiting the activity of SuSy-c, and promoted the accumulation of glucose and fructose by increasingthe activities of AI and NI. Exogenous spraying with GABA increased GABA biosynthesis byincreasing GAD activity, thereby increasing the rate of the TCA cycle, the activities of CS, ACO, NADIDH,PEPC and NAD-MDH, and NADP-ME activity were significantly improved, promoting the accumulationof oxalic acid, tartaric acid, shikimic acid, fumaropimaric acid, citrate acid, α-ketoglutaric acidand malate, and then improved the grape flavor quality, with the best efficacy of 10 mmol · L- 1 GABAtreatment.