二氧化硫对葡萄采后有机酸含量及苹果酸代谢途径的调控作用

Regulation of Sulfur Dioxide on Organic Acids Content and Malate Metabolism Pathway of Grapes in Postharvest

摘要:

为探究二氧化硫（sulfur dioxide，SO2）对木纳格葡萄采后果实中有机酸含量及苹果酸代谢调控的影响。基于高效液相色谱（high performance liquid chromatography，HPLC）测定果实贮藏过程中酒石酸、L-苹果酸、L-抗坏血酸和柠檬酸含量的变化，采用转录组测序（RNA sequencing，RNA-Seq）分析SO2调控果实苹果酸代谢的主要途径。并通过测定苹果酸脱氢酶基因（malate dehydrogenase，MDH）、细胞质苹果酸脱氢酶基因（cytoplasmic malate dehydrogenase，cytMDH）、线粒体苹果酸脱氢酶基因（mitochondrial malate dehydrogenase，mtMDH）、乳酸脱氢酶基因（L-lactate dehydrogenase，LDH）、NADP-苹果酸酶基因（NADP-dependent malic enzyme，NADP-ME）、丙酮酸脱羧酶1基因（pyruvate decarboxylase1，PDC1）、丙酮酸脱羧酶2基因（pyruvate decarboxylase2，PDC2）和乙醇脱氢酶基因（alcohol dehydrogenase，ADH）的表达差异性，进一步验证转录组测序的结果。结果表明：贮藏第60 d，SO2处理组果实中酒石酸、L-抗坏血酸和柠檬酸分别比CK组高0.13 mg/g、0.34 mg/100 g、0.02 mg/g；L-苹果酸比CK组低0.64 mg/g。SO2可以维持木纳格葡萄果实中的酒石酸、L-抗坏血酸和柠檬酸含量，通过上调mtMDH、LDH、NADP-ME、PDC1和下调MDH、cytMDH、PDC2、ADH的相对表达量，促进果实中L-苹果酸含量的分解，保持果实的风味特征。本研究为研究SO2对鲜食葡萄采后果实有机酸代谢的调控作用提供理论依据。

Abstract:

The effects of sulfur dioxide (SO2) on the content of organic acids and the regulation of malate metabolism of ‘Munage’ grapes during postharvest storage were investigated. The changes in the contents of tartaric acid, L-malic acid, L-ascorbic acid and citric acid during fruit storage were measured by high performance liquid chromatography (HPLC), and RNA sequencing (RNA-Seq) was used to analyze the main pathways of SO2 to regulate malate metabolism. The differences in the expression of malate dehydrogenase (MDH), cytoplasmic malate dehydrogenase (cytMDH), mitochondrial malate dehydrogenase (mtMDH), lactate dehydrogenase (LDH), NADP-dependent malic enzyme (NADP-ME), pyruvate decarboxylase 1 (PDC1), pyruvate decarboxylase 2 (PDC2), and ethanol dehydrogenation enzyme dehydrogenase (ADH) genes were determined to verify further the results of RNA-Seq. The results showed that on the 60th day of storage, the contents of tartaric acid, L-ascorbic acid and citric acid in the fruits of the SO2-treatment group were 0.13 mg/g, 0.34 mg/100g, and 0.02 mg/g (which were all higher than those of the CK group), with the content of L-malic acid lower than that of the CK group by 0.64 mg/g. SO2 can maintain the contents of tartaric acid, L-malic acid, L-ascorbic acid and citric acid in ‘Munage’ grapes, through up-regulating the expressions of mtMDH, LDH, NADP-ME and PDC1, while down-regulating the expressions of MDH, cytMDH, PDC2 and ADH, to promote the decomposition of L-malic acid and preserve the flavor characteristics of the fruit. The study can provide a theoretical basis for the investigations on the regulatory role of SO2 in malate metabolism of grapes.