不同基因型猕猴桃果实抗坏血酸代谢基因差异变化

Variation of Ascorbic Acid Metabolism Genes in Different Kiwifruit Genotypes

抗坏血酸(AsA)即维生素C,是维持人类生长发育所必需的化合物,为了探明不同基因型猕猴桃果实AsA水平差异机制,本实验以‘红阳’和‘海沃德’猕猴桃果实为材料,测定其生长发育过程中As A和总抗坏血酸(T-AsA)含量,并分析了AsA代谢过程相关酶基因的表达水平。结果表明,两个品种AsA和T-AsA含量均呈现不断下降的变化趋势,且在整个生长过程中,‘红阳’果实AsA和T-AsA含量显著高于‘海沃德’果实。荧光定量PCR结果表明,果实AsA的积累是合成、循环和降解途径协同作用的结果,并证实了L-半乳糖途径是猕猴桃果实As A合成的主要途径,L-半乳糖途径的大多数基因均参与调控As A的合成,其中AdPMI、AdPMM、AdGME2和AdGalLDH基因在‘红阳’果实中具有较高的转录水平,推测这4个基因是猕猴桃种间AsA水平存在差异的重要因素。此外,我们还发现循环途径的AdMDHAR2、AdDHAR和AdGR基因以及降解途径的AdAPX基因,同样在两品种间有差异表达,因此AsA的循环再生也可能是引起‘红阳’果实高AsA水平的重要原因。

Ascorbic acid(AsA), also known as vitamin C, is a necessary compound to maintain human growth and development. In order to explore the mechanism of AsA levels difference in the genotypes of kiwifruit, ’Hongyang’ and ’Hayward’ kiwifruit were used to determine As A and T-AsA content and expression levels of enzyme genes related to AsA metabolism. Results showed that AsA and T-AsA content in the two varieties exhibited a declining trend, and maintained a high level in ’Hongyang’ fruit during the whole development. Real time quantitative PCR showed that AsA biosynthesis, recycling and degradation pathways jointly promote AsA accumulation and confirmed that L-galactose pathway was the main pathway of AsA biosynthesis in kiwifruit. Most of the L-galactose pathway genes are involved in the regulation of AsA biosynthesis, the high transcriptional levels of AdPMI, AdPMM, AdGME2 and AdGalLDH genes were observed in ’Hongyang’ fruit, it is speculated that these four genes are the important factors for the difference of AsA level among kiwifruit species. In addition, we found that AdMDHAR2, AdDHAR and AdGR genes in recycling pathway and AdAPX genes in degradation pathway were differentially expressed between the two varieties, which suggest that the oxidative regeneration of AsA maybe also an important element for the high level of AsA in ’Hongyang’ fruit.