Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
J Plant Physiol. 2010 Jun 15;167(9):739-48. doi: 10.1016/j.jplph.2009.12.017. Epub 2010 Mar 1.
Recent data indicate the existence of at least three L-ascorbic acid (AsA) biosynthetic pathways in plant cells. Studying their occurrence in different plant organs and species may help to decipher the precise role(s) of AsA in plant cell physiology. In grape berries, AsA is of particular importance since it is known to be the precursor of tartaric acid, an essential component of the grape fruit. The concentration of AsA increases during development of the fruit to reach a maximum at the full ripe stage. We followed the expression of genes related to the various AsA biosynthetic pathways in this plant organ during fruit ontogeny by real time RT-PCR. Among them, a gene (VvGalUR), showing high homology to one from strawberry encoding a D-galacturonate reductase, was up-regulated during fruit ripening in parallel to the AsA content increase. Cloning of the corresponding full length cDNA showed highest similarity to the strawberry gene (FaGalUR). Moreover, VvGalUR gene expression in grape was also up-regulated by high light, a condition that increased AsA content in grape fruits, while none of the genes involved in the other possible biosynthetic pathways analyzed increased their transcript levels. The results are discussed in relation to the presence of several AsA biosynthetic pathways in grape fruits.
最近的数据表明，植物细胞中至少存在三种 L-抗坏血酸（AsA）的生物合成途径。研究它们在不同植物器官和物种中的存在情况，有助于解析 AsA 在植物细胞生理学中的精确作用。在葡萄浆果中，AsA 尤为重要，因为它是酒石酸的前体，而酒石酸是葡萄果实的重要成分。AsA 的浓度在果实发育过程中增加，在完全成熟阶段达到最大值。我们通过实时 RT-PCR 研究了这个植物器官在果实发生过程中与各种 AsA 生物合成途径相关的基因的表达。其中，一个基因（VvGalUR）与草莓中编码 D-半乳糖酸还原酶的基因具有高度同源性，在果实成熟过程中与 AsA 含量的增加呈平行上调。克隆相应的全长 cDNA 显示与草莓基因（FaGalUR）具有最高的相似性。此外，高光照也会上调葡萄中的 VvGalUR 基因表达，这种情况会增加葡萄果实中的 AsA 含量，而分析中涉及的其他可能生物合成途径的基因则没有增加其转录水平。结果与葡萄果实中存在多种 AsA 生物合成途径有关。
