Ascorbate biosynthesis during early fruit development is the main reason for its accumulation in kiwi.
Ascorbate biosynthesis during early fruit development is the main reason for its accumulation in kiwi.
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果实发育早期抗坏血酸生物合成是其在猕猴桃体内积累的主要原因
DOI：
10.1371/journal.pone.0014281
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发表时间：
2010-12-09
期刊：
影响因子：
3.7
通讯作者：
Wang Y
中科院分区：
文献类型：
--
作者：
Li M;Ma F;Liang D;Li J;Wang Y
抗坏血酸(ASA)是一种独特的抗氧化剂，也是一种酶辅因子。虽然它在植物中有多种作用，但目前还不清楚它的积累是如何在表达水平上被控制的，特别是在库区组织中。猕猴桃(猕猴桃)因其高抗坏血酸含量而闻名。我们的目标是确定AsA是主要通过生物合成在果实中积累，还是因为它是从叶子进口的。我们系统地研究了猕猴桃(A.deliciosa cv.)中AsA的水平、生物合成能力以及参与AsA生物合成的基因的mRNA表达。秦美)。在果实发育过程中和不同组织类型之间也监测了循环利用和AsA定位。随着时间的推移，具有较高生物合成能力和较低再循环能力的ASA的数量在开花后30天(DAA)达到峰值，然后显著下降至60DAA，然后下降较慢。除L-半乳糖-1，4-内酯脱氢酶和L-半乳糖-1-磷酸磷酸酶外，其他关键基因的表达变化规律相似。而GPP与AsA积累速率有很好的相关性。这些基因在茎的韧皮部以及叶和果实的叶柄中都有表达。此外，果实叶柄的抗坏血酸含量较高，尽管这是大多数基因表达最低的部位。果实微管组织的AsA也较高。然而，外源AsA在这些叶柄上的应用并没有导致其转运到果实中，而且抗坏血酸在果实中的分布是细胞特有的，更多的积累发生在较大的细胞中。这些结果表明，猕猴桃果实发育早期AsA的生物合成是其在果实中积累的主要原因。我们还假设GPP是调节AsA生物合成的一个很好的候选者，而GDP-L-半乳糖-1-磷酸磷酸化酶不是。
Ascorbic acid (AsA) is a unique antioxidant as well as an enzyme cofactor. Although it has multiple roles in plants, it is unclear how its accumulation is controlled at the expression level, especially in sink tissues. Kiwifruit (Actinidia) is well-known for its high ascorbate content. Our objective was to determine whether AsA accumulates in the fruits primarily through biosynthesis or because it is imported from the foliage. We systematically investigated AsA levels, biosynthetic capacity, and mRNA expression of genes involved in AsA biosynthesis in kiwi (A. deliciosa cv. Qinmei). Recycling and AsA localization were also monitored during fruit development and among different tissue types. Over time, the amount of AsA, with its capacity for higher biosynthesis and lower recycling, peaked at 30 days after anthesis (DAA), and then decreased markedly up to 60 DAA before declining more slowly. Expression of key genes showed similar patterns of change, except for L-galactono-1,4-lactone dehydrogenase and L-galactose-1-phosphate phosphatase (GPP). However, GPP had good correlation with the rate of AsA accumulation. The expression of these genes could be detected in phloem of stem as well as petiole of leaf and fruit. Additionally, fruit petioles had greater ascorbate amounts, although that was the site of lowest expression by most genes. Fruit microtubule tissues also had higher AsA. However, exogenous applications of AsA to those petioles did not lead to its transport into fruits, and distribution of ascorbate was cell-specific in the fruits, with more accumulation occurring in larger cells. These results suggest that AsA biosynthesis in kiwi during early fruit development is the main reason for its accumulation in the fruits. We also postulate here that GPP is a good candidate for regulating AsA biosynthesis whereas GDP-L-galactose-1-phosphate phosphorylase is not.
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