Influence of light on ascorbate formation and metabolism in apple fruits
Influence of light on ascorbate formation and metabolism in apple fruits
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DOI：
10.1007/s00425-009-0925-3
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发表时间：
2009-06-01
期刊：
影响因子：
4.3
通讯作者：
Liang, Dong
中科院分区：
文献类型：
--
作者：
Li, Mingjun;Ma, Fengwang;Liang, Dong
为了进一步了解光对植物库器官抗坏血酸（AsA）形成的调控机制，对不同遮荫程度下的苹果（Malus Domestica Borkh）果实中AsA水平、两种关键生物合成酶的活性及其mRNA表达以及回收进行了系统研究。全树用约50%~55%的阳光遮荫20天后，果皮、果肉和叶片中的AsA含量显着下降，而L-半乳糖脱氢酶（L-GalDH，EC 1.1.1.117）和L-半乳糖-1,4-内酯脱氢酶（L-GalLDH，EC 1.3.2.3）的mRNA表达量和活性以及回收酶是 叶子和果皮明显下降，但果肉没有下降。仅遮光20 d，果皮中AsA水平、L-GalDH和L-GalLDH相对mRNA水平和活性以及回收酶活性均出现明显下降，但果肉中无明显下降。然而，在移除完全遮荫并将这些水果重新暴露在自然光下 5 天后，果皮中的含量显着增加。结果表明，光影响果皮和叶中AsA的生物合成和循环，但不影响新鲜果皮和叶中AsA的生物合成和循环。结果还表明，苹果果实有可能通过 L-半乳糖途径生物合成 AsA，并且果实中的 AsA 含量可能部分取决于叶片中 AsA 或受光控制的其他光化学水平。
To further understand the regulatory mechanism of light on the formation of ascorbic acid (AsA) in the sink organs of plants, a systematical investigation on AsA levels, activities of two key biosynthsis enzymes and their mRNA expression as well as the recycling was performed in the fruits of apple (Malus domestica Borkh), under different levels of shade. After the whole trees were shaded with the sun-light about 50-55% for 20 days, AsA levels were significantly decreased in fruit peel, flesh and leaves, while mRNA expression levels and activities of L-galactose dehydrogenase (L-GalDH, EC 1.1.1.117) and L-galactono-1,4-lactone dehydrogenase (L-GalLDH, EC 1.3.2.3) as well as activities of recycling enzymes was clearly declined in the leaf and peel but not in the flesh. By shading fruits only for 20 days, AsA levels, relative mRNA levels and activities of L-GalDH and L-GalLDH as well as activities of recycling enzymes all showed obvious decrease in the peel, but not in the flesh. However, their levels in the peel were markedly increased after the full shade was removed and re-exposed these fruits on natural light for 5 days. It is concluded that light affects AsA biosynthesis and recycling in the peel and leaf, but did not in the fresh. Results also suggest that apple fruit is potential to biosynthesize AsA via the L-galactose pathway, and AsA content in the fruits may depend partly on levels of AsA or other photochemistry controlled by light in the leaves.