Influence of light on ascorbate formation and metabolism in apple fruits

• Published in: Planta 2009-06, Vol.230 (1), p.39-51
• Main Authors: Li, Mingjun, Ma, Fengwang, Shang, Peifen, Zhang, Min, Hou, Changming, Liang, Dong
• Format: Article
• Language: English
• Subjects: Agriculture; Apples; Ascorbic Acid - metabolism; Biological and medical sciences; Biomedical and Life Sciences; Biosynthesis; Blotting, Northern; Dehydrogenase; Dehydrogenases; Ecology; Enzymes; Forestry; Fruit - genetics; Fruit - metabolism; Fruit - radiation effects; Fruits; Fundamental and applied biological sciences. Psychology; Galactose Dehydrogenases - genetics; Galactose Dehydrogenases - metabolism; Gene Expression Regulation, Enzymologic - radiation effects; Gene Expression Regulation, Plant - radiation effects; Glutathione - metabolism; Leaves; Life Sciences; Light; Malus - genetics; Malus - metabolism; Malus - radiation effects; Messenger RNA; Metabolism; Natural light; Original Article; Oxidoreductases Acting on CH-CH Group Donors - genetics; Oxidoreductases Acting on CH-CH Group Donors - metabolism; Peels; Photochemistry; Plant Leaves - genetics; Plant Leaves - metabolism; Plant Leaves - radiation effects; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Plants; Recycling; Reverse Transcriptase Polymerase Chain Reaction; Spectrophotometry - methods
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-009-0925-3

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.