Metabolism Of Vitamin C And Vitamin E In Arabidopsis Thaliana And Lettuce

Vitamin C (ascorbic acid) is a key component of the plant antioxidant system and it has a number of other proposed physiological roles. Although plants and most animals can synthesize ascorbic acid (AsA), humans lack L-gulono-1,4-lactone oxidoreductase, which is required for the final step in AsA synthesis. Plants provide the major source of dietary vitamin C for humans. Engineering plant AsA metabolism has now become feasible because of the increased understanding of its biosynthetic pathway and key enzymes.Genes encoding eight enzymes involved in AsA biosynthesis of Arabidopsis were cloned, and genetic manipulations were put forward with these genes in this study. Strategies were given rise to value the role of each individual gene in one plant species system, attempting to enhance the level of AsA content. In addition, expressed location were performed in Arabidopsis and dual-gene transformation in lettuce (Lactuca sativa L. var. logifolia), succeeding in obtaining strains with elevated AsA and tocopherol contents. On the other hand, transgenic lines with target gene(s) overexpression or inhibition could be used to investigate AsA physiology in plant.AsA content was inproved in transgenic Arabidopsis. It has been increased more in transgenic plants with vtc2than others. The highest content of transgenic plants with vtc2increased3.6times, compared with the blank transformation (CK). Expressed location analysis shows that vtc2may be more distributed in the endoplasmic reticulum and vtc4, galdh, galur is evenly distributed in all parts of the cytoplasm, dhar distributed more near the cell membrane, probably because it is a part of the regeneration of AsA from the direct transfer of the cells into the apoplast. gldh may focus on the distribution of mitochondria.In overexpression and RNA i lines of Lettuce, AsA content of gme transgenic plants increased1.5timest; AsA content of dhar transgenic plants increased3.8times; AsA content of aoi transgenic plants increased2.4timest; AsA content of vhb transgenic plants increased2.4timest; AsA content of thvd transgenic plants increased1.9times; tocopherol content of AOi transgenic plants increased1.8times. This study includes AsA and tocopherol biosynthesis, oxidative decomposition and reduction regeneration. All aspects of AsA metabolic network were involved. We evaluated the contribution of multiple genes in multiple metabolic pathways in lettuce. Rransgenic lettuce lines with high content of AsA and tocopherol were obtained. The existing and potential achievements in increasing AsA production would present a better understanding of the internal and external mechanisms of plants that control AsA accumulation and provide the opportunity for enhancing nutritional quality and stress tolerance of crop plants. This study laid the foundation of genetic engineering about optimizing AsA content and other nutrition in plant.