| Tea-oil tree {Camellia oleifera A.) is one of the most important ligneous edible oil trees in China. It has large cultivated area, adsperse distribution and strong adaptivity. 90% of tea-oil is unsaturated fatty acid, such as oleic acid, linolaic acid, linolenic acid and so on. So it is a kind of excellent vegetable oil. Its byproduct also has important use, for example, saponin can be extracted from the withered cake. Besides its economical value, tea-oil tree has importance ecological worth in the south of china. So far, in the world, molecular biology research of Tea-oil tree is scarce, especially the study of key geneswhich regulate the synthesis of unsaturated fatty acid is blank. We constructed a cDNA library with developing tea-oil tree seed, which is close to mature. Base on it, an EST library was constructed and several crucial genes related to fatty acid synthesis were isolated. For this paper, major research conclusion is as follow.1.Firstly and successfully constructed high quality cDNA library with oil transformation peak phage seed of tea-oil tree. The material is developing seeds of great Xianglin-1 and Xianglin-4's clone. The total RNA was separated with lytic method and the mRNA was isolated from the total RNA by MagneSphere technique, and then, synthesized the first strand and the second strand by Superscript II enzyme , filing-in the terminus, linked the adaptor, digested by special RE, reclaimed the cDNA, ligated the cDNA fragment with pBluescript vector, finally, transformed the recombinants into E.coli .The library's capacity is contain 106 clone and recombinants the percent of recombination is as high as 88.21%, and helpful to EST library construction and the gene isolation and determination.2. After large scale of sequencing, constructed tea-oil tree seed EST (expressed sequence tags) library. And primary analyzed expression of genes of seed, which is close to mature. Picking clones at random and sequencing in the 3' end gained 2327 cDNA sequences and constructed the EST library. By homology searching in Internet nucleic acid database, the results showed that 580 sequences have very high homology to nr database of NCBI and dbEST database. According to protein or enzyme function encoded by these sequences, those genes are divided into storage protein gene, fatty acid synthesis gene and related metabolic gene, disease-resistant gene, fight-contrary gene, gene/protein expression gene, signal transmit gene andmany unknown function genes.etc. After clustering analysis and counting gene expression abundance for the 2327 sequences, different type gene has different expression abundance; individual gene just has one sequence for low abundance gene. In the seed there are many Ubiquitin genes related to protein degradation. Genes related fatty acid and wax metabolism have FatB1 gene, SAD gene, FAD2 gene, FAD8 gene, and ACP gene. Besides there are heavy metal detoxicationun protein gene, protein folding factor genes, actin genes, dormin response protein gene, gene related plant hormone such as ACCase gene, genes related seed development and embryo formation etc.3. Firstly and successfully, isolated and determined FAD2 gene, SAD gene, Oleosin gene and ACP gene. Results shown that tea-oil FAD2 cDNA sequence have very high homology with Tung tree, Rape, Sunflower, Sesame, Common Mouse Ear Cress, Peanut, Cotton for cDNA sequence and putative amino sequence by homology research in GenBank database. It's similarity coefficient respectively 96%, 88%, 88%, 88%, 87%, 61%, 6%, homology to Tung tree is up to 96%. Besides relatively conserved sequences, these FAD2 genes still have many difference parts. Each species' FAD2 gene has its own trait. By repeat bi-directional sequencing and bioinformation analysis, the FAD2 gene is a new gene, we has reserved its bacterial colony. By homology research, the SAD cDNA sequences have high homology (beyond to 60%) with SAD gene of different species. The similarity coefficient arrayed from high to low is (Sunflower, Cucumber82%), (Sesame, Alligator pear79%), (Common...
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