ISHS Acta Horticulturae 769: XXVII International Horticultural Congress - IHC2006: International Symposium on Asian Plants with Unique Horticultural Potential
THE CDNA CLONING AND CHARACTERISTIC OF STEAROYL-ACP DESATURASE GENE OF CAMELLIA OLEIFERA |
| Authors: | Dang-Quan Zhang, Xiao-Feng Tan, Lu-Shan Xie, Hong-Peng Chen, Jian Qiu, Fang-Ming Hu |
| Keywords: | Camellia oleifera, unsaturated fatty acids, SAD, structural characteristic, bioinformatic analysis |
| Abstract:
As the most important and special edible oil tree in China, tea-oil tree (Camellia oleifera) has the oil-yielded rate of about 55% from its kernel. The recent researches suggested that the oiliness of tea-oil should be one of the best plant oils, for tea-oil consists of ~90% unsaturated fatty acids (~80% oleic acid, ~10% linoleic acid and linolenic acid). As the enzyme controlling the first-step desaturation during the biosynthesis of plant unsaturated fatty acids, plant SAD (Stearoyl-ACP desaturase) directly regulates the proportion of saturated fatty acids and unsaturated fatty acids by dehydrogenating saturated fatty acids bonded to ACP (Acyl carrier protein) to form oleic acids. However, recent researches on Camellia oleifera were mostly focused on the conventional planting and breeding and characteristic analysis of its products, and lacked those to find out the molecular mechanism of controlling the forming of high content of oleic acids. Therefore, we attempted to clone the full-length cDNA of Camellia oleifera SAD (CoSAD) gene. We successfully constructed a full-length cDNA library using the nearly matured seeds of elite cultivar Xianglin-4 planted widely in China, and then randomly selected hundreds of clones for sequencing from the 5´-end to construct a good representational EST library. Basing on the homological analyses of this EST library, we obtained 3 ESTs of CoSAD, and then obtained the full-length cDNA of CoSAD from the full-length cDNA library by PCR. The result of bioinformatic analyses including three-dimensional homological modeling on the CoSAD cDNA suggested that CoSAD displays high similarity to SADs of different plants, and is more advantageous than other plant SADs to catalyzing saturated fatty acids into oleic acids. This result could explain the higher content of oleic acids than those of other oil plants, presenting theoretical element for the application of CoSAD genes and genetic improvement on other oil plants. | |
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