SAD and FAD2 cDNA Genes Cloned From Camellia Oleifera Abel

Seeds of Camellia oleifera Abel produced high-quality edible oil, important cosmetic ingredients, and bio-fuel, such as poly unsaturated fatty acids (about 90%). Oleic acid transformed from saturated fatty acid in the process of grease biosynthesis catalyzed by stearoyl-ACP desaturase (SAD), then transformed into linoleic acid and other poly unsaturated fatty acids catalyzed by fatty acid desaturase (FAD) family gradually. So the cloning SAD and FAD genes from C. oleifera are very important for revealing the lipids biosynthesis patterns and achieving molecular-aided breeding in C. oleifera. We constructed cDNA and EST libraries of C. oleifera and 3 copies of SAD gene and 3 copies of FAD gene were obtained from the EST library. One of three SAD EST clones was confirmed to be the full-length cDNA and named as co-sad, and 3 FAD2 EST clones were not full-length cDNA by BLAST with SAD and FAD genes from other plants via GenBank, DBJ and EMBL. Bioinformatics analysis showed that co-sad was 1579 bp in length and contained an 1188 bp open reading frame (ORF) encoding 396 amino acids. However, there was no obvious signal peptide and trans-membrane structure in the deduced protein sequence. BLAST results suggested that co-sad shared high homology with SAD genes from Jatropha curcas and Ricinus communis on protein level. The 3 FAD2 EST clones were not full-length cDNA by aligning with FAD genes from other plants in GenBank, DBJ and EMBL. Based on the constructed EST library of C. oleifera, a full-length cDNA of FAD2 gene was obtained by methods of 5’RACE and overlap extension PCR with total RNA extracted from C. oleifera ‘Yanggulao No.1’ seeds. The gene was 1682 bp in length and contained an ORF encoding 382 amino acids, which formed typical conserved domains of FAD2 and showed high homology with those of other plant species. The results of 3D structure prediction indicated that the Co-SAD and Co-FAD2 were much more advantageous than other SAD and FAD2 in lipids biosynthesis. These results could explain the higher content of oleic acid and linoleic acid in C. oleifera than that of other oil plants theoretically and could be applied for breeding high yield teaoil cultivars.