Transcript Profilling, Cloning And Comparative Function Analysis Of Genes Involved In Lipid Biosynthesis From Oil Crops

Oil content and fatty acid composition are the key parameters of varieties in oil crops. It is of importance either theoretically or practically to investigate the genes related to lipid biosynthesis. In this study, the transcriptional profiles of genes involved in lipid biosynthesis during seed development were analyzed with two rapeseed verities by qRT-PCR, in order to elucidate how the transcriptional profiles of these genes responded to the selective pressure against fatty acid composition and oil content. Results showed that the transcriptional levels of 7 genes (FAD3, ACCase, FAE1, GKTP, Caleosin, GAPDH, and PEPC) of the 32 genes investigated were upregulated by 30% to 109%, and 10 genes (KAS3,β-CT, BcRK6, P450, FATA, Oleosin, FAD6, FATB,α-CT and SUC1) were downregulated by 20% to 50% in low erucic acid variety Zhongshuang 9 when compared to the high erucic acid variety Zhongyou 821. The transcription patterns in most of the genes showed significant correlation with fatty acid accumulation patterns, but these correlations in ZS9 were significantly different from those in ZY821.To investigate the function of the genes involed in lipid biosythesis, the full cDNA sequences of such genes were cloned from rapeseed, soybean, sesame and peanut, as oil content related genes ACCase, SUC2, DGAT, thioesterase genes FATA,FATB , and desaturase genes. These sequences were aligned and analyzed by using bioinformatic tools, and incorporated into plant transgenic vectors regulated by Napin promoter. 9 desatrurases were transformed into Arabidopsis mutant according to their putative function, and a lot of positive transformants were obtained. The following results were drawn through the analysis of the fatty acid composition in seed of the T2 transformants by gas chromatography.All the 19 positive transformants with BnFAD2 from rapeseed showed functional complement with the Arabidopsis fad2 mutant, and some transformants even produced much more C18:2 or C18:3 than the wild type. All 12 positive transformants with GmFAD2 from soybean also showed the functional complement with the mutant. When SiFAD2 from sesame were transformed into the mutant, however, only 5 of the 7 positive transformants showed functional complement with the mutant. With AhFAD2 from peanut transformed to the Arabidopsis mutant, only 1 transformant showed functional complement among the 14 positive transformants,.Among 10 positive transformants with BnFAD3 from rapeseed,6 showed functional complement to the phenotype of mutant. Only 7 of 20 positive transformants with GmFAD3 from soybean showed complement to the phenotype of mutant. All the 16 positive transformants with BnFAD6 from rapeseed playedω-6 desaturase function. Of 20 positive transformants with GmFAD6 from soybean only 3 playedω-6 desaturase function.The seed of fad7 mutant contained more C18:1 and less C18:3, indicating that it does work partly asω-3 desaturase in seed. When SiFAD7 from rapeseed was transformed into the mutant, 5 of the 7 positive transformants playedω-3 desaturase function and produced more C18:3 than the wildtype. Results indicated that the genes of desaturases from various oilcrops can mke functional compliment to the mutant of Arapdopsis but they behave differently. Different transgenic events also showed difference in the funcional compliment. This study provides a theoretical basis for the genetic regulation of the lipid biosynthesis in oil crops.