Effects Of Increase Of Unsaturation Of Fatty Acids On Salt And Cold Tolerance In Transgenic Arabidopsis Thaliana

Arabidopsis thaliana is one of the most studied higher plants which is used as a model plant. In order to produce EPA (one of main ingredients in fish oil) in higher plants, Qi et al transformed Arabidopsis thaliana with 3 long chain unsaturated fatty acid specific elongase and desaturase genes by step-wise transformation. Homozygous transgenic Arabidopsis plants were obtained for the single transgenics containing the Isochrysis galbana△9–elongase, the double transgenics containing the Isochrysis galbana△9–elonagse and Euglena gracilus△8-desaturase and the triple transgenics containing the Isochrysis galbana△9–elonagse, Euglena gracilus△8-desaturase and Mortierella alpina△5-desaturase. The fatty acid composition in these transgenic Arabidopsis plants have changed dramatically to include 8 new C20 LC-PUFAs in the triple transgenic plants due to the introduction of the 3 genes. The total content of these newly synthesized C20 LC-PUFA makes up about 20% of the leaf total fatty acids resulting in the increase of the degree of unsaturation of the fatty acid. The elevation of the fatty acid unsaturation should increase the cold tolerance and other stress-related responses in these plants. In order to investigate the correlation of fatty acid composition and the tolerance to stress, WT and the transgenic lines were used to measure photosynthetic and chlorophyll fluorescence parameters, chloroplastic reactive oxygen species and activities of antioxidant enzymes under salt stress. The results were as follows:1.The results show that in normal condtion ,transgenic seeds have higher germination than WT,and transgenic seedings grow better than WT.These indicate that transgenics grow better than WT and have higher stress tolerance. ability.2. In order to investigate the correlation of fatty acid composition and the tolerance of photosystem to salt stress,photosynthetic and chlorophyll fluorescence parameters were measured. The maximal photochemical efficiency of PSII (Fv/Fm) and photosynthetic rates (Pn) in transgenic lines decreased less compared to the wild type plants under salt stress.3. Compared to WT, the transgenic lines could maintain higher activities of chloroplastic SOD and APX, lower content of chloroplastic O2 and H2O2 under salt stress.4. Compared to WT, transgenic lines could accumulate more soluable sugars and free proline under salt stress, so the osmotic adjustment ability increased. The results showed that the increase in unsaturation of fatty acids enhanced osmotic adjustment ability in transgenic Arabidopsis thaliana plants under salt stress.5. Under salt stress, compared to WT, the increace of relative electronic conductance in transgenic Arabidopsis leaves is less.Under cold sress,the result is similar,and the tendency is more obvious.