Study On Genetic Transformation Of E2s Gene From T.androssowii And Abiotic Stress Resistance

The gene encoding a ubiquitin conjugating enzymes (E2s) was obtained from the Tamarix androssowii cDNA library. The plant genomic expression vector, pROK II, with the E2s gene was constructed and transferred into Nicotiana tabacum L via Agrobacterium-mediated transformation procedure. Moreover, the function of the exogenous E2s gene was examined under salt and drought stress.Sixty-eight resistant lines were obtained through kanamycin selection, and 15 well grown lines which subjected to PCR assay all showed positive. In PCR-Southern hybridization, we checked 6 transgenic plants selected from the 15 plants randomly. The result showed that the foreign target gene had been integrated into tobacoo genome. Real time RT-PCR method was employed to study the expression of the E2s gene, indicated that it was expressed but the expression rates varied. Among the six lines, TL3 and TL1 had the highest expression rate, TL10 and TL11 lines are lower, and TL5 and TL7 had the lowest expression rate.Contents of malondialdehyde (MDA) , activity of superoxide dismutase (SOD) . rate of conductivity, growth rate, content of chlorophyll and radication rate of the 6 lines were determined and analysised under NaCl and drought stress. When the transgenic lines were treated with 440mM NaCl. the average relative conductivity and MDA content are respectively 27.1% and 22.6% lower than the control. The SOD activity of TL5 was lowest in all the transgenic lines, which is still 47.5% higher than the control. The TL10 and TL3 have the highest and the lowest chlorophyll content among the six lines, they are 64.4% and 29.7% higher than the control. The radication rate of transgenic lines was about 50-70%, whereas the control line was only 30% in 220mM NaCl stress condition. The above results indicated that the transgenic lines suffered minor damage under NaCl stress.In the tenth day of drought stress, the average relative conductivity is 19.6% lower than control line, the MDA content of transgenic and control lines is 4.9~6.3μmolg~-1 and 7.7μmol g~-1 respectively. The average chlorophyll and SOD content is 64.5% and 32.3% higher than the control, the average SOD content of transgenic lines is 1.01mg/g. In this time, relative growth rate was ranged from 59% to 83% but the control line is about 29.7%. These results demonstrated that the introduced exogenous E2s gene enhanced the drought stress tolerance of tobacco.All the experiments results indicated that the constitutively expressed E2s gene from T. androssowii can improve the stability of cell membrane, increase the SOD activity andchlorophyll content, and enhance the relative growth rate under adverse environment. That was Els gene could ehance the tolerance of salt and drought stress of plant.