Study Of The Stress Tolerance Of The Lea And MnSOD Gene From Tamarix Androssowii

Both Lea and MnSOD gene are important stress tolerance genes. To further understand theroles in stress tolerance of the Lea (DQ663481) and MnSOD (AY573576) gene, the yeastexpression system and plant transgenic method were conducted to study the stress tolerance ofthe Lea and MnSOD.The Lea gene was inserted into pYES2 and transformed into yeast cells (Saccharomycescerevisiae). The transgenic yeast cells harboring the Lea gene were generated under the controlof inducible GAL promoter (pYES2 vector); yeast cells transformed with pYES2 empty vectorwere also generated as .a control. Northern blot demonstrated that the Lea gene wassuccessfully expressed in S. cerevisiae, reaching a maximum expression leveal at the inductionof 12 h. Stress tolerance tests showed that the Lea yeast transformants exhibited a highertolerance to the stresses of high temperature, freezing, NaCl, Na₂CO₃, NaHCO₃, drought andultraviolet radiation than the control transformants cells do, indicating that the Lea gene istolerant to the above abiotic stresses. These results suggest that the Lea gene is resistant to awider repertoire of stresses than previously acknowledged and may play a common role inplant acclimation to the examined stress conditions. Our study has made a solid base onimprovements stress tolerance of plants by introducing this Lea gene into plants cell.The MnSOD gene was inserted into the plant expressive vector of pROKII. The MnSODgene was transformed into Populus davidiana×p. bolleana by Agrobacterium mediated genetictransformation. Eight excellent transgenic lines were examined by PCR and Southern blottinghybridization, confirming that MnSOD gene have been integrated into the genome of Populusdavidiana×P. bolleana. Northern hybridization approved that the foreign MnSOD gene wassuccessfully expressed in all the transgenic lines. However, there were differences inexpression level among the lines, lines of S9 and S11 having a highest expression level.Five transgenic Populus davidiana×P. bolleana lines were subjected to salt stress, andtheir salt tolerance were analyzed. The results revealed that the most of the transgenic seedlingscould grow well in the medium containing 0.8% (w/v) NaCl, with a rate of rooting more than40% and the weight gains of 319～614mg (30 d); however, the control lines could not root andtheir weight gains were only 31.3mg in average. These results demonstrated that the salttolerance of MnSOD transgenic lines was improved significantly.The SOD activities of the 5 transgenic lines were determined before and after NaCl stress.The SOD activities of transgenic and nontransgenic plants were all increased before and afterNaCl stress. After NaCl treatment, the SOD activity of control increased 18.5%; however,transgenic lines increased 19.4%～51.5%. These results proved that MnSOD gene increased the SOD activity in transgenic Populus davidiana×P. bolleana.The relative electric conductivity and MDA content of transgenic and nontransgenic lineswere measured before and aider NaCl stress. The results showed that the relative electricconductivity and MDA content of the transgenic and control plants were all increased afterNaCl stress, but they were both significantly lower than that of control, indicating that thetransgenic lines suffered a slight injure compared with nontransgenic lines under NaCl stress.