The Analysis Of Salt And Alkali Stress Resistence Of Transgenic Populus Davidiana×P.Bolleana Overexpressing TaLEA Gene

Late-embryogenesis-abundant (LEA) genes are expressed in plant seeds during maturation and development, and in dehydrated nutritional tissues upon stress stimuli. The resulting LEA proteins accumulate and help to improve stress tolerance. Additionally, LEA genes have no specificity when expressed in other tissues, such as cotyledons and anthotaxy, roots, stems and leaves. There is a large number of studies have shown that the overexpressing exogenous LEA gene in Arabidopsis, tobacco and so on, can significantly improve its resistance to abiotic stress.So,we transferred the TaLEA into Populus davidiana×P. bolleana and obtain6TaLEA kanamycin-resistant lines. PCR showed a positive result in all six TaLEA transgenic lines, Northern hybridization showed hybridization bands in the six TaLEA-transferred lines, indicating TaLEA mRNA successfully expressed in all six transgenic lines.The six transgenic lines and the non-transgenic line have been tested under0.8%NaCl and0.6%NaHCO3respectively.In order to analysis the tolerance of transgenic lines, the relative rate of height growth and survival rate, chlorophy Ⅱ fluorescence kinetic parameters,Na+content in leaf were determined under0.8%NaCl and the net growth of height,net growth of ground diameter, survival rate, salt stress index,photosynthesis parameters, chlorophy II fluorescence kinetic parameters were determined, NBT staining,DAB staining were observed under0.6%NaHCO3.The results showed that the survival rate of transgenic lins after rehydration were all higher than the NT,the relative rate of height growth in four tansgenic lines were higher than the NT.The Fv/Fm, qP、ΦPSII of SL2declined less than other lines,and the NPQ of it rose less than other lines under salt stress. Na+levels in transgenic lines’young leaves were lower than controls’, but higher in yellow and withered leaves, suggesting transgenic Populus davidiana x P. bolleana transport Na+to the old organization and the aging of tissues and so that the overall content of Na+ion was reduced.The ability of salt tolerance was ranked as SL2, SL1, SL5, SL6, SL3, SL4, NT. While SL2is significantly improved salt tolerance transgenic Populus davidiana×P. bollean under0.8%NaCl stress, the relative rate of height growth reached48.70%,31.02%higher than NT, the survival rate was66.67%after rehydration,5times higher than NT.20days after0.6%NaHCO3treament, the average net growth and diameter of the transgenic lines was increased by22.28%,11.98%, respectively, compared to NT. Average alkali injury index was0.24, lower than that of0.79; average survival was0.85, is nearly three times the NT.The Pn,Tr of each transgenic lines were higher than NT, Gs of SL2and SL5was higher than NT, but the Ci of NT declined slightly, while SL2and SL5rose slightly. Average Fv /Fm of each transgenic line is0.68, NT is only0.45, the qP and φPSⅡ of former only slightly higher than the latter, however, the NPQ of latter is almost6times higher than the former.Under the same stress condition,transgenic Populus davidiana×P.bollean,especially SL2and SL5,can to maintain a strong photosynthetic capacity. NBT staining and DAB staining results showed that low levels of ROS transgenic lines. The ability of salt tolerance was ranked as SL2、SL5、SL1、SL3、SL6、SL4、NT.