Physiological Mechanisms Of Transgenic Poplar With Enhanced Tolerance To Drought Stress By Expressing IbLEA14 Or CodA Gene

Drought has become an increasingly serious environmental problem in the world,which has seriously affected the growth and distribution of trees.Poplars play an important role in the aspects of conservation of soil and water,windbreak and sand fixation.However,it is difficult to grow normally in arid and semi-arid areas because of its sensitivity to drought.Choline oxidase can convert choline to betaine directly and enhance plants'resistance to drought stress.Serving as a multifunctional protein,late embryogenesis abundant protein respond to various stresses actively.And therefore,it can provide a theoretical basis for the drought resistance breeding and application of popla it can provide a theoretical basis for the drought resistance breeding and application of poplar by investigating the response mechanisms of transgenic poplar expressing choline oxidase?codA?gene or IbLEA14 gene to drought stress.The transgenic poplars are expected to play an important role in improving soil desertification in the future.The changes of plant growth and physiological characteristics of transgenic poplar and non-transgenic poplar were studied by treatment of drought stress and rehydration,to explore the physiological mechanisms of enhanced drought tolerance in transgenic poplar expressing IbLEA14 or codA gene.The main conclusions of the study are as follows:1.Under drought stress condition,the plant height growth and total biomass accumulation of poplar were inhibited,but the growth of transgenic lines were better than that of non-transgenic poplar and recovered faster after rewatering.It can be seen that drought tolerance of transgenic poplar expressing IbLEA14 or codA gene was enhanced.2.The leaves'water content and water holding capacity of transgenic lines expressing IbLEA14 or codA gene were significantly higher than those of non-transgenic poplar under drought stress condition.In the dry environment,photosyntheticv rate?Pn?,stomatal conductance?Gs?,transpiration rate?Tr?and contents of chlorophyll decreased evidently in all poplar lines than those in the normal environment,but the photosynthetic capacity and chlorophyll content?Chl?of transgenic lines were significantly higher than that of non-transgenic poplar.Under drought stress condition,the contents of hydrogen peroxide?H₂O₂?and malondialdehyde?MDA?were significantly higher in non-transgenic poplar than in the transgenic lines.Thus,transgenic lines with IbLEA14 or codA gene have better water conditions,photosynthetic capacity and antioxidant capacity,and then improved the tolerance of poplar to drought stress.3.Under drought stress condition,the contents of free proline and glycinebetaine in leaves of transgenic poplar plants expressing codA gene were significantly higher than those in non-transgenic poplar.Besides,the osmotic potential of transgenic poplar expressing codA gene is lower than that of non-transgenic poplar.After putting on drought stress for a certain period of time,the activities of SOD,POD,CAT and APX in leaves gradually increased with the extension of drought time,and then decreased after rehydration.Except POD,the other three antioxidant enzyme activities were significantly higher in transgenic line expressing codA gene than those in non-transgenic poplar.It indicated that increasing osmotic adjustment material contents and enhancing the antioxidant enzyme activities could enhance drought resistance and recovery ability of transgenic poplar expressing codA gene.4.Under drought stress condition,the content of free proline was significantly higher in transgenic poplar expressing IbLEA14 gene than that in non-transgenic poplar.Also,the osmotic potential of transgenic poplar expressing IbLEA14 gene is lower than that of non-transgenic poplar,indicating that transgenic poplar expressing IbLEA14 gene protected itself from damage of drought stress through osmotic adjustment.Based on the above results,we can see that under the drought stress condition,transgenic poplar expressing codA gene could enhance the drought tolerance and recovery ability of poplar by improving the osmotic adjustment ability and antioxidant ability of poplar.Under the drought stress induction,transgenic poplar expressing IbLEA14 gene increased the water retention capacity and osmotic adjustment ability,and had better water condition and photosynthetic rate,which improved the drought tolerance of it.