Functional Analysis Of Chloroplast APX In Poplar

During the growth and development of plants suffering from abiotic stresses,such as salinity,drought,etc.,a large amount of reactive oxygen species?ROS?will be produced in the cells.Excessive accumulation of ROS can cause cell oxidative damage,leading to cell membrane lipid peroxidation,protein and other cell components are damaged,serious cells or plants can die.Whether the plant can effectively remove ROS produced under stress can be very important to improve its resistance.Ascorbate peroxidase?APX?is an important antioxidant enzyme,through the AsA-GSH cycle involved in the removal of H₂O₂ in plants,especially in the chloroplast H₂O₂ removal.Chloroplast ascorbate peroxidase?chlAPX?is a key enzyme to protect chloroplast and other cell components from H₂O₂ poisoning.Therefore,it is very important to study the relationship between chlAPX gene and plant resistance to abiotic stresses.In this study,the effects of chlAPX gene on the resistance of poplar were analyzed from the tissue and cell level using the poplar and the callus of wild-type and positive and antisense chlAPX genes and their callus as experimental materials.The main findings are as follows:1.Under normal conditions,compared with the wild type,the rooting rate of the transgenic chlAPX gene was low,the number of rooting was low and the growth period was slow.The rooting rate of the chlAPX gene was high,the number of rooting was high and the growth period was fast.2.After treated with NaCl,the antisense chlAPX gene showed the first symptom.The activity of antioxidant enzymes APX,GR and SOD decreased first and then decreased with the increase of salt stress time,and the content of nonenzymatic antioxidant decreased and the antisense chlAPX gene decreased more significantly in different transgenic plants and wild type plants.The photosynthetic rate and Fv/Fm decreased continuously,but the photosynthetic efficiency of the chlAPX gene was higher,while the MDA,relative conductivity,Na+ content and H₂O₂ content increased gradually.This indicated that poplarcould alleviate the damage of salt stress through the antioxidant enzyme system in vivo,and the overexpression of chlAPX gene could reduce the accumulation of reactive oxygen species more effectively under salt stress,protect the photosystem and protect the plants against salt stress stronger.3.The addition of exogenous AsA under salt stress increased the antioxidant enzyme activity,the chlorophyll degradation rate and the MDA content of the plant,which reduced the damage caused by salt stress and decreased the degree of membrane lipid peroxidation.Improve.4.Under the condition of exogenous H₂O₂,the APX activity of both wild type and different transgenic poplar was increased first and then decreased,but the APX activity of transgenic plant was significantly higher than that of wild type.The degree of plasma membrane damage of poplar was higher than that of wild type,and the degree of plasma membrane injury of transgenic chlAPX gene was higher than that of wild type.5.Under the condition of 100 mmol· L-1 NaCl,the activities of antioxidant enzymes in the callus of wild type or different transgenic lines were decreased and the content of MDA increased under the light condition.The callus was also similar in dark condition result.But the protective enzyme activity in the callus was higher than that in the dark under the same treatment time.Among them,the callus activity of chl APX was higher than that of wild type and transgenic callus,and the decrease of enzyme activity was also smaller.Indicating that chlAPX can alleviate cell damage caused by salt stress.In conclusion,under the condition of certain stress,the chlAPX gene increased the resistance to salt tolerance?salt tolerance and antioxidant?,while the antisense chlAPX gene reduced the plant's resistance to stress.The salt sensitivity of in vitro cultured cells was higher than the complete plant.This study could provide a theoretical basis for further study on the molecular mechanism of chlAPX gene involved in regulating the tolerance of poplar and lay a good foundation for the practical application of transgenic resistant poplar.