Identification Of APX Gene Family In Moso Bamboo(Phyllostachys Edulis) And Functional Analysis Of PeAPX5

As an important bamboo species for shoot and timber products,moso bamboo（Phyllostachys edulis）grows fast and has a wide range of uses.However,there are various stress conditions in its process of growth and development,such as drought,low temperature.Under these conditions,the dynamic balance between the production and removal of reactive oxygen species in plant cells was broken,resulting in oxidative stress,thus affecting the growth and development of plants,and even causing plant death.As an important active oxygen scavenging enzyme,ascorbate peroxidase（APX）,plays an major role in the removal of H₂O₂.Therefore,the study of APX gene function can establish theoretical foundation for study of stress resistant mechanism of moso bamboo,also provide high-quality genes for the molecular stress-resistant breeding of bamboo.In this study,the function of APX gene in moso bamboo was studied by identification,real-time fluorescence quantitative PCR,gene cloning,genetic transformation.The main results are as follows:1.Seven APX genes were identified based on moso bamboo genome database,named as PeAPX1～PeAPX7.They could be divided into three subfamilies including cytoplasmic（PeAPX1,PeAPX2,PeAPX5）,peroxisome（PeAPX3,PeAPX4）and chloroplast/mitochondrion（PeAPX6,PeAPX7）types based on the prediction of subcellular localizations.PeAPXs were closely related to Os APXs in rice by phylogenetic analysis with other APX proteins.The same subfamilies had similar conserved domains and conserved motifs.The promoter region of PeAPXs contains many light response elements、hormone response elements and stress response elements.2.qRT-PCR was used to analyze the expression patterns of PeAPXs under drought,low temperature and salt stress,and the results revealed that there were great differences in the expression pattern of each gene under drought,salt and low temperature stress.PeAPX2 was maintained high level expression under three stresses.The expression of PeAPXs were induced by low temperature stress.Under drought stress,the expression of PeAPX1 was down-regulated,the expressions of PeAPX2、PeAPX4 and PeAPX5 were up-regulated,while the expressions of PeAPX3,PeAPX6 and PeAPX7 were not detected.Under salt stress,all of PeAPXs were up-regulated except PeAPX3 and PeAPX5.Therefore,PeAPXs may be involved in different abiotic stress processes and play an important role in the growth and development stage of moso bamboo.The results of transcriptome data analysis showed that PeAPXs were tissue specific expressed in moso bamboo seedlings.In summary,the results indicated that PeAPXs involved in the growth and development and abiotic stress response process.3.Based on the results of qRT-PCR,PeAPX5 which respond to these three stresses was selected for further functional studies,it encoded 250 amino acids and located in the cytoplasm.The PeAPX5 gene was transformed into Arabidopsis mediated by agrobacterium tumefaciens.The phenotype and DAB staining of leaves showed that transgenic lines accumulated less H₂O₂under drought conditionsand;physiological indexes were detected under low temperature and salt stress,results showed that the content of MDA in transgenic Arabidopsis is lower while content of soluble sugar and the activity of CAT,SOD and APX in transgenic Arabidopsis were lower than those in wild type.The results demonstrated that overexpression of PeAPX5 improved the drought,cold and salt tolerance of transgenic Arabidopsis.