Transcriptomic Study On Differential Expressed Genes Of Populus×xiaohei T.S.Hwang Et Liang Roots Induced By Different Concentrations Of Nitrate Nitrogen

In this study,the hydroponic seedlings of Populus×xiaohei T.S.Hwang et Liang were used as experimental materials.The sampling times of transcriptome sequencing was determined by the differences of root length and plant height,the changes of nitrate nitrogen content in roots,stems and leaves,and the expression modes of nitrogen assimilation related genes in roots.Illumina high-throughput sequencing technology was used to determine the transcriptome of Populus×xiaohei T.S.Hwang et Liang roots.Using different bioinformatics methods for analysis,the results are as follows:(1)Transcriptome sequencing results showed that different concentrations of nitrate nitrogen could cause changes in the transcription level of Populus×xiaohei T.S.Hwang et Liang.A total of 6,740 differentially expressed genes were obtained from the roots of Populus×xiaohei T.S.Hwang et Liang in five periods of 0.3 mM nitrate nitrogen treatment,and a total of 8,185 differentially expressed genes were obtained from the roots of Populus×xiaohei T.S.Hwang et Liang treated with 3 mM nitrate nitrogen.(2)Analysis of GO enrichment of differentially expressed genes under 0.3 mM and 3.0 mM nitrate nitrogen treatment showed that the enrichment of some GO items in different periods was different,such as photosynthesis,light system,defense response,kinase activity and ubiquitin-protein ligase activity.(3)Pathway analysis showed that under 0.3 mM nitrate nitrogen and 3.0 mM nitrate nitrogen treatment,the enrichment of the main carbohydrate metabolism,lipid metabolism,cell wall synthesis and other biological pathways related genes were different.(4)After treatment with 0.3 mM nitrate nitrogen and 3 mM nitrate nitrogen,genes of YABBY,HAP3,HSF,TCP,and DOF transcription factor family appeared specifically in different treatment periods.However,the relative abundances of bZIP,HB,GRAS and C2H2 family genes in different periods were quite different.(5)Using WGCNA method analysis,6 and 4 characteristic modules were obtained under different treatment periods of 0.3 mM nitrate nitrogen and 3 mM nitrate nitrogen,respectively.Among them,signalling and RNA transcription regulation accounted for a relatively high proportion.The enrichment of the main carbohydrate metabolism and nitrogen metabolism were different under different concentrations of nitrate nitrogen treatment.(6)Using the genes and transcription factors in the characteristic modules of WGCNA to construct co-expressed gene networks,7 and 38 key transcription factors were obtained under high and low concentrations of nitrate nitrogen,respectively.These results provide an important theoretical basis for elucidating the molecular mechanism of the differences in growth and physiological changes of Populus×xiaohei T.S.Hwang et Liang under high and low concentrations of nitrate nitrogen,and provide a strong basis for the next step to verify the important role of related genes in the root system of Populus×xiaohei T.S.Hwang et Liang in response to nitrate nitrogen.