Transcriptomics Of Populus × Xiaohei T.S.Hwang Et Liang Roots In Response To Ammonium Nitrogen

Nitrogen nutrition is one of the necessary material bases for plant life activities.Different forms and concentrations of nitrogen have different nutritional effects on trees.Ammonium nitrogen is one of the main inorganic nitrogen in soil.Different concentrations of ammonium nitrogen will cause changes in plant root growth morphology and physiology,but the molecular mechanism of regulating these changes is not clear.In this experiment,hydroponic method was used to study the growth morphology and phenotypic changes of roots,stems and leaves of Populus × xiaohei T.S.Hwang et Liang under high and low concentration of ammonium nitrogen;the changes of ammonium nitrogen and amino acid contents in plants;the expression changes of some genes related to nitrogen assimilation were analyzed by qRT-PCR method;based on the changes of growth morphology,physiology and transcription level of Populus x xiaohei T.S.Hwang et Liang,the sampling time was determined and RNA-Seq analysis was carried out.The results show that:(1)Compared with 3.0 mM,0.3 mM ammonium nitrogen could promote the root growth of Populus × xiaohei T.S.Hwang et Liang,and reached a significant difference in 14 d,and the dry weight was heavier,and the contents of ammonium nitrogen and free amino acids in plants began to change at 2 h.(2)Under ammonium nitrogen treatment,GOGAT/GS enzyme activity was found that GOGAT enzyme activity 30 min began to increase,but the difference was not significant.Under ammonium treatment,the expression of gene family members related to nitrogen assimilation,such as GS1.2 and GS2,increased significantly within 0.5 h;within 0-24 h,the expression of AlaAT3 and AlaAT4 decreased at first and then increased;the expression of other family members showed different fluctuations.(3)Based on the analysis of transcriptome data of 0-120 min root system of Populus ×xiaohei T.S.Hwang et Liang under 3.0 mM and 0.3 mM ammonium nitrogen,it was found that the entries of amino acid phosphorylation of GO enrichment protein of different hypercluster genes were enriched in low ammonium 30-120 min and only in 30 min in high ammonium.According to the enrichment of biological processes related to primary metabolism in superfamily clustering,it was found that there were differences in the enrichment time points of the main biological processes related to carbohydrate,cell wall,DNA synthesis and chromosome structure and developmental under high and low concentrations of ammonium nitrogen treatment.According to the analysis of the type and quantity of transcription factors in different hyperclusters,it was found that there was a large difference in the relative abundance of transcription factors such as MYB,GRAS and bHLH at the same time point.(4)WGCNA analysis showed that RNA transcriptional regulation accounted for the highest proportion of biological processes in most modules,and there were differences in TCA,lipid metabolism,transport and nitrogen metabolism between low and high concentration ammonium.(5)The co-expression network map of the genes and transcription factors of the characteristic module of WGCNA was constructed,and it was found that the WRKY41 gene,a member of the WRKY transcription factor family,had high connectivity in 30 min treated with 0.3 mM ammonium nitrogen.When 120 min was treated with 3.0 mM ammonium nitrogen,it was found that ANAC083,a member of NAC transcription factor family,had the highest connectivity.These results lay an important foundation for revealing the difference between high-affinity and low-affinity ammonium signal response of poplar,and provide candidate genes for further use of genetic engineering to improve ammonium absorption of poplar.