Research On The Molecular Mechanism Of Populus Trichocarpa In Response To Cold Stress

In the process of plant growth,plants may suffer from various biotic and abiotic stresses,in which chilling damage can disturb or destroy the cell structure,disorder the physiological and biochemical metabolism of plants,which seriously affects the growth and development of plants.It is of great significance to improve plant resistance to cold by studying the molecular mechanism of plant response to cold stress and understanding the adaptive evolution process of species under stress.In this paper,we selected the herbaceous model plant Arabidopsis thaliana(A.thaliana)and woody model plant Populus trichocarpa(P.trichocarpa)as research materials to explore their molecular evolution mechanism of cold acclimation.The main research contents are as follows:Filichkin et al.(SRA acc no:ERP021848)data were used to analyze the transcriptome of different tissues(leaf,stem and root)of P.trichocarpa under different cold stress times(24 h and 7 d),we found that the response of different tissues to cold stress is both similar and specific.Compared with the gene expression difference before and after cold stress treatment,the gene expression difference among different tissues is more significant.By analyzing the gene expression of plants under different periods of cold stress,we found that the cold response genes that were under short-term cold stress in different tissues were mainly related to signal transduction,while the cold response genes under long-term cold stress were mainly related to gene function.In order to further explore the core genes that respond to cold stress in different tissues,we conducted weighted gene co-expression network analysis(WGCNA)of differentially expressed genes(DEGs)under cold stress.We found that most of the down-regulated genes in different tissues under cold stress were related to growth and development.However,different organizations have different responses to cold stress,as different tissues trait matched to different significant module genes.We used Cytoscape software to map the gene correlation network in the optimal module of each trait,and then identified the core genes responding to cold stress according to the level of connectivity between genes,and verified the expression of these core genes under cold stress by qRT-PCR.The results showed that the expression trend of selected genes was consistent with the analysis results.We further explored the differences in the expression of homologous genes between A.thaliana and P.trichocarpa under cold stress and their similarities and differences in the ICE-CBF signaling pathway.The results showed that the responses of A.thaliana and P.trichocarpa to cold stress were conservative but more diverse.By analyzing the direction of homologous differentially expressed genes,it was found that there were 87 genes that were specifically up-regulated and 147 genes that were specifically down-regulated in A.thaliana,but no homologous genes were found in P.trichocarpa.By comparing their responses in ICE-CBF molecular regulatory pathway,we found that CBF1-4 and homologous gene AT5G52020 in A.thaliana were up-regulated under cold stress,and Potri.015G136300 and Potri.012G134000 in P.trichocarpa were up-regulated.ICE1 and its homologous gene ICE2 were up-regulated under cold stress.The orthologous genes of ICEs in P.trichocarpa,Potri.015G105200 and Potri.012G106000,were also up-regulated.The fold change of Potri.015G105200 was more than 4,which was significantly higher than the expression of ICEs in A.thaliana.Therefore,we speculated that although the ICE regulated cold stress response was conservative in A.thaliana and P.trichocarpa,the pathway might be strengthened in P.trichocarpa.