| With the development of industry,heavy metal pollutants enter the water,such as oceans and lakes.Heavy metals are wide range of sources and difficult to degrade.They can accumulate with the food chain and food web and have an important toxic effect on living organisms.Among them,copper is a common heavy metal element.Cu2+ can promote the growth of organisms when it in a low level,but Cu2+ may threaten the normal life of organisms when it in a high level.Paramecium is a common single-celled organism.It has cell nucleus,more cell surface area,short generation time,and complete organelle structure.It is an important model organism for studying the ecotoxicology of eukaryotes.To learn the important transport way and the pathway under the heavy metal,we studied the change in transcriptome under Cu2+ stress.In this study,we used Paramecium as the test organism to study the effects under different action times(24 h,96 h)and different action concentrations(0.01 mg/L,0.02 mg/L).Through the transcriptome sequencing,several different were found in different group.The main conclusions are as follows:(1)When the Paramecium were treated by 0.01 mg/L Cu2+for 24 h,there are 283 genes were up-regulated and 296 genes were down-regulated;when they were treated by 0.02 mg/L Cu24 for 24 h,there were about 246 genes were up-regulated and 357 genes were down-regulated;under 0.01 mg/L for 96 h,there are 413 genes were up-regulated and 411 genes were down-regulated;under 0.02 mg/L for 96 h,there are 17 genes were up-regulated and 13 genes were down-regulated;(2)The different genes were annotated in the GO database.When the Paramecium was treated in 0.01mg/L for 24 h,the differences can be found in metal ion binding,GTP binding and so on.When the Paramecium was treated in 0.02 mg/L for 24 h,the same conclusion can be found compared to the concentration of 0.01 mg/L.But more GO entries were annotated,indicating that heavier Cu2+may cease more life processes and biological components changed in Paramecium.When the different genes were annotated in KEGG database,the low copper stress mainly cease the changes in ribosomes,kinase activation,meiosis and other metabolic processes,and some genes was annotation in MAPK signaling pathway,cAMP signaling pathway,Rapl signaling pathway,AMPK signaling pathway and so on.There were some pathway that annotation in both two concentration,such as mRNA monitoring pathway,AMPK signaling pathway,cell cycle,Gap gap junction,endocytosis and MAPK signaling pathway.The MAPK and the AMPK signaling pathway are meaningful to the cell growth,and these two pathway can effect on differentiation,transcription and signal transduction.Paramecium may adapt the environment by regulating energy metabolism and cell transcription under the copper stress.(3)When the Paramecium was treated in 0.01 mg/L for 96 h,the different genes were enriched in metal ion binding,ATP binding,ribosomal structure composition,ribosome binding,zinc ion binding,DNA binding,membrane components in GO database;Under the Cu2+stress of 0.02 mg/L for 96 h,the different genes were enriched in ATP binding,membrane components,transmembrane transport and cation transfer.But the high concentration of copper ions annotated less entries.The reason of these phenomenon may be the Paramecium changed a lot in gene under the high concentration and pass the feature to next generation.In KEGG database annotations,the metabolic pathways such as elongation factors,large subunit ribosomal proteins,histone deacetylases,ATP-dependent RNA helicases,tubulin beta,carbon metabolism and the Citrate cycle were noted.It can be seen that the differential genes of Paramecium are more concentrated in the metabolic pathways related to life activities with the time over,which may be related to the metal ion fixation,the absorption of heavy metals and the copper resistance of Paramecium.(4)The protein interaction analysis of the sequencing results showed that several protein including XP-001439374.1,XP-001441029.1,XP-001440423.1 may play an important role in the copper resistance mechanism of Paramecium,which needs further experimental verification. |
