Transcriptome Analysis Of Oyster Crassostrea Viginica Exposed To Nano Nickel Oxide

With the rapid development of nanotechnology,the negative effects of nanomaterials on the ecological balance and social security have also attracted great attention.In this paper,oysters(Crassostrea viginica)were used as test organisms to study the gene expression profile and differential gene expression effects of different concentrations of nano-nickel oxide(nNiO)(0,1,10 and 100 mg/L)on the oysters after acute exposure for 96 h,and that reveals the molecular mechanism of oyster in response to nNiO and provides a theoretical basis for the study of the toxic effects of nano-metal oxides on bivalve molluscs.The main results were as follows:1.De novo assembly and transcriptomic analysis of C.viginica were conducted using Illumina Hiseq2000 high-throughput sequencing technology.There were 76,985 unigenes assembled and the average length was 1539 bp.Based on GO and KEGG analysis,a total of 1541 transcripts involved in the immune pathway,446 transcripts involved in the apoptotic process,and 296 transcripts involved in the xenobiotics metabolism were obtained.2.The results of gene expression profiling analysis of oyster exposed to different concentrations nNiO indicated that the 10 mg/L groups have the highest number of DEGs both in gills and digestive glands,indicating that the 10 mg/L induced the biological response more active in oysters.It was also found that the number of DEGs in the gills was higher than that in the digestive glands.It may be related to the fact that the gill is the first defense barrier.3.Different tissues have slightly different defense mechanisms against nNiO.The genes MRP and MT are up-regulated in gills,which may be related to the function of gills of forming the first defense barrier;while the detoxification enzyme genes CYP450 and GST are higher expressed in the digestive glands,indicating that the digestive gland tissue is the main detoxification organ for bivalve molluscs in response to environmental pollutants.4.The STEM analysis was used to perform the trend analysis to investigate the DEGs under the exposure of different concentrations of nNiO.The results showed that with the nNiO exposure concentration continue to rising,the expression of DEGs involved in immune and apoptosis-related pathways was increased,but the expression of DEGs engaged in basal metabolic related pathways was gradually decreased in the gills;while the expression level of immunity related and metabolism of xenobiotics was gradually increased in digestive glands.4.The STEM analysis was used to perform the trend analysis based on the transcriptome data to investigate the DEGs under the exposure of different concentrations of nNiO.The results showed that with the nNiO exposure concentration continue to rising,the expression of DEGs involved in immune and apoptosis-related pathways was increased,but the expression of DEGs engaged in basal metabolic related pathways was gradually decreased in the gills;while the expression level of immunity related and metabolism of xenobiotics was gradually increased in digestive glands.5.Through in-depth analysis of the functional annotation information of differential genes,it is found that there are three main metabolic pathways for oysters to respond to nNiO:(1)Toll-like receptor-mediated immune response;(2)Tumor necrosis factor-mediated apoptosis process;(3)CP450,GST and MRP involved in detoxification mechanism.In summary,this study use high-throughput sequence technology to establish transcriptome databases of American oysters response to nNiO for the first time,which provided data support for the future research on the molecular mechanism of bivalve molluscs response to heavy metal.