| As a temperature-changing animal living in water,fishes will have different degrees of influence on various aspects of the fish body.When the temperature change is within the appropriate temperature range of the fish,the fish can perform normal growth and reproduction activities,but when the ambient temperature changes too much,beyond their ability to bear Various life activities have an adverse effect,and in severe cases,it is very likely to cause disease or death.Tilapia is a cultured fish of great economic value.The persistent high temperature in summer and the intensification of global warming have a great impact on the growth and culture of tilapia.Therefore,the exploration of the molecular mechanism of tilapia under high temperature stress has important guidance and practical significance for tilapia breeding management technology and its application under persistent high temperature.However,the research on the continuous high temperature stress of tilapia at the transcription level is still weak,and the molecular mechanism of high temperature conditions affecting the growth of tilapia has not been reported.The brain and liver are important temperature-responsive regulatory organs for fish.In this study,Nile tilapia juveniles were used as experimental materials.During continuous high-temperature processing,their physiological indexes of body length and body weight were counted,and high-temperature groups were collected(36℃)and control(28℃)brain and liver tissue samples,based on RNA-seq for transcriptome analysis of each tissue sample.The results are as follows:In this experiment,the body length and weight physiological indexes of tilapia under different periods of high temperature stress were counted.The growth of tilapia is restricted,and the growth rate becomes slower as the duration of the continuous high temperature treatment increases.We performed transcriptome analysis on brain tissue samples of tilapia high-temperature experimental group and control group.The results showed that 6 brainlibraries obtained a total of 41.37 Gb Clean Data.Between 28℃control group and 36℃treatment group between 30 d,50d and 70 days.2777,2873 and 3284 differentially expressed genes were identified.In the 30 d comparison group,1613 genes were up-regulated and 1164 genes were down-regulated.In the 50 d comparison group,1250 genes were up-regulated and 1623 genes were down-regulated.In the 70 d comparison group,1800 genes were up-regulated and 1484 genes were down-regulated.Further analysis by GO and KEGG found that high temperature stress response involves multiple biological pathways,such as cell regulation,amino acid metabolism,and immune regulation.Among them,MAPK signaling pathway,Gn RH signaling pathway,cell cycle and other pathways are significantly enriched.We further analyzed the cell cycle pathway and found that the expression of most genes was down-regulated,which indirectly inhibited the growth of tilapia.Finally,8 differential genes in the Gn RH signaling pathway and other related pathways were verified by RT-q PCR experiments,which confirmed the reliability of the RNA-seq results.We performed transcriptome analysis on liver tissue samples of tilapia high-temperature experimental group and control group.The results showed that 6 liver libraries obtained a total of 39.23 Gb Clean Data.Between 28℃control group and 36℃treatment group between 30 d,50d and 70 days.4342,3139 and 3042 differentially expressed genes were identified.In the 30 d comparison group,3026 genes were up-regulated and 1316 genes were down-regulated.In the 50 d comparison group,1352 genes were up-regulated and 1787 genes were down-regulated.In the 70 d comparison group,1702 genes were up-regulated and 1340 genes were down-regulated.Further analysis by GO and KEGG found that multiple pathways related to energy metabolism,protein folding,and immunity were significantly enriched.We further analyzed the protein processing pathway of the endoplasmic reticulum and found that the expression of the vast majority of differential genes is up-regulated and is involved in mediating apoptosis.We verified the 8 differential genes in the m TOR signaling pathway and related pathways by RT-q PCR experiments,which confirmed the reliability of the transcriptome sequencing results.We also further confirmed the phenotypes by apoptosis experiments.Finally,by comparing the transcriptomes of tilapia brain and liver,we found that the regulation of tilapia neuroendocrine inhibited the growth of tilapia to some extent.In summary,this study explored the regulatory mechanism of brain and liver tissues of tilapia subjected to high temperature stress through transcriptome analysis,and analyzed the differential genes and regulatory pathways related to tilapia under high temperature conditions.The regulation mechanism of tilapia response to hightemperature stress lays a theoretical foundation and provides a reference for the development of tilapia high temperature healthy breeding management technology. |
