| The red-eared turtle(Trachemys scripta elegans)was listed as one of the most dangerous invasive species around the world by the World Conservation Union(IUCN)because of its biological characteristics with early sexual maturity,strongly reproductive capacity,polyphagy,strong tolerance to stress and strong competition ability with other turtles(such as food and bathing space,etc).Now it has successfully invaded all over the world except Antarctica,also including in China.Field investigation and laboratory study has showed that T.s.elegans can survive in brackish water.Currently,much studies focus on salinity tolerance and the physiological adaptation mechanism on T.s.elegans,but molecular mechanism of adaptation to salinity stress still remains unclear.This study contribute to understand osmotic regulation gene and molecular regulation network under salinity stress through the high-throughput sequencing and the measurement of physiological indicators,in order to better understand the invasion mechanism of T.s.elegans.Healthy T.s.elegans were obtained from local turtle farm in Hainan,China.T.s.elegans were acclimated in three cement pools half filled with freshwater for 2 weeks.And then,healthy T.s.elegans(466.39 ± 69.61g)were divided into 3 groups(190 cm × 65 cm × 32 cm),one in freshwater serving as the control(0 practical salinity unit,0 psu),and the other two challenged with 5 ‰(5 psu)and 15 ‰(15 psu)saltwater.During the acclimation and experimental periods,the turtles were fed a commercial diet for turtles each Monday and Thursday because of their slow metabolism rate.After 8 weeks of salinity stress,livers were sampled from 3 turtles in each cement pool for RNA extraction for transcriptomic analysis by Hiseq4000 Truseq SBS Kit v3-HS(Illumina),the blood from 6 turtles in each cement pool for the measurement of phyisiolgical indicators.The results showed that:1.A total of 157.21 million reads and 23.58 billion bases were obtained from T.s.elegans,including 50.68 million reads in the group of 0 psu,57.91 million in the group of 5 psu and 48.62 million in 15 psu.After quality trimming and adapter clipping,152.52 million reads accounting for 97.02% of the total reads were obtained including 48.92 million reads in 0 psu,56.50 million in 5 psu and 47.10 million in 15 psu.In addition,205,138 unigenes with an average length of 620.1 bp were obtained by de novo assembly using Trinity software after splicing and removing redundancy.Among the unigenes,the largest and smallest unigenes were 22,866 bp and 201 bp,respectively.2.1019 genes were significantly up or down regulated,including 445 genes significant up-regulation and 574 genes significant down-regulation in 0 vs 5.1194 genes were significantly differential expression,including 526 genes significant up-regulation and 668 genes significant down-regulation in 0 vs15.and 1180 genes were significantly differential expression,including 548 genes significant up-regulation and 632 genes significant down-regulation in 5 vs 15.3.Through analyzing and screening out GO enrichment,KCNH5(potassium voltage-gated channel Eag-related subfamily H member 5),SCN1B(voltage-gated sodium channel type I beta),NPPA(Natriuretic peptide precursor A),GLUL(gln A,glutamine synthetase),SLC38A2(SNAT2,solute carrier family 38(sodium-coupled neutral amino acid transporter),member 2),ASS1(arg,argininosuccinate synthase),OAZ3(ornithine decarboxylase antizyme 3),ATPe FOA(MTATP6,ATP6,F-type H+-transporting ATPase subunit a),GCK(glucokinase),SIK(Salt-Inducible Kinase),ACDC(adiponectin)and CYP17A(steroid 17alpha-monooxygenase/ 17 alpha-hydroxyprogesterone deacetylase)were important genes in relation to osmotic adjustment.Then these genes draw interaction network.4.There were 4 significantly changed KEGG pathways in 0 vs 5 group,including Cell adhesion molecules(CAMs),Antigen processing and presentation,Phagosome and Natural killer cell mediated cytotoxicity.There were 2 significantly changed KEGG pathways in 0 vs 15 group,including Hematopoietic cell lineage and Natural killer cell mediated cytotoxicity.There were 6 significantly changed KEGG pathways in 5 vs 15 group,including Cell adhesion molecules(CAMs),Natural killer cell mediated cytotoxicity,Antigen processing and presentation,Phagosome,Hematopoietic cell lineage and Complement and coagulation cascades.5.When the salinity increased,the concentration of plasma Na+ and Cl-increased.There are significant differences in [Na+] between salinity 5 and 15 group(P < 0.05).The concentration of Cl-in the control group,salinity 5 group and salinity 15 group have significant difference(P < 0.05).Plasma [K+] declined with the increase of salinity,significant difference existed in 0 vs 5 group and 0 vs 15 group(P < 0.05).In addition,plasma urea nitrogen increased significantly with the increase of salinity(P < 0.05).Osmotic pressure in blood increased significantly with the increase of salinity except in 0 vs 5 group(P < 0.05).Plasma glucose decreased with the increase of salinity.However,plasma cortisol decreased and then increased with the increase of salinity,and there were no significant differences between groups(P > 0.05).The results showed that Na+,Cland urea nitrogen are necessary to improve blood osmotic pressure under salinity stress,and within a certain range of salinity,higher concentration of blood glucose were consumed to provide energy. |
PDF Full Text Request