In this study,juvenile A.japonicus (experimental group) were purchased from northern China and reared in southern China under natural water temperature for one year.The same age seedlings of juvenile A.japonicus (control group) were directly collected from northern China to compare their thermal resistance with those of the experimental group.The study of thermal limits showed that the sublethal temperature of A.japonicus in the experimental group was 32 °C,significantly higher than the 30 °C in the control group.The ULTs50 of A.japonicus in the experimental and control groups were 33.1 °C and 31.9 °C,respectively.These results demonstrated that the thermal history influenced the upper thermal limit of A.japonicus,and A.japonicus undergoing continuous thermal shock would possess stronger thermal resistance.Additionally,the expression patterns of HSP90a,gp96,HSP70,HSP26,and proeintl(2)efl genes after heat shock for 1,2,and 3 hours between the experimental and control groups were analyzed using qRT-PCR.The expression patterns of HSP90a,gp96,HSP70,HSP26,and proeintl(2)efl genes were different between the experimental and control groups.At 30 °C heat shock,the gene expressions of HSP90a,gp96,HSP70,and HSP26 in the control group did not noticeably increase after stimulation for 1 and 2 hours but were significantly up-regulated at 3 hours,with expression values reaching (9.801±1.303),(2.508±0.910),(8.649±1.936),and (34.787±4.978),respectively.However,all of the HSP90a,gp96,HSP70,and HSP26 gene expressions in the experimental group were dramatically up-regulated at 1 hour at 30 °C,with expression values reaching (42.000±8.798),(20.019±6.224),(218.750±78.701),and (93.710±5.674),respectively.These four temperature-tolerant related genes detected in the present study in the experimental group were up-regulated earlier than those in the control group,indicating a higher ability of A.japonicus in the experimental group to respond adaptively to heat shock than that in the control group.Therefore,the research showed that A.japonicus undergoing high temperature acclimation could respond earlier to external environmental heat conditions.
