Expression of LINE1 in Zebrafish (Danio rerio) During Cold Acclimation

Abstract:

The long-spread nuclear element-1 (LINE1) retrotransposon is a mobile element in genome. Previous comparative genomic studies found that Antarctic Notothenioid fish underwent a long low-temperature adaptation evolution, and compared with Notothenioid fish outside the Antarctic circle, LINE1 genes were duplicated by 8~300 fold. The link between this augmentation and the resistance of fish to cold is not known. In this study, zebrafish (Danio rerio) embryonic fibroblasts ZF4 were exposed to a low temperature (18℃) for 5 days and 30 days, and adult zebrafish were exposed to a low temperature (10℃) for 3 h, 6 h, 1 d, 3 d, and 5 d. The mRNA expression of LINE1 was examined using RT-qPCR. The promoter regions of zebrafish LINE1 gene were cloned and the biological activity of LINE1 5'UTR at low temperature were verified in ZF4 cells by using the dual-luciferase reporter system. The following results were obtained: (1) In ZF4 cells, LINE1 mRNA expression was decreased by short-term low temperature treatment, but was significantly increased by long-term low temperature treatment. (2) In adult fish, LINE1 mRNA expression was decreased by short-term low temperature treatment, but was significantly increased in long-term low temperature treatment. (3) The LINE1 5'UTR was found to be biologically active in ZF4 cells. (4) It was found that during low temperature treatment (18℃, 3 d), the reporter gene signal was weakened, which indirectly indicated that the LINE1 promoter activity was weakened. The results showed that low temperature stress affected LINE1 expression in fish, which presents a foundation for further study on the mechanism of action of LINE1 in fish adaptation to a low temperature environment.