Comparative transcriptome analyses reveal changes of gene expression in larvae hatched from fresh and cryopreserved kelp grouper (Epinephelus moara) embryos

Abstract

For the first time in fish, this study investigated the changes of gene expression in larvae hatched from fresh and cryopreserved embryos using RNA-seq. The transcriptome of kelp grouper from 1-day larvae hatched from fresh and cryopreserved embryos were obtained by high-throughput sequencing and analyzed by KEGG and GO database. The analysis results showed that 1815 unigenes were significantly differentially expressed (1165 up-regulated vs 650 down-regulated). Significantly down-regulated genes were enriched for eye development, cranial nerve development, sensory light stimulation and neurotransmitter transport terms, predicting that dehydration/rehydration or freezing/thawing during cryopreservation may affect development of the central nervous system, including the primordia of the eye. Moreover, many down-regulated genes were involved in calcium ion regulation, which may affect cell structure, as well as cell proliferation and differentiation. Meanwhile, gene expression of some proteins that protect neurons from the toxic effects of high concentrations of extracellular neurotransmitters significantly decreased, further suggesting that cryopreservation may have an effect on the central nervous system of larvae. In addition, huge amounts of primary data provided in present paper contribute to the genome and proteome databases of the grouper. These results will help other researchers better understand the effect of cryopreservation on fish embryos and improve exploration of the molecular mechanism of fish embryo cryoinjury.