Pelodiscus sinensis embryos infected with Aeromonas hydrophila show higher survival rates than infected Mauremys reevesiis embryos

Emydidae and Trionychidae used different strategies to adapt to the environmental condition. However, the differences in the immune responses are not yet fully understood. In this study, Pelodiscus sinensis (P. sinensis) embryos infected with Aeromonas hydrophila (A. hydrophila) showed significantly higher survival rates than infected Mauremys reevesiis (M. reevesiis) embryos. Transcriptomic profiles of infected and non-infected M. reevesiis and P. sinensis embryos were explored. In total, 8,358 differentially expressed unigenes were detected, of which 3,294 and 5,064 genes were considered to be up- and down-regulated in P. sinensis compared to those in M. reevesiis. Six differentially expressed genes (DEGs) were randomly selected for further validation by qRT-PCR, and the results agreed with the RNA-seq data. Analysing the transcriptome data, eight significantly up/down-regulated immune genes (basic transcription factor 3 (BTF3); patched domain containing 1 (PTCHD1); Sep (O-phosphoserine) tRNA: Sec (selenocysteine) tRNA synthase (SEPSECS); zinc finger FYVE-type containing 16 (ZFYVE16); EF-hand domain family member D2 (EFHD2); zinc finger MYM-type containing 4 (ZMYM4); histone deacetylase 9 (HDAC9); interleukin 10 receptor subunit beta (IL-10RB)) were found. Expression patterns of eight selected genes after A. hydrophila injection were detected via qRT-PCR. In the early developmental stages of infected embryos, HDAC9 and IL-10RB significantly up-regulated which play a key role in the activation of NK cells and Th cells in P. sinensis, while M. reevesiis up-regulated BTF3 and ZFYVE16 first to start proliferation of B-lymphoid cells. We provide new insights into the immunity difference between Emydidae and Trionychidae, facilitating the development of new methods to treat bacterial infections in turtles.