Gill transcriptome analysis reveals the molecular response to the acute low-salinity stress in Cyclina sinensis

Salinity is an important environmental factor that has a profound impact on the growth, reproduction, survival, and development of mollusk. To investigate the molecular changes in response to acute low-salinity stress, the clams were transferred from 25 parts per thousand to 8 parts per thousand. According to the exposure times of 0, 12, 24, 48, 72, 96, and 120 h, the treatment consisted group T0 (the control), T1, T2, T3, T4, T5, and T6, respectively. Gills were collected, and then transcriptome analysis was conducted. Compared to the control, 3008 DEGs were obtained, including 1127 up-regulated and 1881 down-regulated genes, respectively. Up-regulations of 924, 176, 11, 6, 3, and 7 DEGs, and down-regulations of 1216, 416, 157, 59, 23, and 10 DEGs were observed in T6, T5, T4, T3, T2, and T1 groups, respectively. The related molecular biological processes, and potential functions were explored from enrichment analyses, including energy metabolism, material metabolism, and immune responses. There were 13, 10, 16, 30, 62, and 97 KEGG pathways enriched in T1, T2, T3, T4, T5, and T6 groups, respectively. 13 genes down-regulated, and only one gene up-regulated were found in more than four groups. In addition, the verification of the expression changes of the candidate genes (PCK1, IAP, BIRC2, and LOC102459116) provided insights into responses to salinity change in the gills of the clams. This will be of great value in understanding the molecular basis of low-salinity adaptation in the clam.