Transcriptomic Analysis Reveals Molecular Mechanisms of Fleeing, Adhesion, and Thanatosis Patterns in Sea Cucumber Apostichopus japonicus.

Sea cucumbers (Apostichopus japonicus) show fleeing, adhesion, and thanatosis patterns upon exposure to various stressors. However, the molecular mechanisms underlying these contrasting stress response patterns remain largely unknown. In the present study, we performed a transcriptomic analysis of coelomocytes on stressed sea cucumbers to elucidate the potential molecular mechanisms. The RNA-seq results revealed that several matrix metalloproteinase (MMP) family genes, along with HTR4, HRH2, and ADRA1D (which are involved in neuroactive ligand-receptor interactions), were significantly upregulated in the fleeing pattern. These genes may facilitate rapid movement. In the adhesion pattern, PHKA and PGK were significantly downregulated, and the differentially expressed genes (DEGs) were significantly enriched in the longevity regulating pathway, accompanied by downregulation of KRAS and HSPA1. These genes and the pathway may be involved in the reallocation of energy resources during the adhesion pattern. In the thanatosis pattern, DEGs were significantly enriched in the MAPK signaling pathway (including upregulation of ANGPT1 and FGFR1) and in the Rap1 and Ras signaling pathways (with downregulation of key genes: RAPGEF4, RRAS2, and RaLA). These genes potentially contribute to sustaining the thanatosis pattern. These transcriptomic profiles provide novel insights into the distinct molecular signatures underlying each stress response pattern in A. japonicus.