Reactive oxygen species (ROS) potentially affected survival rate after ionizing radiation in scallops

Ionizing radiation (IR) accelerates aging and increases the risk of death in organisms. The two scallops, Argopecten purpuratus (7-10 years) and A. irradians (less than 14 months), have markedly different lifespans and exhibited different tolerance to IR. However, little information was available for understanding why the A. purpuratus had a higher survival rate after IR. In the present study, we first investigated genetic responses to IR in the two scallops by comparative transcriptome analysis. After IR exposure, the A. purpuratus has more significantly up-regulated expressed genes (mainly involved in neuroactive ligand-receptor interaction, peroxisome, autophagy, and DNA repair), but the A. irradians has more significantly down-regulated expressed genes (mainly involved in lysosome, peroxisome, autophagy, DNA repair, and apoptosis). In addition, the main genes and pathways that respond to IR are completely different between the two scallops. The expression of ATG5, BAX, CTSL, CTSB, ULK2, and ATG9A, which are important genes for autophagy, was significantly downregulated in the A. irradians, which may contribute to its early mortality. However, the expression of SOD1, CAT, SCD, and ACOX1, which perform the function of antioxidation, significantly increased in the A. purpuratus, potentially mitigating ROS-induced cellular damage. In addition, the ROS level in the A. purpuratus was significantly lower than the A. irradians after IR. These findings suggested that ROS potentially contribute to bivalve tolerance to IR, and also suggest potential biomarkers for breeding scallops with a high survival rate.