The formin-like regulates innate immunity and antibacterial immune responses in Scylla paramamosain

The formin family of proteins, recognized for their evolutionary conservation across species, plays a pivotal role in the regulation of actin polymerization, thereby influencing cellular growth and cytoskeletal integrity. Recent studies have identified formin-like genes as crucial components in the regulation of innate immune responses and hematopoiesis in the anthropomorphic species Scylla paramamosain. This research investigates the function of formin-like genes in the innate immune system of S. paramamosain through targeted gene knockdown using double-stranded RNA (dsRNA). The expression levels of genes associated with the innate immunity, such as Astakine, STAT, MCM7, Myosin, Crustin, and TLR, were observed to be down-regulated by formin-like knockdown. In contrast, the expression of immune genes like p53, Caspase-3, and Relish was observed to be up-regulated by formin-like knockdown. The suppression of formin-like expression affected the expression of the immune-related genes, thereby influencing the innate immunity in S. paramamosain. Analysis of enzyme activities demonstrated an increase in the activities of superoxide dismutase (SOD), glutathione (GSH), and peroxidase (POD), whereas the activities of lysozyme (LZM) and alkaline phosphatase (AKP) were reduced after formin-like knockdown. Upon knockdown of formin-like, a notable reduction in reactive oxygen species (ROS) levels was observed in the knockdown group, suggesting formin-like may affect the antioxidant capacity of S. paramamosain. The reduction in hemocyte phagocytosis rates and the reduced expression of phagocytosis-related genes like Myosin and MCM7 after formin-like knockdown suggested that formin-like affect the phagocytic capacity of the hemocytes to engulf bacteria. Furthermore, the reduced activities of lysozyme (LZM) and alkaline phosphatase (AKP) indicated that knockdown of formin-like affected the antimicrobial capacity of S. paramamosain. This conclusion is supported by the decreased survival rate of crabs challenged with Vibrio alginolyticus after formin-like knockdown. These findings suggested that formin-like may regulate both antioxidant and antimicrobial capacities of S. paramamosain, and plays an important role in the innate immunity.