The ELAVL gene family in large yellow croaker: LcELAVL1a is an immune-active member with direct antibacterial and cell-protective functions.

The embryonic lethal abnormal vision-like (ELAVL) gene family encodes a group of conserved RNA-binding proteins involved in post-transcriptional regulation and immune function. In this study, five ELAVL family members (Lcelavl1a, Lcelavl1b, Lcelavl2, Lcelavl3, and Lcelavl4) were identified and characterized in large yellow croaker (Larimichthys crocea). The five members exhibited a progressive motif distribution pattern and typical RNA recognition motif (RRM)-fold architectures, and phylogenetic analysis confirmed their orthologous relationships with ELAVL proteins in other vertebrates, indicating that the ELAVL family is highly conserved among teleosts. Among these five members, Lcelavl1a showed significantly higher expression levels during Aeromonas hydrophila and Pseudomonas plecoglossicida infection, suggesting an important immune-related role. It was therefore selected for further functional investigation. Lcelavl1a was detected in all nine examined tissues, with the highest expression in the gonads. Following Vibrio parahaemolyticus challenge, Lcelavl1a was significantly upregulated in the head kidney, spleen, liver, and gill. Recombinant LcELAVL1a (rELAVL1a) inhibited the growth of V. parahaemolyticus, Edwardsiella tarda, and Staphylococcus aureus in a concentration-dependent manner and bound directly to all three bacterial species, indicating broad-spectrum antibacterial activity. At the cellular level, overexpression of Lcelavl1a in large yellow croaker kidney cells (PCK) elevated the basal mRNA levels of il-1β, il-6, and tnf-α, and reduced bacteria-induced cell injury. Moreover, rELAVL1a treatment improved the viability of bacteria-infected PCK cells. Taken together, these results demonstrate that LcELAVL1a functions as an immune-active protein in large yellow croaker and provide new insights into the functional diversity of the ELAVL family in teleost fish.