Frizzled 5 activates JNK/c-Jun and contributes to the growth of Litopenaeus vannamei

Growth is a critical economic trait in shrimp aquaculture. While the canonical Wnt/β-catenin pathway is known to regulate shrimp growth, the function of its key receptor, Frizzled (FZD), remains largely unexplored. This study functional characterized an FZD gene in Litopenaeus vannamei , designated as LvFZD5. Phylogenetic analysis confirmed its classification within the FZD5/8 subfamily. LvFZD5 was highly expressed in nerves, hepatopancreas, and eyestalks. A co-immunoprecipitation assay demonstrated a specific physical interaction between LvFZD5 and its putative ligand, LvWnt5. Functional investigations revealed that LvWnt5 signals through its receptor LvFZD5 to activate the downstream transcription factor c-Jun, establishing a conserved LvWnt5-LvFZD5-Lvc-Jun signaling axis. Furthermore, activated Lvc-Jun was shown to induce several Wnt genes, whereas Lvc-Jun knockdown reduced LvFZD5 transcription, creating a positive feedback loop. Transcriptomic analysis of hepatopancreas tissue following LvFZD5 knockdown further revealed its global regulatory impact, notably suppressing pathways such as ribosome biogenesis. Crucially, in vivo RNA interference-mediated knockdown of LvFZD5 significantly impaired shrimp growth, resulting in reduced final body length, body weight, and weight gain. Collectively, these findings identify LvFZD5 as a positive regulator of shrimp growth and demonstrate its involvement in LvWnt5-dependent JNK/c-Jun signaling, offering a novel molecular target for genetic breeding programs.