Involvement of the JNK signaling pathway in regulating yolk accumulation in the swimming crab, Portunus trituberculatus

The c-Jun N-terminal kinase (JNK) signaling pathway regulates the development of ovaries and synthesis of vitellogenin (Vg) in the swimming crab Portunus trituberculatus, but the underlying molecular mechanism remains unclear. In this study, we cloned the essential c-fos gene of the JNK signaling pathway using the rapid amplification of complementary DNA end method. The full-length cDNA of c-fos was 2829 bp long and had a 1497 bp open reading frame encoding a 498 amino acid protein and containing a basic leucine zipper domain. After injecting c-jun-double stranded (ds) RNA to silence the JNK signaling pathway target gene c-jun, the expression levels of key JNK signaling pathway genes (c-jun, JNK, Vg, and c-fos) in the hepatopancreas were significantly down-regulated (P < 0.05). In ovarian tissue, the expression levels of c-jun, c-fos, and Vg genes were significantly down-regulated (P < 0.05), but no significant change was detected for JNK gene expression. Hematoxylin-eosin staining indicated that the oocytes in the c-jun-dsRNA group and the Vg-dsRNA group developed slowly, and an enzyme-linked immunosorbent assay confirmed that the accumulation of vitellin in the ovary was significantly reduced by 56% and 52% in the two groups, respectively. Co-immunoprecipitation results showed that c-Jun and c-fos proteins play a regulatory role by forming a heterodimeric transcription factor activator protein 1. These results indicated that the JNK signaling pathway of P. trituberculatus regulated the synthesis of Vg through the transcription factor activator protein 1, thereby regulating the accumulation of yolk. The results of this study provided a theoretical basis and technical guidance for P. trituberculatus production.

Automated summary

In this study, the researchers cloned the essential c-fos gene of the JNK signaling pathway and found that the JNK pathway regulates the synthesis of vitellogenin (Vg) in the swimming crab Portunus trituberculatus through the transcription factor activator protein 1. Silencing the JNK signaling pathway target gene c-jun resulted in down-regulation of key JNK signaling pathway genes and decreased accumulation of vitellin in the ovary.