Metabolomic and transcriptomic analysis reveals immune and hormone modulation at the molting stage of juvenile mud crabs challenged with Staphylococcus aureus and Vibrio alginolyticus

Abstract

The mud crab (Scylla paramamosain) is an important economic breeding species along the southeast coast of China. As a crustacean, molting is critical for growth and reproduction. At each molting, a new external cuticle of mud crab is inherently regenerated, but along with molting the crabs are easily susceptible to pathogenic infection that might result in a low survival rate particularly at juvenile stages. To elucidate the potential response mechanism of juvenile mud crabs infected with bacteria in the molting process, integrated transcriptomic and metabolomic techniques were applied and the hormones, associated-hormone genes or immune genes modulated by challenge with Staphylococcus aureus or Vibrio alginolyticus were analyzed. The omic analysis showed that S. aureus or V. alginolyticus infection caused decreases in steroid hormones (cortisol, cortodoxone, cortisone, deoxycorticosterone) and fatty acid-derived hormones (prostaglandin A2, Δ17–6-keto prostaglandin F1α, 13,14-Dihydro-15-keto-tetranor prostaglandin F1α, prostaglandin B2, 2,3-Dinor-11β-prostaglandin F2α, thromboxane B2, and 11-Dehydro thromboxane B2). Correspondingly, transcriptomic analysis revealed that both S. aureus and V. alginolyticus infection downregulated the expression levels of fatty acid-derived hormone synthases. In addition, both bacterial infections caused upregulation in Toll, IMD, the Jak/Stat pathway, antimicrobial peptide, and the prophenoloxidase system. The study provides a new insight into the effects of bacteria on the juvenile crab molting process in vivo that lead to the modulation of both immune-associated genes and hormones.