Transcriptome analysis provides molecular evidence for muscle growth regulation in Litopenaeus vannamei infected with Ecytonucleospora hepatopenaei (EHP).

Hepatopancreatic microsporidiosis (HPM) in Litopenaeus vannamei caused by Ecytonucleospora hepatopenaei (EHP) mainly manifests as growth retardation. Hitherto, the mechanism by which it inhibits growth remains unclear. In this study, muscle transcriptome sequencing was conducted on shrimp artificially challenged with EHP for 10 d, and the expression characteristics of genes related to the mTOR pathway were investigated to explore the molecular mechanism underlying muscle growth inhibition in EHP-infected shrimp. A total of 1289 differentially expressed genes were identified, including 726 up-regulated and 563 down-regulated genes. Significant down-regulation of growth-related genes was detected in EHP-infected shrimp, especially those encoding actin and myosin. Moreover, the expression levels of cell division-related gene cyclin dependent kinase 1 (CDK1) and the molting-related gene β-N-acetylhexosaminidase 20 (HEX) were also significantly inhibited. However, the gene expression of mTOR and its related negative regulatory factors (unc-51, Tsc1 and FNIP1) was significantly up-regulated, along with immune-related genes such as anti-lipopolysaccharide factor (ALF) and prophenoloxidase-activating factor 3 (PPAF3). In contrast, the expression of NLR family CARD domain containing 4 (NLRC4) was significantly down-regulated. Functional enrichment analyses revealed that EHP infection mainly affected protein synthesis and glucose metabolism pathways. Furthermore, the expression of key genes in the mTOR pathway was detected to be significantly up-regulated within 20 d post EHP challenge. These findings indicate that EHP infection triggered an immune response and disrupted muscle cell division, protein synthesis, and molting processes, providing valuable resources for clarifying the molecular mechanism of growth regulation in shrimp after EHP infection.