Characterization of a newly identified vitellogenin-like gene (LvVTG-like) and its role in the defense against Vibrio parahaemolyticus infection in Litopenaeus vannamei.

The Pacific white shrimp (Litopenaeus vannamei) faces significant threats from Acute Hepatopancreatic Necrosis Disease (AHPND), caused by Vibrio parahaemolyticus. Identifying disease resistance-related genes and elucidating resistance mechanisms represent crucial approaches to mitigate the risk of AHPND. While vitellogenin family proteins are well known for their roles in reproduction, the role in immunology, particularly during bacterial infection, remains underexplored. This study aimed to investigate the function of a newly identified vitellogenin-like gene, LvVTG-like, in immune defense against V. parahaemolyticus infection of L. vannamei and to elucidate its underlying regulatory mechanisms. Through gene expression analysis, RNA interference (RNAi), transcriptome sequencing, and 16S rRNA gene sequencing, we demonstrated that the LvVTG-like is an important disease-resistant gene. The RNAi of LvVTG-like significantly improved shrimp survival rates (∼58.3% reduction in mortality) and substantially reduced bacterial loads (∼99.38% reduction) following V. parahaemolyticus challenge. Transcriptomic analysis revealed that LvVTG-like knockdown resulted in the significant enrichment of the PI3K-Akt and nucleocytoplasmic transport pathways, upregulating genes for immune barrier reinforcement and innate immune responses. Furthermore, 16S rRNA gene sequencing of the LvVTG-like knockdown individuals showed beneficial gut microbiota remodeling, characterized by decreased relative abundance of pathogenic Vibrio and increased beneficial bacteria. These findings highlight LvVTG-like as a negative immune regulator and a promising molecular target for the molecular regulation of anti-V. parahaemolyticus immunity and molecular breeding in L. vannamei.