Gut Microbiotic Hemeostasis Regulation in shrimp Marsupenaeus japonicus

The mechanism of microbiota homeostasis in host intestines has been well studied in mammals and Drosophila. The reactive oxygen species (ROS) and antimicrobial peptides have been reported to play important roles in homeostasis. However, how to maintain the microbiota homeostasis in crustacean intestine needs to be elucidated. Two dual oxidases (MjDUOX1 and 2) involved in ROS production in kuruma shrimp, Marsupenaeus japonicus. After the shrimp were challenged with pathogenic bacteria via oral infection, the mRNA level of MjDUOXs and the free ionic calcium of cytoplasm were both upregulated. When MjDUOXs were knocked down by RNA interference (RNAi) and then oral infection, the survival rate of the MjDUOXs-RNAi shrimp was declined. Besides, bacteria number increased in the MjDUOXs-RNAi shrimp intestinal lumen than those in the control groups. We also identified a novel catalase (MjCAT) involved in ROS elimination in the shrimp. After the shrimp were challenged with pathogenic bacteria via oral injection, the expression level of MjCAT was upregulated in the intestine. When MjCAT was knocked down, ROS level increased but the number of bacteria was declined in the shrimp intestinal lumen compared with those in the control group, and the survival rate of shrimp was also declined. Further study demonstrated the aberrant morphological characteristics of the intestine epithelium in MjCAT-knocked down shrimp. All these results suggested that DUOX-CAT participated in the intestinal host-microbe homeostasis by regulating ROS level.