ROS GENERATING GENES OF KURUMA SHRIMP Marsupenaeus japonicus: XANTHINE DEHYDROGENASE AND ALDEHYDE OXIDASE, AND THEIR GENE EXPRESSION ANALYSES AGAINST PATHOGENS
Reactive oxygen species (ROS) play important roles in shrimp physiological reaction. Particularly, the bacteria killing mechanism by ROS in macrophages is a key function for biological defense. ROS is generated by xanthine dehydrogenase (XDH) and aldehyde oxidase (AOX), members of the molybdo-flavoenzyme subfamily. Although these enzymes are found in many vertebrates, some insects and plants, little research has been conducted on in crustaceans.
The entire cDNA sequences of XDH (MjXDH: 4,328 bp) and AOX (MjAOX: 4,425 bp) were cloned from Marsupenaeus japonicus (kuruma shrimp) using reverse transcriptase-polymerase chain reaction (RT-PCR) and random amplification of cDNA ends (RACE). Quantitative real-time RT-PCR transcriptional analyses revealed that MjXDH mRNA is highly expressed in heart and stomach tissues, whereas MjAOX mRNA is highly expressed in the lymphoid organ and intestinal tissues. Furthermore, expression of MjAOX was up-regulated in the lymphoid organ in response to Vibrio penaeicida at 48 and 72 h after injection; in contrast, hydrogen peroxide (H2O2) concentrations increased significantly at 6, 12, 48, and 72 h after injection with white spot syndrome virus (WSSV) and at 72 h after injection with V. penaeicida. This study is the first to have identified and cloned XDH and AOX genes from a crustacean species and clarified the response to pathogens.