Growth arrest and DNA damage-inducible 45 ab gene targeted by miR-20b-5p executes the inflammation and apoptosis by regulating MAPK and NF-κB pathways in black rockfish

Growth arrest and DNA damage-inducible 45 alpha, b gene (gadd45ab) is a key homologue of gadd45a subfamily, which participates in several biological processes, such as inflammation and apoptosis. Black rockfish (Sebastes schlegelii) is an important commercial fish species in China. In current study, black rockfish gadd45ab (Ss_gadd45ab) was characterized as a target gene of miR-20b-5p. The results indicated that high evolutionary conservations were found in the sequence and structure of Ss_gadd45ab, which was also detected to locate on the cytomembrane in the black rockfish intestine. The expressions of Ss_gadd45ab and diverse cytokines related to immune response were significantly induced with different patterns by the infection of E. tarda. Moreover, all tested immune genes were dramatically up-regulated when Ss_gadd45ab was overexpressed in the intestine cells, and significant up-regulations and down-regulations of almost these immune genes were observed in the overexpressed cells during the LPS stimulation at 12 h and 24 h, respectively, which implied the potential regulations of Ss_gadd45ab in the immune system. Meanwhile, the overexpression of Ss_gadd45ab was found to prevent the invasion of E. tarda and promote the cell apoptosis in the intestine cells of black rockfish. Therefore, a profile of a novel regulatory mechanism of Ss_gadd45ab targeted by miR-20b-5p in the inflammatory and apoptotic responses of black rockfish during pathogenic infections was hypothesized. Even though the potential functions of Ss_gadd45ab on the inflammation and apoptosis in the black rockfish intestine during pathogenic infections have been described preliminarily in this study, more efforts are still urgent to be done for the further verification of this regulatory mechanism in black rockfish.

Automated summary

The study reveals that miR-20b-5p plays a key role in the inflammatory and apoptotic responses of black rockfish by targeting the gadd45ab gene. The gadd45ab gene is located on the cytomembrane in the black rockfish intestine and its expression is induced by the infection of E. tarda. Overexpression of Ss_gadd45ab significantly up-regulates multiple immune response-related genes and prevents the invasion of E. tarda while promoting cell apoptosis.