UBE2G1 Is a Critical Component of Immune Response to the Infection of Pseudomonas Plecoglossicida in Large Yellow Croaker (Larimichthys crocea)

Abstract

The large yellow croaker (<i>Larimichthys crocea</i>) is one of the most economically valuable mariculture fish in China. Infection of <i>Pseudomonas plecoglossicida</i> can cause an outbreak of "internal organ white-spot disease", which seriously affects the aquaculture of the large yellow croaker. Ubiquitylation is closely related to the post-translation modification of proteins and plays a vital role in many hosts' immune defense pathways, while the E2-binding enzyme is a key factor in ubiquitination. Our previous genome-wide association study found that the ubiquitin-binding enzyme E2G1 (designed <i>LcUbe2g1</i>) was one of the candidate genes related to disease resistance in large yellow croaker. In this study, we analyzed the molecular characteristics, function, and immune mechanism of the <i>LcUbe2g1</i>. The full-length cDNA is 812 bp, with an open reading frame of 513 bp, encoding 170 amino acid residues. The results of the RT-qPCR and immunohistochemistry analysis revealed that its transcription and translation were significantly activated by the infection of <i>P. plecoglossicida</i> in large yellow croaker. Immunocytochemistry experiments verified the co-localization of <i>Lc</i>UBE2G1 and the ubiquitin proteins in the head kidney cells of large yellow croaker. Through GST pull-down, we found that <i>Lc</i>UBE2G1 interacted with NEDD8 to co-regulate the ubiquitination process. The above results indicate that <i>Lc</i>UBE2G1 is essential in the regulation of ubiquitination against <i>P. plecoglossicida</i> infection in large yellow croaker, which lays a foundation for further study on the resistance mechanism of internal organ white-spot disease.