Reeler Domain-Containing Proteins Involved in the Antibacterial Immunity of Shrimp Litopenaeus vannamei

Like other invertebrates, <i>Litopenaeus vannamei</i> lacks adaptive immunity and relies mainly on innate immunity for defense against foreign pathogens. In this study, three distinct Reeler domain-containing molecules were discovered in <i>L. vannamei</i>, designated as <i>LvReeler1</i>, <i>LvReeler2</i>, and <i>LvReeler3</i>. Analysis of tissue-specific expression patterns indicated that <i>LvReeler1</i> showed predominant expression in the stomach, whereas <i>LvReeler2</i> and <i>LvReeler3</i> demonstrated peak transcriptional activity within gill tissues. The expression of these molecules was induced by <i>Vibrio parahaemolyticus</i>. In vivo interference with <i>LvReelers</i> expressions via dsRNA significantly increased the mortality rate of <i>L. vannamei</i>, while also leading to a marked increase in the bacterial load of <i>V. parahaemolyticus</i> in the gills. Additionally, recombinant proteins of <i>LvReeler1</i> (rLvReeler1), <i>LvReeler2</i> (rLvReeler2), and <i>LvReeler3</i> (rLvReeler3) were successfully expressed in <i>Escherichia coli</i>. Antibacterial assays demonstrated that rLvReelers inhibited the growth of <i>V. parahaemolyticus</i>, <i>Vibrio alginolyticus</i>, and <i>Vibrio harveyi</i>, with rLvReeler3 exhibiting the strongest inhibitory activity. Scanning electron microscopy (SEM) observations revealed that rLvReeler3 caused bacterial aggregates to disintegrate after binding to <i>V. parahaemolyticus</i> and <i>V. alginolyticus</i>. In conclusion, <i>LvReelers</i> play an active role in the antimicrobial immune response of <i>L. vannamei.</i>