LvSlc12A2 Is a Negative Growth Regulator in Whiteleg Shrimp, Litopenaeus vannamei

<i>Litopenaeus vannamei</i>, commonly known as the Pacific white shrimp, is one of the most economically significant species in global aquaculture, valued for its rapid growth and adaptability. However, the mechanisms regulating its growth, especially under high-density farming and environmental stress, remain poorly understood. Previous study predicted that <i>LvSlc12A2</i> was involved in growth regulation. To further reveal the function of this gene in the growth regulation of the whiteleg shrimp, in this study, we explore its function using RT-qPCR, RNA interference, overexpression, and tissue in situ hybridization. RT-qPCR results showed that <i>LvSlc12A2</i> was highly expressed in gills (about 62%), followed by the hepatopancreas, with the lowest expression in muscle (0.08%, compared to the gills). Myostatin (<i>LvMstn</i>) was mainly expressed in the heart, and molt-inhibiting hormone (<i>LvMIH</i>) in the ventral nerve. In situ hybridization of gill tissues using the mRNA of the gene as a probe revealed strong <i>LvSlc12A2</i> signals in the gill stratum and epithelial cells. Overexpression of <i>LvSlc12A2</i>, significantly decreased the osmotic gene aquaporin (<i>LvAqp</i>), while knockdown increased its expression. Additionally, levels of growth-related inhibitory genes <i>LvMstn</i> and <i>LvMIH</i> increased significantly after <i>LvSlc12A2</i> overexpression and were downregulated after its knockdown, suggesting <i>LvSlc12A2</i> negatively regulates growth, possibly in synergy with <i>LvMstn</i> and <i>LvMIH</i>. These findings indicate <i>LvSlc12A2</i> influences growth both by negative regulation and by modulating osmotic balance in gill tissues.