Unraveling the characterization of minichromosome maintenance complex component 2 (MCM2) gene and its SNPs associated with cold-tolerance trait in Pacific white shrimp (Litopenaeus vannamei)

Minichromosome maintenance complex component 2 (MCM2) plays an important role in DNA replication induced by cold stress. In this study, MCM2 cDNA and genomic DNA (gDNA) sequences were isolated from Pacific white shrimp (Litopenaeus vannamei), and the gene was designated Lv-MCM2. The full-length Lv-MCM2 cDNA was 3,138 bp in length, with an open reading frame (ORF) of 2,721 bp encoding 906 amino acids. The Lv-MCM2 gDNA sequence was 7,322 bp in length and consisted of 16 coding segments in the L. vannamei genome. The expression of Lv-MCM2 mRNA was detected in all selected tissues, with the highest levels being observed in the stomach and gills of the shrimp. The transcript levels of Lv-MCM2 in the stomach and gills were found to be significantly affected by low-temperature, high-pH, low-pH, poly(I:C), and lipopolysaccharide (LPS) stimuli, indicating that Lv-MCM2 might play roles in coping with various stresses. Specifically, under low-temperature stress (13 °C), the knockdown of Lv-MCM2 with siRNA significantly decreased the shrimp survival rate, indicating its key roles in the response to low-temperature stress. Additionally, four single-nucleotide polymorphisms (SNPs) in the Lv-MCM2 gene were identified as being significantly associated (P < 0.001) with the cold tolerance trait in a full-sib family of L. vannamei. Our study suggests that the Lv-MCM2 gene itself or closely linked genes might play important roles in the cold tolerance trait in L. vannamei, and the SNPs from the Lv-MCM2 gene provide a basis for developing molecular markers for breeding cold-tolerant Pacific white shrimp seeds in the future.