Expression analysis of the irak1 gene in Siniperca chuatsi against Aeromonas hydrophila and SNP development.

The interleukin-1 receptor-associated kinase 1 (irak1) gene is a key regulator in the innate immunity of fish. In this study, bioinformatics analyses of irak1 from Siniperca chuatsi were performed, and quantitative real-time PCR was used to examine the expression profiles of irak1 following Aeromonas hydrophila infection. Spatial localization of irak1 mRNA and Aeromonas hydrophila DNA was examined using double-label in situ hybridization. Single nucleotide polymorphism (SNP) sites in irak1 were identified by Sanger sequencing, and their association with resistance to Aeromonas hydrophila was analyzed. The results showed that the full-length of irak1 was 2264 bp with a Death domain and a PKC domain. Following infection with Aeromonas hydrophila, irak1 was significantly upregulated in the head kidney, spleen, and liver of Siniperca chuatsi (P < 0.05). In the liver, irak1 mRNA and Aeromonas hydrophila exhibit a high degree of spatial overlap. Four SNP loci were successfully genotyped. The χ2 values for SNP1 (g.31013632 A > T) and SNP3 (g.31013971 T > C) were 2.305 (P = 0.316) and 1.314 (P = 0.518), while those for SNP2 (g.31013633 T > C) and SNP4 (g.31029300 G > T) were 7.829 (P = 0.02) and 11.369 (P = 0.003). However, SNP2 did not fit the Hardy-Weinberg equilibrium (HWE). Taken together, it is concluded that the irak1 gene played an immune regulatory role in resistance to Aeromonas hydrophila. The SNP4 locus showed a highly significant association with resistance to Aeromonas hydrophila and could be a potential molecular marker, but its specific function requires further investigation.