Abstract: Based on the cDNA sequence of GPX in Hyriopsis cumingii, the complete genomic DNA of GPX gene and it′s 5′-flanking region were identified from H. cumingii using PCR and genome walking technique. The length of the complete genomic sequence was 6 708 bp including the 5′-flanking region, two exons, and one intron. Se-quence analysis of the 992 bp 5′-flanking region revealed that it contained a core promoter element (TATA-box) and other transcription regulation elements such as AP1, C/EBP, and CdxA. The sequence lengths of the two exons were 273 bp and 991 bp, respectively, and the intron was 4 491 bp in length. Sixteen single nucleotide polymorphisms (SNPs) were detected in the GPX gene from resistant stock (RS) and susceptible stock (SS) of H. cumingii. These polymorphisms were analyzed with regard to resistance to Aeromonas hydrophila. Among them, three SNPs in-cluding A-99G, A-86C, and A-49C in GPX promoter and five SNPs including A2841T, C2847T, G3146C, A3150G, and G4645T in GPX introns were associated with resistance/susceptibility of H. cumingii to A. hydro-phila, both in genotype and allele frequency. Linkage disequilibrium analysis revealed that A-86C, A-49C, C2847T, A3150G, G4645T, A2841T, and G3146C were in high linkage disequilibrium, and haplotype analysis revealed that the fre-quency of two major predominant haplotypes (ACTGT and TG) in the resistant group was significantly higher than that in the susceptible group. The results suggest that the polymorphic loci in the GPX gene could be potential genetic markers for future molecular selection of strains resistant to diseases.

Key words: Hyriopsis cumingii, glutathione peroxidase, SNP, resistance trait