Genomic Identification and Validation of Candidate Genes Associated with Alkalinity Tolerance in Exopalaemon carinicauda

Abstract

China harbors extensive saline-alkaline water resources with considerable potential for aquaculture development. However, their utilization is constrained by high pH, elevated carbonate alkalinity, and complex ionic composition. Exopalaemon carinicauda, a commercially important shrimp species in China, is recognized for its environmental adaptability, rapid growth, desirable flesh quality, and high economic value. Owing to its resilience to diverse environments, E. carinicauda serves as an ideal model for investigating the molecular mechanisms underlying saline-alkaline adaptation in crustaceans. Yet, the genetic determinants of its alkalinity tolerance remain poorly understood, hindering selective breeding efforts. In this study, bulked segregant analysis (BSA) coupled with next-generation sequencing was employed to identify single nucleotide polymorphisms (SNPs) associated with alkalinity tolerance. DNA from individuals exhibiting extreme phenotypes was pooled, and allelic differences were assessed using Euclidean distance, deep learning, and ΔSNP-index methods. A total of 20,879,626 SNPs were detected, and seven candidate genomic regions spanning 47.53 Mb on chromosomes 4, 11, 13, 18, 26, and 36 were identified, encompassing 194 genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment revealed significant associations with GABAergic synapse, taste transduction, and vasopressin-regulated water reabsorption. Comparative transcriptomic analysis under high-alkalinity stress in hepatopancreas and gills identified 28 genes strongly linked to alkalinity tolerance, including gamma-aminobutyric acid receptor, glutamate receptor ionotropic, and basic salivary proline-rich protein. Two SNP loci, C4-2601 and C8-6550, significantly associated with alkalinity tolerance were validated through PCR-based sequencing. These findings provide critical insights into the genetic architecture of alkalinity tolerance in E. carinicauda, facilitating future genomic and marker-assisted selection strategies.