Genome-Wide Identification, Phylogenetic Analysis and Expression Pattern Profiling of the Aquaporin Family Genes in Leuciscus waleckii

Abstract

Aquaporin (Aqp) is a transmembrane-specific channel for small molecules that help in regulating homeostasis in fishes when adapting to changing environments, but its role in Amur ide’s response to alkaline stress is yet to be revealed. Therefore, the purpose of this study is to investigate the response of the Aqp gene exposed to alkaline water in Amur ide (Leuciscus waleckii) using a genome-transcriptional assay. Based on the results, we classified the Aqps of the L. waleckii (LwAqps) genome and analyzed its transcriptional expression profile and genetic evolution under carbonate alkalinity stress. A total of 18 Aqp genes were identified in four grades in L. waleckii. The highest Aqp gene expression was found in the gill and kidney of L. waleckii from the Wusuli River (WSL) in comparison to those in the Dali Lake (DL), whereas aqp3a, -3ap1, -7, and -9a expressions were found at intensively higher levels in the gill rather than in the kidneys and livers. The experiment of L. waleckii under alkalinity stress (carbonate alkalinity 50 mmol·L−1) and its recovery showed that the expressions of aqp0a, -3a, -3ap1, -7, -8aa, and -9a were upregulated in alkaline water and downregulated in freshwater. We identified 1460 single nucleotide polymorphism (SNP) markers in the Aqp genes. The average value of Fst of SNP markers in the CDS region was 0.177 ± 0.256, and the first 5% SNPs were identified at aqp3a and -11b. Residue Ser66 does not bring about an overall change in the three-dimensional structure of Aqp3a, but may change the penetration of solutes across the membrane. This indicates that Aqp genes are involved in the response of L. waleckii to alkaline stress, and aqp3a is one of the key genes involved in regulating L. waleckii’s adaptation to alkaline environments.