Identification and dimorphic expression of sex-related genes in Pacific abalone (Haliotis discus hannai)

Sex determination is a hot topic in evolutionary biology. The mechanism of sex determination is complex and diverse in shellfish, while no sex chromosomes have been found in mollusks. The Pacific abalone (Haliotis discus hannai) is one of the most economically important cultured shellfish species in China, and its sex determination mechanism is still unclear. Here, we identified the sex-determination region (SDR) of Pacific abalone and developed five stable sex-specific markers through genome-wide association studies (GWAS) based on re-sequencing data from 803 abalones. These markers can be used for sex discrimination in polyploid and sexu-ally immature individuals in abalone breeding projects. In addition, haplotype analysis and quantitative expression of candidate sex-related genes showed that RhoGAPp190, Skp1, Cul2, and Otulin were potentially involved in the sex determination of Pacific abalone by the ubiquitin-mediated proteolysis pathway. Our study could help to better understand the molecular mechanisms that underpin sex determination and reproductive regulation in mollusks.