Molecular mechanisms of infertility in male triploid pacific oysters (Crassostrea gigas)

The development of triploid oysters has resolved supply disruptions linked to the spawning season, allowing oysters to be available throughout the year. However, recent statistics indicate a yearly increase in fertilization occurrences among triploid oysters, potentially leading to the eventual loss of their sterility. This development could have significant implications for the entire oyster aquaculture industry. Therefore, we aim to explore the underlying causes of triploid fertility by identifying key genes through transcriptomic analysis. During our investigation and sampling, we observed a yearly increase in the proportion of fertile triploid male Crassostrea gigas. The main goal of this research is to explore the variations between fertile and infertile triploid male C. gigas. We performed transcriptomic analysis on fertile and infertile triploid male C. gigas, identifying 3016 upregulated DEGs and 1209 downregulated DEGs, respectively. Functional enrichment of these DEGs indicated that the majority of GO terms and KEGG pathways were linked to reproductive processes. Subsequently, we constructed a PPI network based on KEGG pathways related to fertility. We ultimately validated 23 important genes using qPCR, observing consistent downregulation in the infertile triploid male group. The primary cause of infertility was the suppression of gene expression regulating germ cell proliferation, disruption of the mitotic cycle, and failure to produce germ cells. These findings provide a crucial foundation for exploring strategies to reduce the reproductive capability of triploid C. gigas, thereby promoting the breeding of high-quality triploid C. gigas.