Transcriptomic and metabolomic analyses reveal sex-related differences in the gonads of Pinctada fucata martensii

Pinctada fucata martensii is an economically important bivalve mollusk, as this species makes a major contribution to seawater pearl production. Pearl production efficiency varies between the sexes of P. f. martensii, but many aspects of the molecular mechanisms underlying sex determination and sex differentiation in P. f. martensii remain unclear. Here, transcriptomic and metabonomic analyses were conducted to identify the major genes and metabolic changes associated with sex determination and gametogenesis. We identified a total of 3426 differentially expressed genes (DEGs) between females and males. These included Fem-1c and Foxl2, which are involved in sex determination and sex differentiation, and SOHLH2, Nanos1 and TSSK4, which are involved in gametogenesis. We also identified a total of 5231 significant differential metabolites (SDMs) between females and males. These DEGs were enriched in 47 metabolic pathways, including "ABC transporters," "purine metabolism," and "glycerophospholipid metabolism." Our findings provide new insights into the molecular mechanisms underlying sex determination, sex differentiation, and gametogenesis and will aid future studies of P. f. martensii.