Examination of the effects of Nanos gene knockdown on fecundity and reproductive modes in the brine shrimp, Artemia parthenogenetica

Artemia is not only a crucial live food source in fish and crustacean larviculture but also an ideal experimental organism for biological studies. Female Artemia subjects release either diapause-encysted embryos (cysts) via oviparous reproduction or nauplii via ovoviviparous reproduction. As a maternal effector gene, nanos is involved in the differentiation and migration of primordial germ cells. In the present study, the open reading frame (ORF) of the nanos gene of Artemia parthenogenetica was screened and analyzed. Nanos cDNA contained a 933-bp ORF, encoding 310 amino acids with a conserved zinc-finger motif. The expression patterns of nanos in various tissues and during embryo development in Artemia were analyzed by qRT-PCR. The results showed that nanos was specifically expressed in the ovary, with the highest expression being observed during early ovary development. Moreover, nanos knockdown induced by dsRNA injection significantly decreased the gene and protein expression levels of nanos. In addition, knockdown of nanos resulted in an obvious shift from ovoviviparity to oviparity and a reduced number of offspring, corresponding to irregular oocyte shape, cell membrane damage, and cytoplasmic vacuolization. Our study suggests that nanos not only regulates the ovary development and reproductive performance of Artemia but also play a critical role in determining its reproductive mode. This study will improve our knowledge of the role of nanos in the reproductive process of Artemia and the molecular mechanisms underlying reproduction in this shrimp.