The sea cucumber (Apostichopus japonicus) is an economically important mariculture species in Asia. However, the genetic breeding of sea cucumbers is difficult because the sexes cannot be identified by appearance. Therefore, studies on sex-related genes are helpful in revealing the mechanisms of sex determination and differentiation in sea cucumbers. P-element induced wimpy testis (piwi) is a germ cell marker involved in gametogenesis in vertebrates; however, the expression pattern and function during gametogenesis remain unclear in sea cucumbers. In this study, we identified a piwi homolog gene in A. japonicus (Ajpiwi1) and investigated its expression pattern, and function. Ajpiwi1 is a maternal factor and is ubiquitously expressed in adult tissues, including the ovary and testis. Ajpiwi1 expression is strong in early oocytes, spermatocytes, and spermatogonia; weak in mature oocytes; and undetected in spermatids and intra-gonadal somatic cells. The knockdown of Ajpiwi1 by RNA interference (RNAi) led to the downregulation of other conserved sex-related genes such as dmrt1, foxl2, and germ cell-less. Therefore, Ajpiwi1 might play a critical role during gametogenesis in A. japonicus. This study creates new possibilities for studying sex-related gene functions in the sea cucumber and builds a gene function research platform based on RNAi for the first time.

海参（Apostichopus japonicus）是亚洲经济上重要的海水养殖种类。然而，海参的遗传育种很困难，因为无法通过外观鉴定其性别。因此，有关性别相关基因的研究有助于揭示海参性别决定和分化的机制。P元素诱导的w弱睾丸（piwi）是参与脊椎动物配子发生的生殖细胞标记；然而，在海参中配子发生期间的表达模式和功能仍不清楚。在这项研究中，我们确定了A. japonicus（Ajpiwi1）中的piwi同源基因，并研究了其表达模式和功能。Ajpiwi1β1是母体因素，并且在包括卵巢和睾丸的成年组织中普遍表达。Ajpiwi1在早期卵母细胞，精母细胞和精原细胞中的表达很强。成熟的卵母细胞较弱；在精子细胞和性腺内体细胞中未检测到。的敲低Ajpiwi1通过导致的其他保守性相关的基因，诸如下调RNA干扰（RNAi）DMRT1，FOXL2，和生殖细胞较少。因此，Ajpiwi1可能在日本根瘤菌的配子发生过程中起关键作用。这项研究为研究海参中与性别相关的基因功能提供了新的可能性，并且首次建立了基于RNAi的基因功能研究平台。