RNA interference with foxl2 leads to upregulation of cyp19b and delayed development of female carp Cyprinus carpio var. koi gonads

FOXL2 and CYP19B are crucial transcription factors in vertebrates and invertebrates that play pivotal roles in sex differentiation and gonadal development. The potential roles of the foxl2 and cyp19b genes in sex determination and gonadal development in Cyprinus carpio var. koi were explored using a non-invasive RNA interference (RNAi) method, histopathological observation and qPCR. Results demonstrate that foxl2 exhibited a sexually dimorphic expression pattern in gonads, with a notable expression in ovaries; cyp19b was expressed in all peripheral tissues, with a particularly prominent expression in brain and gonads. The knockdown of foxl2 by RNAi resulted in delay in the development of the female gonads. Conversely, no notable alterations were discerned in the gonads of C. carpio var. koi following the knockdown of cyp19b. The upregulation of sox9a, amh, and cyp19b following foxl2 knockdown indicates that foxl2 may play a pivotal role in gonadal development. Nevertheless, further investigation is required to ascertain the potential role of cyp19b. This study elucidated the role of foxl2 and enhanced the understanding of the mechanisms of sex determination and gonadal development in C. carpio var. koi.