Super-fast generation of all-female grass carp via transplantation of female germline stem cell into zebrafish

Surrogate reproduction has emerged as a powerful biotechnology in fish breeding, mainly aiming at shortening the maturation period of aquaculture species. Grass carp ( Ctenopharyngodon idellus ), possesses one of the largest body sizes and highest global production yields in freshwater aquaculture. However, the reproduction and genetic breeding of grass carp are significantly hindered, primarily due to its protracted sexual maturation period of nearly five years and the need for extensive cultivation space. In this study, we develop a super-fast strategy to breed all-female grass carp within half a year, leveraging surrogate production in a small-sized laboratory fish, zebrafish ( Danio rerio ). We characterized and purified female germline stem cells (GSCs) from grass carp juvenile ovary at three months post-fertilization, which is the first report of female GSCs in an aquaculture species. The grass carp female GSCs were transplanted into germ cell-depleted zebrafish larvae to generate surrogate zebrafish. The transplanted grass carp female GSCs underwent accelerated spermatogenesis in the zebrafish recipients. Three months after transplantation, the zebrafish recipients developed into males capable of producing all-X sperm derived from donor grass carp female GSCs. When these sperm were fertilized with wildtype grass carp eggs, a population of all-female grass carp was produced. Our study demonstrates that fish female GSCs with XX chromosomes can be differentiated into functional sperm in a short time under the control of zebrafish gonadal somatic niche, which opens a new avenue for precision breeding in aquaculture.