In the complex world of sex development and determination, over 500 teleost fish species display the extraordinary ability to switch sex during adulthood. These organisms undergo remarkable gonadal reconstruction, accompanied by substantial changes in behaviour and external phenotype. Yet, the mechanisms driving this sexual plasticity remain enigmatic, leaving the question of how germ cells transition from one cell fate to another after gonadal development unanswered.
In this study, we offer a comprehensive comparison of the gonadal transcriptomes of two contrasting fish species: the Barramundi, a protandrous fish undergoing male-to-female transition, and the Bluehead wrasse, a protogynous species transitioning from female to male. By constructing weighted gene co-expression networks (WGCNA) of gonadal transcriptomes at various stages of sexual transformation for each fish species, we uncover gene clusters that play pivotal roles at different developmental stages. Within these clusters, we identify highly influential "driver genes" driving the transition processes.
Through a comparative analysis of these networks, we illuminate both the commonalities and distinctions behind this remarkable sexual reorganisation in both directions. Our findings unveil the presence or absence of conserved gene clusters, providing essential pieces to the developmental puzzle of natural sex reversal in fishes.
This newfound knowledge promises to augment our understanding of vertebrate sexual development, potentially revealing valuable gene markers, and peeling away the layers surrounding questions of cell pluripotency and cell fate in these remarkable organisms. These insights could lead to innovative perspectives in the field of developmental biology.