The sex-changing fish team reveal the molecular cascade underlying sex change in the bluehead wrasse in their paper published in Science Advances this week, lead by co-first authors Dr. Erica Todd, Dr. Ann Liu, and PhD candidate Oscar Ortega-Recalde of the Hore Lab.

Natural sex change in fish is one of the most startling transformations in the natural world. In the bluehead wrasse, females can become males in 10 days flat following the loss of a dominant male. How this stunning transformation is achieved at a genetic level has been a mystery for decades.

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A distinctive male (top left) defends a group of females (yellow), one of which will eventually change sex to replace him. Photo credit: Kevin Bryant             

                                                                                    

 The team used cutting-edge epigenetic and RNA sequencing techniques to uncover a complete genetic rewiring of the gonad during sex change. The data suggest that the social stimulus is exerted via the stress axis, that repression of the aromatase gene (encoding the enzyme converting androgens to estrogens) initiates a cascaded collapse of feminizing gene expression, and uncovers duplicated female-pathway genes with unexpected testis-specific roles. The transformation also involves distinct epigenetic reprogramming and an intermediate state with altered epigenetic machinery expression.

 

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Sex change in the bluehead wrasse: Loss of a dominant male signals sex change in a female. The dramatic changes in colouration, behaviour and gonadal anatomy are orchestrated by changes in gene expression.

 

The highly-collaborative project involved members of the Gemmell and Hore Labs plus others in the Department of Anatomy, colleagues in Otago’s Department of Biochemistry, The Godwin Lab at North Carolina State University, USA, and Jenny Graves of La Trobe, Australia.

 

A video showing a transitioning bluehead wrasse (darker colouration) establishing dominance and begin courting females (yellow colouration) can also be seen in a feature of this publication on the EurekAlert! website. The video credit is to John Godwin and William Tyler.

 

The work was funded by the Royal Society of New Zealand Marsden Fund, the Rutherford Foundation, the University of Otago, and the National Science Foundation (USA).

 

Publication has been received with massive interest, with results featured in several international science news agencies, such as ABC News and Inside Science. Erica was also interviewed by the BBC Science in Action radio show.

Follow this link to access the original publication https://advances.sciencemag.org/content/5/7/eaaw7006

 

Publication details:

Erica V. Todd, Oscar Ortega-Recalde, Hui Liu, Melissa S. Lamm, Kim M. Rutherford, Hugh Cross, Michael A. Black, Olga Kardailsky, Jennifer A. Marshall Graves, Timothy A. Hore, John R. Godwin, Neil J. Gemmell. Stress, novel sex genes, and epigenetic reprogramming orchestrate socially controlled sex change. Science Advances 5: eaaw7006