Gene discovery unlocks secrets of salmon puberty and evolution

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A study carried out at the University of Helsinki shows how a single gene in Atlantic salmon can dramatically influence the timing of puberty—a key factor for salmon life cycle and survival.

Researchers discovered that the gene, known as vgll3, acts as a master regulator, controlling thousands of other genes involved in various aspects of salmon sexual maturation. The findings are published in the Proceedings of the National Academy of Sciences.

"Imagine a single switch determining whether puberty begins at age 13 or 20 in humans. Vgll3 plays a similar role in salmon, influencing traits like when reproductive cells start to develop, growth patterns, and behavioral changes.

"Our results explain how genetic variation in a single gene can have such dramatic effects on very complex and multifaceted traits as puberty or maturation age," explains Associate Professor Jukka-Pekka Verta, now at Nord University, Norway, who conducted this study as a part of his post-doctoral research at the University of Helsinki.

This discovery not only explains how complex traits like puberty onset evolve and vary but also highlights a process called "pleiotropy," where one gene affects multiple characteristics, like the conductor of an orchestra.

The Vgll3 gene is involved in controlling pubertal timing in humans, but it has a much smaller influence. The same gene has a much larger effect, and is kind of a switch, on an auto-immune skin disease in humans. This disease, lupus, is much more common in females than in males.

Hydroelectric dams can affect salmon maturation

The findings have far-reaching implications, particularly for understanding rapid evolutionary changes in salmon populations affected by human activities, such as hydroelectric dam development.

As salmon are a migratory species, they need a clear pathway between their breeding grounds in the river and their feeding areas in the ocean. Many hydroelectric dams do not have functioning fish ladders, and this can block all the breeding areas above a dam.

"If the areas for breeding below the dam are only suitable, for example, for smaller salmon, there might be very strong natural selection against the late maturation vgll3 variant, which is a means for the salmon population to adapt to the changed conditions, but this also reduces the diversity of the population, which can have longer term negative consequences.

"Now we better understand what other genes and processes may be affected by such changes," says Professor Craig Primmer from the Faculty of Biological and Environmental Sciences, University of Helsinki.

By altering the frequency of certain vgll3 variants, natural selection can drive significant changes in traits like size, number of eggs and behavior. This research underscores the importance of fundamental evolutionary studies in managing wild populations and predicting how environmental changes impact ecosystems.

More information: Jukka-Pekka Verta et al, A complex mechanism translating variation of a simple genetic architecture into alternative life histories, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2402386121

Journal information: Proceedings of the National Academy of Sciences

Provided by University of Helsinki