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Researchers discover an unexpectedly simple mechanism that controls life cycle in algae.
Scientists at the Max Planck Institute for Biology have discovered a remarkably streamlined strategy for developmental control in brown algae. They could show that a single ARGONAUTE (AGO) protein orchestrates the transition from vegetative growth to sexual reproduction and directs germline establishment.
In brief
One protein, one switch: brown algae rely on just one AGO protein to control some of the most important decisions in their lives: when to switch to reproductive development, and which cells will give rise to the next generation.
A simple solution for a complex life cycle: This single AGO protein is essential for the transition from vegetative growth to sexual development and for proper establishment of the germline.
Power in simplicity: By using a minimal system, one AGO protein and small RNAs, brown algae achieve sophisticated developmental control, demonstrating that evolution can favor elegant simplicity over molecular complexity.
ARGONAUTE proteins are key regulators of gene expression in eukaryotes. They bind small RNAs and use them as guides to control which genes are active, influencing development, defense against genetic parasites, and other crucial cellular processes. In plants and animals, AGO proteins usually occur as large families with specialized roles.
Surprisingly, brown algae, however, encode only one single AGO protein and this one lone protein plays a big role. Researchers from the department of Algal Development and Evolution found that this AGO protein collaborates with small RNAs that act as molecular instructions, helping cells activate or silence specific genes at precisely the right time.
How brown algae decide who gets to reproduce
Most brown algae go through two different stages in their life cycle: one where they have a single set of chromosomes (haploid), and another where they have two sets (diploid). These two stages look and act very differently. The diploid stage, called the sporophyte, is usually the larger, more complex form. It produces tiny reproductive cells called spores through a special kind of cell division called meiosis. These spores grow into the second stage, the haploid gametophyte, which develops into the reproductive cells (like sperm and eggs). Fertilization restores the diploid state, and the cycle begins again. The researchers discovered that when AGO is disrupted, algae can still develop normally as sporophytes and undergo meiosis. However, most of the resulting spores fail to develop, and those that do often adopt the wrong developmental fate. These results show that AGO activity is necessary for gametophyte formation and correct germline specification.
“This is a rare example of a complex multicellular organism relying on a single AGO protein to regulate fundamental developmental transitions,” said Claudia Martinho, the postdoc involved in the study and now Assistant Professor at the University of Dundee. “It suggests that evolutionary minimalism can be just as effective as complexity when it comes to orchestrating life cycle progression.”
This study sheds new light on how organisms control key developmental decisions. It shows that brown algae, unlike plants and animals, manage life cycle transitions using a single AGO protein in combination with minimalistic but sophisticated interactions with small RNAs. By revealing how brown algae manage their life cycles with such a streamlined system, the study offers new perspectives on how different forms of life solve fundamental biological problems. It also highlights algae, often overlooked organisms, as powerful models for understanding evolution, development, and reproduction.
Sometimes, it seems, less really is more.
Prof. Dr. Susana Coelho
Director Department of Algal Development and Evolution
susana.coelho@tuebingen.mpg.de
Jeanette Müller
Press Office
presse-bio@tuebingen.mpg.de
V. Bukhanets, R.A. Batista, F.B. Haas, R. Luthringer, J. Kushkush, M. Zheng, K. Hipp, V. Alva, C. Martinho, & S.M. Coelho
Germline fate determination by a single ARGONAUTE protein in Ectocarpus
Proc. Natl. Acad. Sci. U.S.A. 123 (5) e2518712123
https://doi.org/10.1073/pnas.2518712123
https://www.bio.mpg.de/509502/news_publication_26050712_transferred?c=57217
The brown algae ascophyllum at the sea in Roscoff, France
Copyright: © Prof. Dr. Susana Coelho / Max Planck Institute for Biology Tübingen, Germany
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