How evolution fine tunes molecular mechanisms to create and maintain membrane diversity between species
The cell membrane is a fundamental biological structure. These lipid layers surround and organize every cell, controlling everything from signaling to transport. But for membranes to function properly, their physicochemical properties must sit within a narrow range: for instance, not too rigid or too fluid.
Membrane diversity between species is fine-tuned by evolution, according to new research from the Crick Institute. Cell membranes are essential structures that control various cellular processes, but their properties must remain within a specific range to function properly. Organisms must regulate membrane fluidity, which can be affected by environmental factors like dietary lipids and temperature.
Snezhka Oliferenko, who leads the Comparative Biology of Mitotic Division Lab at the Crick, sees cellular membranes as an ideal system for studying how diversity arises. In a recent study published in Genes & Development, Oliferenko and her team compared two closely related species of fission yeast, Schizosaccharomyces pombe and Schizosaccharomyces japonicus. Despite having very similar genetic makeup, these species exhibit distinct membrane properties.
The key factor in membrane fluidity is unsaturation, which depends on the type of lipids present. S. pombe produces more fluid and flexible membranes, while S. japonicus membranes are more rigid and ordered. To understand how these species maintain their distinct membrane properties, the researchers focused on a feedback loop involving a protein called Mga2.
When membranes become too rigid, Mga2 is activated and triggers the production of Ole1, an enzyme that synthesizes unsaturated fatty acids, restoring membrane fluidity.
The team discovered that each species has a different threshold for membrane rigidity, with S. pombe being more sensitive. This sensitivity is determined by two key evolutionary changes: alterations in the Mga2 protein's cleavage sensitivity and changes in the Ole1 gene, which sets the baseline level of response. The findings suggest that evolution often involves fine-tuning existing systems rather than creating entirely new ones.
The study highlights how subtle shifts in regulatory mechanisms can lead to significant diversity across species.
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