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bioRxiv · 10.1101/2025.09.15.676320

Effect of cellular nutrient economy on the evolution of genome size in phytoplankton

Caceres, C.·Krasovec, M.·Crispi, O.·Gourbiere, S.·Piganeau, G.
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Abstract

The origin of genome size variation remains a central question in evolutionary biology. Previous analyses suggest that the energetic costs of small insertions and deletions (indels) influence genome size by altering the cellular energy budget. Here, we present a theoretical framework for genome evolution in phytoplankton--the main producers of the sunlit ocean--whose growth depends on nutrient availability. We derive an expression for the selection coefficient on indels as a function of the minimum amount of nutrient inside the cell. Parameter estimates indicate that 1-bp indels can be counterselected in phytoplankton with minimal nutrient requirements. We then test three predictions of nutrient-driven selection on genome evolution. Altogether, this model provides a quantitative and mathematical basis for the genome streamlining hypothesis.

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Caceres, C., Krasovec, M., Crispi, O., Gourbiere, S., Piganeau, G.. 2025-09-16. Effect of cellular nutrient economy on the evolution of genome size in phytoplankton. https://doi.org/10.1101/2025.09.15.676320

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