We study the evolution of simple cells that are equipped with a genome, a rudimentary gene regulation network at transcription level and two classes of functional genes: motion effectors allow the cell
to move in response to nutrient gradients while nutrient importers are required to actually feed from the environment. The model is inspired by the protist Naegleria gruberi which can switch between a feeding
and dividing amoeboid state and a mobile agellate state depending on environmental conditions. Simulation results demonstrate how selection in a variable environment affects the gene number and effciency so that the cells can rapidly switch from one expression regime to the other depending on the external conditions
