Genome streamlining and the elemental costs of growth

Pervasive relationships between growth rate, genome size and RNA content exist. One interesting potential consequence of these interrelationships is that selection for high growth rate should be associated with small genomes and high RNA content. Here, we use phosphorus (P) and nitrogen (N) demands of growth along with nucleic acid production as the currency to explore the interrelationships between growth rate and genome size in eukaryotes. We argue that reallocation of P (and eventually N) from DNA to RNA under sustained selection for rapid growth in nutritionally limited environments can lead to genome streamlining in eukaryotes, and that this mechanism might contribute to the evolution of reduced genome size.