Genomic architecture constrains macromolecular allocation in dinoflagellates.

Dinoflagellate genomes have a unique architecture that may constrain their physiological and biochemical responsiveness to environmental stressors. Here we quantified how nitrogen (N) starvation influenced macromolecular allocation and C:N:P of three photosynthetic marine dinoflagellates, representing different taxonomic classes and genome sizes. Dinoflagellates respond to nitrogen starvation by decreasing cellular nitrogen, protein and RNA content, but unlike many other eukaryotic phytoplankton examined RNA:protein is invariant. Additionally, 2 of the 3 species exhibit increases in cellular phosphorus and very little change in cellular carbon with N-starvation. As a consequence, N starvation induces moderate increases in C:N, but extreme decreases in N:P and C:P, relative to diatoms. Dinoflagellate DNA content relative to total C, N and P is much higher than similar sized diatoms, but similar to very small photosynthetic picoeukaryotes such as Ostreococcus. In aggregate these results indicate the accumulation of phosphate stores may be an important strategy employed by dinoflagellates to meet P requirements associated with the maintenance and replication of their large genomes.