Proposed general transcriptional changes under N deprivation. Schematic diagram showing the putative localization of central metabolic pathways of P. tricornutum. Changes in the transcript abundance of associated genes are indicated with the following symbols representing fold changes: ++++ > 5; 5 > +++ > 3; 3 > ++ > 1; 1 > + > 0; 0 < − < −1; -1 < −−− < −3; -3 < −−− < −5; −−− < −5. The symbol denotes the overall changes of predicted isoenzymes. Some co-substrates or co-products of some reactions are omitted for clarity. The one “+” in the fatty acid synthesis in plastids denotes the overall transcriptional changes of the enzymes involved. Detailed fold changes are listed in Additional file 3 and Additional file 1. Enzymes were based on the genome annotation and prediction. Locus tags of some ambiguous isoenzymes are indicated. The localization of most of the enzymes are based on prediction and have not been determined experimentally.