Proposed C4 metabolism of P. tricornutum based on gene expression and gene localizations. Carbon-assimilation gene expression during nutrient depletion and initial lipid accumulation as compared to nutrient replete conditions (Q2 vs. Q1) (A). Carbon-assimilation gene expression during extended nutrient depletion and lipid accumulation as compared to nutrient replete conditions (Q3 vs. Q1) (B). Differences in fold change are based on log2 scale and the color scale represents up-expressed (green) and down-expressed (red) genes. Font size is adjusted to the transcript abundances of C4 metabolism genes relative to each other.