Differential transcriptome of R. toruloides in response to nitrogen limitation . ( a ) Global profi ling of gene expression changes. ( b ) Gene
ontology enrichment analysis of differentially expressed genes. GO terms of biological process (level 3) were analysed and signifi cantly enriched
catalogues (when compared with the entire proteome, and P -value < 0.05, Pearson ’ s χ2 - test) are indicated with asterisks. ( c ) Expression changes
(upregulation in red) of NCR-related genes. Pathways of urate and urea utilization, central nitrogen metabolism, vacuolar protein degradation and
nitrogenous compound uptake were induced. ( d ) Relative expression levels (upregulation in red and downregulation in blue) of 65 ribosomal
protein-encoding genes.