Figure 2.

Codon usage bias in C. impatiens and C. resedifolia orthologous genes. Mean values of the frequency of the optimal codon (Fop) are reported for genes functionally characterized as cold responsive genes (CRG), and for genes annotated as involved either in cold response (CGO), photosynthesis (PGO) and general stress responses (SGO). Text in bars denotes the number of genes; error bars denote the standard error of the mean. The mean values of each functional class were compared to the mean estimated for the genes not in that functional class (identified by red dots) using a Wilcoxon test: * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001.