Fig. 7

Internal correspondence analysis of single-exon genes with different GC3 content in rice. The total codon usage variability is decomposed into the synonymous codon usage variability (a, d, g), amino acid usage variability (b, e, h), and variability of within (a, b, c) and between different GC3 content groups (d, e, f). The performance of ICA yields nine elementary analyses (a–i). In each peculiar analysis, the contribution to the total codon usage variability is indicated, where only the first 10 eigenvalues are represented for comparison