CA is the most commonly used multivariate statistical analysis at present (Greenacre, 1984) . This method can successfully present variation trends among genes, and then distribute them along the continuous axis by using RSCU value as variable data. In CA, all genes were plotted in a 59-dimensional hyperspace, according to the usage of the 59 sense codons. Major variation trends can be determined using these RSCU values and genes ordered according to their positions along the major axis, which can also be used to distinguish the major factors influencing the codon usage of a gene.