Fig. 1.

—Relative frequency of the codons of the two codon pairs coding for RVD NI counted at RVD positions only, in complete TALE sequences, and in all coding sequences of Xanthomonas genomes. In case of the codon pair AATATT (left), both codons of the pair occur with higher frequency in RVD positions than in the remainder of TALE sequences and than in all coding sequences. In case of the codon pair AATATA (right), the codon at position 13 occurs with exceptionally low frequency in all regions considered.