Frequency of co-occurring ACGT elements compared to random 4 bp palindromic and non-palindromic nucleotides. By comparing the spacer length wise frequency across all four species with 8 other random control sequences, it became apparent that co-occurring ACGT elements are not specifically preferred in terms of frequency over other random base pair sequences. Although a few high frequencies were present in rice and Arabidopsis, co-occurring ACGT elements were not predominant throughout the genomes of sorghum and soybean.
Mehrotra et al. BMC Genomics 2013 14:203 doi:10.1186/1471-2164-14-203