Figure 2: Distributions of genomic features in O. brachyantha and O. sativa on chromosome 4.

The two Oryza genomes showed similar distributions of gene and repeat elements: DNA transposons (DNA-TEs) showed a relatively even distribution along the chromosomes, whereas retrotransposons (RTs) were negatively correlated with the distribution of genes. The overall level of RTs was higher in O. sativa than in O. brachyantha, in which the short arms and the proximal regions of the long arms of chromosome 4 showed much obvious contrast. These highly repetitive regions also showed reduced levels of transcription and gene collinearity. The 4',6-diamidino-2-phenylindole-stained pachytene chromosomes for O. brachyantha and O. sativa were put along the genomic tracks of chromosome 4. The black arrows indicate the transition region of euchromatin/heterochromatin, whereas the red arrows indicate the centromere positions.