Genomic and genetic characterization of rice Cen3 reveals evolutionary remnants of a complex centromere (mRNA data)

The centromere is the chromosomal site for assembly of the kinetochore where spindle fibers attach during cell division. In most muticellular eukaryotes, centromeres are composed of long tracks of satellite repeats that are recalcitrant to sequencing and fine scale genetic mapping. Here we report the genomic and genetic characterization of the complete centromere of rice chromosome 3. Using a DNA fiber-fluorescence in situ hybridization approach, we demonstrated that the centromere of chromosome 3 (Cen3) contains ~414 kb of the centromeric satellite repeat CentO. Cen3 includes a ~1,851-kb domain associated with CENH3, the centromere-specific histone H3 variant. This CENH3-associated chromatin domain is embedded within a 3,083-kb region that lacks genetic recombination. We detected several active genes within the CENH3-binding domain based on a comprehensive annotation and a survey for matches with mRNA signatures. However, the gene density in the CENH3-binding domain is significantly lower than in the pericentromeric domains. In contrast, the CENH3-binding domain contains a higher percentage of repetitive DNA sequences than the pericentromeric regions. These results suggest that Cen3 is in the process of evolving from a genic region toward an accumulation of satellite repeats and transposable elements that is more characteristic of centromeres in most complex eukaryotic species. Keywords: MPSS, mRNA, transcriptome, rice, centromere, Cen3, chromosome 3 MPSS was performed to sequence small RNAs that derived from 16 untreated and 6 abiotic-treated diverse tissue libraries. The method for the MPSS sequencing of mRNAs is described in Brenner et al. (Nat Biotechnol. 2000 18:630).