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Maize Centromere Structure and Evolution: Sequence Analysis of Centromeres 2 and 5 Reveals Dynamic Loci Shaped Primarily by Retrotransposons

Figure 4

Successive centromere invasion by different CRM1 recombinant subgroups and CRM2 document centromere location over time and the progressive split of centromere 5.

CRM elements are graphed by chromosome coordinate and insertion time (κ) for (A) centromere 2 and (B) centromere 5. Note that the more recent insertions represented by the more recently derived recombinant CRM1 elements R4 and R5 are tightly associated with the present-day CENH3 region. Older elements indicate CENH3 location in the past. Linear regression lines were calculated for all elements of the ancestral CRM1 B/R1 subfamily and document the shift of the centromeres over time. Boxes denote approximate centromere positions at different times based on CRM elements for which the time of insertion could be calculated, except for box C′, the left and right borders of which are based on the CENH3 data and the sole CRM element, respectively. Boxes illustrate the gradual increase in size of “I” over time. Green bars denote approximate positions of CentC clusters.

Figure 4