Structural analysis and physical mapping of a pericentromeric region of chromosome 5 of Arabidopsis thaliana

The Arabidopsis thaliana CIC YAC 2D2, 510 kb long and containing a small bl ock of 180 bp satellite units was subcloned after EcoR1 digestion in the pB luescript plasmid. One of these clones was mapped genetically in the perice ntromeric region of chromosome 5. The analysis of 40 subclones of this YAC showed that they all contain repeated sequences with a high proportion of t ransposable elements. Three new retrotransposons, two Ty-3 Gypsy-like and o ne Ty-l Copia, were identified in addition to two new tandem-repeat familie s. A physical map of the chromosome 5 pericentromeric region was establishe d using CIC YAC clones, spanning around 1000 kb. This contig extends from t he CIC YAC 9F5 and 7A2 positioned on the left arm of chromosome 5 to a 5S r DNA genes block localized by in-situ hybridization in the pericentromeric r egion. Hybridization of the subclones on the CIC YAC library showed that so me of them are restricted to the pericentromeric region of chromosome 5 and represent specific markers of this region.