Riggs, Dan , delaPaz, Joelle , Stronghill, Patti , Douglas, Scott , Saravia, Sandy , Wright, Stephen , Hasenkampf, Clare .
Large pericentromeric deletions near the BREVIPEDICELLUS locus are associated with MARS binding sites and regions of ancestral chromosomal fusion events in Arabidopsis.
Mutations in the BREVIPEDICELLUS gene of Arabidopsis thaliana condition a pleiotropic phenotype that include defects in internode elongation, homeotic conversion of internode to node tissue, and downward pointing flowers and pedicels. We have characterized five mutant alleles of BP, generated by EMS, fast neutrons, x-rays, and aberrant T-DNA insertion events. Curiously, all of these mutagens resulted in large deletions that range from 140kb to over 900kb just south of the centromere of chromosome 4 (CEN4). The breakpoints of these mutants were established by employing inverse PCR and DNA sequencing. The south breakpoints of all alleles cluster in BAC T12G13, while the north breakpoint locations are quite variable. Sequence analysis of the T12G13 area does not reveal clues about the apparent genomic instability of this region. An alternative interpretation is that one or more double strand breaks are initiated by the mutagen, and are subsequently resected until they are delimited by a specific chromatin structure (e.g. a boundary element) or attachment points to the nuclear matrix. We therefore conducted southwestern blotting with breakpoint sequence probes and a matrix associated protein AHL1. These experiments revealed that several matrix attachment regions are present near the breakpoints. Surprisingly,comparisons of fluorescence in situ hybridization signals in the mutants and their wildtype parental lines revealed a significant difference in intersignal contour lengths for some probesets, implying heretofore unrecognized chromosomal polymorphisms that are due to gross chromosomal rearrangements or alterations in chromatin compaction. Epigenomic datamining revealed that there are dramatic transitions in different histone modifications near the boundaries of the pericentric chromatin in these regions. These landmarks can be generally correlated with evolutionary events that have given rise to ecotype specific differences in chromosome 4 of Arabidopsis thaliana (a pericentric inversion to create a heterochromatic knob north of CEN4). In addition, these regions are near sites on chromosome 4 where fusion events involving chromosomes 6 and 7 of the progenitor species Arabidopsis lyrata occurred to give rise to the Arabidopsis thaliana chromosome4.
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1 - University of Toronto, Biological Sciences, 1265 Military Trail, Toronto, ON, M1C1A4, Canada
3 - University of Toronto, Biological Sciences
4 - University of Toronto, Ecology and Evolutionary Biology, Toronto, ON, M1B5M2, Canada
5 - University of Toronto
Presentation Type: Oral Paper:Papers for Topics
Location: Union B/Hyatt
Date: Monday, July 9th, 2012
Time: 10:30 AM