Centromeres and parental genome conflict

Centromeres are chromosomal landmarks that mediate accurate segregation of chromosomes during cell division. Centromeres are epigenetically determined by the unique deposition of a centromere specific histone variant(CENH3), which replaces canonical histone H3 in a subset of nucleosomes of centromeric chromatin. Using the plant model Arabidopsis thaliana,we have shown that in zygotic mitosis, centromere differences between a parent expressing hypomorphic CENH3 variants can induce genetic conflict with otherparental genome that expresses wild-type(WT) CENH3. As a consequence, a massivegenome catastrophic event is triggered during embryogenesis leading to an aberrantcell division process resulting in either partial or total elimination of the parental genome expressing hypomorphic CENH3, producing viable aneuploid and uniparental WT haploid embryo respectively. Characterization of the aneuploids revealed massive structural chromosomal aberrations such asdeletion, duplication and translocation events suggestive of a complex chromosomal rearrangement(CCR) process. Preliminary evidence suggests that thisrearrangement might be due to chromosome fragmentation event initiated duringthe genome elimination process, followed by an aberrant DNA repair event mostlyinvolving non-homologous end joining(NHEJ) of the broken DNA fragments. This phenomena resembles a recently discovered chromosomal rearrangement mechanism observed in cancer cells called chromothripsis. Since most aneuploids harboring such complex chromosomal rearrangements are viable and produce progeny, this makes Arabidopsis an ideal model to understand the molecular events that initiate chromothripsis, a poorly understood process in cancer cells. At the end, I will highlight how can we manipulate centromere mediated geneticconflict to create new plant biotechnological tools for crop improvement.