Dynamics of CENH3-Mediated Genome Elimination in Early Arabidopsis Embryos

Centromeres are chromosomal loci that attach to spindle microtubules during cell division and are required for chromosome inheritance. CENH3 is a histone H3 variant which is essential for centromere specification and function. In Arabidopsis, crossing cenh3 mutant plants expressing synthetic CENH3 variants to wild type leads to complete elimination of chromosomes from the cenh3 mutant parent and results in haploid progeny carrying only wild type genetic material. Here we present preliminary results from observing genome elimination in embryo of Arabidopsis cenh3 mutant x wild type crosses. Intact embryos were dissected from fertilized ovules as early as the 2-cell stage, and the altered CENH3 and NUF2, a kinetochore protein are visualized with tagged fluorescent proteins. Two distinct populations of fluorescent signals (five bright and five faint) were observed for both CENH3 and NUF2 foci from early embryos. These observations suggest either differential specification of parental centromeres in the early embryo or epigenetic memory of their parental origin initiates genome elimination.