GENOME-SPECIFIC DNA FRAGMENTATION AND ELIMINATION DURING EARLY EMBRYOGENSIS AFTER WHEAT AND PEARL MILLET CROSSING

¹ Institute of Plant Genetics and Crop Plant Research (IPK), 06466 Gatersleben, Germany

The instability of uniparental chromosomes and preferential elimination of one of the parent chromosomes have been reported for some inter-species hybrids, as such as wheat x pearl millet. Identifying the mechanisms by which parental genomes are eliminated or retained during embryo development of hybrids could enable the development of more efficient haploidyzation or species combination techniques. Uniparental chromosome elimination is generally thought to be caused due to imperfect segregation of one of the parental chromosomes set and subsequent micronuclei formation. However, we have first evidence that uniparental DNA can also be removed from the nucleus by a novel micronucleation mechanism that is initiated by genome-specific fragmentation of DNA during the interphase. Insight into the mechanisms underlying the selective elimination of pearl millet DNA was obtained by combination of in situ hybridisation and terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP-fluorescein nick end-labelling (TUNEL) method on developing embryos of wheat and pearl millet crosses. Given the complexity of the eukaryotic genome the ability of the cell to cleave pearl millet-DNA with specificity and to discriminate it from the wheat genome is unlikely. More likely a specific chromatin topology dictates genome-specific endonuclease activation and a subsequent genome-specific DNA fragmentation and elimination.