Meiotic transmission rates correlate with physical features of rearranged centromeres in maize

The centromere of the maize B chromosome was used as a model to study the p hysical features of a functional centromere. Pulsed-field gel electrophores is was previously used to determine the organization of a repetitive sequen ce (referred to as the B-specific repeat) localized in the centromeric regi on of the maize B chromosome. The centromere is composed mostly of this rep eat. In this report, a collection of 25 B chromosome derivatives that suffe red from misdivision of the centromere was examined for the content and org anization of the B repeat. Meiotic transmission of these derivatives was al so determined and compared with rearrangements within the centromere. This analysis revealed that there is a strong correlation between the size of th e centromere and meiotic transmission. In addition, the loss of a particula r PmeI fragment of 370 kb considerably reduced meiotic transmission. This s equence contains a 55-kb EcoRI fragment that is also present in all but fou r derivatives. Because the centromere of the maize B chromosome can be divi ded by successive misdivisions to derivatives with centromeres of <300 kb, it should be possible for artificial chromosomes to be produced in maize.