Sequences associated with A chromosome centromeres are present throughout the maize B chromosome.
Maize chromosome spreads containing the supernumerary B chromosome were hybridized with probes from various repetitive elements including CentC, CRM, and CentA, which have been localized to centromeric regions on the A chromosomes. Repetitive elements that are enriched or found exclusively near the centromeres of A chromosomes hybridized to many sites distinct from the centromere on the B chromosome. To examine whether these elements recruit kinetochore proteins at locations other than the canonical B centromere, cells were labeled with antibodies against CENH3, a key kinetochore protein. No labeling was detected outside the normal centromere and no evidence of B chromosome holocentromeric activity was observed. This finding suggests that, as in other higher eukaryotes, DNA sequence alone is insufficient to dictate kinetochore location in plants. Additionally, examination of the B centromere region in pachytene chromosomes revealed that the B-specific element ZmBs hybridizes to a much larger region than the site of hybridization of CentC, CRM, and CentA and the labeling by anti-CENH3 antibodies.
Lamb
Jonathan C
JC
Division of Biological Sciences, University of Missouri, 117 Tucker Hall, Columbia, MO 65211, USA.
Kato
Akio
A
Birchler
James A
JA
D002503:Centromere / Q000235:genetics*; D032461:Chromosomes, Plant / Q000235:genetics*; D018744:DNA, Plant; D017343:Genes, Plant; D017404:In Situ Hybridization, Fluorescence; D018386:Kinetochores / Q000378:metabolism*; D018626:Retroelements / Q000235:genetics*; D017422:Sequence Analysis, DNA; D020080:Tandem Repeat Sequences / Q000235:genetics; D003313:Zea mays / Q000235:genetics*
D018744:DNA, Plant; D018626:Retroelements