Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize.
The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.
State Key Laboratory of Plant Cell and Chromosome Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Yalin
Y
Liu
State Key Laboratory of Plant Cell and Chromosome Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Handong
H
Su
University of Chinese Academy of Sciences, Beijing 100049, China State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
Junling
J
Pang
Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400; and.
Zhi
Z
Gao
State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
Xiu-Jie
XJ
Wang
Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400; and fphan@genetics.ac.cn birchlerj@missouri.edu.
James A
JA
Birchler
State Key Laboratory of Plant Cell and Chromosome Engineering, fphan@genetics.ac.cn birchlerj@missouri.edu.
Fangpu
F
Han
D020029:Base Pairing / Q000235:genetics; D002503:Centromere / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D032461:Chromosomes, Plant / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008540:Meiosis / Q000235:genetics; D003313:Zea mays / Q000166:cytology / Q000235:genetics*
centromere inactivation; centromere misdivision; de novo centromere; epigenetics