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Published online 2 October 2000. doi:10.1083/jcb.151.1.131
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© The Rockefeller University Press, 0021-9525/2000//131 $5.00
The Journal of Cell Biology, Volume 151, Number 1, , 2000 131-142

Original Article

Functional Redundancy in the Maize Meiotic Kinetochore



Hong-Guo Yua and R. Kelly Dawea,b

a Department of Botany, University of Georgia, Athens, Georgia 30602
b Department of Genetics, University of Georgia, Athens, Georgia 30602
Department of Botany, Miller Plant Sciences Bldg., University of Georgia, Athens, GA 30602.706-542-1805706-542-1658

Kinetochores can be thought of as having three major functions in chromosome segregation: (a) moving plateward at prometaphase; (b) participating in spindle checkpoint control; and (c) moving poleward at anaphase. Normally, kinetochores cooperate with opposed sister kinetochores (mitosis, meiosis II) or paired homologous kinetochores (meiosis I) to carry out these functions. Here we exploit three- and four-dimensional light microscopy and the maize meiotic mutant absence of first division 1 (afd1) to investigate the properties of single kinetochores. As an outcome of premature sister kinetochore separation in afd1 meiocytes, all of the chromosomes at meiosis II carry single kinetochores. Approximately 60% of the single kinetochore chromosomes align at the spindle equator during prometaphase/metaphase II, whereas acentric fragments, also generated by afd1, fail to align at the equator. Immunocytochemistry suggests that the plateward movement occurs in part because the single kinetochores separate into half kinetochore units. Single kinetochores stain positive for spindle checkpoint proteins during prometaphase, but lose their staining as tension is applied to the half kinetochores. At anaphase, ~6% of the kinetochores develop stable interactions with microtubules (kinetochore fibers) from both spindle poles. Our data indicate that maize meiotic kinetochores are plastic, redundant structures that can carry out each of their major functions in duplicate.

Key Words: kinetochore • checkpoint • meiosis • misdivision • afd1

© 2000 The Rockefeller University Press

Abbreviations used in this paper: 3D, three-dimensional; afd1, absence of first division 1; CENPC, centromere protein C; CentC, maize centromeric tandem repeat.


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