Plant Physiol, June 2001, Vol. 126, pp. 622-630
Male Meiotic Spindle Lengths in Normal and Mutant Arabidopsis
Cells1
Ming
Yang2 and
Hong
Ma*
Department of Biology and The Life Sciences Consortium,
Pennsylvania State University, 519 Wartik Lab, University Park,
Pennsylvania 16802
Spindle elongation is crucial to normal chromosome separation in
eukaryotes; in particular, it is required for or associated with the
extension of distance between spindle poles and the further moving
apart of the already separated chromosomes. However, little is known
about the relationship between spindle elongation and the status of
chromosome separation, and it is unknown whether spindle elongation in
different organisms shares any quantitative feature. The Arabidopsis
ask1-1 mutant might be a unique material for addressing
these questions because it appears to have functional spindles, but a
severe defect in homolog separation at male anaphase I (M. Yang, Y. Hu,
M. Lodhi, W.R. McCombie, H Ma [1999] Proc Natl Acad Sci USA 96:
11416-11421). We have characterized male meiotic spindle lengths in
wild-type and the ask1-1 mutant plants. We observed that
during meiosis I some ask1-1 cells had spindles that
were similar in length to fully elongated normal spindles, but the
chromosomes in these cells did not show appreciable movement from the
equator. Furthermore, greater movement of chromosomes from the equator
was usually found in the ask1-1 cells that had longer
than normal spindles. These results suggest that additional elongation
of ask1-1 spindles occurred; one possible reason for the
extra-long spindles may be that it is a consequence of chromosome non-separation. We also found that normal and ask1-1
spindle lengths are clustered at discrete values, and their differences
are of multiples of 0.7 µm. A search of the literature revealed that in each of several organisms, spindle lengths also differ by multiples of 0.7 µm. These findings strongly suggest that the spindle elongates in response to status of chromosome separation, and perhaps there are
conserved mechanisms controlling the extent of spindle
elongation.
1
This work was supported by the Biology
Department and the Life Science Consortium at Pennsylvania State
University and by the National Science Foundation (grant no.
MCB-9728772 to H.M.). M.Y. was a recipient of a National Institutes of
Health/National Research Service Award postdoctoral fellowship.
2
Present address: Plant Gene Expression Center, 800 Buchanan Street, Albany, CA 94710.
*
Corresponding author; e-mail hxm16{at}psu.edu; fax 814-863-1357.
© 2001 American Society of Plant Physiologists
