Variable distribution
of meiotic homologs; on-line spinning projections of 3D data from chromosome
painting and telomere FISH analysis of OMAd9.2
--Bass, HW, Bordoli, SJ
We have developed a 3D FISH system to study
meiotic telomere behavior and homologous chromosome interactions during
meiotic prophase (Bass et al., 1997, J. Cell Biol., 137:5-18). In a recent
chromosome painting study, the 3D intranuclear distribution of homologs
was characterized in pollen mother cells before and during meiotic prophase
(Bass et al., 2000 J. Cell Sci. 113:1033-1042). Examination of deconvolution
image data revealed a surprising diversity of homolog arrangements and
dispositions, relative to each other, and relative to the position of the
telomere cluster-defined bouquet. In particular, many bouquet-stage nuclei
(mostly at zygotene) contained spatially separated homologs. This observation,
along with the published measurements of inter-homolog distances in well-preserved
nuclei indicate that premeiotic pairing does not contribute much, if anything,
to the zygotene synapsis that is required for proper homolog disjunction.
Thus, the homology search appears to function during meiotic prophase,
after chromosomes have reorganized into condensed and extended fibers,
and largely coincident with the bouquet stage when the telomeres are clustered
on the nuclear envelope.
Computer-assisted inspection of the
3D data conveys a great deal of information. In order to make the visual
data more accessible, we have prepared an on-line supplemental data page
for some of the meiotic nuclei analyzed by Bass et al., (2000). The web
page, http://bio.fsu.edu/~bass/mv/bq2/, contains a table with links to
Quicktime movies that can be downloaded or viewed with web browsers. For
each movie, projections of the FISH signals are shown for the telomeres
(purple) and the maize-9 homologs (green). The DAPI image, which marks
the entire nucleus (42 oat plus 2 maize chromosomes), was omitted. Each
movie is made from a cropped down cube of data in which a single spherical
nucleus is centered.
This form of data display may be useful
to researchers and educators who are interested in the native structure
of meiotic chromosomes and the function of the telomere bouquet. The movies
convey some of the spatial and topological aspects of meiotic chromosome
pairing and synapsis. The original data are archived as DeltaVision image
data (A.P.I. Seattle, WA) and the optical sections can be distributed as
grey scale TIFF files upon request from HWB ([email protected]).
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.
Return to the MNL 75 On-Line Index
Return to the Maize Newsletter Index
Return to the MaizeGDB Homepage