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Fig. 5. DNA content of endosperm nuclei derived from glc central
cell. DNA content of the sporophytic integument nuclei (blue bars), the
single nucleus (orange or yellow bars) in glc seeds and the endosperm
nuclei in wild-type seed (yellow bars). (A,B) glc
selfed seeds. (C-F) Out-crossed glc seeds. (G)
Wild-type seed. Each graph displays data from one seed. Each seed had its own
diploidy reference owing to the laser-scanning settings and variation in dye
penetration from seed to seed. As the integument cells of early seeds are
simultaneously dividing and expanding
(Haughn and Chaudhury, 2005),
their nuclei have different amounts of DNA depending on where the cells are in
the cell cycle. The nuclei with the lowest DNA content represent 2n
at G1 (2n=2C), the nuclei with the highest DNA content represent
2n at G2 (2n=4C), and the nuclei with the DNA content
between these two values represent the amount of DNA from the mother nucleus
plus that from the replicating DNA strands (equivalent to
2C<2n<4C). For each series of 15 sporophytic nuclei of each
glc seed, the average of the DNA contents of the three nuclei with
the lowest fluorescence intensity was taken as 2C, and of the three nuclei
with the highest fluorescence intensity as 4C. The x-axis depicts
separate nuclei; the y-axis shows the fluorescence intensity sum of
the propidium iodide-stained nuclei. Horizontal dotted lines represent the
average 2C level; horizontal dashed lines represent the average 4C level.
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