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Fig. 3. Mutations in the polo boxes disrupt Plo1 function in vivo. Diploid strains
were constructed in which one copy of plo1+ is disrupted
by the his3+ gene and plo1 mutant gene marked
with the ura4+ gene is integrated at one of the
leu1 loci. The diploids were sporulated and germinated under the
selective condition (His Ura), which allows the growth of only
the plo1 disruptant expressing mutant plo1 genes. Cells were
fixed and stained with DAPI. (A) plo1 disruptant cells expressing
plo1YQL508AAA. (B) plo1 disruptant cells expressing
plo1DHK625AAA. Both types of cells exhibit similar cytological
defects to the plo1 disruptant. These defects include mitotic arrest
with overcondensed chromosomes (left panels), disorganised septum (middle) and
a failure of septation (right). Round cells seen in B are ungerminated spores.
Bar, 10 µm.