SIC1 rescues low-Clb cell cycles and some low-Clb cells
show multiple SIC1pr-YFP oscillations. All strains in A-M have
one copy of a GAL1-SIC1 construct. '+': WT
except for GAL1-SIC1. A: Experimental set-up for panels
A–J. B–D: Distribution of times T between the first budding to
nuclear division in glucose (budneck marker: Myo1-GFP, nuclear marker:
Htb2-mCherry). Plots from B underlaid in C in grey for comparison. E–J:
A subset of low-Clb cells reveal extra peaks and oscillations in
SIC1pr-YFP. Time courses aligned so that first budding
after GAL1-SIC1 shut-off is at time 0'; Square symbol:
time of nuclear division. Same vertical scale is used in all time course plots.
EH: SIC1pr-YFP levels in cells that complete a cell cycle (note
extra bump in low-Clb cell in panel G). Thin lines: sample time courses; thick
lines: mean. Mean time course for '+' cells plotted in black for
reference. I: Subset of arrested clb2Δsic1Δ
cells 14%(6/43) show SIC1pr-YFP oscillations. J: In the
majority of arrested clb2Δsic1Δ cells, strong
SIC1pr-YFP activity cannot be easily detected during the
arrest. K: Experimental set-up for experiment in panel M. L: Clb2-YFP was
recorded in each cell using time lapse fluorescence microscopy. M:
sic1Δ cells which fire Clb2-YFP more slowly take
longer to finish nuclear division (and fail significantly more often) than
SIC1 cells. Plot of time from budding to nuclear division T
versus slope of Clb2-YFP at budding (normalized by Clb2-YFP at budding). The
median Clb2-YFP slope at budding is indicated by a dashed vertical line. The
circles on the horizontal line at T=100' indicate cells that took
T≥100' to complete budding to nuclear division (numbers
indicated). For cells with T<100', slopes were collected in 8
equal-width bins covering the range of slopes observed, the mean ± SEM
is indicated by horizontal lines for each bin, and a large circle
(clnΔ*) or diamond
(clnΔ*sic1Δ) indicates the median in each
bin; the linear regression lines for T<100' populations are also
indicated. Statistical significance of differences is indicated as :
p<0.1, : p<0.05, : p<0.001 (log-rank test). In B-D, the
difference between strains is only statistically significant if indicated. In M,
the statistical significance refers to the difference of the slopes of the
linear regression lines.