Partitioning of assimilated carbon between alternative sinks
changes in response to both high and low temperature
Measurements of the three major carbon sinks in Arabidopsis leaves -
starch, malate, and fumarate - were taken in control conditions, and on
the 1st and the 7th day of cold and
warm treatment, respectively (Fig. 3). To measure the carbon accumulated
during the photoperiod, the beginning of day concentrations were
subtracted from the end of day concentrations for each carbon sink. Each
of these accumulates in an approximately linear fashion across the
8-hour photoperiod under controlled environment conditions (Dyson et
al., 2016). On the 1st day of treatment, diurnal
accumulation of malate was unaffected by either cold or warm in Col-0
and C24 plants (Fig. 3a,b; Fig. S5a-c). Fumarate accumulation, however,
increased in response to both treatments in these genotypes (Fig. 3c,d;
Fig. S5d-f), this response being most pronounced in the cold and in the
Col-0 genotype. Consistent with previous published data
(Riewe et
al ., 2016), C24 accumulated less fumarate than Col-0 in all conditions,
however it accumulated similar amounts of malate. The fum2 mutant
did not accumulate fumarate but increased its malate accumulation on the
1st day of cold and warm treatment. Organic acid
accumulation continued to increase in the cold over the week but not in
the warm (Fig. 3; Fig. S6). All three genotypes increased their diurnal
starch production in response to cold on the 1st day
and maintained that increase on the 7th day (Fig. 3e).
In the warm, starch accumulation did not change significantly, except in
C24 plants on the 7th day of treatment, where it
increased (Fig. 3f).