B - Plant Physiology

control and shown as mean (±SD) of three independent samples. Statistical differences as
determined by student’s t-test (II) are indicated (*, P < 0.05; **, P < 0.001).
Figure 5: SnRK1 activity is inhibited by T6P in growing potato tubers. (A) SnRK1 activity in
extracts prepared from growing potato tubers was assayed with or without the addition of 1
mM T6P. Addition of 1 mM sucrose-6-phosphate (S6P) served as a control. Values represent
the mean (± SD) of three biological replicates. ** denotes a significant difference (P < 0.001)
compared to the control without T6P or S6P. (B) SnRK1 activity in extracts from mature
potato tubers (n=4, ± SD) in the presence of increasing concentrations of T6P. Numbers on
the graph indicate estimated in vivo T6P concentrations: 1, WT; 2, B33-TPP tubers; 3, B33-
TPS line 16; 4, B33-TPS line 29. All estimations assume T6P residing exclusively in the
cytosol and further assume the volume of the cytosol to be 12% of the total cell volume.
Figure 6: Exogenous application of sucrose to excised tuber discs increases T6P levels.
Freshly cut discs from tubers stored for one week at room temperatures were fed with 100
mM of indicated sugars. After 4 hours the T6P content was determined using HPLC-MS/MS.
Values represent mean (±SD) of six independent tubers. *denotes significant difference
P