WHEN GROWING POTATO-TUBERS ARE DETACHED FROM THEIR MOTHER PLANT THEREIS A RAPID INHIBITION OF STARCH SYNTHESIS, INVOLVING INHIBITION OF ADP-GLUCOSE PYROPHOSPHORYLASE
P. Geigenberger et al., WHEN GROWING POTATO-TUBERS ARE DETACHED FROM THEIR MOTHER PLANT THEREIS A RAPID INHIBITION OF STARCH SYNTHESIS, INVOLVING INHIBITION OF ADP-GLUCOSE PYROPHOSPHORYLASE, Planta, 193(4), 1994, pp. 486-493
Labelling experiments in which high-specific-activity [U-C-14]sucrose
or [U-C-14]hexoses were injected into potato (Solanum tuberosum L. cv.
Desiree) tubers showed that within 1 d of detaching growing tubers fr
om their mother plant, there is an inhibition of starch synthesis, a s
timulation of the synthesis of other major cell components, and rapid
resynthesis of sucrose. This is accompanied by a general increase in p
hosphorylated intermediates, an increase in UDP-glucose, and a dramati
c decrease of ADP-glucose. No significant decline in the extracted act
ivity of enzymes for sucrose degradation or synthesis, or starch synth
esis is seen within 1 d, nor is there a significant decrease in sucros
e, amino acids, or fresh weight. Over the next 7 d, soluble carbohydra
tes decline. This is accompanied by a decline in sucrose-synthase acti
vity, hexose-phosphate levels, and the synthesis of structural cell co
mponents. It is argued that a previously unknown mechanism acting at A
DP-glucose pyrophosphorylase allows sucrose-starch interconversions to
be regulated independently of the use of sucrose for cell growth.