Sugar signaling of fructan metabolism: New insights on protein phosphatases in sucrose-fed wheat leaves.

Protein phosphatase type 2A (PP2A) activity is required for the sucrose induction of fructan metabolism in wheat leaves, as shown in experiments with the addition of the specific inhibitor okadaic acid (OA) together with sucrose. However, a decrease in total PP2A activity has been found along sucrose treatment. Here we analyze the effect of sucrose feeding to wheat leaves on PP2A activity profiles after Deae-Sephacel and Superose separation, in comparison with those of control leaves. The results show no evidence of changes in PP2A activity profiles as a consequence of sucrose feeding. In all, our data suggest that constitutive levels of PP2A activity may be sufficient for the sucrose-mediated induction of fructan metabolism and that general decrease of PP2A activity produced by long-term treatment with sucrose may be due to a negative feedback regulation.