The role of abscisic acid in the response of a specific vacuolar invertase to water stress in the adult XXXX leaf.

@entity2272 @entity69571 @entity2829 @entity948 @entity969 @entity413
Among the numerous molecular and physiological modifications induced by water deficit, one of the earliest events observed in @entity2829 mature leaves subjected to water deprivation was a strong enhancement of acid vacuolar invertase activity, which occurred before the classical reduction in gas exchange due to stomatal closure. The increase in invertase activity coincided with the rapid accumulation of @entity413 and @entity948 that reached 8-fold the control leaf value. In addition, acid vacuolar invertase activity appeared to be highly correlated with xylem sap ABA concentration. In order to investigate the nature of the relationship between ABA and invertase activity, and to disconnect ABA from a likely @entity969 side-effect, excised leaves were supplied with ABA or @entity969 . As a consequence of ABA supply, a peak in leaf ABA appeared 4 h later which was followed by an enhancement of vacuolar invertase activity. @entity2272 supply also produced a second maximum in leaf ABA. The transcript level of the @entity69571 gene encoding one vacuolar invertase presented the same two peaks pattern as leaf ABA, with a 2 h lag. This response was specific since the other invertase genes were not responding. Thus, ABA appeared to be a powerful enhancer of the @entity69571 vacuolar invertase activity and expression. In the present conditions, the addition of @entity969 had no effect on the enzyme activity.
