Trouverie Jacques, Thevenot Claudine, Rocher Jean-Paul, Sotta Bruno, Prioul Jean-Louis
Equipe Structure et Métabolisme des Plantes, Institut de Biotechnologie des Plantes (UMR-CNRS 8618), Bâtiment 630, Université Paris-Sud, 91405 ORSAY Cedex, France.
J Exp Bot. 2003 Sep;54(390):2177-86. doi: 10.1093/jxb/erg234.
Among the numerous molecular and physiological modifications induced by water deficit, one of the earliest events observed in maize 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 glucose and fructose 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 sucrose side-effect, excised leaves were supplied with ABA or sucrose. 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. ABA supply also produced a second maximum in leaf ABA. The transcript level of the Ivr2 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 IVR2 vacuolar invertase activity and expression. In the present conditions, the addition of sucrose had no effect on the enzyme activity.
在水分亏缺诱导的众多分子和生理变化中，在遭受水分剥夺的玉米成熟叶片中最早观察到的事件之一是酸性液泡转化酶活性的强烈增强，这发生在由于气孔关闭导致的经典气体交换减少之前。转化酶活性的增加与葡萄糖和果糖的快速积累同时发生，其积累量达到对照叶片值的8倍。此外，酸性液泡转化酶活性似乎与木质部汁液脱落酸（ABA）浓度高度相关。为了研究ABA与转化酶活性之间关系的本质，并将ABA与可能的蔗糖副作用分开，给离体叶片供应ABA或蔗糖。供应ABA的结果是，4小时后叶片ABA出现峰值，随后液泡转化酶活性增强。ABA供应还使叶片ABA出现第二个最大值。编码一种液泡转化酶的Ivr2基因的转录水平与叶片ABA呈现相同的两个峰值模式，但滞后2小时。这种反应是特异性的，因为其他转化酶基因没有反应。因此，ABA似乎是IVR2液泡转化酶活性和表达的有力增强剂。在当前条件下，添加蔗糖对酶活性没有影响。
