Stress-responsive zinc finger gene ZPT2-3 plays a role in drought tolerance in petunia

The petunia gene, ZPT2-3, encodes a Cys(2)/His(2)-type zinc finger protein. Here, we describe the expression of ZPT2-3 in response to various stresses and the effects of ZPT2-3 overexpression in transgenic petunia. Mechanical wounding induced accumulation of ZPT2-3 transcript, and the activity of ZPT2-3::luciferase was conferred by the 1668-bp ZPT2-3 upstream sequence, both locally and systemically. This induction was mediated by a jasmonic acid (JA)-dependent and ethylene-independent pathway. ZPT2-3 expression was also induced by cold, drought, and heavy metal treatments. The same ZPT2-3 promoter sequence showed similar responsiveness to wounding, cold, drought, and JA treatments in Arabidopsis when investigated in a beta-glucuronidase (GUS) reporter gene, indicating conservation of similar signaling pathways between the two plant species. ZPT2-3 functioned as an active repressor in a transient assay using Arabidopsis leaves. Constitutive overexpression of ZPT2-3 in transgenic petunia plants increased tolerance to dehydration. These results demonstrate the involvement of ZPT2-3 in plant response to various stresses, and suggest its potential utility to improve drought tolerance.