PeABF3 Enhances Drought Tolerance via Promoting ABA-induced Stomatal Closure by directly Regulating PeADF5 in Poplar.

Water availability is a main limiting factor for plant growth, development and distribution throughout the world. Stomatal movement mediated by abscisic acid (ABA) is particularly important for drought adaptation, but the molecular mechanisms in trees are largely unclear. Here, we isolated an ABA-responsive element binding factor PeABF3 in Populus euphratica. PeABF3 was preferentially expressed in the xylem and young leaves, and was induced by dehydration and ABA treatments. PeABF3 showed transactivation activity and located in the nucleus. To study its functional mechanism in poplar responsive to drought stress, the transgenic triploid white poplars (P. tomentosa 'YiXianCiZhu B385') overexpressing PeABF3 (oxPeABF3) were generated. PeABF3 overexpressing significantly enhanced stomatal sensitivity to exogenous ABA. When subjected to drought stress, oxPeABF3 maintained higher photosynthetic activity and promoted cell membrane integrity, resulting in increased water-use efficiency (WUE) and enhanced drought tolerance compared to WT (wild-type) controls. Moreover, yeast one-hybrid assay and electrophoretic mobility shift assay revealed that PeABF3 activated the expression of PeADF5 (Actin-Depolymerizing Factor-5) by directly binding to its promoter, promoting actin cytoskeleton remodeling and stomatal closure in poplar under drought stress. Taken together, our results indicate that PeABF3 enhances drought tolerance via promoting ABA-induced stomatal closure by directly regulating the PeADF5 expression.