Regulation of drought tolerance in Arabidopsis involves the PLATZ4-mediated transcriptional repression of plasma membrane aquaporin PIP2;8.

Plant A/T-rich protein and zinc-binding protein (PLATZ) transcription factors play important roles in plant growth, development, and abiotic stress responses. However, how PLATZ regulates plant drought tolerance remains poorly understood. The present study showed that PLATZ4 increased drought tolerance in Arabidopsis thaliana by causing stomatal closure. Transcriptional profiling analysis revealed that PLATZ4 affected the expression of a set of genes involved in water and ion transport, antioxidant metabolism, small peptides, and abscisic acid (ABA ) signaling. Among these genes, the direct binding of PLATZ4 to the A/T-rich sequences in the plasma membrane intrinsic protein 2;8 (PIP2;8) promoter was identified. PIP2;8 consistently reduced drought tolerance in Arabidopsis via decreasing stomatal closure. PIP2;8 was localized in plasma membrane, exhibited water channel activity in Xenopus laevis oocytes and acted epistatic to PLATZ4 in regulating drought stress response in Arabidopsis. PLATZ4 increased ABA sensitivity via upregulating the expression of ABA insensitive 3 (ABI3), ABI4 and ABI5. The transcripts of PLATZ4 were induced to high levels in vegetative seedlings under drought and ABA treatments within 6 and 3 h, respectively. Collectively, these findings reveal that PLATZ4 positively regulates plant drought tolerance through regulating the expression of PIP2;8 and genes involved in ABA signaling.