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

SUMMARY: 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 influences 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 through inhibiting stomatal closure. PIP2;8 was localized in the plasma membrane, exhibited water channel activity in Xenopus laevis oocytes and acted epistatically to PLATZ4 in regulating the drought stress response in Arabidopsis. PLATZ4 increased ABA sensitivity through upregulating the expression of ABSCISIC ACID 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 influences plant drought tolerance through regulating the expression of PIP2;8 and genes involved in ABA signaling. Significance Statement: PLATZs have been demonstrated to play important roles in plant growth, development and responses to environmental stimuli, but how they affect drought stress remain unknown. For these purposes, we reveal that PLATZ4 increases drought tolerance by regulating the expression of PIP2;8 and genes involved in ion transport, antioxidant metabolism, small peptides and abscisic acid signaling. We also reveal the aquaporin activity of PIP2;8 and its roles in regulating drought stress. These findings extend the current view about the regulatory mechanism of PLATZs and the function of PIP2;8. [ABSTRACT FROM AUTHOR]