AtGATA5 contributes to ABA-mediated seed germination by promoting NCED3 and ABI4 expression in Arabidopsis thaliana

Abscisic acid (ABA) is a key phytohormone that regulates seed germination, stomatal closure, and responses to abiotic stresses. The biosynthesis and signaling of ABA are controlled by a complex gene network, with NCED3 serving as the rate-limiting enzyme in ABA biosynthesis and ABI4 acting as a central transcription factor in ABA signaling. However, upstream regulators that coordinately control both processes during seed germination remain incompletely understood. In this study, we investigated the role of AtGATA5, a GATA transcription factor in Arabidopsis thaliana, in ABA-mediated seed germination. To assess the germination phenotype under ABA treatment and the expression of ABA-related genes, we performed a transient activity assay (TAA) using Arabidopsis protoplasts and gene expression analysis in transgenic plants. AtGATA5-overexpression (AtGATA5-OX) plants exhibited significantly reduced germination rates under exogenous ABA compared with wild type (WT), and gata5 mutant, generated by CRISPR/Cas9-mediated genome editing, showed a similar ABA-hypersensitive phenotype. The expression levels of NCED3 and ABI4 were markedly elevated in AtGATA5-OX plants, and TAA confirmed that AtGATA5 upregulates the promoter activities of both NCED3 and ABI4. These findings suggest that AtGATA5 plays a functional role in ABA-mediated seed germination by modulating NCED3 and ABI4 expression, and that AtGATA5 may represent a novel regulator of ABA homeostasis in plants.