The TaSDIR1-4A-TaASR4-3D module regulates ABA-related drought responses in wheat seedlings.

Drought is a major constraint on global wheat productivity. Although the phytohormone abscisic acid (ABA) is a well-established regulator of drought responses, its regulatory mechanisms in wheat remain unclear. Here, we identify the abscisic acid-, stress- and ripening-induced (ASR) transcription factor TaASR4-3D as a negative regulator of drought tolerance in wheat. Constitutive overexpression of TaASR4-3D increased drought sensitivity, disrupted reactive oxygen species (ROS) homeostasis and reduced stomatal closure capacity, whereas taasr4-3d mutants showed enhanced drought tolerance. RNA sequencing and biochemical assays revealed that TaNCED2-5D and TaRD17-6D are direct targets of TaASR4-3D, which represses their expression by binding to CACCG-containing motifs in their promoters. Furthermore, the RING-type E3 ubiquitin ligase TaSDIR1-4A physically interacts with TaASR4-3D and promotes its ubiquitination and 26S proteasome-mediated degradation. Collectively, these results show that TaASR4-3D negatively regulates ABA-related drought responses and affects ROS homeostasis in wheat seedlings, whereas TaSDIR1-4A interacts with TaASR4-3D and promotes its degradation. These findings provide molecular insights for future improvement of drought tolerance in wheat.