CaSnRK2.4 ‐Mediated Phosphorylation of CabZIP032 Regulates CaABI5 and CaSPS1 Expression to Modulate ABA Signalling and Sucrose Metabolism During Drought Tolerance in Pepper

ABSTRACT Drought stress severely impacts plant growth and productivity; however, the molecular mechanisms underlying stress adaptation in non‐model crops remain incompletely understood. In this study, we discovered that the SnRK2 kinase CaSnRK2.4 and the bZIP transcription factor CabZIP032 positively regulate drought tolerance through ABA and sucrose signalling pathways. Yeast two‐hybrid and in planta assays confirmed direct interaction between CaSnRK2.4 and CabZIP032, with CaSnRK2.4 phosphorylating CabZIP032 at serine 251 (Ser251). Phosphorylation‐defective CabZIP032 S251A mutants exhibited protein stability and compromised drought tolerance, whereas phosphomimetic CabZIP032 S251D mutants showed enhanced stress resilience. Functional analyses revealed that CabZIP032 binds to the promoters of CaABI5 , an ABA‐responsive gene, and CaSPS1 , a sucrose biosynthesis gene, activating their transcription via specific recognition of ACGT and G‐box cis‐elements, respectively. Silencing of CaABI5 or CaSPS1 results in increased drought sensitivity and reduced ABA and soluble sugar levels. Notably, exogenous applications of ABA or sucrose rescued drought tolerance in CabZIP032 ‐silenced plants, while phosphorylation at Ser251 further potentiated CabZIP032 transcriptional activity. Collectively, these findings establish a CaSnRK2.4‐CabZIP032 signalling module that orchestrates drought adaptation by stabilising CabZIP032 through phosphorylation, thereby promoting ABA signalling and sucrose accumulation. This study reveals a conserved regulatory mechanism in pepper and provides potential molecular targets for engineering drought‐resilient crops.