Isolation of CsHB33 from cucumber and its ectopic expression in Arabidopsis promotes leaf growth but impairs drought tol-erance
The ZF-HD transcription factors play key roles in plant development and stress responses, yet their functions in cucumber remain poorly understood. Here, we characterized a cucumber ZF-HD gene, CsHB33, and investigated its role in leaf development and drought toler-ance. CsHB33 was highly expressed in developing leaves. Its expression was significantly sup-pressed by abscisic acid (ABA) and down-regulated under drought stress. Heterologous overex-pression of CsHB33 in Arabidopsis promoted leaf growth by increasing cell size, but simultane-ously enhanced sensitivity to osmotic and drought stress, accompanied by higher stomatal aper-ture and water loss. Transcriptomic analysis revealed that CsHB33 overexpression up regulated genes associated with leaf enlargement, while under drought it led to constitutive activation of aromatic amino acid biosynthesis, particularly tryptophan metabolism. This metabolic disturb-ance likely contributes to the drought-sensitive phenotype. Our findings reveal that CsHB33 exerts opposing effects on leaf growth and drought tolerance, providing new insights into ZF HD gene function in cucumber and identifying a potential target for improving stress resilience in breed-ing.