Functional characterization of the γ-polyglutamic acid-induced GhZAT10 gene in cotton drought stress response

Drought stress is a major abiotic factor that severely limits cotton productivity. While the C2H2-type zinc finger transcription factor GhZAT10 was identified, its specific role in cotton drought tolerance and its relationship with stress-mitigating agents like γ-polyglutamic acid (γ-PGA) remained unknown. GhZAT10 expression was significantly induced by drought, γ-PGA, and abscisic acid (ABA). Silencing GhZAT10 in cotton impaired drought tolerance, leading to severe wilting, reduced relative water content, proline accumulation, and antioxidant enzyme activities, while increasing malondialdehyde levels. Conversely, overexpressing GhZAT10 in Arabidopsis enhanced drought tolerance, improving germination and root growth under osmotic stress. Notably, γ-PGA-mediated drought tolerance was partially compromised in GhZAT10 -silenced plants: under drought, γ-PGA treatment normally increased ABA and decreased Indole-3-acetic acid (IAA) content, but these hormonal responses were weakened when GhZAT10 was silenced. Transcriptome analysis identified 3,228 differentially expressed genes, significantly enriched in auxin biosynthesis and signaling pathways, and hormone measurements confirmed GhZAT10 ’s association with altered auxin and ABA accumulation under drought. GhZAT10 acts as a positive regulator of drought tolerance, likely by modulating the antioxidant defense system, stomatal conductance, and auxin-related responses. It also partially contributes to γ-PGA-induced drought resilience through the regulation of ABA and IAA homeostasis. The findings position GhZAT10 as a promising candidate gene for drought-resistance breeding in cotton, though the proposed γ-PGA–ABA– GhZAT10 –auxin cascade remains largely correlative and requires further validation of its direct targets.