γ‑polyglutamic acid‑induced GhJAZ8 positively regulates drought tolerance in cotton associated with phytohormone signaling.

Cotton growth is frequently constrained by drought stress. Previous studies demonstrated that γ-PGA enhances cotton drought tolerance. Transcriptome analysis of γ-PGA-treated cotton revealed that multiple TIFY family members were markedly induced, among which GhJAZ8 showed the most pronounced upregulation. Sequence analysis indicated that GhJAZ8 belongs to the JAZ/TIFY5A subfamily, and its expression was significantly upregulated under drought stress. Virus-induced gene silencing of GhJAZ8 markedly decreased drought tolerance in cotton, evidenced by aggravated leaf wilting, reduced RWC, elevated MDA content, weakened antioxidant enzyme activities, and decreased proline accumulation. Conversely, overexpression of GhJAZ8 in Arabidopsis significantly enhanced drought tolerance. Furthermore, γ-PGA treatment improved drought tolerance in both TRV2 and GhJAZ8-silenced plants, but the effect was more pronounced in TRV2 plants, indicating that GhJAZ8 is required for the full effect of γ-PGA. Exogenous MeJA treatment only partially alleviated the drought-sensitive phenotype of GhJAZ8-silenced plants. Transcriptome analysis revealed that DEGs were predominantly enriched in ABA, JA, and SA signaling pathways, and hormone quantification further confirmed that GhJAZ8 silencing significantly altered endogenous ABA, JA, and SA levels. Taken together, this study reveals that GhJAZ8 functions as a positive regulator in cotton drought response and acts as an important downstream component of the γ-PGA-mediated drought tolerance pathway by modulating multiple phytohormone signaling pathways, providing a candidate gene resource for drought-tolerant cotton breeding.