Identification of GASA Protein Family Expression Levels in Cotton (Gossypium hirsutum L.) Affected by Verticillium wilt.

Verticillium wilt, caused by Verticillium dahliae, is a major constraint on cotton production. The GASA (Gibberellic Acid-Stimulated in Arabidopsis) proteins are cysteine-rich peptides induced by gibberellin signaling; however, their systemic role in upland cotton (Gossypium hirsutum) resistance to Verticillium wilt remains elusive. Here, we identified 40 GhGASA members from the G. hirsutum genome, which were clustered into three subfamilies. All members possessed a typical gibberellin-regulated domain, and segmental duplication was the primary driver of family expansion. Transcriptomic analyses revealed tissue-specific expression, with high abundance in pistils and roots, and distinct responsive patterns to salt, drought, and cold stresses. Quantitative real-time PCR (qRT-PCR) showed that multiple GhGASA genes were significantly upregulated following V. dahliae inoculation, with transcript levels being much higher in roots and stems than in leaves. Notably, GhGASA17, harboring ethylene-responsive elements, was identified as a key candidate involved in the defense response. Overall, this study provides a comprehensive characterization of the GhGASA gene family, offering a theoretical foundation for understanding its regulatory functions in Verticillium wilt resistance and delivering potential genetic resources for molecular breeding in cotton.