Hui Sun

The S-locus-specific glycoprotein/EP1 gene family encodes a class of epidermis-specific secretory glycoproteins involved in plant responses to abiotic stress. However, their role in cotton (Gossypium hirsutum) drought response remains unclear. Here, we identified 12 GhEP1 genes from the G. hirsutum genome, clustered into three subfamilies. Structural predictions indicated that most GhEP1 proteins are hydrophilic and localised to the outer side of the plasma membrane or nucleus, with a few containing transmembrane domains. Collinearity analysis revealed that segmental and tandem duplications drove family expansion, with a high degree of collinearity conservation among dicotyledonous plants. Transcriptomic data showed generally low GhEP1 expression across tissues, but GhEP1-2, GhEP1-6, GhEP1-7 and GhEP1-8 responded significantly to NaCl, PEG-induced drought and cold stresses. qRT-PCR further confirmed that the expression of most GhEP1 genes was significantly up-regulated in roots under drought stress, while GhEP1-3 was induced in leaves, indicating tissue-specific regulatory divergence. This study systematically characterises the GhEP1 family and provides potential genetic resources for improving drought tolerance in cotton.

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.