Genome-Wide Identification and Integrative Analysis of the Fruit-Weight 2.2-Like Family Suggests Potential Roles in Fiber Development and Stress Responses in Gossypium hirsutum

The Fruit-Weight 2.2-Like (FWL) gene family plays crucial roles in determining organ size and stress responsiveness in plants. However, the FWL family members remain largely unexplored in Gossypium species. In this study, we identified and characterized the FWL family in Gossypium hirsutum to investigate their gene expansion, functional evolution, and potential association with key agronomic traits. A total of 51 GhFWLs were identified, and their gene structures, domain compositions, and phylogenetic relationships were comprehensively analyzed. Expression profiling under heat, cold, salt, and drought stress conditions revealed that most GhFWLs participate in abiotic stress response pathways. Haplotype-based association analysis revealed significant associations for 14 GhFWLs with fiber-related traits, suggesting their potential functions in regulating fiber development. Furthermore, silencing the family member GhMCA1 provided supporting evidence for its role in salt stress tolerance. Our findings provided insightful information about the FWL gene family in G. hirsutum and highlighted candidate genes for improving fiber-related traits and stress tolerance through molecular breeding approaches.