Evolutionary divergence and characterization of aquaporins in salt tolerance and fiber development in tetraploid cotton

Abstract Background Aquaporins (AQPs) are integral membrane proteins belonging to the major intrinsic protein (MIP) family, playing a crucial role in water transport, cell elongation, and stress responses. However, their evolutionary dynamics and functional roles in Gossypium species remain poorly characterized. Results In the present study, a total of 55, 54, 54, 103, 106, 108, and 104 AQP genes were found in G. herbaceum , G. arboreum , G. raimondii , G. barbadense , G. tomentosum , G. mustelinum , and G. darwinii , respectively. Phylogenetic analysis classified them into five conserved subfamilies (PIP, TIP, NIP, SIP, and XIP), with 95 genes showing synteny across species and 17 displaying divergence, suggesting subgenome differentiation. Transcriptome analysis revealed that specific GbAQP genes are involved in early salt stress responses and fiber development. Physiological assays demonstrated stronger salt tolerance in tetraploid cottons, particularly G. darwinii , compared with diploids. Co-expression network analysis linked AQPs to abiotic stress and fiber traits, and virus-induced gene silencing (VIGS) confirmed four AQP genes as critical for salt tolerance. Conclusion This study provides comprehensive insights into the evolution, expression, and functional roles of AQPs in cotton, identifying key candidate genes for improving salt tolerance and fiber quality in Gossypium species.