Comparative analysis of the Aquaporin gene family in Cucurbitaceae: insights into evolutionary patterns and functional diversity

Aquaporins (AQPs) are important for regulating water and solute transport in plants, particularly under stress conditions. While AQP gene families have been reported in a few Cucurbitaceae species (Watermelon, Cucumber, Melon, and Bottle gourd), a comprehensive analysis across multiple Cucurbitaceae species is lacking. Our study identified and characterised 528 putative AQP-encoding genes across fourteen Cucurbitaceae using BLASTp and HMM searches. These are grouped into five subfamilies- PIPs (212), TIPs (118), NIPs (146), SIPs (39), and XIPs (13), based on phylogenetic analysis. Further, conserved gene structures and motifs support this subfamily-specific evolutionary relationship. Whole-genome duplication (WGD) and transposed duplication (TRD) were the primary drivers of AQP expansion, with WGD common in Cucurbiteae and Sicyoeae tribes, while TRD in Benincaseae. Correlation between genome size and AQP abundance revealed a positive trend in Cucurbiteae and negative trends in Sicyoeae & Benincaseae tribes. Functional analysis predicted the transport of urea, boric acid, H2O2, CO2, and ammonia by AQPs in addition to water. Promoter analysis identified abiotic/biotic stress-related cis-regulatory elements, with ARE and WUN-motifs predominant. This study provided novel insights into the evolution and role of AQPs in Cucurbitaceae, providing a valuable foundation for future research on stress adaptation.