Identification of aquaporins and deciphering their role under salinity stress in pomegranate ( Punica granatum )

Aquaporins (AQPs), pore-forming proteins, are known to involve in the transport of water and many other small solutes, and play a diverse role in physiological processes. In this study, 38 AQPs were identified from pomegranate ( Punica granatum ) genome based on the phylogenetic distribution and homology with known AQPs from Arabidopsis thaliana and Oryza sativa . The pomegranate AQPs were further classified into five subgroup representing 12 plasma membrane intrinsic proteins (PIPs), 8 Nod26-like intrinsic proteins (NIPs), 14 tonoplast intrinsic proteins (TIPs), three small and basic intrinsic proteins (SIPs) and one uncategorized intrinsic protein (XIPs). Extensive computational analysis was performed to understand the pore morphology, exon–intron structure, and subcellular localization of the AQPs. The identified AQPs were further confirmed for the conserved NPA motifs, ar/R selectivity filters, and Froger’s residues. Analysis of the available transcriptomic data revealed tissue specific expression of different aquaporins, for instance, under salinity stress PgNIP6-1 showed increased expression in root. The co-expression has been observed among PgTIP3-1, PgTIP1-4, PgTIP1-8, PgTIP1-1, PgSIP1-1, PgPIP2-4, PgPIP1-3, and PgPIP1-2. Moreover, PgTIP3-1 showed a negative correlation with remaining seven AQPs. Further, the expression analysis of PgNIP6-1, PgTIP3-1 and PgNIP3-1 using quantitative real-time PCR showed increased transcript level of these genes under salinity stress suggesting their key role in stress related mechanism. The information presented here will provide insights into AQPs role in development and stress tolerance in plants.