Evolutionary and Predictive Functional Insights into the Aquaporin Gene Family in the Allotetraploid Plant Nicotiana tabacum .

Aquaporins (AQPs) are a class of integral membrane proteins that facilitate the membrane diffusion of water and other small solutes.Nicotiana tabacumis an important model plant, and its allotetraploid genome has recently been released, providing us with the opportunity to analyze theAQPgene family and its evolution. A total of 88 full-lengthAQPgenes were identified in theN. tabacumgenome, and the encoding proteins were assigned into five subfamilies: 34 plasma membrane intrinsic proteins (PIPs); 27 tonoplast intrinsic proteins (TIPs); 20 nodulin26-like intrinsic proteins (NIPs); 3 small basic intrinsic proteins (SIPs); 4 uncharacterized X intrinsic proteins (XIPs), including two splice variants. We also analyzed the genomes of twoN. tabacumancestors,NicotianatomentosiformisandNicotianasylvestris,and identified 49AQPgenes in each species. Functional prediction, based on the substrate specificity-determining positions (SDPs), revealed significant differences in substrate specificity among the AQP subfamilies. Analysis of the organ-specificAQPexpression levels in theN. tabacumplant and RNA-seq data ofN. tabacumbright yellow-2 suspension cells indicated that many AQPs are simultaneously expressed, but differentially, according to the organs or the cells. Altogether, these data constitute an important resource for future investigations of the molecular, evolutionary, and physiological functions of AQPs inN. tabacum.