Genome-wide identification and expression analysis of aquaporins in salt cress ( Eutrema salsugineum )

Aquaporins (AQPs) serve as water channel proteins and belong to major intrinsic proteins (MIPs) family, functioned in rapidly and selectively transporting water and other small solutes across biological membranes. Importantly, AQPs have been shown to play critical roles in abiotic stress response of plants. Eutrema salsugineum is close to Arabidopsis thaliana and proposed as a model system for studying plant salt resistance. Here we identified 35 full-length AQP genes in E. salsugineum . Phylogenetic analysis showed EsAQPs were similar with AtAQPs and grouped into four subfamilies including 12 plasma membrane intrinsic proteins (PIPs), 11 tonoplast intrinsic proteins (TIPs), 9 NOD-like intrinsic proteins (NIPs), and 3 small basic intrinsic proteins (SIPs). Gene structure, also the conserved motifs (MEME) of EsAQPs in each subfamily shared high similarities. In detailed sequence analysis, EsAQPs comprised 237-323 amino acids, with a theoretical molecular weight (MW) of 24.31-31.80 kDa and an isoelectric point (pI) value of 4.73-10.49. Functional prediction based on the NPA motif, aromatic/arginine (ar/R) selectivity filter, Froger’s position and specificity-determining position suggested there was a big difference in the specificity of substrate transport between EsAQPs. Gene expression profiles illustrated EsAQP genes could be detected in all organs and appear to play an important role in response salt, cold and drought signals. These results will bring a better understanding on the characterizations of AQPs in E. salsugineum and its complex transport networks in homeostasis control.