Substitution of a single amino acid residue in the aromatic/arginine selectivity filter alters the transport profiles of tonoplast aquaporin homologs

► Isolation and structural characterization of two TIP genes from tulip petals. ► Construction of TIP mutants to mimic the ar/R constrictions of 9 TIPs in Arabidopsis. ► Building of 3D models and analysis of pore conformations of TIP water channels. ► Expression and functional analysis of wild and mutant TIP homologs. ► Amino acid at LE2 position in ar/R constriction determines the substrate selectivity