Isolation and functional analysis of the glycerol permease activity of two new nodulin-like intrinsic proteins from salt stressed roots of the halophyte Atriplex nummularia

We have isolated and characterized transcripts for two major intrinsic proteins (MIPs), AnNIP1; 1 and AnNIP1;2, from salt stressed roots of the halophyte Atriplex nummularia. Conserved amino acids and phylogenetic analysis of these MIPs clusters them into the plant nodulin-like intrinsic protein (NIP) subgroup. Functional characterization by heterologous expression of both proteins in yeast confirmed their capacity to transport glycerol. fpslDelta Yeast mutants expressing functional AnNIP1:1 and AnNIP1:2 showed increased glycerol uptake, and intra- and extracellular glycerol contents in agreement with their glycerol permease activity. Proper functional expression of AnNIP proteins in yeast needed the removal of the unique hydrophilic N-terminal domain of both proteins, which did not show to be necessary for their transport activities. (C) 2003 Elsevier Ireland Ltd. All rights reserved.