Expansins are cell wall loosening proteins that appear to permit the microfibril matrix network to slide in growing plant cell walls, thereby enabling the wall to expand. To scrutinize possible impacts on plant growth and development when expansins are over-expressed, we characterized phenotypic alterations of the transgenic plants that constitutively expressed AtEXP3 or AtEXP-beta 1 under control of 35S-CaMV promoter. Our results suggest that both AtEXP3-OX and AtXP beta 1-OX are very sensitive to salt stress. However, the mechanisms underlying their enhanced salt sensitivity appear to be different.