A method for increasing drought tolerance in a plant or photosynthetic organism is disclosed, where the tolerance is increased by introducing nucleic acid sequences coding for polypeptides with monooxigenase activity or by the modification of endogenous nucleic acid sequences that increase the endogenous TMAO content in plants as well as to nucleic acid constructs, recombinant vectors, cells, transgenic plants, crops, propagation material, compositions and harvestable parts of a plant comprising nucleic acid sequences in order to increase water stress tolerance and so on.