The gene MIZU-KUSSEI 1 (MIZ1) has been shown to regulate root hydrotropism in Arabidopsis thaliana, but its role in plant growth and survival under natural conditions is not yet fully known. Iwata et al. establish moisture gradients in soil and examine root system architecture, biomass production and survival of the A. thaliana mutant miz1 in comparison with transgenic plants over-expressing MIZ1 (MIZ1OE) and with wild-type plants. They find that wild-type plants develop their root systems in regions with higher water potential and this asymmetrical pattern is more pronounced in the transgenic MIZ1OE plants, but the response is lacking in the miz1 mutants. Shoot biomass and the number of plants that survive under drought conditions are much greater in MIZ1OE plants, demonstrating that MIZ1 over-expression has potential for improving productivity in arid areas.