Abstract
Roots display tropisms in response to environmental cues such as gravity, light, physical contact, and moisture gradients. Hydrotropism is a directed growth towards higher water potential or moisture, and has long been thought to play an important role in drought avoidance. But, it was difficult to separate hydrotropism from gravitropism because of the constant presence of gravity. We recently developed systems to study hydrotropism of Arabidopsis thaliana, and isolated an ahydrotropic mutant, miz-kussei1 (miz1), and identified MIZ1 as a gene responsible for hydrotropism. MIZ1 encodes a unique domain (MIZ domain), which is highly conserved among terrestrial plants, but not in known genomes of other organisms such as green and red algae, cyanobacteria, or animals. Here, we found three MIZ1 homologues, PpMIL(MIZ1-Like) 1-3 in the moss Physcomitrella patens. With the gene-targeting method, we established the disruptant line for each PpMIL gene, the PpMIL1/2 double and the PpMIL1/2/3 triple disruptant lines. We are now analyzing the phenotypes of these disruptant lines.
