Figure 6.

A model involving AtMTM and ATX1 activities in the drought response. This model builds on and extends an earlier model suggesting that the lipid ligand PtdIns5P increases upon osmotic stress and negatively regulates ATX1 activity.⁹ Water withdrawal negatively affects ATX1 activity (bar 1); AtMTM1 has phosphatase activity generating the ligand (bar 2); excess cellular AtMTM1 affects transcript levels of the shared target genes like loss of ATX1 function does (bar 3). The model assumes that the effects of AtMTM1 and drought stress upon ATX1 activity are mediated by the lipid. however, the increase of PtdIns5P under stress in Arabidopsis remains to be shown (broken bar); Arrows and T-shaped bars indicate activation and repression events, respectively.