Going in the right direction Cellular mechanisms underlying root halotropism

Worldwide salinization of the soils threatens our food supply. Although the salt tolerance of crops is improving, not in all cases the underlying mechanisms of the tolerances are known. However, this is important if solutions need to be made applicable to multiple crops. One major response to salinity in plants is the change of root system architecture, including root growth direction under influence of altered local concentrations of the plant hormone auxin, and auxin symmetry in the root. In this thesis, I focus on unraveling the mechanisms behind the halotropic response, during which the root growth is directed away from a high local salt concentration, using both a physiological and cell biological approach in the plant model system Arabidopsis. The importance of the re-localization of the auxin carrier proteins is studied. And. more specifically, the roles of the Phospholipase D ζ 1 (PLDζ1), Epsin-like Clathrin Adaptor 1 (ECA1) and Epsin-like Clathrin Adaptor 4 (ECA4) genes in the salt stress response are elucidated. Interestingly, PLDζ1 was found to be involved in the localization of auxin carrier proteins and thus influencing the halotropic response. Next to that, the ECA proteins show different roles in the salt response, indicating multiple roles for clathrin-mediated endocytosis during the salt stress response.