Environment-dependent self-organization of positional information field in chemotaxis of Physarum plasmodium

Physarum plasmodium shows highly coordinated tactic migration accompanied by a reorganization of its body shape, even in a complicated environment. We experimentally investigated the information integration mechanism to achieve such environment-dependent coordination from the viewpoint of self-organization of the positional information field. Since the organism is known to process information by mutual entrainment in distributed intracellular oscillators, we analysed the relationship between the global phase wave and migration velocity in the tactic response. It was thus clarified that the phase gradient in the wave linearly decreases according to the relative distance from the wave source corresponding to the best-conditioned site, and the migration velocity in each part was regulated by the phase gradient in position-dependent manner. These results indicate that the organized phase gradient pattern represents the environment-dependent positional information field which encodes the relative positional relationship between each part and the best-conditioned site in the whole system. Therefore, through the self-referential interaction process between self-organization of this information field and its interpretation, environmental information is integrated, and tactic migration towards the most suitable environment can be coordinately and relevantly controlled. (C) 1996 Academic Press Limited