Figure 1.

Slug tips release cAMP upon light irradiation. A dissected slug tip was placed in a field of preaggregation cells and overlaid with an agar film (2% wt/vol KK₂ buffer, pH6.8). Each column shows three consecutive 10-min periods from 50 to 80 min after the overlay. White lines indicate cell movement during the 10-min period; red dots indicate the final positions of the cells. (a–c) Wild-type NC-4 cells. Cell tracks of preaggregation cells in the dark. The slug tip is visible at the center of each image. (d–f) Wild-type NC-4 cells. Light irradiation was started 60 min after the agar overlay (e). The tip is visible at the right-bottom corner of each image. The experiment was repeated six times with the same result. (g–i) Mutant car1−/car3− cells. Light irradiation was started 60 min after the agar overlay (h). Mutant cells were not as motile as wild-type cells (short tracks) and showed no orientation toward the tip. (Bar = 0.2 mm).