Developmental defects in RasGEF Q–null cells (gefQ⁻). (A) Development of gefQ⁻ cells plated on nonnutrient agar. The top shows wild-type tipped aggregate (13 h), migratory slug (16 h), and fruiting body (24 h). The middle shows that gefQ⁻ aggregates break up into smaller aggregates (13 h), multiple tipped structures (16 h), and fruiting bodies (24h). The bottom shows development of cells overexpressing GFP-GEF. Bars, 200 μm. (B) Altered slug motility in phototaxis assays in gefQ⁻ and GFP-GEF–expressing cells. Wild-type AX2, GFP-GEF expressing AX2, and gefQ⁻ cells, as well as gefQ⁻ cells expressing GFP-GEF or GFP-Δ-GEF-GEFQ, were allowed to develop on phosphate agar plates placed in a black opaque box for 36 h with a unidirectional light source from an open slit. Migratory pattern of slugs were determined by transferring slime trails and cellular materials onto nitrocellulose membrane. Membranes were stained with 0.1% amido black. (C) Altered cell-type spatial patterning in gefQ⁻ mutants. (a) 10% AX2 cells labeled with GFP was mixed with 90% unlabeled wild-type cells. (b) 10% labeled wild-type cells was mixed with 90% unlabeled gefQ⁻ cells. (c) 10% labeled gefQ⁻ cells was mixed with 90% AX2 cells and were codeveloped as a chimera. Images were taken at the slug stage using a fluorescent microscope (Leica DMR) at 5× magnification. Imaging medium was air at 22°C. Images were acquired with a camera (DC 350 FX; Leica). Bar, 200 nm.