Fig. 5. Cells with the pI^-/II^-/scar^- triple mutation are tight aggregate mutants and show abnormal F-actin staining. As described in Materials and Methods, strains were produced that were null for profilin I and profilin II and Scar.

(A,B) Development of profilin double mutants (pI^-/II^-) and triple mutants (pI^-/II^-/scar^-), respectively. The absence of Scar does not significantly alter the profilin-null developmental phenotype. However, cortical F-actin staining as visualized with TRITC-phalloidin was significantly reduced in the triple mutant (D) relative to the double profilin mutant (C). TRITC-phalloidin staining of wild-type (E) and Scar null cells (F) are included for comparison. The arrow identifies a forming F-actin-rich macropinosome in control cells (E), structures that are absent from all the mutant cell lines. Bar, 10 µm.