Actin phenotypes of ARP2 ts mutants. (A) Phalloidin staining of wild-type YMW201U(a) and mutant YMW221U, YMW231U, YMW241U, YMW261U, and YMW271U (a) strains containing ARP2 point mutations. Cells were grown to early log phase in complete medium at 25°C. Part of the culture was shifted to 37°C for 2 h. (B) Strain FDW23GK (a/α) containing an ARP2:GFP C-terminal fusion. Cells were treated as in A and then fixed and stained with TRITC-phalloidin as described in MATERIALS AND METHODS. The left panels were photographed with a GFP bandpass filter, and the right panels were photographed with a rhodamine filter. Bar, 5 μm.