Development of cells expressing mutant actins. Images of the cell lines analyzed in Fig. 9 were taken after development for 48 h. As discussed under “Results,” Y/Y, Y/F, Y/W, and Y/L cells formed mature fruiting bodies similar to those formed by WT cells except that their heads were 25% smaller. Y/A cells never developed beyond the mound stage, and only about half of the mounds of Y/E cells developed into fruiting bodies by 48 h, with heads 25% smaller than those of Y/Y cells.