Par-1 and Dia promote cap actin bundles, and Arp3 promotes a separate cap actin network. (A) Tubulin staining shows cell cycle stage (note spindles). Phalloidin shows F-actin. Control mCherry RNAi caps show a combination of punctate and bundle-like F-actin (arrows) at prophase. Both pools persist to metaphase with many bundles then around the cap periphery. par-1 or dia RNAi caps display only punctate F-actin and no bundles at both stages. Arp3 RNAi caps dominated by actin bundles at both stages (arrows). Images deconvolved (squares show the detection of actin bundles and puncta in single caps without deconvolution). (B) Dia and GFP–Par-1 (expressed from a UAS construct) in Arp3 RNAi caps. Arrows indicate phalloidin-stained actin bundles. (C) Actin bundle quantifications for cycle 10 prophase of the embryo numbers and genotypes indicated. Asterisks indicate significant differences versus control RNAi.