Branched actin polymerization is essential for pore expansion and stabilization and modes of exocytosis in the SG. (A) Time-lapse sequence (SRRF intensity-projection) of representative LSVs from WT SGs undergoing full collapse (FC; top; fusion pore - dual arrowheads), kiss-and-run (KAR w actomyosin—second row; KAR w/o actomyosin—third row; fusion—asterisk; “deforming LSV”—dashed line), and Stalling (bottom; vesicle recruits actin [01:45] but does not release its content; also in Video 3). (B) Time-lapse sequence of representative LSVs from Arp3^KD SGs (SRRF intensity-projection; complementary to Fig. 2 A) undergoing FC (top; fusion pore—double arrowheads) and KAR (middle—KAR w actomyosin; “deforming LSV”—dashed line; LSV fuse again at 08:27—asterisk; bottom—KAR w/o actomyosin; consecutive fusion events of the same LSV at 00:00 and 01:05—asterisk). Glue-GFP (green) and LifeAct-Ruby (magenta). UAS-based expression in A driven by c135-GAL4 in B driven by fkh-GAL4. Time mm:ss; relative to fusion. Scale bars = 1 µm.