Dual-color SRRF imaging was performed on a spinning disc confocal microscope (14 (link)). HMRef and Alexa Fluor 647 phalloidin excitation was conducted with a 488-nm/150-mW diode laser (LM-488-150, Andor) and a 637-nm/140-mW diode laser (LM-637-140, Andor), respectively. The two lasers were fiber coupled (seven-line laser combiner, multimode ×2, single mode ×1; LC-ILE-700-M2-S1, Andor) to a spinning disk confocal unit (CR-DFLY505, Andor) equipped with a multiband dichroic mirror (DFly laser dichroic for 405/488/561/640). The fluorescence was processed with appropriate filter sets for HMRef (TR-DFLY-F525-050, Andor) and Alexa Fluor 647 (TR-DFLY-F700-075, Andor) to capture fluorescence images with a charge-coupled device (CCD) camera (iXion Life 888, Andor), driven by Fusion software (version 2.0 for Fig. 2 and version 2.2 for fig. S19; Andor). Images were taken using a 60× objective (APON60XOTIRF, numerical aperture (NA) 1.49, Olympus], mounted on an inverted microscope (IX83, Olympus), and equipped with Z-drift compensator (IX3-ZDC2, Olympus).