 (C-E) Embryos expressing either of the optogenetic anchor proteins and RhoGEF2-CRY2::mCherry were imaged during late cellularization. (C) z-projections of confocal image stacks show the localization of the respective GFP-tagged optogenetic anchor. Please note that the construct PatJ-CIBN (indicated by asterisk) lacks a fluorescent marker and its localization was thus inferred from the recruited RhoGEF2-CRY2::mCh. All anchor proteins showed predominantly basal localization during cellularization and at the onset of ventral furrow formation. Scale bars, 20 μm. (D) A region of interest (right side of the dashed line) in a 10 µm-sized stack was photo-activated using two-photon illumination for 30 s before acquiring the RhoGEF2-CRY2::mCherry signal using confocal microscopy. All anchor proteins were able to recruit RhoGEF2-CRY2::mCherry specifically to the activated region. Scale bars, 10 μm. (E) Although all basal anchors were effective at recruiting RhoGEF2-CRY2::mCherry to the cell base, only PatJ-CIBN::GFP-pm resulted in effective myosin-II recruitment and actomyosin ring constriction 