Movie 7.

AFBp cells form a sheet-like tissue by establishing lateral contacts with neighboring cells. Representative high-magnification movie of AFB formation in the tergite by AFBp cells expressing CD4::tdGFP driven by 31F09-Gal4 plus Ay-Gal4 during 56-72 h APF. At first, AFBp cells were highly polarized and extended lamellipodia-like and filopodia-like protrusions. By 60 h APF, their cell bodies became flattened while their fine protrusions partly remained. Flattened cells made lateral contacts with neighboring cells and merged into a sheet-like tissue, with their cell-cell boundaries becoming obscure. Anterior is to the left, and dorsal is up.