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Fig. 11 | BMC Developmental Biology

Fig. 11

From: Distinct shape-shifting regimes of bowl-shaped cell sheets – embryonic inversion in the multicellular green alga Pleodorina

Fig. 11

Model of the inversion process and subsequent development in P. californica. A schematic presentation of inversion as deduced from time-lapse transmitted light microscopy, light microscopy of semi-thin sections and transmitted electron microscopy of thin sections. Mid-sagittal cross-sections of an embryo of P. californica during inversion and subsequent development. Cell content is shown in green; red lines indicate the position of the CB network; nuclei are shown in blue. The directions of the cell layer movements are indicated by black arrows. Frames show the approximate localization of the details presented in Figs. 5, 6, 7, 8, and 9. a Pre-inversion stage. b, c Early inversion stage: the peripheral (anterior) region of the plakea bends outwards. d-f Mid-inversion stage: Bending of the peripheral region of the cell sheet continuous and, simultaneously, the centrally located posterior region of the plakea moves towards the opening of the bowl-shaped cell sheet. g, h Late inversion stage: the entire cell sheet proceeds to bend so that the previously concave plakea becomes more and more convex; at the end of inversion the cell sheet is two-thirds closed. i-k Post-inversion stage: the cells round up and the opening (phialopore) closes; ECM biosynthesis begins. l Young adult shortly after release from its mother spheroid; the cells are embedded in a considerable amount of ECM material

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