Figure 9.
Furrow directed cortical flows and compression are higher at the cortex of the leading than the lagging edge. (A) Leading (top) and lagging (bottom) cortex of unconfined GFP::NMY-2 expressing embryos (z-projection of four planes) for indicated time points. Time zero represents the disappearance of the leading cortex from the imaging field after the leading edge ingression. The lagging cortex starts to bend inward and ingress around 20 s later. The anterior (A) pole is oriented to the left and the posterior (P) pole toward the right. The orientation of the transverse embryo axis is also shown. (B) Leading (top) and lagging (bottom) cortex of GFP::NMY-2 expressing embryos with measured vector field (magenta) at 10 s after the leading edge ingression. (C) GFP::NMY-2 flow velocities were measured from the anterior to the posterior pole of the embryo. A bidirectional A–P flow has positive X-values in the anterior region and negative X-values in the posterior region. (D and E) The flow velocities along the A–P axis were measured and plotted for indicated time points for the leading (D) and lagging (E) cortex. At 10 s, the leading cortex bent inwards and therefore flow velocities could not be calculated at the furrow region. For this reason, the line of the graph at the furrow region is depicted in a lighter color. A schematic summary of the measured flow velocities and their directions at −10 s are shown (right). The arrows reflect the flow velocities at 20% (anterior arrow) and 80% (posterior arrow) A–P embryo length and are to scale to each other. (F–H) The divergence of flow vectors was measured along the width of the embryo (transverse axis) at the cell equator (F) and is plotted for indicated time points for the leading (G) and lagging (H) cortex. (I) Mean divergence at the cell equator for the leading (Lead) and lagging (Lag) cortex at −15 s and −10 s before inward bending of the leading cortex. P values were calculated using two-tailed Student’s t test and are **P < 0.01. Please note that the measurements at the cell equator were performed before the furrow moved inward and away from the coverslip to avoid measurement artifacts due to inward bending. For all: error bars are SEM and n = number of embryos analyzed, scale bars are 5 µm.

Furrow directed cortical flows and compression are higher at the cortex of the leading than the lagging edge. (A) Leading (top) and lagging (bottom) cortex of unconfined GFP::NMY-2 expressing embryos (z-projection of four planes) for indicated time points. Time zero represents the disappearance of the leading cortex from the imaging field after the leading edge ingression. The lagging cortex starts to bend inward and ingress around 20 s later. The anterior (A) pole is oriented to the left and the posterior (P) pole toward the right. The orientation of the transverse embryo axis is also shown. (B) Leading (top) and lagging (bottom) cortex of GFP::NMY-2 expressing embryos with measured vector field (magenta) at 10 s after the leading edge ingression. (C) GFP::NMY-2 flow velocities were measured from the anterior to the posterior pole of the embryo. A bidirectional A–P flow has positive X-values in the anterior region and negative X-values in the posterior region. (D and E) The flow velocities along the A–P axis were measured and plotted for indicated time points for the leading (D) and lagging (E) cortex. At 10 s, the leading cortex bent inwards and therefore flow velocities could not be calculated at the furrow region. For this reason, the line of the graph at the furrow region is depicted in a lighter color. A schematic summary of the measured flow velocities and their directions at −10 s are shown (right). The arrows reflect the flow velocities at 20% (anterior arrow) and 80% (posterior arrow) A–P embryo length and are to scale to each other. (F–H) The divergence of flow vectors was measured along the width of the embryo (transverse axis) at the cell equator (F) and is plotted for indicated time points for the leading (G) and lagging (H) cortex. (I) Mean divergence at the cell equator for the leading (Lead) and lagging (Lag) cortex at −15 s and −10 s before inward bending of the leading cortex. P values were calculated using two-tailed Student’s t test and are **P < 0.01. Please note that the measurements at the cell equator were performed before the furrow moved inward and away from the coverslip to avoid measurement artifacts due to inward bending. For all: error bars are SEM and n = number of embryos analyzed, scale bars are 5 µm.

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