Valve anatomy and origins.

<p>(A) Diagram of the valve with neighboring pharyngeal and intestinal cells; see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003772#pgen.1003772.s001" target="_blank">Figure S1</a> for full cell names. (B) Left sagittal (S^(L)) optical plane through a live embryo expressing reporters for all plasma membranes (<i>pie-1</i>::mCherry::PH(PLC1∂1)) and for intestinal cells (F22B7.9::GFP). The embryo also expresses a <i>pax-1</i>::HIS-GFP reporter used for spatial reference; this reporter is expressed in the nuclei of all three groups of marginal cells (numbered 1,2, or 3 throughout this report), pm8 and v1. The solid white line indicates the margins of the double plate. The germ cell precursors (G) and a cell death (x) are visible in this plane. (C) Images from 3D reconstruction of the cell interface between the double plate and E16 intestinal primordia; see also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003772#pgen.1003772.s007" target="_blank">Video S1</a>. Transverse views show all pharyngeal or valve cells that contact intestinal cells, and then selected subsets as labeled. Cells that undergo an additional division are labeled according to their daughters; for example, M5/I6 is the parent of the M5 and I6 neurons, and g2L/x is the parent of the left g2 gland cell and a cell death (x). (D) Reconstruction of the cyst-E16 interface. The pharyngeal and valve cells have acquired wedge shapes through apical constriction. The midline (M) is indicated here and elsewhere by a dashed arrow pointing to the anterior. Note that v3D has shifted dorsally, and begun to center on the left-right boundary between the int1^p cells. The intestinal cell int2D has shifted dorsally and behind the left int1^p cell, and is not visible in this transverse view; see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003772#pgen.1003772.s007" target="_blank">Video S1</a>. (E) Reconstruction of the cyst-E20 interface. The int1^p cells have divided to form the final int1 ring, and both v3D and v3V are centered on the left-right boundaries of the intestinal cells. Bars: (B) 5 microns.