Examples of ultrastructural phenotypes of doubly or multiply mutant embryos.

<p>Images of neuromuscular bouton profiles (A–H) and close-ups of their respective synapses (A′–H′) in late stage 17 embryos of wildtype (<b>A</b>) or animals carrying the following mutant allele combinations: <i>CadN-CadN2(ΔN14)</i>, <i>stan¹⁹²</i> in homozygosis (<b>B</b>), <i>CadN-CadN2(Δ14)</i>, <i>stan¹⁹²</i>; <i>Nrx-1^Δ83</i>, <i>Nrx-IV⁴³⁰⁴</i> in homozygosis (<b>C</b>), <i>lanA^9.32</i>/<i>lanA^9.32</i> (<b>D</b>), <i>lanA^9.32</i>/<i>Df(3L)Excel8101</i> (<b>E</b>), <i>lanB1^DEF</i>/<i>lanB1^DEF</i> (<b>F</b>), <i>CadN-CadN2(ΔN14)</i>, <i>stan¹⁹²; lanA^9.32</i> in homozygosis (<b>G</b>), <i>GluRIIC¹; lanA^9.32</i> in homozygosis (<b>H</b>; see further info on GluRIIC in the legend of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036339#pone-0036339-g002" target="_blank">Fig. 2</a>). Symbols and abbreviations are consistently used for all micrographs throughout this manuscript: Bo, presynaptic bouton; Mu, postsynaptic muscle; Hl, haemolymph; black arrows, active zones; arrow heads, BMs; curved arrows, demarcate neuromuscular contacts; double chevrons, demarcate synapses; white arrow heads, cell surfaces lacking BMs. No changes in adhesion index or synaptic structure were detected in A–C, whereas the adhesion index in D–H was changed from ∼50% to ∼25% in the absence of any further structural changes (quantified in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036339#pone-0036339-g002" target="_blank">Fig. 2A–D</a>). Scale bar in A represents 500 nm in A–H and 200 nm in A′–H′.