The BDU posterior process connects to the anterior branch of PLM.

<p>(A) Schematic drawing of the BDU-PLM connection. The posterior tip of BDU is connected to the anterior branch of PLM at region (a). The PLM branch, where the chemical synapses are localized, is labeled by (b). Arrows point to the BDU and PLM cell bodies. (B–D) P<i>unc-53</i>::GFP (green) labels BDU and P<i>mec-7</i>::mCherry (red) labels PLM. The arrowhead in (D) indicates where the BDU and PLM neurites meet. (E–H) shows the embryonic development of BDU-PLM connections. (E) BDU (green asterisk) and PLM (red asterisk) neurons are born at the 1.5–2 fold embryonic stage (450 min after the first cell division). The anterior process of PLM extends a significant length, while no posterior process of BDU is noticeable at 570 min (F). At 690 min, both the BDU posterior process and the PLM anterior process are visible (G). By the end of embryonic elongation, the BDU-PLM connection is formed (H). The tips of the BDU posterior process and the PLM anterior process are indicated by green and red arrowheads respectively. The white arrowhead (H) indicates the junction of the BDU posterior process and the PLM anterior process. Below the images are schematic representations of BDU (in green) and PLM (in red). (I) The BDU cell at different developmental stages in the absence of PLM. Green asterisks indicate the BDU cell bodies. Arrowheads point to the tip of the BDU posterior process. (J) Quantification of relative BDU neurite length at different developmental stages in wild type (gray column) or in the absence of PLM cell (black column). The neurite length was measured 0 hr, 12 hr, 24 hr, and 36 hr after hatching. (K) The PLM cell at different developmental stages in the absence of BDU cell. Red asterisks indicate the PLM cell bodies. Arrowheads point to the tip of the PLM posterior process. (L) Quantification of relative PLM neurite length at different developmental stages in wild type (gray column) or in the absence of BDU cell (black column). The neurite length was measured 0 hr, 12 hr, 24 hr, and 36 hr after hatching. Error bars in (J) and (L) represent the standard error of the mean (SEM). ** p<0.01; NS, not significant. Scale bars represent 10 µm.