Figure 7.

Mapping larval sensorimotor circuits using Split Gal4 and connectomics. (A) The R23E07^p65AD ∩ V002081^Gal4DBD Split Gal4 driver was identified in a synaptic suppression screen to identify neurons involved in larval chemotaxis. This driver labels a single pair of descending neurons (PDM-DN). (B) Representation of the EM reconstructed neurons in the circuit for larval chemotaxis. Connectomics analysis revealed that the PDM-DN receives input from two lateral horn neurons, LH-LN1 and LH-LN1 (light and dark purple, respectively) and innervate three neurons in the SEZ, one of which is shown (SEZ-DN1, blue). The LH neurons are downstream of unpaired olfactory projection neurons (PN, orange) that receive input from Or42a and Or42b olfactory receptor neurons (yellow). The SEZ-DN1 neuron is the same SEZ neuron identified downstream of the larval “mooncrawler” neurons (i.e., Pair1) and connects to the posterior A27 h premotor neurons (teal). (C) Although certain details remain to be determined, such as the identity of the PNs that innervate the LH neurons and the functional interactions of the LH and PDM-DN neurons, the identified components of the larval chemotaxis circuit span the entire neuraxis from the sensory periphery to the final common pathway of the motor neurons [Adapted from Tastekin et al. (2018)].