A STIM dependent dopamine-neuropeptide axis maintains the larval drive to feed and grow in Drosophila.

Appropriate nutritional intake is essential for organismal survival. In holometabolous insects such as Drosophila melanogaster, the quality and quantity of food ingested as larvae determines adult size and fecundity. Here we have identified a subset of dopaminergic neurons (THD') that maintain the larval motivation to feed. Dopamine release from these neurons requires the ER Ca2+ sensor STIM. Larvae with loss of STIM stop feeding and growing, whereas expression of STIM in THD' neurons rescues feeding, growth and viability of STIM null mutants to a significant extent. Moreover STIM is essential for maintaining excitability and release of dopamine from THD' neurons. Optogenetic stimulation of THD' neurons activated neuropeptidergic cells, including median neuro secretory cells that secrete insulin-like peptides. Loss of STIM in THD' cells alters the developmental profile of specific insulin-like peptides including ilp3. Loss of ilp3 partially rescues STIM null mutants and inappropriate expression of ilp3 in larvae affects development and growth. In summary we have identified a novel STIM-dependent function of dopamine neurons that modulates developmental changes in larval feeding behaviour and growth.