Amidated neuropeptides of the FMRFamide class regulate numerous physiological processes including synaptic efficacy at the Drosophilaneuromuscular junction (NMJ). We demonstrate here that mutations in wishful thinking (wit) a gene encoding a DrosophilaBmp type 2 receptor that is required for proper neurotransmitter release at the neuromuscular junction, also eliminates expression of FMRFa in that subset of neuroendocrine cells (Tv neurons) which provide the systemic supply of FMRFa peptides. We show that Gbb, a Bmp ligand expressed in the neurohemal organ provides a retrograde signal that helps specify the peptidergic phenotype of the Tv neurons. Finally, we show that supplying FMRFa in neurosecretory cells partially rescues the witlethal phenotype without rescuing the primary morphological or electrophysiological defects of wit mutants. We propose that Wit and Gbb globally regulate NMJ function by controlling both the growth and transmitter release properties of the synapse as well as the expression of systemic modulators of NMJ synaptic activity.
Note added in proof
While this paper was under review, a similar set of findings were described by Allan et al. (Allan et al.,2003).
