Serotonergic neuron ribosomes regulate the neuroendocrine control of Drosophila development.

The regulation of ribosome function is a conserved mechanism of growth control. While studies in single cell systems have defined how ribosomes contribute to cell growth, the mechanisms that link ribosome function to organismal growth are less clear. Here we explore this issue using Drosophila Minutes, a class of heterozygous mutants for ribosomal proteins (Rps). These animals exhibit a delay in larval development caused by decreased production of the steroid hormone ecdysone, the main regulator of larval maturation. We found that this developmental delay is not caused by decreases in either global ribosome numbers or translation rates. Instead, we show that they are due in part to loss of Rp function specifically in a subset of serotonin (5-HT) neurons that innervate the prothoracic gland to control ecdysone production. We found that these 5-HT neurons have defective secretion in Minute animals, and that overexpression of synaptic vesicle proteins in 5-HTergic cells can partially reverse the Minute developmental delay. These results identify a cell-specific role for ribosomal function in the neuroendocrine control of animal growth and development.