Abstract
In Drosophila, neurosecretory cells that release peptide hormones play a prominent role in the regulation of development, growth, metabolism, and reproduction. Several types of peptidergic neurosecretory cells have been identified in the brain of Drosophila with release sites in the corpora cardiaca and anterior aorta. We show here that in adult flies the products of three neuropeptide precursors are colocalized in five pairs of large protocerebral neurosecretory cells in two clusters (designated ipc-1 and ipc-2a): Drosophila tachykinin (DTK), short neuropeptide F (sNPF) and ion transport peptide (ITP). These peptides were detected by immunocytochemistry in combination with GFP expression driven by the enhancer trap Gal4 lines c929 and Kurs-6, both of which are expressed in ipc-1 and 2a cells. This mix of colocalized peptides with seemingly unrelated functions is intriguing and prompted us to initiate analysis of the function of the ten neurosecretory cells. We investigated the role of peptide signaling from large ipc-1 and 2a cells in stress responses by monitoring the effect of starvation and desiccation in flies with levels of DTK or sNPF diminished by RNA interference. Using the Gal4-UAS system we targeted the peptide knockdown specifically to ipc-1 and 2a cells with the c929 and Kurs-6 drivers. Flies with reduced DTK or sNPF levels in these cells displayed decreased survival time at desiccation and starvation, as well as increased water loss at desiccation. Our data suggest that homeostasis during metabolic stress requires intact peptide signaling by ipc-1 and 2a neurosecretory cells.
Highlights
Hormonal regulation of development, growth, metabolism and reproduction has been extensively studied in insects, including Drosophila
We demonstrate here that five pairs of large neurosecretory cells in the adult Drosophila brain produce colocalized neuropeptides derived from three precursor genes: dtk, snpf and itp
No ipc-2a cells express ion transport peptide (ITP) in the larva. [17,47]. We found that both short neuropeptide F (sNPF) and Drosophila tachykinin (DTK) immunoreactive axons extend to the same areas as shown for ITP (Fig. 4)
Summary
Growth, metabolism and reproduction has been extensively studied in insects, including Drosophila (reviewed in [1,2,3,4,5,6,7,8]). Many types of neurosecretory cells (NSCs) that release peptide hormones into the circulation have been identified in the brain of various insect species [4,9,10,11,12,13]. The brain complement of NSCs is complex with cell bodies in several locations and axonal projections to different neurohemal release sites in contact with the circulation. Already the anatomy suggests that in the adult brain NSCs are functionally heterogeneous and efforts so far to map different hormonal peptides to the Drosophila NSCs has certainly underscored the complexity of the NSC systems in the brain
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