Abstract
Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance.Gene expression and labelled DH44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH44 in neurons of the pars intercerebralis and DH44 receptor (DH44-R2) in Malpighian tubule principal cells, indicate that suppression of DH44 signalling improves desiccation tolerance of the intact fly.Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH44 neurons as well as in stellate cells of the Malpighian tubules. LKR knockdown in DH44-expressing neurons reduces Malpighian tubule-specific LKR, suggesting interactions between DH44 and LK signalling pathways.Finally, although a role for DK in desiccation tolerance was not defined, we demonstrate a novel role for Malpighian tubule cell-specific LKR in starvation tolerance. Starvation increases gene expression of epithelial LKR. Also, Malpighian tubule stellate cell-specific knockdown of LKR significantly reduced starvation tolerance, demonstrating a role for neuropeptide signalling during starvation stress.
Highlights
Diuretic and anti-diuretic hormones act on the insect excretory system [12] and are produced by neurosecretory cells in the brain and ventral ganglia
Given that LKR is expressed in DH44 neurons, and that both DK and DH44 are diuretic peptides, putative roles for DH44 and DK signalling in desiccation stress were explored by measuring gene expression of DH44, the DK gene (LK) and brain-specific DH44-R1 in wild type flies, and non-neural LKR and DH44 Receptor 2 (DH44-R2) in bodies of wildtype flies, after exposure to 24 h of desiccation, or 24 h of starvation, and compared to a non-stressed control groups
We demonstrate that suppressing the DH44 signalling pathways, either by manipulating the DH44 neurons or by impacting the
Summary
Diuretic and anti-diuretic hormones act on the insect excretory system [12] and are produced by neurosecretory cells in the brain and ventral ganglia. They are released into the haemolymph via neurohemal sites, where they activate their G protein-coupled receptors (GPCRs) located in the Malpighian tubules [2]. Several diuretic peptides have been identified and functionally characterized in Drosophila melanogaster, including CRF-like (DH44) and kinin (Drome-kinin, DK). DH44 peptide is produced by neuroendocrine cells in the brain, in three bilateral pairs of cells in the pars intercerebralis (PI) with axons extending to the retrocerebral complex of the corpus cardiacum [4]. DH44 neurons are activated in response to nutritive sugars, a response that could underlie a coordinated response by the gut and Malpighian tubules to feeding [20]
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