The neuropeptide natalisin and its receptor, were first identified and characterized in three different insects: Drosophila melanogaster, Tribolium castaneum, and Bombyx mori (Jiang et al., 2013). The C-terminus of natalisin (FX1PX2Ramide, or FX1X2X3Ramide) bears some similarities to tachykinin-related peptides (TRPs) of invertebrates (FXGXRamide). The Drosophila natalisin receptor (CG6515) was previously known as NKD or TakR86C and considered a receptor for tachykinin-related peptide 6 (DTK6) which has the C-terminal sequence FVAVRamide and thus activate CG6515 at higher concentrations. There are 5 natalisins encoded by the precursor (CG34388) in Drosophila, 2 in Tribolium, and 11 in Bombyx mori. The natalisin ligand and receptor appear to be ancestrally related to the TRP/TRP receptor system. Natalisin and its receptor seem to be lacking in the honey bee A. mellifera and the wasp Nasonia vitripennis (Jiang et al., 2016).
In the three holometabolus insects investigated, natalisin expression was found in 3–4 pairs of interneurons in the brain (possibly a few neurosecretory cells in pars intercerebralis?).
Genetic knockdown of the natalisin signaling components leads to defects in reproductive behavior of male and female Drosophila and natalisin-RNAi injections reduce fecundity in Tribolium. The name natalisin is derived from the Latin word natalis, birth, to reflect it’s role in reproduction.
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