Peptidergic control in a fruit crop pest: The spotted-wing drosophila, Drosophila suzukii

Neuropeptides play an important role in the regulation of feeding in insects and offer potential targets for the development of new chemicals to control insect pests. A pest that has attracted much recent attention is the highly invasive Drosophila suzukii, a polyphagous pest that can cause serious economic damage to soft fruits. Previously we showed by mass spectrometry the presence of the neuropeptide myosuppressin (TDVDHVFLRFamide) in the nerve bundle suggesting that this peptide is involved in regulating the function of the crop, which in adult dipteran insects has important roles in the processing of food, the storage of carbohydrates and the movement of food into the midgut for digestion. In the present study antibodies that recognise the C-terminal RFamide epitope of myosuppressin stain axons in the crop nerve bundle and reveal peptidergic fibres covering the surface of the crop. We also show using an in vitro bioassay that the neuropeptide is a potent inhibitor (EC50 of 2.3 nM) of crop contractions and that this inhibition is mimicked by the non-peptide myosuppressin agonist, benzethonium chloride (Bztc). Myosuppressin also inhibited the peristaltic contractions of the adult midgut, but was a much weaker agonist (EC50 = 5.7 μM). The oral administration of Bztc (5 mM) in a sucrose diet to adult female D. suzukii over 4 hours resulted in less feeding and longer exposure to dietary Bztc led to early mortality. We therefore suggest that myosuppressin and its cognate receptors are potential targets for disrupting feeding behaviour of adult D. suzukii

Peptidergic control in a fruit crop pest: The spotted-wing drosophila, <i>Drosophila suzukii</i>

<div><p>Neuropeptides play an important role in the regulation of feeding in insects and offer potential targets for the development of new chemicals to control insect pests. A pest that has attracted much recent attention is the highly invasive <i>Drosophila suzukii</i>, a polyphagous pest that can cause serious economic damage to soft fruits. Previously we showed by mass spectrometry the presence of the neuropeptide myosuppressin (TDVDHVFLRFamide) in the nerve bundle suggesting that this peptide is involved in regulating the function of the crop, which in adult dipteran insects has important roles in the processing of food, the storage of carbohydrates and the movement of food into the midgut for digestion. In the present study antibodies that recognise the C-terminal RFamide epitope of myosuppressin stain axons in the crop nerve bundle and reveal peptidergic fibres covering the surface of the crop. We also show using an <i>in</i> vitro bioassay that the neuropeptide is a potent inhibitor (EC₅₀ of 2.3 nM) of crop contractions and that this inhibition is mimicked by the non-peptide myosuppressin agonist, benzethonium chloride (Bztc). Myosuppressin also inhibited the peristaltic contractions of the adult midgut, but was a much weaker agonist (EC₅₀ = 5.7 μM). The oral administration of Bztc (5 mM) in a sucrose diet to adult female <i>D</i>. <i>suzukii</i> over 4 hours resulted in less feeding and longer exposure to dietary Bztc led to early mortality. We therefore suggest that myosuppressin and its cognate receptors are potential targets for disrupting feeding behaviour of adult <i>D</i>. <i>suzukii</i>.</p></div

Immunostaining of the crop and crop nerve of <i>D</i>. <i>suzukii</i> using an antibody recognising the RFamide epitope.

<p>Arrows point towards 2 crop nerves that run alongside the crop duct (star) before ramifying across the surface of the crop sac. Scale bar,100 μm.</p

Inhibition of crop and midgut contractions.

<p>The effect of myosuppressin (Dms, A and B) and benzethonium chloride (Bztc, C and D) on the spontaneous contractions of the crop (A and C) and midgut (B and D). Data are expressed as the % change in activity (contractions counted in a 1 min period) after the addition of the agonist, as described in the methods section. Values are the mean of 5 determinations using fresh tissues for each determination. Non-linear regression analysis (GraphPad Prism 7.01) was performed to calculate EC₅₀ values and to generate the 95% confidence bands.</p

The effect of Bztc on the uptake and excretion of sucrose/food dye by adult female <i>D</i>. <i>suzukii</i>.

<p>The amount of dye in the faeces after 4 h of feeding was determined spectrophotometrically (595 nm) and the results are expressed as the mean ± SEM (n = 12). Differences in the means values are statistically significant (t-test, P <0.001).</p

Locomotor activity of adult female <i>D</i>. <i>suzukii</i>.

<p>Flies were maintained in a 12 h:12 h light:dark cycle on (A) sucrose/agar, (B) sucrose/agar with 5 mM Bztc and (C) agar only. Activities for individual flies were recorded using the Trikinetics activity monitors and are expressed as the mean number of beam breaks per hour (n = 32). White and black bars indicate day-time and night-time, respectively. (D) Time of the last recorded activity of the same flies expressed as the mean ± SEM (n = 32). Differences in the mean values are statistically significant (t-test, P <0.001).</p

The genome of the African trypanosome Trypanosoma brucei

African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of &lt;i&gt;Trypanosoma brucei&lt;/i&gt;. The 26-megabase genome contains 9068 predicted genes, including ~900 pseudogenes and ~1700 &lt;i&gt;T. brucei&lt;/i&gt;–specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of &lt;i&gt;T. brucei&lt;/i&gt;, &lt;i&gt;T. cruzi&lt;/i&gt;, and &lt;i&gt;Leishmania major&lt;/i&gt; reveals the least overall metabolic capability in &lt;i&gt;T. brucei&lt;/i&gt; and the greatest in &lt;i&gt;L. major&lt;/i&gt;. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified