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Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein–encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.

Transmission from an infected mosquito to a host is an essential process in the life cycle of mosquito-borne flaviviruses. Numerous studies have demonstrated that mosquito saliva facilitates viral transmission. Here we find that a saliva-specific protein, named Aedes aegypti venom allergen-1 ( Aa VA-1), promotes dengue and Zika virus transmission by activating autophagy in host immune cells of the monocyte lineage. The AG6 mice ( ifnar1 –/– ifngr1 –/– ) bitten by the virus-infected Aa VA-1-deficient mosquitoes present a lower viremia and prolonged survival. Aa VA-1 intracellularly interacts with a dominant negative binder of Beclin-1, known as leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), and releases Beclin-1 from LRPPRC-mediated sequestration, thereby enabling the initialization of downstream autophagic signaling. A deficiency in Beclin-1 reduces viral infection in mice and abolishes Aa VA-1-mediated enhancement of ZIKV transmission by mosquitoes. Our study provides a mechanistic insight into saliva-aided viral transmission and could offer a potential prophylactic target for reducing flavivirus transmission. Mosquito saliva affects transmission of flaviviruses, but underlying mechanisms are incompletely understood. Here, the authors show that Aedes aegypti venom allergen-1 ( Aa VA-1) promotes dengue and Zika virus transmission by activating autophagy in host immune cells of the monocyte lineage.

In “excitable” cells, like neurons and muscle cells, a difference in electrical potential is used to transmit signals across the cell membrane. This difference is regulated by opening or closing ion channels in the cell membrane. For example, mutations in human voltage-gated sodium (Na v ) channels are associated with disorders such as chronic pain, epilepsy, and cardiac arrhythmia. Pan et al. report the high-resolution structure of a human Na v channel, and Shen et al. report the structures of an insect Na v channel bound to the toxins that cause pufferfish and shellfish poisoning in humans. Together, the structures give insight into the molecular basis of sodium ion permeation and provide a path toward structure-based drug discovery. Science , this issue p. eaau2486 , p. eaau2596 Structures provide insight into how voltage-gated sodium channels function and how they can be inhibited. Animal toxins that modulate the activity of voltage-gated sodium (Na v ) channels are broadly divided into two categories—pore blockers and gating modifiers. The pore blockers tetrodotoxin (TTX) and saxitoxin (STX) are responsible for puffer fish and shellfish poisoning in humans, respectively. Here, we present structures of the insect Na v channel Na v PaS bound to a gating modifier toxin Dc1a at 2.8 angstrom-resolution and in the presence of TTX or STX at 2.6-Å and 3.2-Å resolution, respectively. Dc1a inserts into the cleft between VSD II and the pore of Na v PaS, making key contacts with both domains. The structures with bound TTX or STX reveal the molecular details for the specific blockade of Na + access to the selectivity filter from the extracellular side by these guanidinium toxins. The structures shed light on structure-based development of Na v channel drugs.

Insects are one of the major sources of antimicrobial peptides/proteins (AMPs). Since observation of antimicrobial activity in the hemolymph of pupae from the giant silk moths Samia Cynthia and Hyalophora cecropia in 1974 and purification of first insect AMP (cecropin) from H. cecropia pupae in 1980, over 150 insect AMPs have been purified or identified. Most insect AMPs are small and cationic, and they show activities against bacteria and/or fungi, as well as some parasites and viruses. Insect AMPs can be classified into four families based on their structures or unique sequences: the α-helical peptides (cecropin and moricin), cysteine-rich peptides (insect defensin and drosomycin), proline-rich peptides (apidaecin, drosocin, and lebocin), and glycine-rich peptides/proteins (attacin and gloverin). Among insect AMPs, defensins, cecropins, proline-rich peptides, and attacins are common, while gloverins and moricins have been identified only in Lepidoptera. Most active AMPs are small peptides of 20–50 residues, which are generated from larger inactive precursor proteins or pro-proteins, but gloverins (~14 kDa) and attacins (~20 kDa) are large antimicrobial proteins. In this mini-review, we will discuss current knowledge and recent progress in several classes of insect AMPs, including insect defensins, cecropins, attacins, lebocins and other proline-rich peptides, gloverins, and moricins, with a focus on structural-functional relationships and their potential applications.

Background: Increased amino acid availability stimulates muscle protein synthesis (MPS), which is critical for maintaining or increasing muscle mass when combined with training. Previous research suggests that whey protein is superior to soy protein in regard to stimulating MPS and muscle mass. Nevertheless, with respect to a future lack of dietary protein and an increasing need for using eco-friendly protein sources it is of great interest to investigate the quality of alternative protein sources, like insect protein. Objective: Our aim was to compare the postprandial amino acid (AA) availability and AA profile in the blood after ingestion of protein isolate from the lesser mealworm, whey isolate, and soy isolate. Design: Six healthy young men participated in a randomized cross-over study and received three different protein supplementations (25 g of crude protein from whey, soy, insect or placebo (water)) on four separate days. Blood samples were collected at pre, 0 min, 20 min, 40 min, 60 min, 90 min, and 120 min. Physical activity and dietary intake were standardized before each trial, and participants were instructed to be fasting from the night before. AA concentrations in blood samples were determined using 1H NMR spectroscopy. Results: A significant rise in blood concentration of essential amino acids (EAA), branched-chain amino acids (BCAA) and leucine was detected over the 120 min period for all protein supplements. Nevertheless, the change in AA profile was significantly greater after ingestion of whey than soy and insect protein (p < 0.05). Area under the curve (AUC) analysis and AA profile revealed comparable AA concentrations for soy and insect protein, whereas whey promoted a ~97% and ~140% greater AUC value than soy and insect protein, respectively. A tendency towards higher AA concentrations beyond the 120 min period was observed for insect protein. Conclusion: We report that ingestion of whey, soy, and insect protein isolate increases blood concentrations of EAA, BCAA, and leucine over a 120 min period (whey > insect = soy). Insect protein induced blood AA concentrations similar to soy protein. However, a tendency towards higher blood AA concentrations at the end of the 120 min period post ingestion was observed for insect protein, which indicates that it can be considered a “slow” digestible protein source.

Insects are the most speciose group of animals, but the phylogenetic relationships of many major lineages remain unresolved. We inferred the phylogeny of insects from 1478 protein-coding genes. Phylogenomic analyses of nucleotide and amino acid sequences, with site-specific nucleotide or domain-specific amino acid substitution models, produced statistically robust and congruent results resolving previously controversial phylogenetic relationships. We dated the origin of insects to the Early Ordovician [~479 million years ago (Ma)], of insect flight to the Early Devonian (~406 Ma), of major extant lineages to the Mississippian (~345 Ma), and the major diversification of holometabolous insects to the Early Cretaceous. Our phylogenomic study provides a comprehensive reliable scaffold for future comparative analyses of evolutionary innovations among insects.

Olfactory systems must detect and discriminate amongst an enormous variety of odorants 1 . To contend with this challenge, diverse species have converged on a common strategy in which odorant identity is encoded through the combinatorial activation of large families of olfactory receptors 1 – 3 , thus allowing a finite number of receptors to detect a vast chemical world. Here we offer structural and mechanistic insight into how an individual olfactory receptor can flexibly recognize diverse odorants. We show that the olfactory receptor Mh OR5 from the jumping bristletail 4 Machilis hrabei assembles as a homotetrameric odorant-gated ion channel with broad chemical tuning. Using cryo-electron microscopy, we elucidated the structure of Mh OR5 in multiple gating states, alone and in complex with two of its agonists—the odorant eugenol and the insect repellent DEET. Both ligands are recognized through distributed hydrophobic interactions within the same geometrically simple binding pocket located in the transmembrane region of each subunit, suggesting a structural logic for the promiscuous chemical sensitivity of this receptor. Mutation of individual residues lining the binding pocket predictably altered the sensitivity of Mh OR5 to eugenol and DEET and broadly reconfigured the receptor’s tuning. Together, our data support a model in which diverse odorants share the same structural determinants for binding, shedding light on the molecular recognition mechanisms that ultimately endow the olfactory system with its immense discriminatory capacity. Structural and functional analysis of an insect olfactory receptor shed light on how receptors can be activated by diverse odorants.

Antifreeze proteins (AFPs) are specific proteins that are able to lower the freezing point of aqueous solutions relative to the melting point. Hyperactive AFPs, identified in insects, have an especially high ability to depress the freezing point by far exceeding the abilities of other AFPs. In previous studies, we postulated that the activity of AFPs can be attributed to two distinct molecular mechanisms: (i) short-range direct interaction of the protein surface with the growing ice face and (ii) long-range interaction by protein-induced water dynamics extending up to 20 Å from the protein surface. In the present paper, we combine terahertz spectroscopy and molecular simulations to prove that long-range protein–water interactions make essential contributions to the high antifreeze activity of insect AFPs from the beetle Dendroides canadensis . We also support our hypothesis by studying the effect of the addition of the osmolyte sodium citrate.

PIWI-interacting RNAs (piRNAs) of between approximately 24 and 31 nucleotides in length guide PIWI proteins to silence transposons in animal gonads, thereby ensuring fertility 1 . In the biogenesis of piRNAs, PIWI proteins are first loaded with 5′-monophosphorylated RNA fragments called pre-pre-piRNAs, which then undergo endonucleolytic cleavage to produce pre-piRNAs 1 , 2 . Subsequently, the 3′-ends of pre-piRNAs are trimmed by the exonuclease Trimmer (PNLDC1 in mouse) 3 – 6 and 2′- O -methylated by the methyltransferase Hen1 (HENMT1 in mouse) 7 – 9 , generating mature piRNAs. It is assumed that the endonuclease Zucchini (MitoPLD in mouse) is a major enzyme catalysing the cleavage of pre-pre-piRNAs into pre-piRNAs 10 – 13 . However, direct evidence for this model is lacking, and how pre-piRNAs are generated remains unclear. Here, to analyse pre-piRNA production, we established a Trimmer-knockout silkworm cell line and derived a cell-free system that faithfully recapitulates Zucchini-mediated cleavage of PIWI-loaded pre-pre-piRNAs. We found that pre-piRNAs are generated by parallel Zucchini-dependent and -independent mechanisms. Cleavage by Zucchini occurs at previously unrecognized consensus motifs on pre-pre-piRNAs, requires the RNA helicase Armitage, and is accompanied by 2′- O -methylation of pre-piRNAs. By contrast, slicing of pre-pre-piRNAs with weak Zucchini motifs is achieved by downstream complementary piRNAs, producing pre-piRNAs without 2′- O -methylation. Regardless of the endonucleolytic mechanism, pre-piRNAs are matured by Trimmer and Hen1. Our findings highlight multiplexed processing of piRNA precursors that supports robust and flexible piRNA biogenesis. A silkworm model recapitulates key steps of Zucchini-mediated cleavage of pre-pre-piRNA and provides insights into Zucchini-mediated and -independent pathways that generate pre-piRNAs, which converge to a common piRNA maturation step.

Diapause, the dormancy common to overwintering insects, evokes a unique pattern of gene expression. In the flesh fly, most, but not all, of the fly's heat shock proteins (Hsps) are up-regulated. The diapause up-regulated Hsps include two members of the Hsp70 family, one member of the Hsp60 family (TCP-1), at least four members of the small Hsp family, and a small Hsp pseudogene. Expression of an Hsp70 cognate, Hsc70, is uninfluenced by diapause, and Hsp90 is actually down-regulated during diapause, thus diapause differs from common stress responses that elicit synchronous up-regulation of all Hsps. Up-regulation of the Hsps begins at the onset of diapause, persists throughout the overwintering period, and ceases within hours after the fly receives the signal to reinitiate development. The up-regulation of Hsps appears to be common to diapause in species representing diverse insect orders including Diptera, Lepidoptera, Coleoptera, and Hymenoptera as well as in diapauses that occur in different developmental stages (embryo, larva, pupa, adult). Suppressing expression of Hsp23 and Hsp70 in flies by using RNAi did not alter the decision to enter diapause or the duration of diapause, but it had a profound effect on the pupa's ability to survive low temperatures. We thus propose that up-regulation of Hsps during diapause is a major factor contributing to cold-hardiness of overwintering insects.