Crystal structure of silkworm Bombyx mori JHBP in complex with 2-methyl-2,4-pentanediol: plasticity of JH-binding pocket and ligand-induced conformational change of the second cavity in JHBP

Structural basis of selective beta-carotene binding by a soluble protein

β-carotene (BCR) is the most abundant carotenoid, a colorant, antioxidant, and provitamin A. The extreme hydrophobicity of this hydrocarbon requires special mechanisms for distribution in aqueous media, including water-soluble carotenoproteins. However, all known carotenoproteins prefer oxygenated carotenoids and bind BCR inefficiently. Here, we present the crystal structure of the BCR-binding protein (BBP) from gregarious male locusts, which is responsible for their vivid yellow body coloration, in complex with its natural ligand, BCR. BBP forms an antiparallel tubular homodimer with α/β-wrap folded monomers, each forming a hydrophobic 47 Å long, coaxial tunnel that opens outward and is occupied by one s-cisC6-C7, all-trans BCR molecule. In the BCR absence, BBP accepts a range of xanthophylls, with reduced efficiency depending on the position and number of oxygen atoms, but rejects lycopene. The structure captures a pigment complex with a Takeout 1 protein and inspires potential applications of BBP as a BCR solubilizer.

Genome-Wide Identification and Analysis of Family Members with Juvenile Hormone Binding Protein Domains in Spodoptera frugiperda

Juvenile hormone binding proteins (JHBPs) are carrier proteins that bind to juvenile hormone (JH) to form a complex, which then transports the JH to target organs to regulate insect growth and development. Through bioinformatics analysis, 76 genes encoding JHBP in S. frugiperda were identified from whole genome data (SfJHBP1-SfJHBP76). These genes are unevenly distributed across 8 chromosomes, with gene differentiation primarily driven by tandem duplication. Most SfJHBP proteins are acidic, and their secondary structures are mainly composed of α-helices and random coils. Gene structure and conserved motif analyses reveal significant variations in the number of coding sequences (CDS) and a high diversity in amino acid sequences. Phylogenetic analysis classified the genes into four subfamilies, with a notable presence of directly homologous genes between S. frugiperda and S. litura, suggesting a close relationship between the two species. RNA-seq data from public databases and qPCR of selected SfJHBP genes show that SfJHBP20, SfJHBP50, and SfJHBP69 are highly expressed at most developmental stages, while SfJHBP8 and SfJHBP14 exhibit specific expression during the pupal stage and in the midgut. These findings provide a theoretical basis for future studies on the biological functions of this gene family.

Juvenile hormone mimics with phenyl ether and amide functionality to be insect growth regulators (IGRs): synthesis, characterization, computational and biological study

A series of substituted phenyl ethers derivatives as juvenile hormone (JH) mimics (V₁-V₈) have been synthesized. Substituted phenoxyacetic acid and amino acid ethyl ester hydrochloride were prepared using NaOH, SOCl₂. DCC method has been used for amide linkage. The structure of prepared compounds has been confirmed by Fourier Transform Infra-Red (FT-IR), Electrospray ionization-Mass spectrometry (ESI-MS), Proton and Carbon-13 nuclear magnetic resonance (¹H-NMR, ¹³C-NMR) spectroscopic techniques. Biological efficacy of synthesized analogs has been carried out under laboratory conditions. Galleria mellonella (honey bee pest) has been chosen as testing insect. Juvenile hormone (JH) activity of synthesized compounds has been tested at different concentrations and compared with the standard juvenile hormone analogs (JHAs) pyriproxyfen (M₁) and fenoxycarb (M₂) against the fifth larval instar of G. mellonella. Compound ethyl 2-[2-(4-methylphenoxy)aminoacetyl]-3-phenyl-propanoate (V₆) exhibited better activity among all the synthesized compounds (V₁-V₈) with LC₅₀ and LC₉₀ values of 0.11 mg/mL and 0.56 mg/mL respectively. Compounds showed insect growth regulating (IGR) activity at lower concentrations. In silico screening of all synthesized compounds with the W-cavity of juvenile hormone-binding protein (JHBP) of insect G. mellonella has been carried out. Chemical reactivity of synthesized series has been studied using DFT/B3LYP/6-311 + G(d,2p) method. Non-toxic behavior of molecules has also been observed from ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) study using discovery studio client 3.0.Communicated by Ramaswamy H. Sarma.

Soldier Caste-Specific Protein 1 Is Involved in Soldier Differentiation in Termite Reticulitermes aculabialis

Termite soldiers are a unique caste among social insects, and their differentiation can be induced by Juvenile hormone (JH) from workers through two molts (worker–presoldier–soldier). However, the molecular mechanism underlying the worker-to-soldier transformation in termites is poorly understood. To explore the mechanism of soldier differentiation induced by JH, the gene soldier caste-specific protein 1 (RaSsp1, NCBI accession no: MT861054.1) in R. aculabialis was cloned, and its function was studied. This gene was highly expressed in the soldier caste, and the protein RsSsp1 was similar to the JHBP (JH-binding protein) domain-containing protein by Predict Protein online. In addition, JHIII could be anchored in the hydrophobic cage of RaSsp1 as the epoxide of the JHBP-bound JH according to the protein ligand molecular docking online tool AutoDock. The functional studies indicated that knocking down of the RaSsp1 shorted the presoldier’s head capsule, reduced mandible size, delayed molting time and decreased molting rate (from worker to presoldier) at the beginning of worker gut-purging. Furthermore, knocking down of the RaSsp1 had a more pronounced effect on soldier differentiation (from presoldier to soldier), and manifested in significantly shorter mandibles, rounder head capsules, and lower molting rate (from worker to presoldier) at the beginning of presoldier gut-purging. Correspondingly, the expressions of JH receptor Methoprene-tolerant (Met), the JH-inducible transcription factor Krüppel homolog1 (Kr-h1) and ecdysone signal genes Broad-complex (Br-C) were downregulated when knocking down the RaSsp1 at the above two stages. All these results that RaSsp1 may be involved in soldier differentiation from workers by binding and transporting JH.

Antennal Proteome of the Solenopsis invicta (Hymenoptera: Formicidae): Caste Differences in Olfactory Receptors and Chemosensory Support Proteins

Little is known about the expression pattern of odorant and pheromone transporters, receptors, and deactivation enzymes in the antennae of ants carrying out different tasks. In order to begin filling in this information gap, we compared the proteomes of the antennae of workers and males of the red fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Male ants do not perform any colony work, and their only activity is to leave the nest on a mating flight. Previous studies showed that male ants express fewer types of odorant receptors than workers. Thus, we expected to find large differences between male and worker antennae for expression of receptors, transporters, and deactivators of signaling chemicals. We found that the abundance of receptors was consistent with the expected caste-specific signaling complexity, but the numbers of different antenna-specific transporters and deactivating enzymes in males and workers were similar. It is possible that some of these proteins have antenna-specific functions that are unrelated to chemosensory reception. Alternatively, the similar complexity could be a vestige of ant progenitors that had more behaviorally active males. As the reduced behavior of male ants evolved, the selection process may have favored a complex repertoire of transporters and deactivating enzymes alongside a limited repertoire of odorant receptors.

Transcriptomic analysis of interactions between Hyphantria cunea larvae and nucleopolyhedrovirus

BACKGROUND

Hyphantria cunea is a destructive forest pest. To utilise H. cunea nucleopolyhedrovirus (HcNPV) for biological control, understanding insect-virus interactions is essential.

RESULTS

Four cDNA libraries were constructed from H. cunea larvae (two HcNPV-infected and two uninfected groups) and 76 004 expressed genes were obtained by next-generation sequencing. Compared with controls, 272 differentially expressed genes (DEGs) were identified in infected groups, including 162 up-regulated and 110 down-regulated genes. Transcription levels of 20 random DEGs were consistent with the Solexa expression profiles obtained by quantitative real-time PCR. DEGs associated with innate immunity were grouped into several categories, including pattern recognition proteins, heat-shock proteins, UDP-glycosyltransferases, cytochrome P450s, antimicrobial peptides and hormonal signalling proteins. Interestingly, up-regulated host genes included farnesoic acid O-methyltransferase, two juvenile hormone (JH) binding proteins, and a circadian clock-controlled protein related to JH regulation. Pathway enrichment analysis indicates that mitogen-activated protein kinase (MAPK) signalling pathways, key candidate genes and important biological pathways may be associated with molecular modification in H. cunea larvae in response to virus stress.

CONCLUSION

These findings provide insight for future research on the molecular mechanisms of HcNPV invasion and anti-HcNPV mechanisms in H. cunea. A better understanding of gene regulation following HcNPV invasion could help to develop the virus as a bio-insecticide. © 2018 Society of Chemical Industry.

Genome-wide identification and analysis of JHBP-domain family members in the silkworm Bombyx mori

Juvenile hormone (JH) regulates the insect growth and development. JH appears in the hemolymph bound by a specific glycoprotein, juvenile hormone-binding protein (JHBP), which serves as a carrier to release the hormone to target tissues and cells. However, JHBP family candidates, expression patterns, and functional implications are still unclear. In this study, we identified 41 genes-containing conserved JHBP domains distributed across eight chromosomes of the silkworm Bombyx mori. A phylogenetic tree showed that the silkworm JHBP (BmJHBP) genes could be classified into two major branches and four subfamilies. Microarray data revealed that BmJHBP genes exhibit various expression patterns and are expressed in different tissues, periods, and sexes. The expression of BmJHBP genes was generally higher in the head, integument, midgut, fat body, testis, and ovary than in the anterior of the silk gland (ASG), median of the silk gland (MSG), posterior of the silk gland (PSG), hemocyte, and Malpighian tubule. BmJHBPd2, in particular, was investigated by Western Blotting, and immunofluorescent assay and was found to be highly expressed in the PSG cytoplasm on day 3 of the fifth instar, coinciding with silk production. Taken together, our findings will be useful in improving understanding the complexity of the JHBP family, and will lay the foundation of explaining functional characterization for further research.

Comparative transcriptomic analysis of silkworm Bmovo-1 and wild type silkworm ovary

The detailed molecular mechanism of Bmovo-1 regulation of ovary size is unclear. To uncover the mechanism of Bmovo-1 regulation of ovarian development and oogenesis using RNA-Seq, we compared the transcriptomes of wild type (WT) and Bmovo-1-overexpressing silkworm (silkworm^+Bmovo-1) ovaries. Using a pair-end Illumina Solexa sequencing strategy, 5,296,942 total reads were obtained from silkworm^+Bmovo-1 ovaries and 6,306,078 from WT ovaries. The average read length was about 100 bp. Clean read ratios were 98.79% for silkworm^+Bmovo-1 and 98.87% for WT silkworm ovaries. Comparative transcriptome analysis showed 123 upregulated and 111 downregulated genes in silkworm^+Bmovo-1 ovaries. These differentially expressed genes were enriched in the extracellular and extracellular spaces and involved in metabolism, genetic information processing, environmental information processing, cellular processes and organismal systems. Bmovo-1 overexpression in silkworm ovaries might promote anabolism for ovarian development and oogenesis and oocyte proliferation and transport of nutrients to ovaries by altering nutrient partitioning, which would support ovary development. Excessive consumption of nutrients for ovary development alters nutrient partitioning and deters silk protein synthesis.