Transcriptome analysis of sexually dimorphic Chinese white wax scale insects reveals key differences in developmental programs and transcription factor expression

The transcriptome of Icerya aegyptiaca (Hemiptera: Monophlebidae) and comparison with neococcoids reveal genetic clues of evolution in the scale insects

BACKGROUND

Scale insects are worldwide sap-sucking parasites, which can be distinguished into neococcoids and non-neococcoids. Neococcoids are monophyletic with a peculiar reproductive system, paternal genome elimination (PGE). Different with neococcoids, Iceryini, a tribe in non-neococcoids including several damaging pests, has abdominal spiracles, compound eyes in males, relatively abundant wax, unique hermaphrodite system, and specific symbionts. However, the current studies on the gene resources and genomic mechanism of scale insects are mainly limited in the neococcoids, and lacked of comparison in an evolution frame.

RESULT

We sequenced and de novo assembled a transcriptome of Icerya aegyptiaca (Douglas), a worldwide pest of Iceryini, and used it as representative of non-neococcoids to compare with the genomes or transcriptomes of other six species from different families of neococcoids. We found that the genes under positive selection or negative selection intensification (simplified as "selected genes" below) in I. aegyptiaca included those related to neurogenesis and development, especially eye development. Some genes related to fatty acid biosynthesis were unique in its transcriptome with relatively high expression and not detected in neococcoids. These results may indicate a potential link to the unique structures and abundant wax of I. aegyptiaca compared with neococcoids. Meanwhile, genes related to DNA repair, mitosis, spindle, cytokinesis and oogenesis, were included in the selected genes in I. aegyptiaca, which is possibly associated with cell division and germ cell formation of the hermaphrodite system. Chromatin-related process were enriched from selected genes in neococcoids, along with some mitosis-related genes also detected, which may be related to their unique PGE system. Moreover, in neococcoid species, male-biased genes tend to undergo negative selection relaxation under the PGE system. We also found that the candidate horizontally transferred genes (HTGs) in the scale insects mainly derived from bacteria and fungi. bioD and bioB, the two biotin-synthesizing HTGs were exclusively found in the scale insects and neococcoids, respectively, which possibly show potential demand changes in the symbiotic relationships.

CONCLUSION

Our study reports the first I. aegyptiaca transcriptome and provides preliminary insights for the genetic change of structures, reproductive systems and symbiont relationships at an evolutionary aspect. This will provide a basis for further research and control of scale insects.

The Complete Mitochondrial Genome of the Chinese White Wax Scale Insect, Ericerus pela Chavannes (Hemiptera: Coccidae), with Novel Gene Arrangement and Truncated tRNA Genes

The Chinese white wax scale insect, Ericerus pela Chavannes (Hemiptera: Coccidae), is one of the scale insects with great economic value and has been dispersed and reared in China for over one thousand years. Its mitochondrial genome provides essential information for the molecular identification and genetic study of this species. We assembled the complete mitochondrial genome of E. pela based on PacBio sequencing and analyzed its genomic features. The genome was 17,766 bp in length with 13 protein-coding genes, 22 tRNAs, and two rRNA genes. The analysis results showed E. pela had significant gene rearrangements involving tRNAs compared with other Coccoidea species. Furthermore, E. pela's nine tRNAs were identified to have obvious truncated structures. The phylogenetic tree compiled of the species showed a long branch of the Coccoidea lineage, which indicated the high evolutionary rate in this group. Our study revealed the mitochondrial characteristics of E. pela and enriched the mitochondrial genetic information on Coccoidea species. It also determined the occurrence of gene rearrangement for the species in this superfamily.

Chromosome-level genome assembly reveals potential epigenetic mechanisms of the thermal tolerance in the oriental fruit fly, Bactrocera dorsalis

The oriental fruit fly, Bactrocera dorsalis (Hendel), has very strong ecological adaptability and phenotypic plasticity. Here, the genome of B. dorsalis was assembled into 549.45 Mb sequences with a contig N50 length of 12.81 Mb. Among, 95.67 % assembled genome sequences were anchored on six chromosomes with an N50 length of 94.63 Mb. According to the basic characteristics of the sex chromosomes of Tephritidae, the X chromosome of B. dorsalis was identified. Significant gene expansions were detected in several important gene families related to adaptability. In particular, we annotated 50 histone modification enzymes (HMEs) in this genome. A comparative transcriptome analysis indicated that 12 HME genes were differentially expressed in two thermo-tolerant strains (heat and cold). Interestingly, four and seven of the 12 HME genes responded to heat shock or cold hardening, respectively. These evidences suggested that the histone modification as an epigenetic modification may be involved in the thermal tolerance of B. dorsalis, but with different regulation mechanisms in thermal acclimation and hardening. The high quality genome of B. dorsalis provides an invaluable resource for further functional genomic study. Moreover, comparative genomic analysis will shed insights on revealing the mechanisms of adaptive evolution in this fly.

Identification of the Key Pathways and Genes Involved in the Wax Biosynthesis of the Chinese White Wax Scale Insect (Ericerus pela Chavannes) by Integrated Weighted Gene Coexpression Network Analysis

The white wax secreted by the male insects of the Chinese white wax scale (CWWS) is a natural high-molecular-weight compound with important economic value. However, its regulatory mechanism of wax biosynthesis is still unclear. In this study, a weighted gene coexpression network analysis (WGCNA) was used to analyze transcriptome data of first- and second-instar females, early and late female adults, and first- and second-instar males. A total of 19 partitioned modules with different topological overlaps were obtained, and three modules were identified as highly significant for wax secretion (p < 0.05). A total of 30 hub genes were obtained through screening, among which elongation of very-long-chain fatty acids protein (ELOVL) and fatty acyl-CoA reductase (FAR) are important catalytic enzymes of fatty acid metabolism. Furthermore, their metabolic catalytic products are involved in the synthesis of wax biosynthesis. The results demonstrate that WGCNA can be used for insect transcriptome analysis and effectively screen out the key genes related to wax biosynthesis.

MicroRNA-190-5p confers chlorantraniliprole resistance by regulating CYP6K2 in Spodoptera frugiperda (Smith)

The fall armyworm Spodoptera frugiperda (Smith) (FAA) is responsible for considerable losses in grain production, and chemical control is the most effective strategy. However, frequent insecticide application can lead to the development of resistance. In insects, cytochrome P450 plays a crucial role in insecticide metabolism. CYP6K2 is related to FAA resistance to chlorantraniliprole. However, the regulatory mechanism of CYP6K2 expression is poorly understood. In this study, a conserved target of isolated miRNA-190-5p was located in the 3' UTR of CYP6K2 in FAA. A luciferase reporter analysis showed that in FAA, miRNA-190-5p can combine with the 3'UTR of CYP6K2 to suppress its expression. Injected miRNA-190-5p agomir significantly reduced CYP6K2 abundance by 54.6% and reduced tolerance to chlorantraniliprole in FAA larvae, whereas injected miRNA-190-5p antagomir significantly increased CYP6K2 abundance by 1.77-fold and thus improved chlorantraniliprole tolerance in FAA larvae. These results provide a basis for further research on the posttranscriptional regulatory mechanism of CYP6K2 and will facilitate further study on the function of miRNAs in regulating tolerance to chlorantraniliprole in FAA.

Two Cladosporium Fungi with Opposite Functions to the Chinese White Wax Scale Insect Have Different Genome Characters

Insects encounter infection of microorganisms, and they also harbor endosymbiosis to participate in nutrition providing and act as a defender against pathogens. We previously found the Chinese white wax scale insect, Ericerus pela, was infected and killed by Cladosporium sp. (pathogen). We also found it harbored Cladosporium sp. (endogensis). In this study, we cultured these two Cladosporium fungi and sequenced their genome. The results showed Cladosporium sp. (endogensis) has a larger genome size and more genes than Cladosporium sp. (pathogen). Pan-genome analysis showed Cladosporium sp. (endogensis)-specific genes enriched in pathways related to nutrition production, such as amino acid metabolism, carbohydrate metabolism, and energy metabolism. These pathways were absent in that of Cladosporium sp. (pathogen). Gene Ontology analysis showed Cladosporium sp. (pathogen)-specific genes enriched in the biosynthesis of asperfuranone, emericellamide, and fumagillin. These terms were not found in that of Cladosporium sp. (endogensis). Pathogen Host Interactions analysis found Cladosporium sp. (endogensis) had more genes related to loss of pathogenicity and reduced virulence than Cladosporium sp. (pathogen). Cytotoxicity assay indicated Cladosporium sp. (pathogen) had cytotoxicity, while Cladosporium sp. (endogensis) had no cytotoxicity. These characters reflect the adaptation of endosymbiosis to host-restricted lifestyle and the invader of the entomopathogen to the host.

Transcriptome analyses and weighted gene coexpression network analysis reveal key pathways and genes involved in the rapid cold resistance of the Chinese white wax scale insect

The Chinese white wax scale insect, Ericerus pela, is an important resource insect in China. The rapid response of E. pela to decreasing temperatures plays key roles in the population distribution. In this study, we analyzed the gene expression of E. pela treated with low temperature using transcriptome analyses and weighted gene coexpression network analysis (WGCNA). The results showed that the cold resistance of E. pela involved changes in the expression of many genes. The genes were mainly involved in alcohol formation activity, lipid metabolism, membrane and structure, and oxidoreductase activity. According to the WGCNA results, some pathways related to cold resistance were found in the genes in the modules, such as cytoskeleton proteins, cytoskeleton protein pathway, biosynthesis of unsaturated fatty acids, glycerophospholipid metabolism, ether lipid metabolism, and thermogenesis. Some of the hub genes were nonspecific lipid-transfer proteins, DnaJ homolog subfamily C member 13, paramyosin, tropomodulin, and tubulin beta chain. In particular, the hub genes of the tan module included the heat shock protein (hsp) 10, hsp 60, hsp 70, and hsp 90 genes. Thirty-five antifreeze protein (afp) genes were identified according to the annotation results. Three afp genes were further identified among the hub genes. Six of these genes were selected for heterogeneous protein expression. One of them was expressed successfully. The thermal hysteresis activity (THA) analyses showed that the THA was 1.73°C. These results showed that the cytoskeleton, lipid metabolism, thermogenesis, HSPs and AFPs may play important roles in the cold resistance of E. pela.

Effect of policosanol from insect wax on amyloid β-peptide-induced toxicity in a transgenic Caenorhabditis elegans model of Alzheimer's disease

Background

Alzheimer’s disease (AD), an age-related neurodegenerative disorder and a serious public health concern, is mainly caused by β-amyloid (Aβ)-induced toxicity. Currently, a limited number of drugs are effective against AD, and only a few are used for its treatment. According to traditional Chinese medicine, white wax is mainly composed of policosanol, hexacosanol, and octacosanol. Policosanol has been shown to reduce lipid levels in blood and alleviate the symptoms associated with diabetic complications and neurodegenerative disorders, such as Parkinson’s disease and AD. However, the efficacy of policosanol depends on the purity and composition of the preparation, and the therapeutic efficacy of policosanol derived from insect wax (PIW) in AD is unknown.

Methods

Here, we identified the main components of PIW and investigated the effects of PIW on Aβ-induced toxicity and life-span in a transgenic Caenorhabditis elegans model of AD, CL4176. Furthermore, we estimated the expression of amyloid precursor-like protein (apl-1) and the genes involved in various pathways associated with longevity and alleviation of AD-related symptoms in PIW-fed CL4176.

Results

PIW mainly consists of tetracosanol, hexacosanol, octacosanol, and triacontanol; it could decrease the Aβ-induced paralysis rate from 86.87 to 66.97% (P < 0.01) and extend the life-span from 6.2 d to 7.8 d (P < 0.001) in CL4176 worms. Furthermore, PIW downregulated apl-1, a gene known to be associated with the levels of Aβ deposits in C. elegans. Additionally, our results showed that PIW modulated the expression of genes associated with longevity-related pathways such as heat shock response, anti-oxidative stress, and glutamine cysteine synthetase.

Conclusion

Our findings suggest that PIW may be a potential therapeutic agent for the prevention and treatment of AD. However, its effects on murine models and patients with AD need to be explored further.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03278-2.

Diversity of Insect Sesquiterpenoid Regulation

Insects are arguably the most successful group of animals in the world in terms of both species numbers and diverse habitats. The sesquiterpenoids juvenile hormone, methyl farnesoate, and farnesoic acid are well known to regulate metamorphosis, reproduction, sexual dimorphism, eusociality, and defense in insects. Nevertheless, different insects have evolved with different sesquiterpenoid biosynthetic pathway as well as products. On the other hand, non-coding RNAs such as microRNAs have been implicated in regulation of many important biological processes, and have recently been explored in the regulation of sesquiterpenoid production. In this review, we summarize the latest findings on the diversity of sesquiterpenoids reported in different groups of insects, as well as the recent advancements in the understanding of regulation of sesquiterpenoid production by microRNAs.

Silencing of Cytochrome P450 in Spodoptera frugiperda (Lepidoptera: Noctuidae) by RNA Interference Enhances Susceptibility to Chlorantraniliprole

Fall armyworm, Spodoptera frugiperda (Smith), has caused significant losses for crop production in China. The fall armyworm is mainly controlled by the chemical insecticides, whereas the frequent application of insecticides would result in the resistance development. Insect cytochrome P450 monooxygenases play an essential part in the detoxification of insecticides. In this study, five P450 genes were selected to determine the role in response to insecticides by RNA interference (RNAi). Developmental expression pattern analysis revealed that S. frugiperda CYP321A8, CYP321A9, and CYP321B1 were highest in second-instar larvae among developmental stages, with 2.04-, 3.39-, and 8.58-fold compared with eggs, whereas CYP337B5 and CYP6AE44 were highest in adult stage, with 16.3- and 10.6-fold in comparison of eggs, respectively. Tissue-specific expression pattern analysis exhibited that CYP321A8, CYP321B1, and CYP6AE44 were highest in the midguts, with 3.56-, 3.33-, and 3.04-fold compared with heads, whereas CYP321A9 and CYP337B5 were highest in wings, with 3.07- and 3.36-fold compared with heads, respectively. RNAi was also conducted to explore detoxification effects of the five P450 genes on chlorantraniliprole. The second-instar larvae became more sensitive to chlorantraniliprole with a higher mortality rate than the control, after silencing CYP321A8, CYP321A9, and CYP321B1, respectively. These findings strongly supported our viewpoint that CYP321A8, CYP321A9, and CYP321B1 may play a critical role in insecticide detoxification. It will provide a basis for further study on regulation of P450 genes and the management of S. frugiperda.

The Roles of DNA Methyltransferases 1 (DNMT1) in Regulating Sexual Dimorphism in the Cotton Mealybug, Phenacoccus solenopsis

The cotton mealybug, Phenacoccus solenopsis, is an invasive pest that can cause massive damage to many host plants of agricultural importance. P. solenopsis is highly polyphagous, and shows extreme sexual dimorphism between males and females. The functions of DNA methyltransferase (DNMT) enzymes in the cotton mealybug have not been well studied. Here, we carried out an investigation of DNMTs in cotton mealybug to study their roles in sexual dimorphism. We found that the cotton mealybug has two copies of PsDnmt1, but Dnmt3 is absent. We then amplified the full-length cDNAs of PsDnmt1A (2,225 bp) and PsDnmt1B (2,862 bp) using rapid amplification cDNA ends (RACE). Quantitative reverse transcriptase PCR shows that both PsDnmt1A and PsDnmt1B are highly expressed in adult males, while the expression of PsDnmt1B is 30-fold higher in gravid females than in virgin females. We knocked down PsDnmt1A and PsDnmt1B with small interfering RNAs (siRNAs), and both genes were successfully down-regulated after 24 h or 72 h in adult females and pupa (t-test, p < 0.05). Down-regulating the expression of these two DNMT genes led to offspring lethality and abnormal body color in adult females. Furthermore, the silencing of PsDnmt1B induced abnormal wing development in emerged adult males. Our results provide evidence that PsDnmt1 plays a crucial role in regulating sexual dimorphism in the cotton mealybug.

Transcriptome Analysis of Female and Male Conopomorpha sinensis (Lepidoptera: Gracilariidae) Adults With a Focus on Hormone and Reproduction

Conopomorpha sinensis Bradley is the dominant borer pest of litchi and longan in the Asian-pacific area. Reduction or interference of reproduction and mating of adult moths is one of the most used strategies to control C. sinensis. Insect reproduction is a critical biological process closely related to endocrine control. Conopomorpha sinensis genome and transcriptome information is limited, hampering both our understanding of the molecular mechanisms underlying hormone activity and reproduction and the development of control strategies for this borer pest. To explore the sex differences in gene expression profiles influencing these biological processes, de novo transcriptomes were assembled from female and male adult C. sinensis specimens. This analysis yielded 184,422 unigenes with an average length of 903 bp and 405,961 transcripts after sequencing and assembly. About 45.06, 22.41, 19.53, 34.05, 35.82, 36.42, and 19.85% of the unigenes had significant matches in seven public databases. Subsequently, gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis revealed comprehensive information about the function of each gene and identified enriched categories and pathways that were associated with the 2,890 female-biased genes and 2,964 male-biased genes. In addition, we identified some important unigenes related to hormone activity and reproduction among the sex-differentially expressed genes (DEGs), including unigenes coding for ecdysone-induced protein 78C, juvenile hormone (JH)-regulated gene fatty acyl-CoA reductase, vitellogenin, etc. Our findings provide a more comprehensive portrait of the sex differences involved in the relationship of two important physiological features-hormone activity and reproduction in C. sinensis and members of the family Gracillariidae.

Regulation of Hormone-Related Genes in Ericerus pela (Hemiptera: Coccidae) for Dimorphic Metamorphosis

Insect hormones regulate metamorphosis including that leading to sexual dimorphism. Using RNA-Seq, we discovered that the second-instar male larva (SM) of the white wax insect, Ericerus pela, have 5,968 and 8,620 differentially expressed transcripts compared with the second-instar female larva (SF) and the first-instar male larva (FM), respectively. The expression levels of genes involved in the apoptosis of old tissues and the reconstruction of new ones in the SM significantly enhanced, while the SF mainly has enhanced expression levels of anabolic genes such as chitin. We predicted that the second-instar larvae are the developmental origin of sexual dimorphic metamorphosis. Meanwhile, in the juvenile hormone (JH) metabolic pathway, CYP15A1 and JH esterase (JHE) are differentially expressed; and in the 20-hydroxyecdysone (20E) metabolic pathway, CYP307A1, CYP314A1, and CYP18A1 are differentially expressed. In the SM, the expression levels of CYP307A1 and CYP314A1 are significantly increased, whereas the expression level of CYP18A1 is significantly decreased; in the SF, the expression levels of the above genes are opposite to that of the SM. Expression trends of RNA-seq is consistent with the expression level of qRT-PCR, and seven of them are highly correlated (R ≥ 0.610) and four are moderately correlated (0.588 ≥ R ≥ 0.542).

Genome sequence of the Chinese white wax scale insect Ericerus pela: the first draft genome for the Coccidae family of scale insects

BACKGROUND

The Chinese white wax scale insect, Ericerus pela, is best known for producing wax, which has been widely used in candle production, casting, Chinese medicine, and wax printing products for thousands of years. The secretion of wax, and other unusual features of scale insects, is thought to be an adaptation to their change from an ancestral ground-dwelling lifestyle to a sedentary lifestyle on the higher parts of plants. As well as helping to improve its economic value, studies of E. pela might also help to explain the adaptation of scale insects. However, no genomic data are currently available for E. pela.

FINDINGS

To assemble the E. pela genome, 303.92 Gb of data were generated using Illumina and Pacific Biosciences sequencing, producing 277.22 Gb of clean data for assembly. The assembled genome size was 0.66 Gb, with 1,979 scaffolds and a scaffold N50 of 735 kb. The guanine + cytosine content was 33.80%. A total of 12,022 protein-coding genes were predicted, with a mean coding sequence length of 1,370 bp. Twenty-six fatty acyl-CoA reductase genes and 35 acyltransferase genes were identified. Evolutionary analysis revealed that E. pela and aphids formed a sister group and split ∼241.1 million years ago. There were 214 expanded gene families and 2,219 contracted gene families in E. pela.

CONCLUSION

We present the first genome sequence from the Coccidae family. These results will help to increase our understanding of the evolution of unique features in scale insects, and provide important genetic information for further research.

Differential expression of genes in greenbug (Schizaphis graminum Rondani) treated by imidacloprid and RNA interference

BACKGROUND

Insecticides act as toxins, inhibitors of digestion and deterrents, and affect the expression of many genes in insects. To assess key genes associated with the detoxification or regulation of imidacloprid in greenbug, Schizaphis graminum (Rondani), the transcriptome and digital gene expression (DGE) profile were analyzed using Illumina sequencing.

RESULTS

In total, 48 763 494 clean reads were obtained by sequencing. Expression profile analysis showed that 2782 unigenes were differently expressed between the imidacloprid treatment and control groups. After exposure to imidacloprid, the expression levels of 1846 unigenes were upregulated and 936 were downregulated in comparison with controls. Expression patterns of the top 20 highly expressed genes show that they could be involved in the detoxification of imidacloprid. Silencing of multidrug resistance-associated gene (MRA), GATA-binding gene (GAT) and takeout-like precursor gene (TLP) resulted in increasing susceptibility to imidacloprid.

CONCLUSIONS

The differentially expressed genes in S. graminum have potential regulatory or detoxification roles in response to imidacloprid. These results should be useful in understanding the molecular mechanisms of greenbug adaption to imidacloprid. © 2018 Society of Chemical Industry.

Sexual Dimorphism in Wax Secretion Offers Ecological Adaptability During Ericerus pela (Hemiptera: Coccidae) Evolution

The scale insect, Ericerus pela Chavannes, shows a typical sexual dimorphism. Males and females are different not only in morphology, but also in their ability to secrete wax and ecological adaptability. Here we report the morphological and structural characteristics of wax glands on E. pela females and males. The differences in wax glands and wax secretion between females and males reflect their different needs for living habitats and different ecological strategies. Sciophilous male nymphs are with five types of wax glands, and the wax glands on the dorsum secrete a layer of wax filaments plausibly for protection against direct light irradiation. On the other hand, five types of wax glands were found on the abdomen of females. Heliophilous female nymphs hardly secrete any wax, but the wax glands located along the spiracle on the abdomen may help this insect to breathe. Female adults secrete wax filaments on eggs to protect them from predators and prevent themselves from sticking to each other. In summary, males appear to secreted wax for creating a shaded niche that fits their sciophilous life style, whereas females are likely to adopt an ecological strategy with thickened epidermis for heliophilous acclimatization and overwintering.

Characterization and functional assay of a fatty acyl-CoA reductase gene in the scale insect, Ericerus pela Chavannes (Hemiptera: Coccoidae)

Ericerus pela Chavannes (Hemiptera: Coccoidae) is an economically important scale insect because the second instar males secrete a harvestable wax-like substance. In this study, we report the molecular cloning of a fatty acyl-CoA reductase gene (EpFAR) of E. pela. We predicted a 520-aa protein with the FAR family features from the deduced amino acid sequence. The EpFAR mRNA was expressed in five tested tissues, testis, alimentary canal, fat body, Malpighian tubules, and mostly in cuticle. The EpFAR protein was localized by immunofluorescence only in the wax glands and testis. EpFAR expression in High Five insect cells documented the recombinant EpFAR reduced 26-0:(S) CoA and to its corresponding alcohol. The data illuminate the molecular mechanism for fatty alcohol biosynthesis in a beneficial insect, E. pela.

A Lethal Fungus Infects the Chinese White Wax Scale Insect and Causes Dramatic Changes in the Host Microbiota

The Chinese white wax scale insect (Ericerus pela) is an economically valuable species with an important role in wax production. Recently, in a greenhouse in Kunming, we identified a genus of fungus that infects and kills E. pela females. This study sought to perform the molecular detection of entomopathogens and analyze the changes in the host microbiota after entomopathogen infection. We used library construction, high-throughput sequencing and real-time quantitative polymerase chain reaction (RT-qPCR) to identify the fungi infecting adult E. pela, to understand the changes in the host organism, and to determine the distribution of the entomopathogens. Cladosporium langeronii and C. sphaerospermum were the main pathogenic species that infected the E. pela females, and they were most prevalent in the dorsal cuticle. In vivo, after infection, the proportion of Cladosporium clearly increased. The infection had little influence on the fungal community but had a strong influence on the bacterial community. After infection, Arsenophonus was dominant, and numerous bacterial genera disappeared. However, Rickettsia, instead of Arsenophonus, became dominant in the Cladosporium-infected individuals that had also been infected with Rickettsia. We identified the species that infected E. pela females and determined the influence of infection on the host microorganisms.

In vivo evaluation of insect wax for hair growth potential

Insect wax is secreted by Ericerus pela Chavanness. It has been traditionally used to treat hair loss in China, but few reports have been published on the hair growth-promoting effect of insect wax. In this work, we examined the hair growth-promoting effects of insect wax on model animals. Different concentrations of insect wax were topically applied to the denuded backs of mice, and 5% minoxidil was applied topically as a positive control. We found that insect wax significantly promoted hair growth in a dose-dependent manner, 45% and 30% insect wax both induced hair to regrow, while less visible hair growth was observed in blank controls on the 16^th day. The experimental areas treated with 45% and 30% insect wax exhibited significant differences in hair scores compared to blank controls, and hair lengths in the 45% and 30% insect wax group was significantly longer than in blank controls on the 16^th and 20^th days. There were no new hair follicles forming in the treated areas, and the hair follicles were prematurely converted to the anagen phase from the telogen phase in experimental areas treated with 45% and 30% insect wax. Both 45% and 30% insect wax upregulated vascular endothelial growth factor expression. The results indicated that 45% and 30% insect wax showed hair growth-promoting potential approximately as potent as 5% minoxidil by inducing the premature conversion of telogen-to-anagen and by prolonging the mature anagen phase rather than increasing the number of hair follicles, which was likely related to the upregulation of VEGF expression. The dissociative policosanol in insect wax was considered the key ingredient most likely responsible for the hair growth promoting potential.

De novo transcriptome of the mayfly Cloeon viridulum and transcriptional signatures of Prometabola

Mayflies (Ephemeroptera) display many primitive characters and a unique type of metamorphosis (Prometabola). However, information on the genomes and transcriptomes of this insect group is limited. The RNA sequencing study presented here generated the first de novo transcriptome assembly of Cloeon viridulum (Ephemeroptera: Baetidae), and compared gene expression signatures among the young larva (YL), mature larva (ML), subimago (SI), and imago (IM) stages of this mayfly. The transcriptome, based on 88 Gb of sequence data, comprised a set of 81,185 high quality transcripts. The number of differentially expressed genes (DEGs) in YL vs. ML, ML vs. SI, and SI vs. IM, was 4,825, 1,584, and 1,278, respectively, according to the reads per kilobase of transcript per million mapped reads analysis, assuming a false discovery rate <0.05 and a fold change >2. Gene enrichment analysis revealed that these DEGs were enriched in the "chitin metabolic process", "germ cell development", "steroid hormone biosynthesis", and "cutin, suberine, and wax biosynthesis" pathways. Finally, the expression pattern of a selected group of candidate signature genes for Prometabola, including vestigial, methoprene-tolerant, wingless, and broad-complex were confirmed by quantitative real time-PCR analysis. The Q-PCR analysis of larval, subimaginal, and imaginal stages of C. viridulum suggests that the development of mayflies more closely resembles hemimetamorphosis than holometamorphosis.

Polysaccharide extracted from Chinese white wax scale ameliorates 2,4-dinitrochlorobenzene-induced atopic dermatitis-like symptoms in BALB/c mice

Atopic dermatitis (AD) is a common inflammatory skin disease with high rates of morbidity and is associated with erythema, pruritus, scaling of affected areas of skin. It is extremely important to introduce a therapeutic agent which has significant anti-inflammatory effect with less side-effect for treatment of AD. This study evaluated the effect of a natural compound from herbal extracts, the crude polysaccharide extracted from the white wax scale (CWPS), on AD-like mice. Repeated applications of 2,4-dinitrochlorobenzene (DNCB) were performed on ear and dorsal skin of BALB/c mice to induce AD-like symptoms and skin lesions. Oral administration of CWPS decreased serum IgE level and limited the infiltration of mast cells and eosinophils to the dermal tissues in the DNCB-induced AD mice. In addition, CWPS reduced Th1 and Th17 responses, leading to an attenuated cutaneous inflammatory response. Furthermore, in vitro study also demonstrated that CWPS limited T cell activation and cytokines (i.e. IFN-γ and IL-17) production induced by DNCB. We conclude that CWPS attenuates DNCB-induced AD-like skin lesion through modulating T cell-elicited immune responses and CD4+ T cell polarization, and could be exploited as a new therapeutic approach for AD.

Transcriptome analysis on the exoskeleton formation in early developmetal stages and reconstruction scenario in growth-moulting in Litopenaeus vannamei

Exoskeleton construction is an important issue in shrimp. To better understand the molecular mechanism of exoskeleton formation, development and reconstruction, the transcriptome of the entire developmental process in Litopenaeus vannamei, including nine early developmental stages and eight adult-moulting stages, was sequenced and analysed using Illumina RNA-seq technology. A total of 117,539 unigenes were obtained, with 41.2% unigenes predicting the full-length coding sequence. Gene Ontology, Clusters of Orthologous Group (COG), the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and functional annotation of all unigenes gave a better understanding of the exoskeleton developmental process in L. vannamei. As a result, more than six hundred unigenes related to exoskeleton development were identified both in the early developmental stages and adult-moulting. A cascade of sequential expression events of exoskeleton-related genes were summarized, including exoskeleton formation, regulation, synthesis, degradation, mineral absorption/reabsorption, calcification and hardening. This new insight on major transcriptional events provide a deep understanding for exoskeleton formation and reconstruction in L. vannamei. In conclusion, this is the first study that characterized the integrated transcriptomic profiles cover the entire exoskeleton development from zygote to adult-moulting in a crustacean, and these findings will serve as significant references for exoskeleton developmental biology and aquaculture research.

Differential expression of genes in the alate and apterous morphs of the brown citrus aphid, Toxoptera citricida

Winged and wingless morphs in insects represent a trade-off between dispersal ability and reproduction. We studied key genes associated with apterous and alate morphs in Toxoptera citricida (Kirkaldy) using RNAseq, digital gene expression (DGE) profiling, and RNA interference. The de novo assembly of the transcriptome was obtained through Illumina short-read sequencing technology. A total of 44,199 unigenes were generated and 27,640 were annotated. The transcriptomic differences between alate and apterous adults indicated that 279 unigenes were highly expressed in alate adults, whereas 5,470 were expressed at low levels. Expression patterns of the top 10 highly expressed genes in alate adults agreed with wing bud development trends. Silencing of the lipid synthesis and degradation gene (3-ketoacyl-CoA thiolase, mitochondrial-like) and glycogen genes (Phosphoenolpyruvate carboxykinase [GTP]-like and Glycogen phosphorylase-like isoform 2) resulted in underdeveloped wings. This suggests that both lipid and glycogen metabolism provide energy for aphid wing development. The large number of sequences and expression data produced from the transcriptome and DGE sequencing, respectively, increases our understanding of wing development mechanisms.

Transcriptome characterization and gene expression analysis related to sexual dimorphism in the ghost moth, Thitarodes pui, a host of Ophiocordyceps sinensis

Thitarodes pui is one of the host species of the Chinese caterpillar fungus Ophiocordyceps sinensis as a traditional Chinese medicine with economic and medical importance. The pupal and adult stages of T. pui are sexually dimorphic. In order to elucidate the molecular mechanisms involved in the sexually dimorphic development of T. pui, we compared the transcriptomes of female and male pupae and adults. We obtained 15,881,734, 16,962,086, 17,514,743, and 17,770,904 clean reads from female pupae, male pupae, female adults, and male adults, respectively. The reads obtained from the four samples were pooled and assembled into 65,165 unigenes, 23,597 of which were annotated. Candidate genes involved in sexual development were identified and analysed. Gene expression analysis revealed that 1406 genes were differentially expressed in male and female pupae, 448 of which were up-regulated in males and 958 were up-regulated in females. A total of 2025 genes were differentially expressed in male and females adults, 1304 of which were up-regulated in males and 721 were up-regulated in females. The functional enrichment of the differentially expressed genes indicated that reproduction and cuticle synthesis were regulated differently between the sexes. The transcriptome data obtained provide significant information regarding the genes involved in sexually dimorphic development, which will improve our understanding of the molecular mechanisms related to sexual dimorphism and helpful for the moth mass rearing which would provide enough host insects for the sustainable utilization of O. sinensis.

Transcriptomic and proteomic analyses on the supercooling ability and mining of antifreeze proteins of the Chinese white wax scale insect

The Chinese white wax scale insect, Ericerus pela, can survive at extremely low temperatures, and some overwintering individuals exhibit supercooling at temperatures below -30°C. To investigate the deep supercooling ability of E. pela, transcriptomic and proteomic analyses were performed to delineate the major gene and protein families responsible for the deep supercooling ability of overwintering females. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that genes involved in the mitogen-activated protein kinase, calcium, and PI3K-Akt signaling pathways and pathways associated with the biosynthesis of soluble sugars, sugar alcohols and free amino acids were dominant. Proteins responsible for low-temperature stress, such as cold acclimation proteins, glycerol biosynthesis-related enzymes and heat shock proteins (HSPs) were identified. However, no antifreeze proteins (AFPs) were identified through sequence similarity search methods. A random forest approach identified 388 putative AFPs in the proteome. The AFP gene ep-afp was expressed in Escherichia coli, and the expressed protein exhibited a thermal hysteresis activity of 0.97°C, suggesting its potential role in the deep supercooling ability of E. pela.

Differential Juvenile Hormone Variations in Scale Insect Extreme Sexual Dimorphism

Scale insects have evolved extreme sexual dimorphism, as demonstrated by sedentary juvenile-like females and ephemeral winged males. This dimorphism is established during the post-embryonic development; however, the underlying regulatory mechanisms have not yet been examined. We herein assessed the role of juvenile hormone (JH) on the diverging developmental pathways occurring in the male and female Japanese mealybug Planococcus kraunhiae (Kuwana). We provide, for the first time, detailed gene expression profiles related to JH signaling in scale insects. Prior to adult emergence, the transcript levels of JH acid O-methyltransferase, encoding a rate-limiting enzyme in JH biosynthesis, were higher in males than in females, suggesting that JH levels are higher in males. Furthermore, male quiescent pupal-like stages were associated with higher transcript levels of the JH receptor gene, Methoprene-tolerant and its co-activator taiman, as well as the JH early-response genes, Krüppel homolog 1 and broad. The exposure of male juveniles to an ectopic JH mimic prolonged the expression of Krüppel homolog 1 and broad, and delayed adult emergence by producing a supernumeral pupal stage. We propose that male wing development is first induced by up-regulated JH signaling compared to female expression pattern, but a decrease at the end of the prepupal stage is necessary for adult emergence, as evidenced by the JH mimic treatments. Furthermore, wing development seems linked to JH titers as JHM treatments on the pupal stage led to wing deformation. The female pedomorphic appearance was not reflected by the maintenance of high levels of JH. The results in this study suggest that differential variations in JH signaling may be responsible for sex-specific and radically different modes of metamorphosis.