UDP-glycosyltransferases act as key determinants of host plant range in generalist and specialist Spodoptera species.

Phytophagous insects have evolved sophisticated detoxification systems to overcome the antiherbivore chemical defenses produced by many plants. However, how these biotransformation systems differ in generalist and specialist insect species and their role in determining insect host plant range remains an open question. Here, we show that UDP-glucosyltransferases (UGTs) play a key role in determining the host range of insect species within the Spodoptera genus. Comparative genomic analyses of Spodoptera species that differ in host plant breadth identified a relatively conserved number of UGT genes in generalist species but high levels of UGT gene pseudogenization in the specialist Spodoptera picta. CRISPR-Cas9 knockouts of the three main UGT gene clusters of Spodoptera frugiperda revealed that UGT33 genes play an important role in allowing this species to utilize the poaceous plants maize, wheat, and rice, while UGT40 genes facilitate utilization of cotton. Further functional analyses in vivo and in vitro identified the UGT SfUGT33F32 as the key mechanism that allows generalist S. frugiperda to detoxify the benzoxazinoid DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one), a potent insecticidal phytotoxin produced by poaceous plants. However, while this detoxification capacity is conserved in several generalist Spodoptera species, Spodoptera picta, which specializes on Crinum plants, is unable to detoxify DIMBOA due to a nonfunctionalizing mutation in SpUGT33F34. Collectively, these findings provide insight into the role of insect UGTs in host plant adaptation, the mechanistic basis of evolutionary transitions between generalism and specialism and offer molecular targets for controlling a group of notorious insect pests.

Trade-offs between the accumulation of cuticular wax and jasmonic acid-mediated herbivory resistance in maize.

Plants have evolved complex physical and chemical defense systems that allow them to withstand herbivory infestation. Composed of a complex mixture of very-long-chain fatty acids (VLCFAs) and their derivatives, cuticular wax constitutes the first physical line of defense against herbivores. Here, we report the function of Glossy 8 (ZmGL8), which encodes a 3-ketoacyl reductase belonging to the fatty acid elongase complex, in orchestrating wax production and jasmonic acid (JA)-mediated defenses against herbivores in maize (Zea mays). The mutation of GL8 enhanced chemical defenses by activating the JA-dependent pathway. We observed a trade-off between wax accumulation and JA levels across maize glossy mutants and 24 globally collected maize inbred lines. In addition, we demonstrated that mutants defective in cuticular wax biosynthesis in Arabidopsis thaliana and maize exhibit enhanced chemical defenses. Comprehensive transcriptomic and lipidomic analyses indicated that the gl8 mutant confers chemical resistance to herbivores by remodeling VLCFA-related lipid metabolism and subsequent JA biosynthesis and signaling. These results suggest that VLCFA-related lipid metabolism has a critical role in regulating the trade-offs between cuticular wax and JA-mediated chemical defenses.

Npas3 deficiency impairs cortical astrogenesis and induces autistic-like behaviors.

Transcription factors with basic-helix-loop-helix (bHLH) motifs can control neural progenitor fate determination to neurons and oligodendrocytes. How bHLH transcription factors regulate astrogenesis remains largely unknown. Here, we report that NPAS3, a bHLH transcription factor, is a critical regulator of astrogenesis. Npas3 deficiency impairs cortical astrogenesis, correlating with abnormal brain development and autistic-like behaviors. Single-cell transcriptomes reveal that Npas3 knockout induces abnormal transition states in the differentiation trajectories from radial glia to astrocytes. Analysis of chromatin immunoprecipitation sequencing data in primary cortical astrocytes shows that NPAS3 binding targets are involved in functions of brain development and synapse organization. Co-culture assay further indicates that NPAS3-impaired astrogenesis induces synaptic deficits in wild-type neurons. Astrocyte-specific knockdown of NPAS3 in wild-type cortex causes synaptic and behavioral abnormalities associated with the core symptoms in autism. Together, our findings suggest that transcription factor NPAS3 regulates astrogenesis and its subsequent consequences for brain development and behavior.

CRISPR/Cas9-mediated Serine protease 2 disruption induces male sterility in Spodoptera litura.

Male fertility is essential for reproduction and population growth in animals. Many factors affect male fertility, such as courtship behavior, sperm quantity, and sperm motility, among others. Seminal Fluid Proteins (SFPs) are vital components of seminal fluid in the male ejaculate, which affect male fertility, sperm activation, and female ovulation. However, the knowledge of SFPs is insufficient; the function of many SFPs remains unknown, and most described functions were mainly characterized in Drosophila or other laboratory models. Here, we focus on the Serine protease 2 (Ser2) gene in the lepidopteran pest Spodoptera litura. The Ser2 gene was specifically expressed in male adults. Disruption of the Ser2 gene mediated by CRISPR/Cas9 induced male sterility but females remained fertile. PCR-based detection of the next-generation mutants showed that male sterility was stably inherited. The qRT-PCR analysis of SlSer2 mutants showed that motor protein family genes and structural protein family genes were down-regulated, while protein modification family genes were up-regulated, suggesting that SlSer2 may be involved in sperm movement and activity. These results demonstrate that Ser2 is an important component of SFPs in seminal fluid and was identified for a useful sterile gene for pest control that may lead to new control strategies for lepidopteran insect pests such as S. litura.

Masculinizer and Doublesex as Key Factors Regulate Sexual Dimorphism in Ostrinia furnacalis.

Sex determination is an important and traditional biological process. In Lepidoptera, Masculinizer (Masc) and doublesex (dsx) are the essential genes for sex determination and play critical roles in sexual differentiation and development. The functions of Masc and dsx have been characterized in several model insect species. However, the molecular mechanism and sex determination functions of Masc and dsx in Ostrinia furnacalis, an agricultural pest, are still unknown. Here, we successfully used the CRISPR/Cas9 genome editing system to knock out OfMasc and Ofdsx. Mutation of OfMasc induced male external genital defects and sterility. Disruptions of the Ofdsx common region caused sex-specific defects in the external genitals and adult sterility. In addition, we found that OfMasc and Ofdsx can regulate the pigmentation genes that control wing pigmentation patterns. These results demonstrate that OfMasc and Ofdsx play key roles in the sex determination of O. furnacalis, and suggest novel genetic control approaches for the management of pests, including O. furnacalis.

Juvenile hormone promotes paracellular transport of yolk proteins via remodeling zonula adherens at tricellular junctions in the follicular epithelium.

Juvenile hormone (JH) acts as a gonadotrophic hormone stimulating insect vitellogenesis and oogenesis. Paracellular transport of yolk proteins through intercellular channels (patency) in the follicular epithelium is a developmentally regulated and evolutionarily conserved process during vitellogenesis. However, the mechanisms underlying patency opening are poorly understood. Using the migratory locust Locusta migratoria as a model system, we report here that JH-regulated remodeling of zonula adherens (ZA), the belt-like adherens junction maintaining physical linking between follicle cells controlled the opening of patency. JH triggered phosphorylation of Partitioning defective protein 3 (Par3) via a signaling cascade including G protein-coupled receptor (GPCR), small GTPase Cell division cycle 42 (Cdc42) and atypical Protein kinase C (aPKC). Par3 phosphorylation resulted in its disassociation from ß-Catenin, the cytoplasmic partner of ZA core component E-Cadherin. Release of Par3 from the ß-Catenin/E-Cadherin complex caused ZA disassembly at tricellular contacts, consequently leading to patency enlargement. This study provides new insight into how JH stimulates insect vitellogenesis and egg production via inducing the opening of paracellular route for vitellogenin transport crossing the follicular epithelium barrier.

Convergent Adaptation of Ootheca Formation as a Reproductive Strategy in Polyneoptera.

Insects have evolved numerous adaptations and colonized diverse terrestrial environments. Several polyneopterans, including dictyopterans (cockroaches and mantids) and locusts, have developed oothecae, but little is known about the molecular mechanism, physiological function, and evolutionary significance of ootheca formation. Here, we demonstrate that the cockroach asymmetric colleterial glands produce vitellogenins, proline-rich protein, and glycine-rich protein as major ootheca structural proteins (OSPs) that undergo sclerotization and melanization for ootheca formation through the cooperative protocatechuic acid pathway and dopachrome and dopaminechrome subpathway. Functionally, OSP sclerotization and melanization prevent eggs from losing water at warm and dry conditions, and thus effectively maintain embryo viability. Dictyopterans and locusts convergently evolved vitellogenins, apolipoprotein D, and laminins as OSPs, whereas within Dictyoptera, cockroaches and mantids independently developed glycine-rich protein and fibroins as OSPs. Highlighting the ecological-evolutionary importance, convergent ootheca formation represents a successful reproductive strategy in Polyneoptera that promoted the radiation and establishment of cockroaches, mantids, and locusts.

Krüppel-homolog 1 exerts anti-metamorphic and vitellogenic functions in insects via phosphorylation-mediated recruitment of specific cofactors.

BACKGROUND: The zinc-finger transcription factor Krüppel-homolog 1 (Kr-h1) exerts a dual regulatory role during insect development by preventing precocious larval/nymphal metamorphosis and in stimulating aspects of adult reproduction such as vitellogenesis. However, how Kr-h1 functions both as a transcriptional repressor in juvenile metamorphosis and an activator in adult reproduction remains elusive. Here, we use the insect Locusta migratoria to dissect the molecular mechanism by which Kr-h1 functions as activator and repressor at these distinct developmental stages. RESULTS: We report that the kinase PKCα triggers Kr-h1 phosphorylation at the amino acid residue Ser154, a step essential for its dual functions. During juvenile stage, phosphorylated Kr-h1 recruits a corepressor, C-terminal binding protein (CtBP). The complex of phosphorylated Kr-h1 and CtBP represses the transcription of Ecdysone induced protein 93F (E93) and consequently prevents the juvenile-to-adult transition. In adult insects, phosphorylated Kr-h1 recruits a coactivator, CREB-binding protein (CBP), and promotes vitellogenesis by inducing the expression of Ribosomal protein L36. Furthermore, Kr-h1 phosphorylation with the concomitant inhibition of E93 transcription is evolutionarily conserved across insect orders. CONCLUSION: Our results suggest that Kr-h1 phosphorylation is indispensable for the recruitment of transcriptional cofactors, and for its anti-metamorphic and vitellogenic actions in insects. Our data shed new light on the understanding of Kr-h1 regulation and function in JH-regulated insect metamorphosis and reproduction.

The vitellogenin receptor functionality of the migratory locust depends on its phosphorylation by juvenile hormone.

Vitellogenin receptor (VgR) plays a pivotal role in ovarian vitellogenin (Vg) uptake and vertical transmission of pathogenic microbes and Wolbachia symbionts. However, the regulatory mechanisms of VgR action as an endocytic receptor and translocation from oocyte cytoplasm to the membrane remain poorly understood. Here, by using the migratory locust Locusta migratoria as a model system, we report that juvenile hormone (JH) promotes VgR phosphorylation at Ser1361 in the second EGF-precursor homology domain. A signaling cascade including GPCR, PLC, extracellular calcium, and PKC-ι is involved in JH-stimulated VgR phosphorylation. This posttranslational regulation is a prerequisite for VgR binding to Vg on the external surface of the oocyte membrane and subsequent VgR/Vg endocytosis. Acidification, a condition in endosomes, induces VgR dephosphorylation along with the dissociation of Vg from VgR. Phosphorylation modification is also required for VgR recycling from oocyte cytoplasm to the membrane. Additionally, VgR phosphorylation and its requirement for Vg uptake and VgR recycling are evolutionarily conserved in other representative insects including the cockroach Periplaneta americana and the cotton bollworm Helicoverpa armigera This study fills an important knowledge gap of low-density lipoprotein receptors in posttranslational regulation, endocytosis, and intracellular recycling.

Juvenile hormone signaling promotes ovulation and maintains egg shape by inducing expression of extracellular matrix genes.

It is well documented that the juvenile hormone (JH) can function as a gonadotropic hormone that stimulates vitellogenesis by activating the production and uptake of vitellogenin in insects. Here, we describe a phenotype associated with mutations in the Drosophila JH receptor genes, Met and Gce: the accumulation of mature eggs with reduced egg length in the ovary. JH signaling is mainly activated in ovarian muscle cells and induces laminin gene expression in these cells. Meanwhile, JH signaling induces collagen IV gene expression in the adult fat body, from which collagen IV is secreted and deposited onto the ovarian muscles. Laminin locally and collagen IV remotely contribute to the assembly of ovarian muscle extracellular matrix (ECM); moreover, the ECM components are indispensable for ovarian muscle contraction. Furthermore, ovarian muscle contraction externally generates a mechanical force to promote ovulation and maintain egg shape. This work reveals an important mechanism for JH-regulated insect reproduction.

Identification of G protein-coupled receptors required for vitellogenesis and egg development in an insect with panoistic ovary.

G protein-coupled receptors (GPCRs), a superfamily of integral transmembrane proteins regulate a variety of physiological processes in insects. Juvenile hormone (JH) is known to stimulate Vitellogenin (Vg) synthesis in the fat body, secretion into the hemolymph and uptake by developing oocytes. However, the role of GPCRs in JH-dependent insect vitellogenesis and oocyte maturation remains elusive. In the present study, we performed transcriptomic analysis and RNA interference (RNAi) screening in vitellogenic females of the migratory locust Locusta migratoria. Of 22 GPCRs identified in ovarian transcriptome, LGR4, OR-A1, OR-A2, Mthl1, Mthl5 and Smo were most abundant in the ovary. By comparison, mAChR-C expressed at higher levels in the fat body, whereas Oct/TyrR, OARß, AdoR and ADGRA3 were at higher expression levels in the brain. Our RNAi screening demonstrated that knockdown of six GPCRs resulted in defective phenotypes of Vg accumulation in developing oocytes, accompanied by blocked ovarian development and impaired oocyte maturation. While LGR4 and Oct/TyrR appeared to control Vg synthesis in the fat body, OR-A1, OR-A2, mAChR-C and CirlL regulated Vg transportation and uptake. The findings provide fundamental evidence for deciphering the regulatory mechanisms of GPCRs in JH-stimulated insect reproduction.

Insulin/IGF signaling and TORC1 promote vitellogenesis via inducing juvenile hormone biosynthesis in the American cockroach.

Vitellogenesis, including vitellogenin (Vg) production in the fat body and Vg uptake by maturing oocytes, is of great importance for the successful reproduction of adult females. The endocrinal and nutritional regulation of vitellogenesis differs distinctly in insects. Here, the complex crosstalk between juvenile hormone (JH) and the two nutrient sensors insulin/IGF signaling (IIS) and target of rapamycin complex1 (TORC1), was investigated to elucidate the molecular mechanisms of vitellogenesis regulation in the American cockroach, Periplaneta americana Our data showed that a block of JH biosynthesis or JH action arrested vitellogenesis, in part by inhibiting the expression of doublesex (Dsx), a key transcription factor gene involved in the sex determination cascade. Depletion of IIS or TORC1 blocked both JH biosynthesis and vitellogenesis. Importantly, the JH analog methoprene, but not bovine insulin (to restore IIS) and amino acids (to restore TORC1 activity), restored vitellogenesis in the neck-ligated (IIS-, TORC1- and JH-deficient) and rapamycin-treated (TORC1- and JH-deficient) cockroaches. Combining classic physiology with modern molecular techniques, we have demonstrated that IIS and TORC1 promote vitellogenesis, mainly via inducing JH biosynthesis in the American cockroach.

Juvenile hormone acts through FoxO to promote Cdc2 and Orc5 transcription for polyploidy-dependent vitellogenesis.

Vitellogenin (Vg) is a prerequisite for egg production and embryonic development after ovipositioning in oviparous animals. In many insects, juvenile hormone (JH) promotes fat body cell polyploidization for the massive Vg synthesis required for the maturation of multiple oocytes, but the underlying mechanisms remain poorly understood. Using the migratory locust Locusta migratoria as a model system, we report here that JH induces the dephosphorylation of Forkhead box O transcription factor (FoxO) through a signaling cascade including leucine carboxyl methyltransferase 1 (LCMT1) and protein phosphatase 2A (PP2A). JH promotes PP2A activity via LCMT1-mediated methylation, consequently triggering FoxO dephosphorylation. Dephosphorylated FoxO binds to the upstream region of two endocycle-related genes, cell-division-cycle 2 (Cdc2) and origin-recognition-complex subunit 5 (Orc5), and activates their transcription. Depletion of FoxO, Cdc2 or Orc5 results in blocked polyploidization of fat body cells, accompanied by markedly reduced Vg expression, impaired oocyte maturation and arrested ovarian development. The results suggest that JH acts via LCMT1-PP2A-FoxO to regulate Cdc2 and Orc5 expression, and to enhance ploidy of fat body cells in preparation for the large-scale Vg synthesis required for synchronous maturation of multiple eggs.

Regulatory Mechanisms of Vitellogenesis in Insects.

Vitellogenesis is pre-requisite to insect egg production and embryonic development after oviposition. During insect vitellogenesis, the yolk protein precursor vitellogenin (Vg) is mainly synthesized in the fat body, transported by the hemolymph through the intercellular spaces (known as patency) in the follicular epithelium to reach the membrane of maturing oocytes, and sequestered into the maturing oocytes via receptor-mediated endocytosis. Insect vitellogenesis is governed by two critical hormones, the sesquiterpenoid juvenile hormone (JH) and the ecdysteriod 20-hydroxyecdysone (20E). JH acts as the principal gonadotropic hormone to stimulate vitellogenesis in basal hemimetabolous and most holometabolous insects. 20E is critical for vitellogenesis in some hymenopterans, lepidopterans and dipterans. Furthermore, microRNA (miRNA) and nutritional (amino acid/Target of Rapamycin and insulin) pathways interplay with JH and 20E signaling cascades to control insect vitellogenesis. Revealing the regulatory mechanisms underlying insect vitellogenesis is critical for understanding insect reproduction and helpful for developing new strategies of insect pest control. Here, we outline the recent research progress in the molecular action of gonadotropic JH and 20E along with the role of miRNA and nutritional sensor in regulating insect vitellogenesis. We highlight the advancements in the regulatory mechanisms of insect vitellogenesis by the coordination of hormone, miRNA and nutritional signaling pathways.

Post-transcriptional regulation of insect metamorphosis and oogenesis.

Metamorphic transformation from larvae to adults along with the high fecundity is key to insect success. Insect metamorphosis and reproduction are governed by two critical endocrines, juvenile hormone (JH), and 20-hydroxyecdysone (20E). Recent studies have established a crucial role of microRNA (miRNA) in insect metamorphosis and oogenesis. While miRNAs target genes involved in JH and 20E-signaling pathways, these two hormones reciprocally regulate miRNA expression, forming regulatory loops of miRNA with JH and 20E-signaling cascades. Insect metamorphosis and oogenesis rely on the coordination of hormones, cognate genes, and miRNAs for precise regulation. In addition, the alternative splicing of genes in JH and 20E-signaling pathways has distinct functions in insect metamorphosis and oogenesis. We, therefore, focus in this review on recent advances in post-transcriptional regulation, with the emphasis on the regulatory role of miRNA and alternative splicing, in insect metamorphosis and oogenesis. We will highlight important new findings of miRNA interactions with hormonal signaling and alternative splicing of JH receptor heterodimer gene Taiman.

Immediate Release of Gastrin-Releasing Peptide Mediates Delayed Radiation-Induced Pulmonary Fibrosis.

Radiation-induced pulmonary fibrosis (RTPF) is a progressive, serious condition in many subjects treated for thoracic malignancies or after accidental nuclear exposure. No biomarker exists for identifying the irradiated subjects most susceptible to pulmonary fibrosis (PF). Previously, we determined that gastrin-releasing peptide (GRP) was elevated within days after birth in newborns exposed to hyperoxia who later developed chronic lung disease. The goal of the current study was to test whether radiation (RT) exposure triggers GRP release in mice and whether this contributes to RTPF in vivo. We determined urine GRP levels and lung GRP immunostaining in mice 0 to 24 after post-thoracic RT (15 Gy). Urine GRP levels were significantly elevated between 24 hours post-RT; GRP-blocking monoclonal antibody 2A11, given minutes post-RT, abrogated urine GRP levels by 6 to 12 hours and also altered phosphoprotein signaling pathways at 24 hours post-RT. Strong extracellular GRP immunostaining was observed in lung at 6 hours post-RT. Mice given one dose of GRP monoclonal antibody 2A11 24 hours post-RT had significantly reduced myofibroblast accumulation and collagen deposition 15 weeks later, indicating protection against lung fibrosis. Therefore, elevation of urine GRP could be predictive of RTPF development. In addition, transient GRP blockade could mitigate PF in normal lung after therapeutic or accidental RT exposure.

Juvenile hormone-dependent Kazal-type serine protease inhibitor Greglin safeguards insect vitellogenesis and egg production.

In addition to preventing insect metamorphosis, juvenile hormone (JH) is known to stimulate aspects of insect reproduction. However, the molecular mechanisms of JH action in insect reproduction remain largely unknown. By reanalyzing the transcriptomic data from adults and other developmental stages of the migratory locust Locusta migratoria, we identified a gene coding for Kazal-type protease inhibitor, previously named Greglin. Greglin is specifically expressed in adult females and most abundant in the fat body and ovaries. Interestingly, Greglin is among the top 3 of highly expressed genes in adult female locusts, after 2 vitellogenin ( Vg) genes. Greglin is induced by JH and expressed at remarkably high levels in the vitellogenic stage. Knockdown of Greglin in adult female locusts results in accelerated degradation of serine protease substrate and significantly reduced levels of Greglin protein in hemolymph and ovaries. The consequent phenotypes include blocked oocyte maturation, arrested ovarian growth and shrunken follicular epithelium, as well as declines in egg number and hatchability. The data provide the first evidence, to our knowledge, that JH-dependent Greglin is involved in locust vitellogenesis and oocyte maturation likely by protecting vitellogenesis and other forms of yolk precursors from proteolysis. The result offers new insights into the regulation of JH and function of protease inhibitors in insect vitellogenesis, oocyte maturation and fecundity.-Guo, W., Wu, Z., Yang, L., Cai, Z., Zhao, L., Zhou, S. Juvenile hormone-dependent Kazal-type serine protease inhibitor Greglin safeguards insect vitellogenesis and egg production.

Clustered miR-2, miR-13a, miR-13b and miR-71 coordinately target Notch gene to regulate oogenesis of the migratory locust Locusta migratoria.

MicroRNAs (miRNAs), ∼22-nt small noncoding RNAs with a crucial role in various biological processes of organisms, are usually clustered in the genome. However, little is known about the miRNA clusters involved in insect reproduction. By small RNA sequencing and quantification followed by qRT-PCR, we found that the expression of invertebrate-specific miR-2/13/71 cluster including miR-2, miR-13a, miR-13b and miR-71 significantly decreased after adult ecdysis of the migratory locust, Locusta migratoria. Luciferase reporter assay and RNA immunoprecipitation demonstrated that miR-2/13/71 bound to the protein coding sequence of Notch and downregulated its expression. Injection of miR-2/13/71 agomiRs led to significant decrease of Notch expression as well as markedly reduced levels of Vitellogenin mRNA, suppressed oocyte maturation and impaired ovarian growth. Moreover, the expression of miR-2/13/71 was repressed by juvenile hormone (JH). Our results thus point to a previously unidentified mechanism by which JH-repressed miR-2/13/71 coordinately downregulates Notch to modulate insect reproduction. The increase of JH and decrease of miR-2/13/71 expression in both previtellogenic and vitellogenic stages of adult females ensure a high level of Notch expression, critically contributing to JH-dependent vitellogenesis and oogenesis.