Drosophila dumpy is a gigantic extracellular protein required to maintain tension at epidermal-cuticle attachment sites

Elasticity of trachea in the silkworm: A role of gene BmMuc91C

Respiration is a vital process essential for organism survival, with most terrestrial insects relying on a sophisticated tubular tracheal network. In the current study, a gene with repetitive sequence was identified within the silkworm genome. Designated as BmMuc91C, it contains a dozen repeated motifs "PSSSYGAPX" and "GGYSSGGX" in its sequence. BmMuc91C exhibits specific expression in the tracheal system of silkworm larvae, with significantly higher expression levels during the molting stage. Overexpression of BmMuc91C in individual silkworms resulted in a marked increase in tracheal diameter, particularly during the molting stage. Immunofluorescence staining using a BmMuc91C antibody revealed a noticeable thickening of the apical extracellular matrix in the trachea. Tensile testing confirmed a considerable enhancement in tracheal elasticity. Additionally, a BmMuc91C mutation strain of silkworms was generated using the clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 system. Although no significant differences were observed in the growth, development, and molting of BmMuc91C mutant silkworms, mechanical tests demonstrated a decrease in tracheal elasticity. Transcriptomic techniques revealed that a significant number of cuticular and chitin-binding proteins were among the differentially expressed genes between mutant and wild-type silkworms. Furthermore, the recombined BmMuc91C protein was successfully expressed using the Escherichia coli system. Cross-linking experiments with horseradish peroxidase demonstrated the formation of macromolecular complexes of BmMuc91C, which exhibited spontaneous luminescent properties under ultraviolet light. This research sheds light on the role of elastic proteins in insect tracheae and provides valuable insights for the development of elastic biomaterials.

Adhesion and shrinkage transform the rounded pupal horn into an angular adult horn in Japanese rhinoceros beetle

Clarifying the mechanisms underlying shape alterations during insect metamorphosis is important for understanding exoskeletal morphogenesis. The large horn of the Japanese rhinoceros beetle Trypoxylus dichotomus is the result of drastic metamorphosis, wherein it appears as a rounded shape during pupation and then undergoes remodeling into an angular adult shape. However, the mechanical mechanisms underlying this remodeling process remain unknown. In this study, we investigated the remodeling mechanisms of the Japanese rhinoceros beetle horn by developing a physical simulation. We identified three factors contributing to remodeling by biological experiments - ventral adhesion, uneven shrinkage, and volume reduction - which were demonstrated to be crucial for transformation using a physical simulation. Furthermore, we corroborated our findings by applying the simulation to the mandibular remodeling of stag beetles. These results indicated that physical simulation applies to pupal remodeling in other beetles, and the morphogenic mechanism could explain various exoskeletal shapes.

Apical cell expansion maintained by Dusky-like establishes a scaffold for corneal lens morphogenesis

The Drosophila corneal lens is entirely composed of chitin and other apical extracellular matrix components, and it is not known how it acquires the biconvex shape that enables it to focus light onto the retina. We show here that the zona pellucida domain-containing protein Dusky-like is essential for normal corneal lens morphogenesis. Dusky-like transiently localizes to the expanded apical surfaces of the corneal lens-secreting cells and prevents them from undergoing apical constriction and apicobasal contraction. Dusky-like also controls the arrangement of two other zona pellucida domain proteins, Dumpy and Piopio, external to the developing corneal lens. Loss of either dusky-like or dumpy delays chitin accumulation and disrupts the outer surface of the corneal lens. We find that artificially inducing apical constriction by activating myosin contraction is sufficient to similarly alter chitin deposition and corneal lens morphology. These results demonstrate the importance of cell shape in controlling the morphogenesis of overlying apical extracellular matrix structures such as the corneal lens.

The zona pellucida protein piopio regulates the metamorphosis and reproduction in Tribolium castaneum

The zona pellucida domain protein piopio (Pio) was only reported to mediate the adhesion of the apical epithelial surface and the overlying apical extracellular matrix in Drosophila melanogaster, but the developmental roles of Pio were poorly understood in insects. To address this issue, we comprehensively analyzed the function of Pio in Tribolium castaneum. Phylogenetic analysis indicated that pio exhibited one-to-one orthologous relationship among insects. T. castaneum pio had a 1236-bp ORF and contained eight exons. During development pio was abundantly expressed from larva to adult and lowly expressed at the late stage of embryo and adult, while it had more transcripts in the head, epidermis, and gut but fewer in the fat body of late-stage larvae. Knockdown of pio inhibited the pupation, eclosion, and reproduction of T. castaneum. The expression of vitellogenin 1 (Vg1), Vg2, and Vg receptor (VgR) largely decreased in pio-silenced female adults. Silencing pio increased the 20-hydroxyecdysone titer by upregulating phm and spo expression but decreased the juvenile hormone (JH) titer through downregulating JHAMT3 and promoting JHE, JHEH-r4, and JHDK transcription. These results suggested that Pio might regulate the metamorphosis and reproduction via modulating the ecdysone and JH metabolism in T. castaneum. This study found the novel roles of pio in insect metamorphosis and reproduction, and provided the new insights for analyzing other zona pellucida proteins functions in insects.

High mechanical property silk produced by transgenic silkworms expressing the Drosophila Dumpy

Extensive research has been conducted on utilizing transgenic silkworms and their natural spinning apparatus to produce high-performance spider silk fibers. However, research on using non-spider biological proteins to optimize the molecular structure of silk protein and improve the mechanical performance of silk fibers is still relatively scarce. Dumpy, a massive extracellular matrix polypeptide, is essential for preserving the shape and structural integrity of the insect cuticle due to its remarkable tension and elasticity. Here, we constructed two transgenic donor plasmids containing the fusion genes of FibH-Dumpy and FibL-Dumpy. The results indicated the successful integration of two exogenous gene expression cassettes, driven by endogenous promoters, into the silkworm genome using piggyBac-mediated transgenic technology. Secondary structure analysis revealed a 16.7% and 13.6% increase in the β-sheet content of transgenic silks compared to wild-type (WT) silk fibers. Mechanical testing demonstrated that, compared to the WT, HDUY and LDUY transgenic silk fibers exhibited respective increases of 39.54% and 21.45% in maximum stress, 44.43% and 45.02% in toughness, and 24.91% and 28.51% in elastic recovery rate. These findings suggest that Drosophila Dumpy significantly enhanced the mechanical properties of silk, positioning it as an excellent candidate for the development of extraordinary-performance fibers. This study provides rich inspiration for using other biological proteins to construct high-performance silk fibers and expands the possibilities for designing and applying novel biomaterials.

Apical cell expansion maintained by Dusky-like establishes a scaffold for corneal lens morphogenesis

The biconvex shape of the Drosophila corneal lens, which enables it to focus light onto the retina, arises by organized assembly of chitin and other apical extracellular matrix components. We show here that the Zona Pellucida domain-containing protein Dusky-like is essential for normal corneal lens morphogenesis. Dusky-like transiently localizes to the expanded apical surfaces of the corneal lens-secreting cells, and in its absence, these cells undergo apical constriction and apicobasal contraction. Dusky-like also controls the arrangement of two other Zona Pellucida-domain proteins, Dumpy and Piopio, external to the developing corneal lens. Loss of either dusky-like or dumpy delays chitin accumulation and disrupts the outer surface of the corneal lens. Artificially inducing apical constriction with constitutively active Myosin light chain kinase is sufficient to similarly alter chitin deposition and corneal lens morphology. These results demonstrate the importance of cell shape for the morphogenesis of overlying apical extracellular matrix structures.

Developmental stage-specific proteome analysis of the legume pod borer Maruca vitrata provides insights on relevant proteins

The spotted pod borer, Maruca vitrata (Lepidoptera: Crambidae) is a destructive insect pest that inflicts significant productivity losses on important leguminous crops. Unravelling insect proteomes is vital to comprehend their fundamental molecular mechanisms. This research delved into the proteome profiles of four distinct stages -three larval and pupa of M. vitrata, utilizing LC-MS/MS label-free quantification-based methods. Employing comprehensive proteome analysis with fractionated datasets, we mapped 75 % of 3459 Drosophila protein orthologues out of which 2695 were identified across all developmental stages while, 137 and 94 were exclusive to larval and pupal stages respectively. Cluster analysis of 2248 protein orthologues derived from MaxQuant quantitative dataset depicted six clusters based on expression pattern similarity across stages. Consequently, gene ontology and protein-protein interaction network analyses using STRING database identified cluster 1 (58 proteins) and cluster 6 (25 proteins) associated with insect immune system and lipid metabolism. Furthermore, qRT-PCR-based expression analyses of ten selected proteins-coding genes authenticated the proteome data. Subsequently, functional validation of these chosen genes through gene silencing reduced their transcript abundance accompanied by a marked increase in mortality among dsRNA-injected larvae. Overall, this is a pioneering study to effectively develop a proteome atlas of M. vitrata as a potential resource for crop protection programs.

The proteolysis of ZP proteins is essential to control cell membrane structure and integrity of developing tracheal tubes in Drosophila

Membrane expansion integrates multiple forces to mediate precise tube growth and network formation. Defects lead to deformations, as found in diseases such as polycystic kidney diseases, aortic aneurysms, stenosis, and tortuosity. We identified a mechanism of sensing and responding to the membrane-driven expansion of tracheal tubes. The apical membrane is anchored to the apical extracellular matrix (aECM) and causes expansion forces that elongate the tracheal tubes. The aECM provides a mechanical tension that balances the resulting expansion forces, with Dumpy being an elastic molecule that modulates the mechanical stress on the matrix during tracheal tube expansion. We show in Drosophila that the zona pellucida (ZP) domain protein Piopio interacts and cooperates with the ZP protein Dumpy at tracheal cells. To resist shear stresses which arise during tube expansion, Piopio undergoes ectodomain shedding by the Matriptase homolog Notopleural, which releases Piopio-Dumpy-mediated linkages between membranes and extracellular matrix. Failure of this process leads to deformations of the apical membrane, tears the apical matrix, and impairs tubular network function. We also show conserved ectodomain shedding of the human TGFβ type III receptor by Notopleural and the human Matriptase, providing novel findings for in-depth analysis of diseases caused by cell and tube shape changes.

Hormonal gatekeeping via the blood-brain barrier governs caste-specific behavior in ants

Here, we reveal an unanticipated role of the blood-brain barrier (BBB) in regulating complex social behavior in ants. Using scRNA-seq, we find localization in the BBB of a key hormone-degrading enzyme called juvenile hormone esterase (Jhe), and we show that this localization governs the level of juvenile hormone (JH3) entering the brain. Manipulation of the Jhe level reprograms the brain transcriptome between ant castes. Although ant Jhe is retained and functions intracellularly within the BBB, we show that Drosophila Jhe is naturally extracellular. Heterologous expression of ant Jhe into the Drosophila BBB alters behavior in fly to mimic what is seen in ants. Most strikingly, manipulation of Jhe levels in ants reprograms complex behavior between worker castes. Our study thus uncovers a remarkable, potentially conserved role of the BBB serving as a molecular gatekeeper for a neurohormonal pathway that regulates social behavior.

Hypoxia-induced tracheal elasticity in vector beetle facilitates the loading of pinewood nematode

Many pathogens rely on their insect vectors for transmission. Such pathogens are under selection to improve vector competence for their transmission by employing various tissue or cellular responses of vectors. However, whether pathogens can actively cause hypoxia in vectors and exploit hypoxia responses to promote their vector competence is still unknown. Fast dispersal of pinewood nematode (PWN), the causal agent for the destructive pine wilt disease and subsequent infection of pine trees, is characterized by the high vector competence of pine sawyer beetles (Monochamus spp.), and a single beetle can harbor over 200,000 PWNs in its tracheal system. Here, we demonstrate that PWN loading activates hypoxia in tracheal system of the vector beetles. Both PWN loading and hypoxia enhanced tracheal elasticity and thickened the apical extracellular matrix (aECM) of the tracheal tubes while a notable upregulated expression of a resilin-like mucin protein Muc91C was observed at the aECM layer of PWN-loaded and hypoxic tracheal tubes. RNAi knockdown of Muc91C reduced tracheal elasticity and aECM thickness under hypoxia conditions and thus decreasing PWN loading. Our study suggests a crucial role of hypoxia-induced developmental responses in shaping vector tolerance to the pathogen and provides clues for potential molecular targets to control pathogen dissemination.

The Osiris family genes function as novel regulators of the tube maturation process in the Drosophila trachea

Drosophila trachea is a premier model to study tube morphogenesis. After the formation of continuous tubes, tube maturation follows. Tracheal tube maturation starts with an apical secretion pulse that deposits extracellular matrix components to form a chitin-based apical luminal matrix (aECM). This aECM is then cleared and followed by the maturation of taenidial folds. Finally, air fills the tubes. Meanwhile, the cellular junctions are maintained to ensure tube integrity. Previous research has identified several key components (ER, Golgi, several endosomes) of protein trafficking pathways that regulate the secretion and clearance of aECM, and the maintenance of cellular junctions. The Osiris (Osi) gene family is located at the Triplo-lethal (Tpl) locus on chromosome 3R 83D4-E3 and exhibits dosage sensitivity. Here, we show that three Osi genes (Osi9, Osi15, Osi19), function redundantly to regulate adherens junction (AJ) maintenance, luminal clearance, taenidial fold formation, tube morphology, and air filling during tube maturation. The localization of Osi proteins in endosomes (Rab7-containing late endosomes, Rab11-containing recycling endosomes, Lamp-containing lysosomes) and the reduction of these endosomes in Osi mutants suggest the possible role of Osi genes in tube maturation through endosome-mediated trafficking. We analyzed tube maturation in zygotic rab11 and rab7 mutants, respectively, to determine whether endosome-mediated trafficking is required. Interestingly, similar tube maturation defects were observed in rab11 but not in rab7 mutants, suggesting the involvement of Rab11-mediated trafficking, but not Rab7-mediated trafficking, in this process. To investigate whether Osi genes regulate tube maturation primarily through the maintenance of Rab11-containing endosomes, we overexpressed rab11 in Osi mutant trachea. Surprisingly, no obvious rescue was observed. Thus, increasing endosome numbers is not sufficient to rescue tube maturation defects in Osi mutants. These results suggest that Osi genes regulate other aspects of endosome-mediated trafficking, or regulate an unknown mechanism that converges or acts in parallel with Rab11-mediated trafficking during tube maturation.

Developmental origin of tendon diversity in Drosophila melanogaster

Myogenesis is a developmental process that is largely conserved in both Drosophila and higher organisms. Consequently, the fruit fly is an excellent in vivo model for identifying the genes and mechanisms involved in muscle development. Moreover, there is growing evidence indicating that specific conserved genes and signaling pathways govern the formation of tissues that connect the muscles to the skeleton. In this review, we present an overview of the different stages of tendon development, from the specification of tendon progenitors to the assembly of a stable myotendinous junction across three different myogenic contexts in Drosophila: larval, flight and leg muscle development. We underline the different aspects of tendon cell specification and differentiation in embryo and during metamorphosis that result into tendon morphological and functional diversity.

Tissue flow regulates planar cell polarity independently of the Frizzled core pathway

Planar cell polarity (PCP) regulates the orientation of external structures. A core group of proteins that includes Frizzled forms the heart of the PCP regulatory system. Other PCP mechanisms that are independent of the core group likely exist, but their underlying mechanisms are elusive. Here, we show that tissue flow is a mechanism governing core group-independent PCP on the Drosophila notum. Loss of core group function only slightly affects bristle orientation in the adult central notum. This near-normal PCP results from tissue flow-mediated rescue of random bristle orientation during the pupal stage. Manipulation studies suggest that tissue flow can orient bristles in the opposite direction to the flow. This process is independent of the core group and implies that the apical extracellular matrix functions like a "comb" to align bristles. Our results reveal the significance of cooperation between tissue dynamics and extracellular substances in PCP establishment.

Crustacean leg regeneration restores complex microanatomy and cell diversity

Animals can regenerate complex organs, yet this process frequently results in imprecise replicas of the original structure. In the crustacean Parhyale, embryonic and regenerating legs differ in gene expression dynamics but produce apparently similar mature structures. We examine the fidelity of Parhyale leg regeneration using complementary approaches to investigate microanatomy, sensory function, cellular composition, and cell molecular profiles. We find that regeneration precisely replicates the complex microanatomy and spatial distribution of external sensory organs and restores their sensory function. Single-nuclei sequencing shows that regenerated and uninjured legs are indistinguishable in terms of cell-type composition and transcriptional profiles. This remarkable fidelity highlights the ability of organisms to achieve identical outcomes via distinct processes.

A single-cell transcriptomic atlas of complete insect nervous systems across multiple life stages

Molecular profiles of neurons influence neural development and function but bridging the gap between genes, circuits, and behavior has been very difficult. Here we used single cell RNAseq to generate a complete gene expression atlas of the Drosophila larval central nervous system composed of 131,077 single cells across three developmental stages (1 h, 24 h and 48 h after hatching). We identify 67 distinct cell clusters based on the patterns of gene expression. These include 31 functional mature larval neuron clusters, 1 ring gland cluster, 8 glial clusters, 6 neural precursor clusters, and 13 developing immature adult neuron clusters. Some clusters are present across all stages of larval development, while others are stage specific (such as developing adult neurons). We identify genes that are differentially expressed in each cluster, as well as genes that are differentially expressed at distinct stages of larval life. These differentially expressed genes provide promising candidates for regulating the function of specific neuronal and glial types in the larval nervous system, or the specification and differentiation of adult neurons. The cell transcriptome Atlas of the Drosophila larval nervous system is a valuable resource for developmental biology and systems neuroscience and provides a basis for elucidating how genes regulate neural development and function.

JiangShi(僵尸): a widely distributed Mucin-like protein essential for Drosophila development

Epithelia exposed to elements of the environment are protected by a mucus barrier in mammals. This barrier also serves to lubricate during organ movements and to mediate substance exchanges between the environmental milieu and internal organs. A major component of the mucus barrier is a class of glycosylated proteins called Mucin. Mucin and mucin-related proteins are widely present in the animal kingdom. Mucin mis-regulation has been reported in many diseases such as cancers and ones involving the digestive and respiratory tracts. Although the biophysical properties of isolated Mucins have been extensively studied, in vivo models remain scarce for the study of their functions and regulations. Here, we characterize the Mucin-like JiangShi protein and its mutations in the fruit fly Drosophila. JiangShi is an extracellular glycoprotein with domain features reminiscent of mammalian nonmembranous Mucins, and one of the most widely distributed Mucin-like proteins studied in Drosophila. Both loss and over-production of JiangShi lead to terminal defects in adult structures and organismal death. Although the physiological function of JiangShi remains poorly defined, we present a genetically tractable model system for the in vivo studies of Mucin-like molecules.

Chitin deacetylases are necessary for insect femur muscle attachment and mobility

We show that interfering with insect chitin deacetylation by down-regulation of specific chitin deacetylase (CDA) isoforms, belonging to subfamily group I, causes breakage of the chitinous internal tendon cuticle at the femur–tibia joint, muscle detachment from both internal and external tendon cells, and defective locomotion. Our studies reveal a previously unrecognized role of CDA-like proteins in cooperation with zona pellucida domain-containing proteins in musculoskeletal connectivity, maintenance of tendon cell microtubule integrity, muscle force transmission, limb movement, and locomotion. We propose an essential function for group I CDAs, which are highly conserved among insect and other arthropod species, in invertebrate musculoskeletal connectivity involving partially deacetylated chitin in the extracellular matrix overlying the tendon cells.

Muscle attachment sites (MASs, apodemes) in insects and other arthropods involve specialized epithelial cells, called tendon cells or tenocytes, that adhere to apical extracellular matrices containing chitin. Here, we have uncovered a function for chitin deacetylases (CDAs) in arthropod locomotion and muscle attachment using a double-stranded RNA-mediated gene-silencing approach targeted toward specific CDA isoforms in the red flour beetle, Tribolium castaneum (Tc). Depletion of TcCDA1 or the alternatively spliced TcCDA2 isoform, TcCDA2a, resulted in internal tendon cuticle breakage at the femur–tibia joint, muscle detachment from both internal and external tendon cells, and defective locomotion. TcCDA deficiency did not affect early muscle development and myofiber growth toward the cuticular MASs but instead resulted in aborted microtubule development, loss of hemiadherens junctions, and abnormal morphology of tendon cells, all features consistent with a loss of tension within and between cells. Moreover, simultaneous depletion of TcCDA1 or TcCDA2a and the zona pellucida domain protein, TcDumpy, prevented the internal tendon cuticle break, further supporting a role for force-dependent interactions between muscle and tendon cells. We propose that in T. castaneum, the absence of N-acetylglucosamine deacetylation within chitin leads to a loss of microtubule organization and reduced membrane contacts at MASs in the femur, which adversely affect musculoskeletal connectivity, force transmission, and physical mobility.

Drosophila Trachea as a Novel Model of COPD

COPD, a chronic obstructive pulmonary disease, is one of the leading causes of death worldwide. Clinical studies and research in rodent models demonstrated that failure of repair mechanisms to cope with increased ROS and inflammation in the lung leads to COPD. Despite this progress, the molecular mechanisms underlying the development of COPD remain poorly understood, resulting in a lack of effective treatments. Thus, an informative, simple model is highly valued and desired. Recently, the cigarette smoke-induced Drosophila COPD model showed a complex set of pathological phenotypes that resemble those seen in human COPD patients. The Drosophila trachea has been used as a premier model to reveal the mechanisms of tube morphogenesis. The association of these mechanisms to structural changes in COPD can be analyzed by using Drosophila trachea. Additionally, the timeline of structural damage, ROS, and inflammation can be studied in live organisms using fluorescently-tagged proteins. The related function of human COPD genes identified by GWAS can be screened using respective fly homologs. Finally, the Drosophila trachea can be used as a high-throughput drug screening platform to identify novel treatments for COPD. Therefore, Drosophila trachea is an excellent model that is complementary to rodent COPD models.

A docked mutation phenocopies dumpy oblique alleles via altered vesicle trafficking

The Drosophila extracellular matrix protein Dumpy (Dpy) is one of the largest proteins encoded by any animal. One class of dpy mutations produces a characteristic shortening of the wing blade known as oblique (dpy^o ), due to altered tension in the developing wing. We describe here the characterization of docked (doc), a gene originally named because of an allele producing a truncated wing. We show that doc corresponds to the gene model CG5484, which encodes a homolog of the yeast protein Yif1 and plays a key role in ER to Golgi vesicle transport. Genetic analysis is consistent with a similar role for Doc in vesicle trafficking: docked alleles interact not only with genes encoding the COPII core proteins sec23 and sec13, but also with the SNARE proteins synaptobrevin and syntaxin. Further, we demonstrate that the strong similarity between the doc¹ and dpy^o wing phenotypes reflects a functional connection between the two genes; we found that various dpy alleles are sensitive to changes in dosage of genes encoding other vesicle transport components such as sec13 and sar1. Doc's effects on trafficking are not limited to Dpy; for example, reduced doc dosage disturbed Notch pathway signaling during wing blade and vein development. These results suggest a model in which the oblique wing phenotype in doc¹ results from reduced transport of wild-type Dumpy protein; by extension, an additional implication is that the dpy^o alleles can themselves be explained as hypomorphs.

Mechano-chemical enforcement of tendon apical ECM into nano-filaments during Drosophila flight muscle development

Contractile tension is critical for musculoskeletal system development and maintenance. In insects, the muscular force is transmitted to the exoskeleton through the tendon cells and tendon apical extracellular matrix (ECM). In Drosophila, we found tendon cells secrete Dumpy (Dpy), a zona pellucida domain (ZPD) protein, to form the force-resistant filaments in the exuvial space, anchoring the tendon cells to the pupal cuticle. We showed that Dpy undergoes filamentous conversion in response to the tension increment during indirect flight muscle development. We also found another ZPD protein Quasimodo (Qsm) protects the notum epidermis from collapsing under the muscle tension by enhancing the tensile strength of Dpy filaments. Qsm is co-transported with Dpy in the intracellular vesicles and diffuses into the exuvial space after secretion. Tissue-specific qsm expression rescued the qsm mutant phenotypes in distant tissues, suggesting Qsm can function in a long-range, non-cell-autonomous manner. In the cell culture assay, Qsm interacts with Dpy-ZPD and promotes secretion and polymerization of Dpy-ZPD. The roles of Qsm underlies the positive feedback mechanism of force-dependent organization of Dpy filaments, providing new insights into apical ECM remodeling through the unconventional interaction of ZPD proteins.

Mechanobiology: Forging a strong matrix at tendons

Nature faces the challenge of stably attaching soft muscles to a stiff skeleton. A new study combines live imaging and fly genetics to reveal that mechanical tension and a putative intracellular chaperone assist in assembling the gigantic extracellular matrix protein Dumpy at fly tendon-skeleton interfaces.

Temperature, rainfall and wind variables underlie environmental adaptation in natural populations of Drosophila melanogaster

While several studies in a diverse set of species have shed light on the genes underlying adaptation, our knowledge on the selective pressures that explain the observed patterns lags behind. Drosophila melanogaster is a valuable organism to study environmental adaptation because this species originated in Southern Africa and has recently expanded worldwide, and also because it has a functionally well-annotated genome. In this study, we aimed to decipher which environmental variables are relevant for adaptation of D. melanogaster natural populations in Europe and North America. We analysed 36 whole-genome pool-seq samples of D. melanogaster natural populations collected in 20 European and 11 North American locations. We used the BayPass software to identify single nucleotide polymorphisms (SNPs) and transposable elements (TEs) showing signature of adaptive differentiation across populations, as well as significant associations with 59 environmental variables related to temperature, rainfall, evaporation, solar radiation, wind, daylight hours, and soil type. We found that in addition to temperature and rainfall, wind related variables are also relevant for D. melanogaster environmental adaptation. Interestingly, 23%-51% of the genes that showed significant associations with environmental variables were not found overly differentiated across populations. In addition to SNPs, we also identified 10 reference transposable element insertions associated with environmental variables. Our results showed that genome-environment association analysis can identify adaptive genetic variants that are undetected by population differentiation analysis while also allowing the identification of candidate environmental drivers of adaptation.

From genes to shape during metamorphosis: a history

Metamorphosis (Greek for a state of transcending-form or change-in-shape) refers to a dramatic transformation of an animal's body structure that occurs after development of the embryo or larva in many species. The development of a fly (or butterfly) from a crawling larva (or caterpillar) that forms a pupa (or chrysalis) before eclosing as a flying adult is a classic example of metamorphosis that captures the imagination and has been immortalized in children's books. Powerful genetic experiments in the fruit fly Drosophila melanogaster have revealed how genes can instruct the behaviour of individual cells to control patterns of tissue growth, mechanical force, cell-cell adhesion and cell-matrix adhesion drive morphogenetic change in epithelial tissues. Together, the distribution of mass, force and resistance determines cell shape changes, cell-cell rearrangements, and/or the orientation of cell divisions to generate the final form of the tissue. In organising tissue shape, genes harness the power of self-organisation to determine the collective behaviour of molecules and cells, which can often be reproduced in computer simulations of cell polarity and/or tissue mechanics. This review highlights fundamental discoveries in epithelial morphogenesis made by pioneers who were fascinated by metamorphosis, including D'Arcy Thompson, Conrad Waddington, Dianne Fristrom and Antonio Garcia-Bellido.

Crucial role of framework with cytoskeletal actin filaments for shaping microstructure of footpad setae in the ladybird beetle, Harmonia axyridis

Insects that can walk on smooth surfaces have specialized structures, footpads, on their legs. Footpads play an important role in adhesion to the substrate surface. Although the morphology and function of footpads have been studied, the mechanism of their formation is still elusive. In the ladybird beetle (Harmonia axyridis), hairy footpads are present on the first and second tarsal segments of the legs. The footpads are covered with hundreds of hairs, i.e. setae, whose tips consist of four types: pointed, lanceolate, spatular, and discoidal. We examined the formation of the footpad during the pupal stage using immuno-staining and fluorescent-conjugated phalloidin staining. We found that a seta was composed of a shaft and a socket and some setae were accompanied by a neuron. By the mid-pupal stages, the shaft cells elongated to form a setal structure. Cytoskeletal actin bundles ramified to create a framework for the setal tip structure of the cells. We examined the effects of the application of cytochalasin D, which inhibits actin polymerization, on the formation of footpad setal structures. The results showed that the setal tips were deformed by the inhibition of actin polymerization. Our observations reveal that cytoskeletal actin filaments are involved in shaping the setae.

Sculpting new structures

The origins of the posterior lobe, a recently evolved structure in some species of Drosophila, have become clearer.

The bicistronic gene würmchen encodes two essential components for epithelial development in Drosophila

Epithelial tissues are fundamental for the establishment and maintenance of different body compartments in multicellular animals. To achieve this specific task epithelial sheets secrete an apical extracellular matrix for tissue strength and protection and they organize a transepithelial barrier function, which is mediated by tight junctions in vertebrates or septate junctions in invertebrates. Here, we show that the bicistronic gene würmchen is functionally expressed in epithelial tissues. CRISPR/Cas9-mediated mutations in both coding sequences reveal two essential polypeptides, Würmchen1 and Würmchen2, which are both necessary for normal epithelial tissue development. Würmchen1 represents a genuine septate junction core component. It is required during embryogenesis for septate junction organization, the establishment of a transepithelial barrier function, distinct cellular transport processes and tracheal system morphogenesis. Würmchen2 is localized in the apical membrane region of epithelial tissues and in a central core of the tracheal lumen during embryogenesis. It is essential during the later larval development.

Evolutionary expansion of apical extracellular matrix is required for the elongation of cells in a novel structure

One of the fundamental gaps in our knowledge of how novel anatomical structures evolve is understanding the origins of the morphogenetic processes that form these features. Here, we traced the cellular development of a recently evolved morphological novelty, the posterior lobe of D. melanogaster. We found that this genital outgrowth forms through extreme increases in epithelial cell height. By examining the apical extracellular matrix (aECM), we also uncovered a vast matrix associated with the developing genitalia of lobed and non-lobed species. Expression of the aECM protein Dumpy is spatially expanded in lobe-forming species, connecting the posterior lobe to the ancestrally derived aECM network. Further analysis demonstrated that Dumpy attachments are necessary for cell height increases during posterior lobe development. We propose that the aECM presents a rich reservoir for generating morphological novelty and highlights a yet unseen role for aECM in regulating extreme cell height.

Pesticide contamination drives adaptive genetic variation in the endemic mayfly Andesiops torrens within a semi-arid agricultural watershed of Chile

Agrichemical contamination can provoke evolutionary responses in freshwater populations. It is a particularly relevant issue in semi-arid regions due to the sensitivity of endemic species to pollutants and to interactions with temperature stress. This paper investigates the presence of pesticides in rivers within a semi-arid agricultural watershed of Chile, testing for their effects on population genetic characteristics of the endemic mayfly Andesiops torrens (Insecta, Ephemeroptera). Pesticides were detected in sediment samples in ten out of the 30 sites analyzed throughout the upper part of the Limarí watershed. To study the evolutionary impact of such contamination on A. torrens, we used a genome-wide approach and analyzed 2056 single nucleotide polymorphisms (SNPs) loci in 551 individuals from all sites. Genetic differentiation was weak between populations, suggesting high gene flow across the study area. While we did not find evidence of pesticide effects on genetic diversity nor on population differentiation, the allele frequency of three outlier SNP loci correlated significantly with pesticide occurrence. Interrogation of genomic resources indicates that two of these SNPs are located within functional genes that encode for the low-density lipoprotein receptor-related protein 2 and Dumpy, both potentially involved in insect cuticle resistance processes. Such genomic signatures of local adaptation are indicative of past adverse effects of pesticide exposure on the locally adapted populations. Our results reveal that A. torrens is sensitive to pesticide exposure, but that a high gene flow may confer resilience to contamination. This research supports the contention that A. torrens is an ideal model organism to study evolutionary responses induced by pesticides on non-target, endemic species.

Comparative proteomics of stenotopic caddisfly Crunoecia irrorata identifies acclimation strategies to warming

Species' ecological preferences are often deduced from habitat characteristics thought to represent more or less optimal conditions for physiological functioning. Evolution has led to stenotopic and eurytopic species, the former having decreased niche breadths and lower tolerances to environmental variability. Species inhabiting freshwater springs are often described as being stenotopic specialists, adapted to the stable thermal conditions found in these habitats. Whether due to past local adaptation these species have evolved or have lost intra-generational adaptive mechanisms to cope with increasing thermal variability has, to our knowledge, never been investigated. By studying how the proteome of a stenotopic species changes as a result of increasing temperatures, we investigate if the absence or attenuation of molecular mechanisms is indicative of local adaptation to freshwater springs. An understanding of compensatory mechanisms is especially relevant as spring specialists will experience thermal conditions beyond their physiological limits due to climate change. In this study, the stenotopic species Crunoecia irrorata (Trichoptera: Lepidostomatidae, Curtis 1834) was acclimated to 10, 15 and 20°C for 168 hr. We constructed a homology-based database and via liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based shotgun proteomics identified 1,358 proteins. Differentially abundant proteins and protein norms of reaction revealed candidate proteins and molecular mechanisms facilitating compensatory responses such as trehalose metabolism, tracheal system alteration and heat-shock protein regulation. A species-specific understanding of compensatory physiologies challenges the characterization of species as having narrow tolerances to environmental variability if that characterization is based on occurrences and habitat characteristics alone.

Egf-like gene is essential for cuticle metabolism in the brown planthopper

Using the mass spectrometry analysis of cuticle casts of brown planthopper (BPH, Nilaparvata lugens) and transcriptome analysis of BPH tissues, we identified a gigantic gene (50,922 bp, 16,973 aa) tentatively called Nlegf-like. Multiple transcripts were found. Nlegf-like encodes an integral membrane protein of 16,973 amino acid residues with 260 EGF-like repeats and 16 Ca²⁺-binding EGF repeats type (cbEGFs) in the extracellular portion. Nlegf-like was highly expressed in the integument and tended to peak at the middle stage or late stage of each nymph instar. Phylogenetic analysis showed this gene is conserved in many other insects. Different double-stranded RNA-mediated RNA interference targeting eight different regions of the Nlegf-like gene resulted in abnormal cuticle formation or molting and lethal phenotypes. Transmission electron microscopy revealed that the newly formed endocuticle was significantly thinner for RNAi-treated BPHs with phenotype of contracted abdomen, or the old cuticle could not be digested sufficiently for those with phenotype of slender body shape or died with molting difficulty when compared with the control group. We suggest that the Nlegf-like is crucial for metabolism of the cuticle in BPH molting.

Effects of Bombyx mori nuclear polyhedrosis virus on serpin and antibacterial peptide expression in B. mori

The silkworm (Bombyx mori) is a typical and economically important lepidopteran species, and research has resulted in the development and accumulation of breeding lines. Studies of immune-related silkworm genes not only promote our understanding of silkworm immune response mechanisms, but they also inform insect immune molecular diversity research. Here, silkworm proteins were screened using proteomics after Bombyx mori nuclear polyhedrosis virus (BmNPV) infection, and 2368 silkworm proteins were identified, including six antimicrobial peptides and 12 serpins. The mRNA expression levels of these 18 proteins were examined at different times. The results indicated that attacin had the highest expression level, while serpin-5 and cecropin-D exhibited a negative regulatory correlation. These results provide a significant step toward a deeper understanding of B. mori immunoregulation.

Morphogenesis of neurons and glia within an epithelium

To sense the outside world, some neurons protrude across epithelia, the cellular barriers that line every surface of our bodies. To study the morphogenesis of such neurons, we examined the C. elegans amphid, in which dendrites protrude through a glial channel at the nose. During development, amphid dendrites extend by attaching to the nose via DYF-7, a type of protein typically found in epithelial apical ECM. Here, we show that amphid neurons and glia exhibit epithelial properties, including tight junctions and apical-basal polarity, and develop in a manner resembling other epithelia. We find that DYF-7 is a fibril-forming apical ECM component that promotes formation of the tube-shaped glial channel, reminiscent of roles for apical ECM in other narrow epithelial tubes. We also identify a requirement for FRM-2, a homolog of EPBL15/moe/Yurt that promotes epithelial integrity in other systems. Finally, we show that other environmentally exposed neurons share a requirement for DYF-7. Together, our results suggest that these neurons and glia can be viewed as part of an epithelium continuous with the skin, and are shaped by mechanisms shared with other epithelia.

Epithelial Viscoelasticity Is Regulated by Mechanosensitive E-cadherin Turnover

Studying how epithelia respond to mechanical stresses is key to understanding tissue shape changes during morphogenesis. Here, we study the viscoelastic properties of the Drosophila wing epithelium during pupal morphogenesis by quantifying mechanical stress and cell shape as a function of time. We find a delay of 8 h between maximal tissue stress and maximal cell elongation, indicating a viscoelastic deformation of the tissue. We show that this viscoelastic behavior emerges from the mechanosensitivity of endocytic E-cadherin turnover. The increase in E-cadherin turnover in response to stress is mediated by mechanosensitive relocalization of the E-cadherin binding protein p120-catenin (p120) from cell junctions to cytoplasm. Mechanosensitivity of E-cadherin turnover is lost in p120 mutant wings, where E-cadherin turnover is constitutively high. In this mutant, the relationship between mechanical stress and stress-dependent cell dynamics is altered. Cells in p120 mutant deform and undergo cell rearrangements oriented along the stress axis more rapidly in response to mechanical stress. These changes imply a lower viscosity of wing epithelium. Taken together, our findings reveal that p120-dependent mechanosensitive E-cadherin turnover regulates viscoelastic behavior of epithelial tissues.

Conserved function of the matriptase-prostasin proteolytic cascade during epithelial morphogenesis

Extracellular matrix (ECM) assembly and remodelling is critical during development and organ morphogenesis. Dysregulation of ECM is implicated in many pathogenic conditions, including cancer. The type II transmembrane serine protease matriptase and the serine protease prostasin are key factors in a proteolytic cascade that regulates epithelial ECM differentiation during development in vertebrates. Here, we show by rescue experiments that the Drosophila proteases Notopleural (Np) and Tracheal-prostasin (Tpr) are functional homologues of matriptase and prostasin, respectively. Np mediates morphogenesis and remodelling of apical ECM during tracheal system development and is essential for maintenance of the transepithelial barrier function. Both Np and Tpr degrade the zona pellucida-domain (ZP-domain) protein Dumpy, a component of the transient tracheal apical ECM. Furthermore, we demonstrate that Tpr zymogen and the ZP domain of the ECM protein Piopio are cleaved by Np and matriptase in vitro. Our data indicate that the evolutionarily conserved ZP domain, present in many ECM proteins of vertebrates and invertebrates, is a novel target of the conserved matriptase-prostasin proteolytic cascade.

Epithelial tissue covers the outside of the animal body and lines internal organs. Its disorganization is the source of approximately 90% of all human cancers. Elaboration of the basic epithelial characteristics has led to an understanding of how complex structures such as the branched tubular networks of vertebrate lung or invertebrate tracheal system are organized. Aside from obvious morphological differences, specific compositions of the epithelial extracellular matrix (ECM) have been noted. For example, while the flexible ECM of the vertebrate skin mainly consists of collagen and elastic fibers, the rigid ECM of invertebrates is chitin-based to serve as an inflexible exoskeleton. We show that a central regulator of ECM differentiation and epithelial development in vertebrates, the matriptase-prostasin proteolytic cascade (MPPC), is conserved and essential for both Drosophila ECM morphogenesis and physiology. The functionally conserved components of the MPPC mediate cleavage of zona pellucida-domain (ZP-domain) proteins, which play crucial roles in organizing apical structures of the ECM in both vertebrates and invertebrates. Our data indicate that ZP-proteins are molecular targets of the conserved MPPC and that cleavage within the ZP-domains is a conserved mechanism of ECM development and differentiation.

Trynity controls epidermal barrier function and respiratory tube maturation in Drosophila by modulating apical extracellular matrix nano-patterning

The outer surface of insects is covered by the cuticle, which is derived from the apical extracellular matrix (aECM). The aECM is secreted by epidermal cells during embryogenesis. The aECM exhibits large variations in structure, function, and constituent molecules, reflecting the enormous diversity in insect appearances. To investigate the molecular principles of aECM organization and function, here we studied the role of a conserved aECM protein, the ZP domain protein Trynity, in Drosophila melanogaster. We first identified trynity as an essential gene for epidermal barrier function. trynity mutation caused disintegration of the outermost envelope layer of the cuticle, resulting in small-molecule leakage and in growth and molting defects. In addition, the tracheal tubules of trynity mutants showed defects in pore-like structures of the cuticle, and the mutant tracheal cells failed to absorb luminal proteins and liquid. Our findings indicated that trynity plays essential roles in organizing nano-level structures in the envelope layer of the cuticle that both restrict molecular trafficking through the epidermis and promote the massive absorption pulse in the trachea.

Development and Function of the Drosophila Tracheal System

The tracheal system of insects is a network of epithelial tubules that functions as a respiratory organ to supply oxygen to various target organs. Target-derived signaling inputs regulate stereotyped modes of cell specification, branching morphogenesis, and collective cell migration in the embryonic stage. In the postembryonic stages, the same set of signaling pathways controls highly plastic regulation of size increase and pattern elaboration during larval stages, and cell proliferation and reprograming during metamorphosis. Tracheal tube morphogenesis is also regulated by physicochemical interaction of the cell and apical extracellular matrix to regulate optimal geometry suitable for air flow. The trachea system senses both the external oxygen level and the metabolic activity of internal organs, and helps organismal adaptation to changes in environmental oxygen level. Cellular and molecular mechanisms underlying the high plasticity of tracheal development and physiology uncovered through research on Drosophila are discussed.

Cell polarity: having and making sense of direction-on the evolutionary significance of the primary cilium/centrosome organ in Metazoa

Cell-autonomous polarity in Metazoans is evolutionarily conserved. I assume that permanent polarity in unicellular eukaryotes is required for cell motion and sensory reception, integration of these two activities being an evolutionarily constrained function. Metazoans are unique in making cohesive multicellular organisms through complete cell divisions. They evolved a primary cilium/centrosome (PC/C) organ, ensuring similar functions to the basal body/flagellum of unicellular eukaryotes, but in different cells, or in the same cell at different moments. The possibility that this innovation contributed to the evolution of individuality, in being instrumental in the early specification of the germ line during development, is further discussed. Then, using the example of highly regenerative organisms like planarians, which have lost PC/C organ in dividing cells, I discuss the possibility that part of the remodelling necessary to reach a new higher-level unit of selection in multi-cellular organisms has been triggered by conflicts among individual cell polarities to reach an organismic polarity. Finally, I briefly consider organisms with a sensorimotor organ like the brain that requires exceedingly elongated polarized cells for its activity. I conclude that beyond critical consequences for embryo development, the conservation of cell-autonomous polarity in Metazoans had far-reaching implications for the evolution of individuality.

The Drosophila Hox gene Ultrabithorax controls appendage shape by regulating extracellular matrix dynamics

Although the specific form of an organ is frequently important for its function, the mechanisms underlying organ shape are largely unknown. In Drosophila, the wings and halteres, homologous appendages of the second and third thoracic segments, respectively, bear different forms: wings are flat, whereas halteres are globular, and yet both characteristic shapes are essential for a normal flight. The Hox gene Ultrabithorax (Ubx) governs the difference between wing and haltere development, but how Ubx function in the appendages prevents or allows flat or globular shapes is unknown. Here, we show that Ubx downregulates Matrix metalloproteinase 1 (Mmp1) expression in the haltere pouch at early pupal stage, which in turn prevents the rapid clearance of Collagen IV compared with the wing disc. This difference is instrumental in determining cell shape changes, expansion of the disc and apposition of dorsal and ventral layers, all of these phenotypic traits being characteristic of wing pouch development. Our results suggest that Ubx regulates organ shape by controlling Mmp1 expression, and the extent and timing of extracellular matrix degradation.

Apical and Basal Matrix Remodeling Control Epithelial Morphogenesis

Epithelial tissues can elongate in two dimensions by polarized cell intercalation, oriented cell division, or cell shape change, owing to local or global actomyosin contractile forces acting in the plane of the tissue. In addition, epithelia can undergo morphogenetic change in three dimensions. We show that elongation of the wings and legs of Drosophila involves a columnar-to-cuboidal cell shape change that reduces cell height and expands cell width. Remodeling of the apical extracellular matrix by the Stubble protease and basal matrix by MMP1/2 proteases induces wing and leg elongation. Matrix remodeling does not occur in the haltere, a limb that fails to elongate. Limb elongation is made anisotropic by planar polarized Myosin-II, which drives convergent extension along the proximal-distal axis. Subsequently, Myosin-II relocalizes to lateral membranes to accelerate columnar-to-cuboidal transition and isotropic tissue expansion. Thus, matrix remodeling induces dynamic changes in actomyosin contractility to drive epithelial morphogenesis in three dimensions.

The Complex Demographic History and Evolutionary Origin of the Western Honey Bee, Apis Mellifera

The western honey bee, Apis mellifera, provides critical pollination services to agricultural crops worldwide. However, despite substantial interest and prior investigation, the early evolution and subsequent diversification of this important pollinator remain uncertain. The primary hypotheses place the origin of A. mellifera in either Asia or Africa, with subsequent radiations proceeding from one of these regions. Here, we use two publicly available whole-genome data sets plus newly sequenced genomes and apply multiple population genetic analysis methods to investigate the patterns of ancestry and admixture in native honey bee populations from Europe, Africa, and the Middle East. The combination of these data sets is critical to the analyses, as each contributes samples from geographic locations lacking in the other, thereby producing the most complete set of honey bee populations available to date. We find evidence supporting an origin of A. mellifera in the Middle East or North Eastern Africa, with the A and Y lineages representing the earliest branching lineages. This finding has similarities with multiple contradictory hypotheses and represents a disentangling of genetic relationships, geographic proximity, and secondary contact to produce a more accurate picture of the origins of A. mellifera. We also investigate how previous studies came to their various conclusions based on incomplete sampling of populations, and illustrate the importance of complete sampling in understanding evolutionary processes. These results provide fundamental knowledge about genetic diversity within Old World honey bee populations and offer insight into the complex history of an important pollinator.

Dual function for Tango1 in secretion of bulky cargo and in ER-Golgi morphology

Tango1 enables ER-to-Golgi trafficking of large proteins. We show here that loss of Tango1, in addition to disrupting protein secretion and ER/Golgi morphology, causes ER stress and defects in cell shape. We find that the previously observed dependence of smaller cargos on Tango1 is a secondary effect. If large cargos like Dumpy, which we identify as a Tango1 cargo, are removed from the cell, nonbulky proteins reenter the secretory pathway. Removal of blocking cargo also restores cell morphology and attenuates the ER-stress response. Thus, failures in the secretion of nonbulky proteins, ER stress, and defective cell morphology are secondary consequences of bulky cargo retention. By contrast, ER/Golgi defects in Tango1-depleted cells persist in the absence of bulky cargo, showing that they are due to a secretion-independent function of Tango1. Therefore, maintenance of ER/Golgi architecture and bulky cargo transport are the primary functions for Tango1.

Transcriptome Analysis of the Triatoma infestans (Hemiptera: Reduviidae) Integument

The insect integument, formed by the cuticle and the underlying epidermis, is essential for insect fitness, regulation of lipid biosynthesis and storage, insect growth and feeding, together with development progress. Its participation in insecticide resistance has also been outlined. Triatoma infestans Klug (Hemiptera: Reduviidae) is one of the major vectors of Chagas disease in South America; however, genomic data are scarce. In this study, we performed a transcriptome analysis of the nymph integument in order to identify which genes are expressed and their putative role. Using the 454 GS-FLX sequencing platform, we obtained approximately 144,620 reads from the integument tissue. These reads were assembled into 6,495 isotigs and 8,504 singletons. Based on BLAST similarity searches, about 8,000 transcripts were annotated with known genes, conserved domains, and/or Gene Ontology terms.The most abundant transcripts corresponded to transcription factors and nucleic acid metabolism, membrane receptors, cell signaling, and proteins related to cytoskeleton, transport, and cell energy processes, among others. More than 10% of the transcripts-encoded proteins putatively involved in the metabolism of fatty acids and related components (fatty acid synthases, elongases, desaturases, fatty alcohol reductases), structural integument proteins, and the insecticide detoxification system (among them, cytochrome P450s, esterases, and glutathione transferases). Real-time qPCR assays were used to investigate their putative participation in the resistance mechanism. This preliminary study is the first transcriptome analysis of a triatomine integument, and together with prior biochemical information, will help further understandthe role of the integument in a wide array of mechanisms.

iTRAQ proteomic analysis of the interactions between Bombyx mori nuclear polyhedrosis virus and silkworm

The silkworm hemolymph is an important defense system against bacteria and viruses. In this study, silkworms were infected with Bombyx mori nuclear polyhedrosis virus to investigate the subsequent immune response at the protein level. Proteomes were analyzed before and after infection using isobaric tags for relative and absolute quantitation and LC-MS. A total of 456 differentially expressed proteins were identified, of which 179 were upregulated and 193 were downregulated. Changes in expression were validated by western blot for several proteins. Eleven of the differentially expressed proteins were involved in immunity. For example, modular serine protease and cecropin, which were downregulated, facilitate Toll and Imd signaling, while autophagy-related protein 3, which was upregulated, protects cells against oxidative damage. Collectively, the data highlight the unique interactions of baculovirus with the silkworm immune system.

BIOLOGICAL SIGNIFICANCE

This is the first time isobaric tags for relative and absolute quantitation were used to analyze B. mori proteins mobilized against B. mori nuclear polyhedrosis virus, and to investigate the immunity-associated proteome in B. mori. The results are a significant step towards a deeper understanding of immunoregulation in B. mori.

SIGNIFICANCE

This is the first time isobaric tags for relative and absolute quantitation were used to analyze B. mori proteins mobilized against B. mori nuclear polyhedrosis virus, and to investigate the immunity-associated proteome in B. mori. The results are a significant step towards a deeper understanding of immunoregulation in B. mori.

Tango1 spatially organizes ER exit sites to control ER export

Exit of secretory cargo from the endoplasmic reticulum (ER) takes place at specialized domains called ER exit sites (ERESs). In mammals, loss of TANGO1 and other MIA/cTAGE (melanoma inhibitory activity/cutaneous T cell lymphoma-associated antigen) family proteins prevents ER exit of large cargoes such as collagen. Here, we show that Drosophila melanogaster Tango1, the only MIA/cTAGE family member in fruit flies, is a critical organizer of the ERES-Golgi interface. Tango1 rings hold COPII (coat protein II) carriers and Golgi in close proximity at their center. Loss of Tango1, present at ERESs in all tissues, reduces ERES size and causes ERES-Golgi uncoupling, which impairs secretion of not only collagen, but also all other cargoes we examined. Further supporting an organizing role of Tango1, its overexpression creates more and larger ERESs. Our results suggest that spatial coordination of ERES, carrier, and Golgi elements through Tango1's multiple interactions increases secretory capacity in Drosophila and allows secretion of large cargo.

Cuticle itself as a central and dynamic player in shaping cuticle

The wide variety of external morphologies has underlain the evolutionary success of insects. The insect exoskeleton, or cuticle, which covers the entire body and constitutes the external morphology, is extracellular matrix produced by the epidermis. How is cuticle shaped during development? Past studies have mainly focused on patterning, differentiation and morphogenesis of the epidermis. Recently, however, it is becoming clear that cuticle itself plays important and active roles in regulation of cuticle shape. Studies in the past several years show that pre-existing cuticle can influence shaping of new cuticle, and cuticle can sculpt its own shape through its material property. In this review, I summarize recent advances and discuss future prospects.

Gene expression boundary scaling and organ size regulation in the Drosophila embryo

How the shape and size of tissues and organs is regulated during development is a major question in developmental biology. Such regulation relies upon both intrinsic cues (such as signaling networks) and extrinsic inputs (such as from neighboring tissues). Here, we focus on pattern formation and organ development during Drosophila embryogenesis. In particular, we outline the importance of both biochemical and mechanical tissue-tissue interactions in size regulation. We describe how the Drosophila embryo can potentially provide novel insights into how shape and size are regulated during development. We focus on gene expression boundary scaling in the early embryo and how size is regulated in three organs (hindgut, trachea, and ventral nerve cord) later in development, with particular focus on the role of tissue-tissue interactions. Overall, we demonstrate that Drosophila embryogenesis provides a suitable model system for studying spatial and temporal scaling and size control in vivo.

Seminal fluid protein genes of the brown planthopper, Nilaparvata lugens

Background

Seminal fluid proteins (SFPs) are produced mainly in the accessory gland of male insects and transferred to females during mating, in which they induce numerous physiological and post-mating behavioral changes. The brown plant hopper (BPH), Nilaparvata lugens, is an economically important hemipterous pest of rice. The behavior and physiology of the female of this species is significantly altered by mating. SFPs in hemipteran species are still unclear.

Results

We applied high-throughput mass spectrometry proteomic analyses to characterize the SFP composition in N. lugens. We identified 94 putative secreted SFPs, and the expression levels of these proteins was determined from the male accessory gland digital gene expression database. The 94 predicted SFPs showed high expression in the male accessory gland. Comparing N. lugens and other insect SFPs, the apparent expansion of N. lugens seminal fluid trypsins and carboxylesterases was observed. The number of N. lugens seminal fluid trypsins (20) was at least twice that in other insects. We detected 6 seminal fluid carboxylesterases in N. lugens seminal fluid, while seminal fluid carboxylesterases were rarely detected in other insects. Otherwise, new insect SFPs, including mesencephalic astrocyte–derived neurotrophic factor, selenoprotein, EGF (epidermal growth factor) domain–containing proteins and a neuropeptide ion transport-like peptide were identified.

Conclusion

This work represents the first characterization of putative SFPs in a hemipeteran species. Our results provide a foundation for future studies to investigate the functions of SFPs in N. lugens and are an important addition to the available data for comparative studies of SFPs in insects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3013-7) contains supplementary material, which is available to authorized users.

Integrity of Narrow Epithelial Tubes in the C. elegans Excretory System Requires a Transient Luminal Matrix

Most epithelial cells secrete a glycoprotein-rich apical extracellular matrix that can have diverse but still poorly understood roles in development and physiology. Zona Pellucida (ZP) domain glycoproteins are common constituents of these matrices, and their loss in humans is associated with a number of diseases. Understanding of the functions, organization and regulation of apical matrices has been hampered by difficulties in imaging them both in vivo and ex vivo. We identified the PAN-Apple, mucin and ZP domain glycoprotein LET-653 as an early and transient apical matrix component that shapes developing epithelia in C. elegans. LET-653 has modest effects on shaping of the vulva and epidermis, but is essential to prevent lumen fragmentation in the very narrow, unicellular excretory duct tube. We were able to image the transient LET-653 matrix by both live confocal imaging and transmission electron microscopy. Structure/function and fluorescence recovery after photobleaching studies revealed that LET-653 exists in two separate luminal matrix pools, a loose fibrillar matrix in the central core of the lumen, to which it binds dynamically via its PAN domains, and an apical-membrane-associated matrix, to which it binds stably via its ZP domain. The PAN domains are both necessary and sufficient to confer a cyclic pattern of duct lumen localization that precedes each molt, while the ZP domain is required for lumen integrity. Ectopic expression of full-length LET-653, but not the PAN domains alone, could expand lumen diameter in the developing gut tube, where LET-653 is not normally expressed. Together, these data support a model in which the PAN domains regulate the ability of the LET-653 ZP domain to interact with other factors at the apical membrane, and this ZP domain interaction promotes expansion and maintenance of lumen diameter. These data identify a transient apical matrix component present prior to cuticle secretion in C. elegans, demonstrate critical roles for this matrix component in supporting lumen integrity within narrow bore tubes such as those found in the mammalian microvasculature, and reveal functional importance of the evolutionarily conserved ZP domain in this tube protecting activity.

Most organs in the body are made up of networks of tubes that transport fluids or gases. These tubes come in many different sizes and shapes, with some narrow capillaries being only one cell in diameter. As tubes develop and take their final shapes, they secrete various glycoproteins into their hollow interior or lumen. The functions of these luminal proteins are not well understood, but there is increasing evidence that they are important for lumen shaping and that their loss can contribute to diseases such as cardiovascular disease and chronic kidney disease. Through studies of the nematode C. elegans, we identified a luminal glycoprotein, LET-653, that is transiently expressed in multiple developing tube types but is particularly critical to maintain integrity of the narrowest, unicellular tubes. We identified protein domains that direct LET-653 to specific apical matrix compartments and mediate its oscillatory pattern of lumen localization. Furthermore, we showed that the LET-653 tube-protecting activity depends on a Zona Pellucida (ZP) domain similar to that found in the mammalian egg-coat and in many other luminal or sensory matrix proteins involved in human disease.