The indispensable contribution of s38 protein to ovarian-eggshell morphogenesis in Drosophila melanogaster

Knockdown of Sec16 causes early lethality and defective deposition of the protein Rp30 in the eggshell of the vector Rhodnius prolixus

In nearly every species of insect, embryonic development takes place outside of the mother's body and is entirely dependent on the elements that the mother had previously stored within the eggs. It is well known that the follicle cells (FCs) synthesize the eggshell (chorion) components during the process of choriogenesis, the final step of oogenesis before fertilization. These cells have developed a specialization in the massive production of chorion proteins, which are essential for the protection and survival of the embryo. Here, we investigate the function of Sec16, a protein crucial for the endoplasmic reticulum (ER) to Golgi traffic, in the oocyte development in the insect Rhodnius prolixus. We discovered that Sec16 is strongly expressed in vitellogenic females' ovaries, particularly in the choriogenic oocyte and it is mainly associated with the FCs. Silencing of Sec16 by RNAi caused a sharp decline in oviposition rates, F1 viability, and longevity in adult females. In the FCs, genes involved in the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and autophagy were massively upregulated, whereas the mRNAs of Rp30 and Rp45-which code for the two major chorion proteins - were downregulated as a result of Sec16 silencing, indicating general proteostasis disturbance. As a result, the outer surface ultrastructure of Sec16-silenced chorions was altered, with decreased thickness, dityrosine crosslinking, sulfur signals, and lower amounts of the chorion protein Rp30. These findings collectively demonstrate the critical role Sec16 plays in the proper functioning of the FCs, which impacts the synthesis and deposition of particular components of the chorion as well as the overall reproduction of this vector.

Comparative Transcriptomic Analysis Revealing the Potential Mechanisms of Erythritol-Caused Mortality and Oviposition Inhibition in Drosophila melanogaster

Erythritol has shown excellent insecticidal performance against a wide range of insect species, but the molecular mechanism by which it causes insect mortality and sterility is not fully understood. The mortality and sterility of Drosophila melanogaster were assessed after feeding with 1M erythritol for 72 h and 96 h, and gene expression profiles were further compared through RNA sequencing. Enrichment analysis of GO and KEGG revealed that expressions of the adipokinetic hormone gene (Akh), amylase gene (Amyrel), α-glucosidase gene (Mal-B1/2, Mal-A1-4, Mal-A7/8), and triglyceride lipase gene (Bmm) were significantly up-regulated, while insulin-like peptide genes (Dilp2, Dilp3 and Dilp5) were dramatically down-regulated. Seventeen genes associated with eggshell assembly, including Dec-1 (down 315-fold), Vm26Ab (down 2014-fold) and Vm34Ca (down 6034-fold), were significantly down-regulated or even showed no expression. However, there were no significant differences in the expression of three diuretic hormone genes (DH44, DH31, CAPA) and eight aquaporin genes (Drip, Big brain, AQP, Eglp1, Eglp2, Eglp3, Eglp4 and Prip) involved in osmolality regulation (all p value > 0.05). We concluded that erythritol, a competitive inhibitor of α-glucosidase, severely reduced substrates and enzyme binding, inhibiting effective carbohydrate hydrolysis in the midgut and eventually causing death due to energy deprivation. It was clear that Drosophila melanogaster did not die from the osmolality of the hemolymph. Our findings elucidate the molecular mechanism underlying the mortality and sterility in Drosophila melanogaster induced by erythritol feeding. It also provides an important theoretical basis for the application of erythritol as an environmentally friendly pesticide.

Finishing the egg

Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.

Nanoscale Prognosis of Colorectal Cancer Metastasis from AFM Image Processing of Histological Sections

Early ascertainment of metastatic tumour phases is crucial to improve cancer survival, formulate an accurate prognostic report of disease advancement, and, most importantly, quantify the metastatic progression and malignancy state of primary cancer cells with a universal numerical indexing system. This work proposes an early improvement to metastatic cancer detection with 97.7 nm spatial resolution by indexing the metastatic cancer phases from the analysis of atomic force microscopy images of human colorectal cancer histological sections. The procedure applies variograms of residuals of Gaussian filtering and theta statistics of colorectal cancer tissue image settings. This methodology elucidates the early metastatic progression at the nanoscale level by setting metastatic indexes and critical thresholds based on relatively large histological sections and categorising the malignancy state of a few suspicious cells not identified with optical image analysis. In addition, we sought to detect early tiny morphological differentiations indicating potential cell transition from epithelial cell phenotypes of low metastatic potential to those of high metastatic potential. This metastatic differentiation, which is also identified in higher moments of variograms, sets different hierarchical levels for metastatic progression dynamics.

Vitelline Membrane Protein 26 Mutagenesis, Using CRISPR/Cas9, Results in Egg Collapse in Plutella xylostella

Vitelline membrane proteins (VMPs) are the main proteins that form the inner shell (vitelline membrane layer) of insect eggs and are an integral part of egg formation and embryo development. Here, we characterized the molecular structure and expression patterns of the VMP26 gene and analyzed its reproductive functions in diamondback moth, Plutella xylostella (L.), a worldwide migratory pest of cruciferous plants. The PxVMP26 gene was shown to be a single exon gene that contained an open reading frame of 852 base pairs (bp) encoding 283 amino acids. Both qPCR and western blot analyses showed that PxVMP26 was specifically expressed in female adults and was significantly highly expressed in the ovary. Further anatomical analysis indicated that the expression level of PxVMP26 in the ovarian tube with an incomplete yolk was significantly higher than that in the ovarian tube with a complete yolk. CRISPR/Cas9-induced PxVMP26 knockout successfully created two homozygous strains with 8- and 46-bp frameshift mutations. The expression deficiency of the PxVMP26 protein was detected in the mutant strains using immunofluorescence and western blot. No significant difference was found in the number of eggs laid within three days between wild and mutant individuals, but there was a lower egg hatchability. The loss of the PxVMP26 gene changed the mean egg size, damaged the structure of the vitelline membrane, and increased the proportion of abnormal eggs due to water loss, resulting in egg collapse. This first analysis of the roles of the VMP gene in the oocyte formation and embryonic development of P. xylostella, using CRISPR/Cas9 technology, provides a basis for screening new genetic control targets of P. xylostella.

Knockdown of E1- and E2-ubiquitin enzymes triggers defective chorion biogenesis and modulation of autophagy-related genes in the follicle cells of the vector Rhodnius prolixus

In insects, the last stage of oogenesis is the process where the chorion layers (eggshell) are synthesized and deposited on the surface of the oocytes by the follicle cells. Protein homeostasis is determined by the fine-tuning of translation and degradation pathways, and the ubiquitin-proteasome system is one of the major degradative routes in eukaryotic cells. The conjugation of ubiquitin to targeted substrates is mediated by the ordered action of E1-activating, E2-conjugating, and E3-ligase enzymes, which covalently link ubiquitin to degradation-targeted proteins delivering them to the proteolytic complex proteasome. Here, we found that the mRNAs encoding polyubiquitin (pUbq), E1, and E2 enzymes are highly expressed in the ovaries of the insect vector of Chagas Disease Rhodnius prolixus. RNAi silencing of pUbq was lethal whereas the silencing of E1 and E2 enzymes resulted in drastic decreases in oviposition and embryo viability. Eggs produced by the E1- and E2-silenced insects presented particular phenotypes of altered chorion ultrastructure observed by high-resolution scanning electron microscopy as well as readings for dityrosine cross-linking and X-ray elemental microanalysis, suggesting a disruption in the secretory routes responsible for the chorion biogenesis. In addition, the ovaries from silenced insects presented altered levels of autophagy-related genes as well as a tendency of upregulation in ER chaperones, indicating a disturbance in the general biosynthetic-secretory pathway. Altogether, we found that E1 and E2 enzymes are essential for chorion biogenesis and that their silencing triggers the modulation of autophagy genes suggesting a coordinated function of both pathways for the progression of choriogenesis.

A comprehensive review on the documented characteristics of four Reticulitermes termites (Rhinotermitidae, Blattodea) of China

Termites are known as social insects worldwide. Presently in China 473 species, 44 genera and 4 families of termites have been reported. Of them, 111 Reticulitermes species are widely spread in different zones of China. The dispersion flight season of these Chinese Reticulitermes species are usually started from February to June, but in some regions different species are distributed, sharing their boundaries and having overlapping flight seasons. These reasons become important sources of hybridization between two different heterospecific populations of termites. It was confirmed that the fertilized eggs and unfertilized eggs of some Reticulitermes termites have the capacity of cleavage. While the unfertilized eggs of R. aculabialis, R. chinensis and R. labralis cleaved normally and the only R. aculabialis unfertilized eggs develop in embryos. While, the R. flaviceps and R. chinensis were observed with their abnormal embryonic development, and not hatching of eggs parthenogenetically. They were reported more threatening to Chinese resources as they propagate with parthenogenesis, hybridization and sexual reproduction. Eggshell and macrophiles of eggs play important roles in species identification and control. Although, they are severe pests and cause a wide range of damages to wooden structures and products in homes, buildings, building materials, trees, crops, and forests in China's Mainland.

Post-mating gene expression of Mexican fruit fly females: disentangling the effects of the male accessory glands

Mating has profound physiological and behavioural consequences for female insects. During copulation, female insects typically receive not only sperm, but a complex ejaculate containing hundreds of proteins and other molecules from male reproductive tissues, primarily the reproductive accessory glands. The post-mating phenotypes affected by male accessory gland (MAG) proteins include egg development, attraction to oviposition hosts, mating, attractiveness, sperm storage, feeding and lifespan. In the Mexican fruit fly, Anastrepha ludens, mating increases egg production and the latency to remating. However, previous studies have not found a clear relationship between injection of MAG products and oviposition or remating inhibition in this species. We used RNA-seq to study gene expression in mated, unmated and MAG-injected females to understand the potential mating- and MAG-regulated genes and pathways in A. ludens. Both mating and MAG-injection regulated transcripts and pathways related to egg development. Other transcripts regulated by mating included those with orthologs predicted to be involved in immune response, musculature and chemosensory perception, whereas those regulated by MAG-injection were predicted to be involved in translational control, sugar regulation, diet detoxification and lifespan determination. These results suggest new phenotypes that may be influenced by seminal fluid molecules in A. ludens. Understanding these influences is critical for developing novel tools to manage A. ludens.

ATG3 Is Important for the Chorion Ultrastructure During Oogenesis in the Insect Vector Rhodnius prolixus

In insects, the last stage of the oogenesis is the choriogenesis, a process where the multiple layers of the chorion are synthesized, secreted, and deposited in the surface of the oocytes by the follicle cells. The chorion is an extracellular matrix that serves as a highly specialized protective shield for the embryo, being crucial to impair water loss and to allow gas exchange throughout development. The E2-like enzyme ATG3 (autophagy related gene 3) is known for its canonical function in the autophagy pathway, in the conjugation of the ubiquitin-like ATG8/LC3 to the membranes of autophagosomes. Although the ATGs were originally described and annotated as genes related to autophagy, additional functions have been attributed to various of these genes. Here, we found that Rhodnius prolixus ATG3 is highly expressed in the ovaries of the adult vitellogenic females. Parental RNAi depletion of ATG3 resulted in a 15% decrease in the oviposition rates of depleted females and in the generation of unviable eggs. ATG3-depleted eggs are small and present one specific phenotype of altered chorion ultrastructure, observed by high resolution scanning electron microscopy. The amounts of the major chorion proteins Rp30, Rp45, Rp100, and Rp200 were decreased in the ATG3-depleted chorions, as well as the readings for dityrosine cross-linking and sulfur, detected by fluorescence emission under ultraviolet excitation and X-ray elemental detection and mapping. Altogether, we found that ATG3 is important for the proper chorion biogenesis and, therefore, crucial for this vector reproduction.

Wolbachia affects reproduction in the spider mite Tetranychus truncatus (Acari: Tetranychidae) by regulating chorion protein S38-like and Rop

Wolbachia-induced reproductive regulation in hosts has been used to control pest populations, but little is known about the molecular mechanism underlying Wolbachia regulation of host genes. Here, reproductive regulation by Wolbachia in the spider mite Tetranychus truncatus was studied at the molecular level. Infection with Wolbachia resulted in decreasing oviposition and cytoplasmic incompatibility in T. truncatus. Further RNA-seq revealed genes regulated by Wolbachia in T. truncatus. Real-time quantitative polymerase chain reaction (qPCR) showed that genes, including chorion protein S38-like and Rop were down-regulated by Wolbachia. RNA interference (RNAi) of chorion protein S38-like and Rop in Wolbachia-uninfected T. truncatus decreased oviposition, which was consistent with Wolbachia-induced oviposition decrease. Interestingly, suppressing Rop in Wolbachia-infected T. truncatus led to increased Wolbachia titres in eggs; however, this did not occur after RNAi of chorion protein S38-like. This is the first study to show that chorion protein S38-like and Rop facilitate Wolbachia-mediated changes in T. truncatus fertility. In addition, RNAi of Rop turned the body colour of Wolbachia-uninfected T. truncatus black, which indicates that the role of Rop is not limited to the reproductive regulation of T. truncatus.

Deficiency of ULK1/ATG1 in the follicle cells disturbs ER homeostasis and causes defective chorion deposition in the vector Rhodnius prolixus

In insects, synthesis and deposition of the chorion (eggshell) are performed by the professional secretory follicle cells (FCs) that surround the oocytes in the course of oogenesis. Here, we found that ULK1/ATG1, an autophagy-related protein, is highly expressed in the FCs of the Chagas-Disease vector Rhodnius prolixus, and that parental RNAi silencing of ULK1/ATG1 results in oocytes with abnormal chorion ultrastructure and FCs presenting expanded rough ER membranes as well as increased expression of the ER chaperone BiP3, both indicatives of ER stress. Silencing of LC3/ATG8, another essential autophagy protein, did not replicate the ULK1/ATG1 phenotypes, whereas silencing of SEC16A, a known partner of the noncanonical ULK1/ATG1 function in the ER exit sites phenocopied the silencing of ULK1/ATG1. Our findings point to a cooperated function of ULK1/ATG1 and SEC16A in the FCs to complete choriogenesis and provide additional in vivo phenotype-based evidence to the literature of the role of ULK1/ATG1 in the ER in a professional secretory cell.