Clustered regulatory interspaced short palindromic repeats (CRISPR)-mediated mutagenesis and phenotype rescue by piggyBac transgenesis in a nonmodel Drosophila species

CRISPR-Cas Genome Editing for Insect Pest Stress Management in Crop Plants

Global crop yield and food security are being threatened by phytophagous insects. Innovative methods are required to increase agricultural output while reducing reliance on hazardous synthetic insecticides. Using the revolutionary CRISPR-Cas technology to develop insect-resistant plants appears to be highly efficient at lowering production costs and increasing farm profitability. The genomes of both a model insect, Drosophila melanogaster, and major phytophagous insect genera, viz. Spodoptera, Helicoverpa, Nilaparvata, Locusta, Tribolium, Agrotis, etc., were successfully edited by the CRISPR-Cas toolkits. This new method, however, has the ability to alter an insect’s DNA in order to either induce a gene drive or overcome an insect’s tolerance to certain insecticides. The rapid progress in the methodologies of CRISPR technology and their diverse applications show a high promise in the development of insect-resistant plant varieties or other strategies for the sustainable management of insect pests to ensure food security. This paper reviewed and critically discussed the use of CRISPR-Cas genome-editing technology in long-term insect pest management. The emphasis of this review was on the prospective uses of the CRISPR-Cas system for insect stress management in crop production through the creation of genome-edited crop plants or insects. The potential and the difficulties of using CRISPR-Cas technology to reduce pest stress in crop plants were critically examined and discussed.

Searching and identifying pigmentation genes from Neocaridina denticulate sinensis via comparison of transcriptome in different color strains

Aquaria species are characterized by their amazing colors and patterns. Research on the breeding molecular genetics of ornamental shrimps is surprisingly limited. We conducted a transcriptome analysis to investigate the expression of encoding genes in the integument of the strains Neocaridina denticulate sinensis. After assembled and filtered, 19,992 unigenes were annotated by aligning with public functional databases (NR, Swiss-Prot, KEGG, COG). 14,915 unigenes with significantly different expressions were found by comparing three strains integument transcriptomes. Ribosomal protein genes, ABC transporter families, calmodulin, carotenoid proteins and crustacyanin may play roles in the cytological process of pigment migration and chromatophore maintenance. Numerous color genes associated with multiple pathways including melanin, ommochrome and pteridines pathways were identified. The expression patterns of 25 candidate genes were analysis by qPCR in red, yellow, transparent and glass strains. The qPCR results in red, yellow and transparent were consistent with the level of RPKM values in the transcriptomes. The above results will advance our knowledge of integument color varieties in N. denticulate sinensis and help the genetic selection of crustaceans with consumer-favored colors. Furthermore, it also provides some candidate pigmentation genes to investigate the correlation between coloration and sympatric speciation in crustaceans.

Microinjection-based CRISPR/Cas9 mutagenesis in the decapoda crustaceans, Neocaridina heteropoda and Eriocheir sinensis

CRISPR/Cas9 technology has been applied to many arthropods. However, application of this technology to crustaceans remains limited due to the unique characteristics of embryos. Our group has developed a microinjection system to introduce the CRISPR/Cas9 system into Neocaridina heteropoda embryos (one-cell stage). Using the developed method, we mutated the target gene Nh-scarlet (N. heteropoda scarlet), which functions in eye development and pigmentation. The results showed that both eye color and shape were altered in individuals in which Nh-scarlet was knocked out. Furthermore, this system was also successfully applied to another decapod crustacean, Eriocheir sinensis. DNA sequencing revealed that the zoeae with red eyes had an edited version of Es-scarlet. This study provides a stable microinjection method for freshwater crustaceans, and will contribute to functional genomics studies in various decapods.

Contact-Chemosensory Evolution Underlying Reproductive Isolation in Drosophila Species

The main theme of the review is how changes in pheromone biochemistry and the sensory circuits underlying pheromone detection contribute to mate choice and reproductive isolation. The review focuses primarily on gustatory and non-volatile signals in Drosophila. Premating isolation is prevalent among closely related species. In Drosophila, preference for conspecifics against other species in mate choice underlies premating isolation, and such preference relies on contact chemosensory communications between a female and male along with other biological factors. For example, although D. simulans and D. melanogaster are sibling species that yield hybrids, their premating isolation is maintained primarily by the contrasting effects of 7,11-heptacosadiene (7,11-HD), a predominant female pheromone in D. melanogaster, on males of the two species: it attracts D. melanogaster males and repels D. simulans males. The contrasting preference for 7,11-HD in males of these two species is mainly ascribed to opposite effects of 7,11-HD on neural activities in the courtship decision-making neurons in the male brain: 7,11-HD provokes both excitatory and inhibitory inputs in these neurons and differences in the balance between the two counteracting inputs result in the contrasting preference for 7,11-HD, i.e., attraction in D. melanogaster and repulsion in D. simulans. Introduction of two double bonds is a key step in 7,11-HD biosynthesis and is mediated by the desaturase desatF, which is active in D. melanogaster females but transcriptionally inactivated in D. simulans females. Thus, 7,11-HD biosynthesis diversified in females and 7,11-HD perception diversified in males, yet it remains elusive how concordance of the changes in the two sexes was attained in evolution.

De novo assembly transcriptome analysis reveals the preliminary molecular mechanism of pigmentation in juveniles of the hard clam Mercenaria mercenaria

Color plays a vital function in camouflage, sexual selection, immunity, and evolution. Mollusca possess vivid shell colors and pigmentation starts at the juvenile stage. The hard clam Mercenaria mercenaria is a widely cultivated bivalve of high economic value. To explore the molecular mechanism of pigmentation in juvenile clams, here, we performed RNA-Seq analysis on non-pigmented, white, and red M. mercenaria specimens. Clean reads were assembled into 358,285 transcripts and 149,234 unigenes, whose N50 lengths were 2107 bp and 1567 bp, respectively. Differentially expressed genes were identified and analyzed for KEGG enrichment. "Melanoma/Melanogenesis", "ABC transporters", and "Porphyrin and chlorophyll metabolism" pathways appeared to be associated with pigmentation. Pathways related to carotenoid metabolism seemed to also play a vital role in pigmentation in juveniles. Our results provide new insights into the formation of shell color in juvenile hard clams.

Impact of Wolbachia infection on Drosophila female germline stem cells

Wolbachia pipientis, one of the most dominant insect-symbiotic bacteria, highjacks the female germline of insects for its own propagation across host generations. Such strict dependence on female gametes in trans-generational propagation has driven Wolbachia to devise ingenious strategies to enhance female fertility. In Drosophila melanogaster females with female-sterile mutant alleles of the master sex-determining gene Sex-lethal (Sxl), Wolbachia colonizing female germline stem cells (GSCs) support the maintenance of GSCs, thereby rescuing the defective ovarian development. In the germ cell cytoplasm, Wolbachia are often found in proximity to ribonucleoprotein-complex processing bodies (P bodies), where the Wolbachia-derived protein TomO interacts with RNAs encoding Nanos and Orb proteins, which support the GSC maintenance and oocyte polarization, respectively. Thus, manipulation of host RNA is the key to successful vertical transmission of Wolbachia.

Behavioral Evolution of Drosophila: Unraveling the Circuit Basis

Behavior is a readout of neural function. Therefore, any difference in behavior among different species is, in theory, an outcome of interspecies diversification in the structure and/or function of the nervous system. However, the neural diversity underlying the species-specificity in behavioral traits and its genetic basis have been poorly understood. In this article, we discuss potential neural substrates for species differences in the courtship pulse song frequency and mating partner choice in the Drosophila melanogaster subgroup. We also discuss possible neurogenetic mechanisms whereby a novel behavioral repertoire emerges based on the study of nuptial gift transfer, a trait unique to D. subobscura in the genus Drosophila. We found that the conserved central circuit composed primarily of fruitless-expressing neurons (the fru-circuit) serves for the execution of courtship behavior, whereas the sensory pathways impinging onto the fru-circuit or the motor pathways downstream of the fru-circuit are susceptible to changes associated with behavioral species differences.

Recent neurogenetic findings in insect courtship behaviour

Insect courtship parades consist of series of innate and stereotyped behaviours that become hardwired-in during the development of the nervous system. As such, insect courtship behaviour provides an excellent model for probing the principles of neuronal assembly, which underlie patterns of behaviour. Here, we present the main advances of recent studies - in species all the way from flies to planthoppers - and we envisage how these could lead to further propitious findings.

CRISPR-Cas9: A New Addition to the Drug Metabolism and Disposition Tool Box

Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9), i.e., CRISPR-Cas9, has been extensively used as a gene-editing technology during recent years. Unlike earlier technologies for gene editing or gene knockdown, such as zinc finger nucleases and RNA interference, CRISPR-Cas9 is comparably easy to use, affordable, and versatile. Recently, CRISPR-Cas9 has been applied in studies of drug absorption, distribution, metabolism, and excretion (ADME) and for ADME model generation. To date, about 50 papers have been published describing in vitro or in vivo CRISPR-Cas9 gene editing of ADME and ADME-related genes. Twenty of these papers describe gene editing of clinically relevant genes, such as ATP-binding cassette drug transporters and cytochrome P450 drug-metabolizing enzymes. With CRISPR-Cas9, the ADME tool box has been substantially expanded. This new technology allows us to develop better and more predictive in vitro and in vivo ADME models and map previously underexplored ADME genes and gene families. In this mini-review, we give an overview of the CRISPR-Cas9 technology and summarize recent applications of CRISPR-Cas9 within the ADME field. We also speculate about future applications of CRISPR-Cas9 in ADME research.

Optogenetic Activation of the fruitless-Labeled Circuitry in Drosophila subobscura Males Induces Mating Motor Acts

It remains an enigma how the nervous system of different animal species produces different behaviors. We studied the neural circuitry for mating behavior in Drosophila subobscura, a species that displays unique courtship actions not shared by other members of the genera including the genetic model D. melanogaster, in which the core courtship circuitry has been identified. We disrupted the D. subobscura fruitless (fru) gene, a master regulator for the courtship circuitry formation in D. melanogaster, resulting in complete loss of mating behavior. We also generated frusoChrimV , which expresses the optogenetic activator Chrimson fused with a fluorescent marker under the native fru promoter. The fru-labeled circuitry in D. subobscura visualized by frusoChrimV revealed differences between females and males, optogenetic activation of which in males induced mating behavior including attempted copulation. These findings provide a substrate for neurogenetic dissection and manipulation of behavior in non-model animals, and will help to elucidate the neural basis for behavioral diversification.SIGNIFICANCE STATEMENT How did behavioral specificity arise during evolution? Here we attempted to address this question by comparing the parallel genetically definable neural circuits controlling the courtship behavior of Drosophila melanogaster, a genetic model, and its relative, D. subobscura, which exhibits a courtship behavioral pattern unique to it, including nuptial gift transfer. We found that the subobscura fruitless circuit, which is required for male courtship behavior, was slightly but clearly different from its melanogaster counterpart, and that optogenetic activation of this circuit induced subobscura-specific behavior, i.e., regurgitating crop contents, a key element of transfer of nuptial gift. Our study will pave the way for determining how and which distinctive cellular elements within the fruitless circuit determine the species-specific differences in courtship behavior.

Progress and Prospects of CRISPR/Cas Systems in Insects and Other Arthropods

Clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-associated gene Cas9 represent an invaluable system for the precise editing of genes in diverse species. The CRISPR/Cas9 system is an adaptive mechanism that enables bacteria and archaeal species to resist invading viruses and phages or plasmids. Compared with zinc finger nucleases and transcription activator-like effector nucleases, the CRISPR/Cas9 system has the advantage of requiring less time and effort. This efficient technology has been used in many species, including diverse arthropods that are relevant to agriculture, forestry, fisheries, and public health; however, there is no review that systematically summarizes its successful application in the editing of both insect and non-insect arthropod genomes. Thus, this paper seeks to provide a comprehensive and impartial overview of the progress of the CRISPR/Cas9 system in different arthropods, reviewing not only fundamental studies related to gene function exploration and experimental optimization but also applied studies in areas such as insect modification and pest control. In addition, we also describe the latest research advances regarding two novel CRISPR/Cas systems (CRISPR/Cpf1 and CRISPR/C2c2) and discuss their future prospects for becoming crucial technologies in arthropods.

CRISPR/Cas9 in insects: Applications, best practices and biosafety concerns

Discovered as a bacterial adaptive immune system, CRISPR/Cas9 (clustered, regularly interspaced, short palindromic repeat/CRISPR associated) is being developed as an attractive tool in genome editing. Due to its high specificity and applicability, CRISPR/Cas9-mediated gene editing has been employed in a multitude of organisms and cells, including insects, for not only fundamental research such as gene function studies, but also applied research such as modification of organisms of economic importance. Despite the rapid increase in the use of CRISPR in insect genome editing, results still differ from each study, principally due to existing differences in experimental parameters, such as the Cas9 and guide RNA form, the delivery method, the target gene and off-target effects. Here, we review current reports on the successes of CRISPR/Cas9 applications in diverse insects and insect cells. We furthermore summarize several best practices to give a useful checklist of CRISPR/Cas9 experimental setup in insects for beginners. Lastly, we discuss the biosafety concerns related to the release of CRISPR/Cas9-edited insects into the environment.

Quantitative analysis of visually induced courtship elements in Drosophila subobscura

We developed a new paradigm for quantitative analysis of courtship behavior in flies, Fly Motion-detector with an Actuator-Coupled Stimulator (FlyMacs), in which the stimulation of a fly with a moving visual target and recording of induced behaviors are automated under computer control. We employ FlyMacs for the identification of motion features that trigger specific courtship elements in Drosophila subobscura, whose mating is suggested to be strongly vision dependent. A female abdomen attached to the actuator, when moved in an appropriate pattern, evokes in the test male tapping-like foreleg motions, midleg swing and proboscis extension, which are considered to be elementary actions in male courtship behavior. Tapping is primarily induced when the target is moving, whereas midleg swing and proboscis extension are most frequently observed after the target stops moving. In contrast to midleg swing, which tends to occur immediately after target cessation (∼3000 ms), the incidence of proboscis extension gradually increases with time after target cessation, reaching a plateau at 3000 ms. The results suggest that tapping, midleg swing and proboscis extension are each induced by different movement features of the visual target. These findings do not support the view that a single key stimulus induces the entire courtship ritual. Rather, courtship behaviors in D. subobscura are correlated with movement and position of the target, which suggests that D. subobscura uses sensory information to pattern its courtship.