Suppression of Laccase 2 severely impairs cuticle tanning and pathogen resistance during the pupal metamorphosis of Anopheles sinensis (Diptera: Culicidae)

Laccase: A Green Biocatalyst Offers Immense Potential for Food Industrial and Biotechnological Applications

Laccase, a multipurpose biocatalyst, is widely distributed across all kingdoms of life and plays a key role in essential biological processes such as lignin synthesis, degradation, and pigment formation. These functions are critical for fungal growth, plant-pathogen interactions, and maintenance of soil health. Due to its broad substrate specificity, multifunctional nature, and environmentally friendly characteristics, laccase is widely employed as a catalyst in various green chemistry initiatives. With its ability to oxidize a diverse range of phenolic and nonphenolic compounds, laccase has also been found to be useful as a food additive and for assessing food quality parameters. Ongoing advancements in research and technology are continually expanding the recognition of laccase's potential to address global environmental, health, and energy challenges. This review aims to provide critical insights into the applications of laccases in the biotechnology and food industry.

Under the radar: Transcriptomic responses of bed bugs to an entomopathogen, environmental bacteria, and a human pathogen

Bed bugs (Hemiptera: Cimicidae) are widely distributed, obligately blood-feeding insects, but they have never been linked to pathogen transmission in humans. Most other hematophagous insects that frequently bite humans transmit pathogens, and it is unclear why bed bugs do not. One hypothesis is that bed bugs have evolved a highly robust immune system because their mating system, traumatic insemination, exposes females to consistent wounding and bacterial infections. Although this has been proposed, very little is known about the bed bug immune system and how bed bugs respond to microbial challenges introduced by wounding. Similarly, there is little known about how the bed bug immune system responds to human pathogens. Understanding the bed bug immune system could give insight to why bed bugs appear not to transmit disease and under what circumstances they could, while also facilitating biological control efforts involving microbes. To investigate the transcriptomic response of bed bugs to immune challenges, we exposed female bed bugs to three bacterial challenges. 1.) Pseudomonas fluorescens, an entomopathogen known to have harmful effects to bed bugs, 2.) bacteria cultured from a bed bug enclosure (99.9 % Bacillus spp.), likely encountered during traumatic insemination, and 3.) Borrelia duttoni, a human vector-borne pathogen that causes relapsing fever. We compared the transcriptomes of infected bed bugs with uninfected matched controls in a pairwise fashion, focusing on immune-related genes. We found many known antimicrobial effector genes upregulated in response to P. fluorescens and traumatic insemination-associated bacteria, but interestingly, not in response to B. duttoni. In the differentially expressed genes that were shared between experiments, we found significant overlap in the P. fluorescens treatment and the traumatic insemination bacteria treatment, and between the P. fluorescens and B. duttoni treatments, but not between the traumatic insemination bacteria treatment and the B. duttoni treatment. Finally, we identify previously overlooked candidates for future studies of immune function in bed bugs, including a peroxidase-like gene, many putative cuticle-associated genes, a laccase-like gene, and a mucin-like gene. By taking a comprehensive transcriptomic approach, our study is an important step in understanding how bed bugs respond to diverse immune challenges.

A life-and-death struggle: interaction of insects with entomopathogenic fungi across various infection stages

Insects constitute approximately 75% of the world's recognized fauna, with the majority of species considered as pests. Entomopathogenic fungi (EPF) are parasitic microorganisms capable of efficiently infecting insects, rendering them potent biopesticides. In response to infections, insects have evolved diverse defense mechanisms, prompting EPF to develop a variety of strategies to overcome or circumvent host defenses. While the interaction mechanisms between EPF and insects is well established, recent findings underscore that their interplay is more intricate than previously thought, especially evident across different stages of EPF infection. This review primarily focuses on the interplay between EPF and the insect defense strategies, centered around three infection stages: (1) Early infection stage: involving the pre-contact detection and avoidance behavior of EPF in insects, along with the induction of behavioral responses upon contact with the host cuticle; (2) Penetration and intra-hemolymph growth stage: involving the initiation of intricate cellular and humoral immune functions in insects, while symbiotic microbes can further contribute to host resistance; (3) Host insect's death stage: involving the ultimate confrontation between pathogens and insects. Infected insects strive to separate themselves from the healthy population, while pathogens rely on the infected insects to spread to new hosts. Also, we discuss a novel pest management strategy underlying the cooperation between EPF infection and disturbing the insect immune system. By enhancing our understanding of the intricate interplay between EPF and the insect, this review provides novel perspectives for EPF-mediated pest management and developing effective fungal insecticides.

Mosquito gene targeted RNAi studies for vector control

Vector-borne diseases are serious public health concern. Mosquito is one of the major vectors responsible for the transmission of a number of diseases like malaria, Zika, chikungunya, dengue, West Nile fever, Japanese encephalitis, St. Louis encephalitis, and yellow fever. Various strategies have been used for mosquito control, but the breeding potential of mosquitoes is such tremendous that most of the strategies failed to control the mosquito population. In 2020, outbreaks of dengue, yellow fever, and Japanese encephalitis have occurred worldwide. Continuous insecticide use resulted in strong resistance and disturbed the ecosystem. RNA interference is one of the strategies opted for mosquito control. There are a number of mosquito genes whose inhibition affected mosquito survival and reproduction. Such kind of genes could be used as bioinsecticides for vector control without disturbing the natural ecosystem. Several studies have targeted mosquito genes at different developmental stages by the RNAi mechanism and result in vector control. In the present review, we included RNAi studies conducted for vector control by targeting mosquito genes at different developmental stages using different delivery methods. The review could help the researcher to find out novel genes of mosquitoes for vector control.

Characterization of five pigmentation genes as transgenic markers in Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (J. E. Smith), has become one of the most damaging pests worldwide since its invasion of Africa, Asia and Oceania from 2016, threatening plants in 76 families including important crops. Genetics-based methods have proved to be an efficient way to control pests, especially invasive species, but many difficulties must be overcome to develop a transgenic insect strain, especially for a non-model species. Here we thus sought to identify a visible marker that would facilitate the distinction between genetically modified (GM) and non-transgenic insects, thereby simplifying mutation identification and facilitating the broader application of genome editing tools in non-model insects. Five genes (sfyellow-y, sfebony, sflaccase2, sfscarlet, and sfok) that are orthologs of well-studied genes in pigment metabolism were knocked out using the CRISPR/Cas9 system to identify candidate gene markers. Two genes, Sfebony and Sfscarlet, were identified responsible for body and compound eye coloration, respectively, in S. frugiperda, and could be potential visual markers for genetics-based pest management strategies.

Structural insights, biocatalytic characteristics, and application prospects of lignin-modifying enzymes for sustainable biotechnology-A review

Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Insect phenoloxidase and its diverse roles: melanogenesis and beyond

Insect life on earth is greatly diversified despite being exposed to several infectious agents due to their diverse habitats and ecological niche. One of the major factors responsible for their successful establishment is having a powerful innate immune system. The most common and effective method used by insects in recognizing pathogen and non-self-substances is the melanization process among others. The key enzyme involved in melanin biosynthesis is the copper containing humoral defense enzyme, phenoloxidase (PO). This review focused on understanding about PO and that had been in research for nearly a century. The review elaborates about evolutionary significance of PO in arthropods, its relationship with mammalian tyrosinases, various substrates, activators and inhibitors involved in the activation of phenoloxidase cascade, as it requires an integrated system of activation that vary among insect species. The enzyme also plays a vital role in insect immunity by involving in several other immune functions like sclerotization, wound healing, opsonization, encapsulation and nodule formation. Further, gene knock down or knock out of PO genes and inhibition of PO-melanization cascade by several mechanisms can also be considered as promising future alternative to control serious pests by making them highly susceptible to any targeted attack.

Production of Sitobion avenae-resistant Triticum aestivum cvs using laccase as RNAi target and its systemic movement in wheat post dsRNA spray

Among the wheat biotic stresses, Sitobion avenae is one of the main factors devastating the wheat yield per hectare. The study's objective was to find out the laccase (lac) efficacy; as a potential RNAi target against grain aphids. The Sitobion avenae lac (Salac) was confirmed by Reverse Transcriptase-PCR. Gene was sequenced and accession number "ON703252" was allotted by GenBank. ERNAi tool was used to design 143 siRNA and one dsRNA target. 69% mortality and 61% reduction in lac expression were observed 8D-post lac DsRNA feeding. Phylogenetic analysis displayed the homology of grain aphid lac gene with peach potato, pea, and Russian wheat aphids. While Salac protein was found similar to the Russian grain, soybean, pea, and cedar bark aphid lac protein multi-copper oxidase. The dsRNAlac spray-induced silencing shows systematic translocation from leaf to root; with maximum lac expression found in the root, followed by stem and leaf 9-13D post-spray; comparison to control. RNAi-GG provides the Golden Gate cloning strategy with a single restriction ligation reaction used to achieve lac silencing. Agrobacterium tumefaciens mediated in planta and in-vitro transformation was used in the study. In vitro transformation, Galaxy 2012 yielded a maximum transformation efficiency (1.5%), followed by Anaj 2017 (0.8%), and Punjab (0.2%). In planta transformation provides better transformation efficiencies with a maximum in Galaxy 2012 (16%), and a minimum for Punjab (5%). Maximum transformation efficiency was achieved for all cultivars with 250 μM acetosyringone and 3h co-cultivation. Galaxy 2012 exhibited maximum transformation efficiency, and aphid mortality post-feeding transgenic wheat.

Insects as source of phenolic and antioxidant entomochemicals in the food industry

Edible insects are a natural resource with profound interest in the food industry. Not only because of their nutritional content and technical production advantage, but also for the presence of bioactive compounds known as entomochemicals. These include phenolic, alkaloid, and terpenoid compounds, as well as amino acids derivatives, among others. This work is focused on phenolic compounds, which have been the best characterized due to their role in food development and bioactive properties. The major taxonomic orders studied in this regard include Orthoptera, Coleoptera, and Lepidoptera, whose edible specimens have antioxidant effects provided by the phenolic compounds contained therein. The use of these insects in the development of nutritious foods will enhance the number of options available for the human population. However, depth research is still needed to guarantee the aforementioned bioactivity in processed foods and ensure its innocuity, thus minimizing the risk of allergic reactions and allowing the full utilization of edible insect species in the food industry. Phenolic derived from edible insects portray an opportunity to improve high quality food, as an alternative to diversify and complement an adequate and functional diet. Future development foods supplemented with insects must consider the preservation of potential benefits of not only nutrients, also de nutraceuticals.

Metal ions in insect reproduction: a crosstalk between reproductive physiology and immunity

Most insects exhibit high reproductive capacity, which demands large amounts of energy, including macronutrients and micronutrients. Interestingly, many proteins involved in oogenesis depend on metals ions, in particular iron (Fe), zinc (Zn), and copper (Cu). Mechanisms by which metal ions influence reproduction have been described in Drosophila melanogaster, but remain poorly understood in hematophagous insects where blood meals include significant ingestion of metal ions. Moreover, there is evidence that some proteins involved in reproduction and immunity could have dual function in both processes. This review highlights the importance of metal ions in the reproduction of non-hematophagous and hematophagous insects. In addition, we discuss how insects optimize physiological processes using proteins involved in crosstalk between reproductive physiology and immunity, which is a double-edge sword in allocating their functions to protect the insect and ensure reproduction.

Involvement of Laccase2 in Cuticle Sclerotization of the Whitefly, Bemisia tabaci Middle East–Asia Minor 1

Cuticle sclerotization is critical for insect survival. Laccase2 (Lac2) is a phenol oxidase that plays a key role in cuticle formation and pigmentation in a variety of insects. However, the function of Lac2 in whitefly, Bemisia tabaci, remains unclear. In this study, we identified a BtLac2 gene in B. tabaci MEAM1 and found that BtLac2 was expressed in all stages. It was highly expressed in the egg stage, followed by nymph and adult. Moreover, the expression of BtLac2 was higher in the cuticle than in other tissues. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate, extended the development duration of nymphs, and decreased the emergence rate of adults. This result demonstrates that BtLac2 plays an important role in the cuticle hardening of B. tabaci and suggests a potential management strategy using RNAi to knock down BtLac2 expression.

Establishing RNAi for basic research and pest control and identification of the most efficient target genes for pest control: a brief guide

RNA interference (RNAi) has emerged as a powerful tool for knocking-down gene function in diverse taxa including arthropods for both basic biological research and application in pest control. The conservation of the RNAi mechanism in eukaryotes suggested that it should-in principle-be applicable to most arthropods. However, practical hurdles have been limiting the application in many taxa. For instance, species differ considerably with respect to efficiency of dsRNA uptake from the hemolymph or the gut. Here, we review some of the most frequently encountered technical obstacles when establishing RNAi and suggest a robust procedure for establishing this technique in insect species with special reference to pests. Finally, we present an approach to identify the most effective target genes for the potential control of agricultural and public health pests by RNAi.

From Aedes to Zeugodacus: a review of dipteran body coloration studies regarding evolutionary developmental biology, pest control, and species discovery

Over the past two decades, evo-devo (evolution of development) studies have elucidated genetic mechanisms underlying novel dipteran body color patterns. Here we review the most recent developments, which show some departure from the model organism Drosophila melanogaster, leading the field into the investigation of more complex color patterns. We also discuss how the robust application of transgenic techniques has facilitated the study of many non-model pest species. Furthermore, we see that subtle pigmentation differences guide the discovery and description of new dipterans. Therefore, we argue that the existence of new field guides and the prevalence of pigmentation studies in non-model flies will enable scientists to adopt uninvestigated species into the lab, allowing them to study novel morphologies.

CONTROL DE Aedes aegypti (DIPTERA: CULICIDAE) MEDIANTE ACTINOBACTERIAS FORMADORAS DE BIOPELÍCULAS

El phylum Actinobacteria incluye miembros productores de compuestos bioinsecticidas. No obstante, la sobreexplotacion de metabolitos derivados de Streptomyces ha conllevado a explorar nuevas moléculas provenientes de bacterias no estreptomicetos para contrarrestar la resistencia a insecticidas químicos en Aedes aegypti. Concordantes con el uso de bioagentes ecológicos, esta investigación caracterizó actinobacterias formadoras de biopelículas con el fin de evaluar su dinámica de crecimiento, actividad larvicida y efectos subletales. La identificación, crecimiento de biopelículas y bioactividades se realizaron por cultivos, análisis de imágenes por fotomicrografía y bioensayos. Los resultados mostraron que las biopelículas pertenecen a Pseudonocardiaceae (PsA1TA) y Corynebacteriaceae (CoA2CA) característicamente dependientes del revestimiento cuticular. PsA1TA coloniza estructuras membranosas de tórax y abdomen con microcolonias aleatoriamente distribuidas que desarrollan a extensas biopelículas mono y biestratificadas, al cubrir cuatro veces la amplitud toracoabdominal (envergadura infectiva entre 1010 µm a 1036 µm). En contraste, CoA2CA envuelve radialmente estructuras esclerotizadas cefálica y anal al triplicar la amplitud de tales órganos (1820 a 2030 µm y 1650 a 1860 µm, respectivamente). Las biopelículas ejercieron mortalidad diferenciada a todos los estadios larvales, no obstante, PsA1TA resultó más mortal y virulento en el segundo estadio larval (58 %-96 horas, TL50: 3,4 días), mientras que CoA2CA lo fue en el cuarto estadio larval (85 %-96 horas, TL50: 2,5 días). CoA2CA indujo emergencia incompleta de adultos farados y despliegue de tarsos curvos en emergentes, además de revestir con robustas biopelículas cadáveres larvarios. Las biopelículas actinobacterianas revelaron ejercer función larvicida y respuestas subletales en A. aegypti.

Glyphosate inhibits melanization and increases susceptibility to infection in insects

Melanin, a black-brown pigment found throughout all kingdoms of life, has diverse biological functions including UV protection, thermoregulation, oxidant scavenging, arthropod immunity, and microbial virulence. Given melanin's broad roles in the biosphere, particularly in insect immune defenses, it is important to understand how exposure to ubiquitous environmental contaminants affects melanization. Glyphosate-the most widely used herbicide globally-inhibits melanin production, which could have wide-ranging implications in the health of many organisms, including insects. Here, we demonstrate that glyphosate has deleterious effects on insect health in 2 evolutionary distant species, Galleria mellonella (Lepidoptera: Pyralidae) and Anopheles gambiae (Diptera: Culicidae), suggesting a broad effect in insects. Glyphosate reduced survival of G. mellonella caterpillars following infection with the fungus Cryptococcus neoformans and decreased the size of melanized nodules formed in hemolymph, which normally help eliminate infection. Glyphosate also increased the burden of the malaria-causing parasite Plasmodium falciparum in A. gambiae mosquitoes, altered uninfected mosquito survival, and perturbed the microbial composition of adult mosquito midguts. Our results show that glyphosate's mechanism of melanin inhibition involves antioxidant synergy and disruption of the reaction oxidation-reduction balance. Overall, these findings suggest that glyphosate's environmental accumulation could render insects more susceptible to microbial pathogens due to melanin inhibition, immune impairment, and perturbations in microbiota composition, potentially contributing to declines in insect populations.

Stressor-Dependant Changes in Immune Parameters in the Terrestrial Isopod Crustacean, Porcellio scaber: A Focus on Nanomaterials

We compared the changes of selected immune parameters of Porcellio scaber to different stressors. The animals were either fed for two weeks with Au nanoparticles (NPs), CeO2 NPs, or Au ions or body-injected with Au NPs, CeO2 NPs, or lipopolysaccharide endotoxin. Contrary to expectations, the feeding experiment showed that both NPs caused a significant increase in the total haemocyte count (THC). In contrast, the ion-positive control resulted in a significantly decreased THC. Additionally, changes in phenoloxidase (PO)-like activity, haemocyte viability, and nitric oxide (NO) levels seemed to depend on the stressor. Injection experiments also showed stressor-dependant changes in measured parameters, such as CeO2 NPs and lipopolysaccharide endotoxin (LPS), caused more significant responses than Au NPs. These results show that feeding and injection of NPs caused an immune response and that the response differed significantly, depending on the exposure route. We did not expect the response to ingested NPs, due to the low exposure concentrations (100 μg/g dry weight food) and a firm gut epithelia, along with a lack of phagocytosis in the digestive system, which would theoretically prevent NPs from crossing the biological barrier. It remains a challenge for future research to reveal what the physiological and ecological significance is for the organism to sense and respond, via the immune system, to ingested foreign material.

The direct and indirect effects of copper on vector-borne disease dynamics

Metal pollution is a growing concern that affects the health of humans and animals globally. Copper is an essential insect micronutrient required for respiration, pigmentation and oxidative stress protection but can also act as a potentially toxic trace element. While several studies have focused on the negative fitness effects of copper on the aquatic larvae of mosquitoes, the effects of larval copper exposure on adult mosquito fitness (i.e., survival and fecundity) and their ability to transmit parasites (i.e., vector competence) remains unclear. Here, using a well-studied model vector-parasite system, the mosquito Aedes aegypti and parasite Dirofilaria immitis, we show that sublethal copper exposure in larval mosquitoes alters adult female fecundity and vector competence. Specifically, mosquitoes exposed to copper had a hormetic fecundity response and mosquitoes exposed to 600 μg/L of copper had significantly fewer infective parasite larvae than control mosquitoes not exposed to copper. Thus, exposure of mosquito larvae to copper levels far below EPA-mandated safe drinking water limits (1300 μg/L) can impact vector-borne disease dynamics not only by reducing mosquito abundance (through increased larval mortality), but also by reducing parasite transmission risk. Our results also demonstrated that larval copper is retained through metamorphosis to adulthood in mosquitoes, indicating that these insects could transfer copper from aquatic to terrestrial foodwebs, especially in urban areas where they are abundant. To our knowledge this is the first study to directly link metal exposure with vector competence (i.e., ability to transmit parasites) in any vector-parasite system. Additionally, it also demonstrates unequivocally that mosquitoes can transfer contaminants from aquatic to terrestrial ecosystems. These results have broad implications for public health because they directly linking contaminants and vector-borne disease dynamics, as well as linking mosquitoes and contaminant dynamics.

Electroporation-mediated nucleic acid delivery during non-embryonic stages for gene-function analysis in Anopheles sinensis

The delivery of exogenous nucleic acids to eggs or non-embryonic individuals by microinjection is a vital reverse genetics technique used to determine gene function in mosquitoes. However, DNA delivery to eggs is complex and time-consuming, and conventional, non-embryonic-injection techniques may result in unobvious phenotypes caused by insufficient absorption of nucleic acid fragments by cells at target body parts or tissues. In this study, we developed a set of electroporation-mediated non-embryonic microinjections for the delivery of exogenous nucleic acids in Anopheles sinensis. Gene silencing using this method led to down-regulation of target gene expression (AsCPR128) by 77% in targeted body parts, compared with only 10% in non-targeted body parts, thus increasing the defect-phenotype rate in the target area by 5.3-fold, compared with non-shock injected controls. Electroporation-mediated somatic transgenesis resulted in stable phenotypic characteristics of the reporter gene at the shocked body parts during the pupal-adult stages in about 69% of individuals. Furthermore, injecting plasmid DNA near the ovaries of female mosquitoes after a blood meal followed by electric shock produced three germline G₁ transgenic lines, with a transformation rate of about 11.1% (calculated from ovulatory G₀ females). Among the positive G₁ lines, 42%, 40%, and 31% of individuals emitted red fluorescence in the larval stage. When the red fluorescent larvae developed into adults, green fluorescence was emitted from the ovaries of the females upon feeding. These results suggest that electroporation-mediated non-embryonic microinjection can be an efficient, rapid, and simple technique for analyzing gene function in non-model mosquitoes or other small insects.

RNAi-Mediated Suppression of Laccase2 Impairs Cuticle Tanning and Molting in the Cotton Boll Weevil (Anthonomus grandis)

The cotton boll weevil, Anthonomus grandis, is the most economically important pest of cotton in Brazil. Pest management programs focused on A. grandis are based mostly on the use of chemical insecticides, which may cause serious ecological impacts. Furthermore, A. grandis has developed resistance to some insecticides after their long-term use. Therefore, alternative control approaches that are more sustainable and have reduced environmental impacts are highly desirable to protect cotton crops from this destructive pest. RNA interference (RNAi) is a valuable reverse genetics tool for the investigation of gene function and has been explored for the development of strategies to control agricultural insect pests. This study aimed to evaluate the biological role of the Laccase2 (AgraLac2) gene in A. grandis and its potential as an RNAi target for the control of this insect pest. We found that AgraLac2 is expressed throughout the development of A. grandis with significantly higher expression in pupal and adult developmental stages. In addition, the immunolocalization of the AgraLac2 protein in third-instar larvae using specific antibodies revealed that AgraLac2 is distributed throughout the epithelial tissue, the cuticle and the tracheal system. We also verified that the knockdown of AgraLac2 in A. grandis resulted in an altered cuticle tanning process, molting defects and arrested development. Remarkably, insects injected with dsAgraLac2 exhibited defects in cuticle hardening and pigmentation. As a consequence, the development of dsAgraLac2-treated insects was compromised, and in cases of severe phenotypic defects, the insects subsequently died. On the contrary, insects subjected to control treatments did not show any visible phenotypic defects in cuticle formation and successfully molted to the pupal and adult stages. Taken together, our data indicate that AgraLac2 is involved in the cuticle tanning process in A. grandis and may be a promising target for the development of RNAi-based technologies.

Multiple roles forlaccase2 in butterfly wing pigmentation, scale development, and cuticle tanning

Lepidopteran wing scales play important roles in a number of functions including color patterning and thermoregulation. Despite the importance of wing scales, however, we still have a limited understanding of the genetic mechanisms that underlie scale patterning, development, and coloration. Here, we explore the function of the phenoloxidase-encoding gene laccase2 in wing and scale development in the nymphalid butterfly Vanessa cardui. Somatic deletion mosaics of laccase2 generated by CRISPR/Cas9 genome editing presented several distinct mutant phenotypes. Consistent with the work in other nonlepidopteran insect groups, we observed reductions in melanin pigmentation and defects in cuticle formation. We were also surprised, however, to see distinct effects on scale development including complete loss of wing scales. This study highlights laccase2 as a gene that plays multiple roles in wing and scale development and provides new insight into the evolution of lepidopteran wing coloration.

The potential risk of Schistosoma mansoni transmission by the invasive freshwater snail Biomphalaria straminea in South China

Schistosomes infect more than 200 million people worldwide, and globally, over 700 million people are at risk of infection. The snail Biomphalaria straminea, as one of the intermediate hosts of Schistosoma mansoni, consecutively invaded Hong Kong in 1973, raising great concern in China. In this study, a malacological survey was conducted over a period of four years, and investigations were performed on the mechanism of susceptibility of B. straminea to S. mansoni. B. straminea was investigated in China from 2014 to 2018. Out of 185 investigated sites, 61 were positive for stages of black B. straminea (BBS), which shows pigmented spots. Twenty of the 61 sites were positive for red B. straminea (RBS), which is partially albino and red colored. Phylogenetic analyses based on cox1 and 18S rRNA sequences demonstrated that both phenotypes were clustered with Brazilian strains. No S. mansoni infections were detected in field-collected snail. However, in laboratory experiments, 4.17% of RBS were susceptible to a Puerto Rican strain of S. mansoni, while BBS was not susceptible. The highest susceptibility rate (70.83%) was observed in the F2 generation of RBS in lab. The density of RBS has increased from south to north and from west to east in Guangdong since 2014. Five tyrosinase tyrosine metabolism genes were upregulated in BBS. Transcriptome comparisons of RBS and BBS showed that ficolin, C1q, MASP-like, and membrane attack complex (MAC)/perforin models of the complement system were significantly upregulated in BBS. Our study demonstrated that B. straminea is widely distributed in Hong Kong and Guangdong Province, which is expanding northwards very rapidly as a consequence of its adaptation to local environments. Our results suggest that B. straminea from South China is susceptible to S. mansoni, implying the high potential for S. mansoni transmission and increased S. mansoni infection risk in China.

Biomphalaria straminea is an important intermediate host for the blood fluke Schistosoma mansoni. B. straminea has spread in Hong Kong and in mainland China since 1973. However, whether resident snails can transmit intestinal schistosomiasis caused by S. mansoni remains unclear. Our results revealed that different types of B. straminea are widespread in cities such as Hong Kong, Shenzhen, Dongguan, Huizhou and Puning and that the distribution of the species has shifted northwards. The most important finding was that one of the phenotypes (red phenotype of B. straminea, RBS), which is highly susceptible to S. mansoni, has spread into the city of Shenzhen since 2016. The density of RBS in Guangdong Province has increased rapidly since 2014, especially since 2016. Transcriptome analysis showed that the high expression levels of ficolin, C1q, MASP-like, and membrane attack complex (MAC)/perforin models of the complement system might be associated with the mechanism of susceptibility. Our study suggested that B. straminea is susceptible to S. mansoni, implying a high potential risk of S. mansoni transmission in South China. More attention should be paid to the potential transmission of S. mansoni, and control measures should be established to prevent the spread of this snail in South China.

RNA interference of tyrosine hydroxylase caused rapid mortality by impairing cuticle formation in Nilaparvata lugens (Hemiptera: Delphacidae)

BACKGROUND

The application of RNA interference (RNAi) technique in controlling agricultural insect pests has been receiving much attention since the discovery of RNAi. The brown planthopper (BPH) Nilaparvata lugens, a notorious pest of rice, has evolved a high level of resistance to many kinds of insecticides. Tyrosine hydroxylase (Th) is an indispensable survival gene in holometabolous insects, playing key roles in cuticle tanning and immunity. In this study, we investigated whether Th could be used as a potential target in controlling N. lugens.

RESULTS

Here, we demonstrated that NlTh had a periodical expression pattern during molting with the highest level observed in epidermis. Dysfunction of NlTH by dsNlTh microinjection or 3-IT feeding similarly caused rapid death of N. lugens. Compared with dsGFP control BPHs, dsNlTh injected BPHs (i) had cuticle pigmentation and sclerotizaton defects; (ii) had less endocuticle lamella in tergum integument; (iii) showed higher mortality during the molting process as a result of defective cuticle shedding; (iv) showed feeding disorders indicated by a low number of probe wound dots on rice; (v) had more vulnerable cuticle.

CONCLUSION

This study demonstrated that TH orthologues play a conservative and crucial role for exocuticle tanning in both holometabolous and hemimetabolous insects, and NlTh could be targeted for RNAi-mediated BPH control. The rapid lethal phenotype of NlTH dysfunction BPHs partly induced by cuticle formation defects. © 2020 Society of Chemical Industry.

Laccases: structure, function, and potential application in water bioremediation

The global rise in urbanization and industrial activity has led to the production and incorporation of foreign contaminant molecules into ecosystems, distorting them and impacting human and animal health. Physical, chemical, and biological strategies have been adopted to eliminate these contaminants from water bodies under anthropogenic stress. Biotechnological processes involving microorganisms and enzymes have been used for this purpose; specifically, laccases, which are broad spectrum biocatalysts, have been used to degrade several compounds, such as those that can be found in the effluents from industries and hospitals. Laccases have shown high potential in the biotransformation of diverse pollutants using crude enzyme extracts or free enzymes. However, their application in bioremediation and water treatment at a large scale is limited by the complex composition and high salt concentration and pH values of contaminated media that affect protein stability, recovery and recycling. These issues are also associated with operational problems and the necessity of large-scale production of laccase. Hence, more knowledge on the molecular characteristics of water bodies is required to identify and develop new laccases that can be used under complex conditions and to develop novel strategies and processes to achieve their efficient application in treating contaminated water. Recently, stability, efficiency, separation and reuse issues have been overcome by the immobilization of enzymes and development of novel biocatalytic materials. This review provides recent information on laccases from different sources, their structures and biochemical properties, mechanisms of action, and application in the bioremediation and biotransformation of contaminant molecules in water. Moreover, we discuss a series of improvements that have been attempted for better organic solvent tolerance, thermo-tolerance, and operational stability of laccases, as per process requirements.

Functional characterization of the horizontally transferred 4,5-DOPA extradiol dioxygenase gene in the domestic silkworm, Bombyx mori

4,5-DOPA dioxygenase (DODA) is a crucial enzyme in the biosynthetic pathway of betalain. Previous studies have shown that DODA is present in plants, fungi and bacteria. Using updated data, here we show that DODA genes (BmDODA) in the domestic silkworm (Bombyx mori) and other lepidopteran insects are most likely to be horizontally transferred from fungi. A synteny analysis indicated that BmDODA1 is orthologous to other lepidopteran DODAs and that BmDODA2 is a paralogous gene. To explore the function of DODA in Lepidoptera, we first examined the expression patterns of BmDODA1. BmDODA1 showed high transcriptional and translational levels in the midgut and head. Then, we exogenously expressed the BmDODA1 gene, detected 4,5-DOPA ring-cleaving activity and calculated the kinetic parameters of the recombinant BmDODA1. We found that the transcription levels of BmDODA1 were significantly induced by the pathogens Bacillus bombyseptieus and Escherichia coli. Thus, the horizontal transfer of the BmDODA gene in the silkworm may be involved in dopa metabolism and contribute to antimicrobial activity in this species. Our results provide a documented example of functional horizontal gene transfer (HGT) between fungi and animals and expand our knowledge of HGT amongst eukaryotes.

Blood-induced differential gene expression in Anopheles dirus evaluated using RNA sequencing

Malaria parasites are transmitted through blood feeding by female Anopheline mosquitoes. Unveiling the blood-feeding process will improve understanding of vector biology. Anopheles dirus (Diptera: Culicidae) is one of the primary malaria vectors in the Greater Mekong Subregion, the epicentre of malaria drug resistance. In this study, differential gene expression between sugar- and blood-fed An. dirus was investigated by RNA sequencing (RNA-seq). A total of 589 transcripts were found to be upregulated and 703 transcripts downregulated as a result of blood feeding. Transcriptional differences were found in genes involved in blood digestion, peritrophic matrix formation, oogenesis and vitellogenesis. The expression levels of several genes were validated by quantitative reverse transcription polymerase chain reaction. The present results provide better understanding of An. dirus biology in relation to its blood feeding.

Opening the toolkit for genetic analysis and control of Anopheles mosquito vectors

Anopheles is the only genus of mosquitoes that transmit human malaria and consequently the focus of large scale genome and transcriptome-wide association studies. Genetic tools to define the function of the candidate genes arising from these analyses are vital. Moreover, genome editing offers the potential to modify Anopheles population structure at local and global scale to provide complementary tools towards the ultimate goal of malaria elimination. Major breakthroughs in Anopheles genetic analysis came with the development of germline transformation and RNA interference technology. Yet, the field has been revolutionised again by precise genome editing now possible through site-specific nucleases. Here we review the components of the current genetic toolkit available to study Anopheles, focusing particularly on how these technical advances are used to gain insight into malaria transmission and the design of genetic methods to control Anopheles vectors.

Silencing cuticular pigmentation genes enables RNA FISH in intact insect appendages

Optical imaging of gene expression by fluorescence in situ hybridisation (FISH) in insects is often impeded by their pigmented cuticle. As most chemical bleaching agents are incompatible with FISH, we developed an RNA interference (RNAi)-based method for clearing cuticular pigmentation which enables the use of whole-mount body appendages for RNA FISH (termed RNA-i-FISH). Silencing laccase2 or tyrosine hydroxylase in two leaf beetles species (Chrysomela populi and Phaedon cochleariae) cleared their pigmented cuticle and decreased light absorbance. Subsequently, intact appendages (palps, antennae, legs) from RNAi-cleared individuals were used to image the expression and spatial distribution of antisense mRNA of two chemosensory genes encoding gustatory receptor and odorant-binding protein. Imaging did not work for RNAi controls because the pigmentation was retained, or for FISH controls (sense mRNA). Several bleaching agents were incompatible with FISH, because of degradation of RNA, lack of clearing efficacy or long incubation times. Overall, silencing pigmentation genes is a significant improvement over bleaching agents, enabling FISH in intact insect appendages.

Two New Polyphenol Oxidase Genes of Tea Plant (Camellia sinensis) Respond Differentially to the Regurgitant of Tea Geometrid, Ectropis obliqua

Polyphenol oxidases (PPOs) have been reported to play an important role in protecting plants from attacks by herbivores. Though PPO genes in other plants have been extensively studied, research on PPO genes in the tea plant (Camellia sinensis) is lacking. In particular, which members of the PPO gene family elicit the defense response of the tea plant are as yet unknown. Here, two new PPO genes, CsPPO1 and CsPPO2, both of which had high identity with PPOs from other plants, were obtained from tea leaves. The full length of CsPPO1 contained an open reading frame (ORF) of 1740 bp that encoded a protein of 579 amino acids, while CsPPO2 contained an ORF of 1788 bp that encoded a protein of 595 amino acids. The deduced CsPPO1 and CsPPO2 proteins had calculated molecular masses of 64.6 and 65.9 kDa; the isoelectric points were 6.94 and 6.48, respectively. The expression products of recombinant CsPPO1 and CsPPO2 in Escherichia coli were about 91 and 92 kDa, respectively, but the recombinant proteins existed in the form of an inclusion body. Whereas CsPPO1 is highly expressed in stems, CsPPO2 is highly expressed in roots. Further results showed that the expression of CsPPO1 and CsPPO2 was wound- and Ectropis obliqua-induced, and that regurgitant, unlike treatment with wounding plus deionized water, significantly upregulated the transcriptional expression of CsPPO2 but not of CsPPO1. The difference between regurgitant and wounding indicates that CsPPO2 may play a more meaningful defensive role against E. obliqua than CsPPO1. Meanwhile, we found the active component(s) of the regurgitant elicited by the expression of CsPPO may contain small molecules (under 3-kDa molecular weight). These conclusions advance the understanding of the biological function of two new PPO genes and show that one of these, CsPPO2, may be a promising gene for engineering tea plants that are resistant to E. obliqua.

Melanization in response to wounding is ancestral in arthropods and conserved in albino cave species

Many species adapted to aphotic subterranean habitats have lost all body pigmentation. Yet, melanization is an important component of wound healing in arthropods. We amputated appendages in a variety of cave-adapted and surface-dwelling arthropods. A dark clot formed at the site of injury in most species tested, including even albino cave-adapted species. The dark coloration of the clots was due to melanin deposition. The speed of wound melanization was uncorrelated with a difference in metabolic rate between surface and cave populations of an amphipod. The chelicerate Limulus polyphemus, all isopod crustaceans tested, and the cave shrimp Troglocaris anophthalmus did not melanize wounds. The loss of wound melanization in T. anophthalmus was an apomorphy associated with adaptation to subterranean habitats, but in isopods it appeared to be a symplesiomorphy unrelated to colonization of subterranean habitats. We conclude that wound melanization i) is an important part of innate immunity because it was present in all major arthropod lineages, ii) is retained in most albino cave species, and iii) has been lost several times during arthropod evolution, indicating melanization is not an indispensable component of wound healing in arthropods.

A Chromosome-Scale Assembly of the Bactrocera cucurbitae Genome Provides Insight to the Genetic Basis of white pupae

Genetic sexing strains (GSS) used in sterile insect technique (SIT) programs are textbook examples of how classical Mendelian genetics can be directly implemented in the management of agricultural insect pests. Although the foundation of traditionally developed GSS are single locus, autosomal recessive traits, their genetic basis are largely unknown. With the advent of modern genomic techniques, the genetic basis of sexing traits in GSS can now be further investigated. This study is the first of its kind to integrate traditional genetic techniques with emerging genomics to characterize a GSS using the tephritid fruit fly pest Bactrocera cucurbitae as a model. These techniques include whole-genome sequencing, the development of a mapping population and linkage map, and quantitative trait analysis. The experiment designed to map the genetic sexing trait in B. cucurbitae, white pupae (wp), also enabled the generation of a chromosome-scale genome assembly by integrating the linkage map with the assembly. Quantitative trait loci analysis revealed SNP loci near position 42 MB on chromosome 3 to be tightly linked to wp Gene annotation and synteny analysis show a near perfect relationship between chromosomes in B. cucurbitae and Muller elements A-E in Drosophila melanogaster This chromosome-scale genome assembly is complete, has high contiguity, was generated using a minimal input DNA, and will be used to further characterize the genetic mechanisms underlying wp Knowledge of the genetic basis of genetic sexing traits can be used to improve SIT in this species and expand it to other economically important Diptera.