Gene identification and enzymatic properties of a membrane-bound trehalase from the ovary of Rhodnius prolixus

The impact of UV-C radiation on the sugar metabolism of the red flour beetle Tribolium castaneum herbst (coleoptera; tenebrionidae)

PURPOSE

Ultraviolet-C (UV-C) is known to induce morphological abnormality in various parts of the red flour beetle, Tribolium castaneum, including its wings, antennae, eyes, legs, and reproductive organs. However, little is known about the effects of UV-C on T. castaneum's sugar content and enzyme activity.

MATERIAL AND METHODS

We investigated the concentrations of glucose and trehalose as well as changes in trehalase activity in different developmental stages following UV-C radiation at different exposure periods (1, 2, 4, 8, 16, 32, and 64 min). In addition, the larval mortality and body weight were examined.

RESULTS

A reduction in glucose content was recorded in 10-, 15- and 20-day-old larvae and trehalase enzyme activity was recorded in 5- and 10-day-old larvae, whereas an increase in trehalose content was found in adults irradiated with UV-C. In addition, UV-C radiation for 1-64 min caused larval mortality on the first and subsequent days post-irradiation. Moreover, UV-C irradiated larvae exhibited lower body weight, which aligned with the reduction of trehalase activity and glucose content from days 1-6 post-exposure, and the degree of these reductions corresponded to the exposure times.

CONCLUSION

UV-C affected sugar content through the reduction of trehalase activity, and glucose declination may cause mortality in T. castaneum; however, further research is needed to provide a better understanding of the impact of UV-C on sugar metabolism.

Effects of insulin-like peptide 7 in Bemisia tabaci MED on tomato chlorosis virus transmission

BACKGROUND

Tomato chlorosis virus (ToCV) is a semi-persistent plant virus that is primarily transmitted by the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae). It causes a serious disease that lowers tomato yield. Insulin-like peptide (ILP), an insulin homolog, regulates trehalose metabolism in a variety of insects. In a previous study, we discovered that trehalose metabolism is required for whiteflies to transmit ToCV effectively. Furthermore, transcriptome sequencing revealed that the BtILP7 gene was highly expressed in B. tabaci infected with ToCV. Therefore, the whitefly ILP7 gene may facilitate the transmission of ToCV and be an attractive target for the control of whiteflies and subsequently ToCV.

RESULTS

The ToCV content in B. tabaci MED was found to be correlated with BtILP7 gene expression. Subsequent RNA interference (RNAi) of the BtILP7 gene had a significant impact on B. tabaci MED's trehalose metabolism and reproductive capacity, as well as ability to transmit ToCV.

CONCLUSIONS

These results indicate that the BtILP7 gene was closely related to ToCV transmission by regulating trehalose metabolism and reproduction behavior, thus providing a secure and environmentally friendly management strategy for the control of whiteflies and ToCV-caused disease. © 2022 Society of Chemical Industry.

Trehalose-6-phosphate synthase regulates chitin synthesis in Mythimna separata

Trehalose is a substrate for the chitin synthesis pathway in insects. Thus, it directly affects chitin synthesis and metabolism. Trehalose-6-phosphate synthase (TPS) is a crucial enzyme in the trehalose synthesis pathway in insects, but its functions in Mythimna separata remain unclear. In this study, a TPS-encoding sequence in M. separata (MsTPS) was cloned and characterized. Its expression patterns at different developmental stages and in diverse tissues were investigated. The results indicated that MsTPS was expressed at all analyzed developmental stages, with peak expression levels in the pupal stage. Moreover, MsTPS was expressed in the foregut, midgut, hindgut, fat body, salivary gland, Malpighian tubules, and integument, with the highest expression levels in the fat body. The inhibition of MsTPS expression via RNA interference (RNAi) resulted in significant decreases in the trehalose content and TPS activity. It also resulted in significant changes in Chitin synthase (MsCHSA and MsCHSB) expression, and significantly decrease the chitin content in the midgut and integument of M. separata. Additionally, the silencing of MsTPS was associated with a significant decrease in M. separata weight, larval feed intake, and ability to utilize food. It also induced abnormal phenotypic changes and increased the M. separata mortality and malformation rates. Hence, MsTPS is important for M. separata chitin synthesis. The results of this study also suggest RNAi technology may be useful for enhancing the methods used to control M. separata infestations.

Knockdown of Two Trehalase Genes by RNA Interference Is Lethal to the White-Backed Planthopper Sogatella furcifera (Horváth) (Hemiptera:Delphacidae)

Trehalase (Tre) is a crucial enzyme involved in trehalose metabolism, and it plays pivotal roles in insect development and metamorphosis. However, the biological function of Tre genes in Sogatella furcifera remains unclear. In the present study, two Tre genes—SfTre1 and SfTre2—were cloned and identified based on the S. furcifera transcriptome data. Bioinformatic analysis revealed that the full-length complementary DNA of SfTre1 and SfTre2 genes were 3700 and 2757 bp long, with 1728- and 1902-bp open reading frame encoding 575 and 633 amino acid residues, respectively. Expression analysis indicated that SfTre1 and SfTre2 were expressed at all developmental stages, with the highest expression in day two adults. Furthermore, the highest expression levels of SfTre1 and SfTre2 were observed in the ovary; enriched expression was also noted in head tissues. The knockdown of SfTre1 and SfTre2 via injecting double-stranded RNAs decreased the transcription levels of the corresponding mRNAs and led to various malformed phenotypes and high lethality rates. The results of our present study indicate that SfTre1 and SfTre2 play crucial roles in S. furcifera growth and development, which can provide referable information for Tre genes as a potential target for planthopper control.

Purification and Functional Characterization of a Soluble Trehalase in Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)

Trehalase is the only enzyme known for the irreversible splitting of trehalose and plays a major role in insect growth and development. In this report, we describe a basic study of the trehalase gene fragment encoding a soluble trehalase from Lissorhoptrus oryzophilus (LoTRE1). Sequence alignment and phylogenetic analysis suggested that LoTRE1 was similar to some known insect trehalases and belongs to the Coleoptera trehalase group. Additionally, LoTRE1 was expressed mainly in the fat body. Purified protein was obtained using heterologous expression of LoTRE1 in Escherichia coli, and the recombinant protein exhibited the ability to decompose trehalose. Enzyme-substrate docking indicated the potential involvement of other residues in the catalytic activity, in addition to Asp 333. Moreover, feeding of adults on LoTRE1 dsRNA silenced the transcription of LoTRE1 and thereby reduced the activity of trehalase and increased the trehalose content; it also led to a 12% death rate. This study reveals essential molecular features of trehalase and offers insights into the structural aspects of this enzyme, which might be related to its function. Taken together, the findings demonstrate that LoTRE1 is indispensable for adults of this pest and provide a new target for the control of L. oryzophilus.

Regulation of a Trehalose-Specific Facilitated Transporter (TRET) by Insulin and Adipokinetic Hormone in Rhodnius prolixus, a Vector of Chagas Disease

Using the blood-sucking kissing bug, Rhodnius prolixus as an experimental model, we have studied the involvement of insulin-like peptides (ILPs) and adipokinetic hormone (AKH) signaling in carbohydrate metabolism, focusing on the regulation of the trehalose-specific facilitated transporter (Rhopr-TRET), particularly in the ovaries. We find that trehalose stores in ovaries increase after feeding, synchronously with the beginning of vitellogenesis, but that the transcript expression of enzymes involved in trehalose synthesis show no changes between unfed and blood-fed animals. However, an eightfold increase in Rhopr-TRET transcript expression is observed in the ovaries post-blood meal. In vivo and ex vivo assays using exogenous insulins and Rhopr-AKH, reveal that Rhopr-TRET is up-regulated in ovaries by both peptide families. In accordance with these results, when ILP and AKH signaling cascades are impaired using RNA interference, Rhopr-TRET transcript is down-regulated. In addition, trehalose injection induces an up-regulation of Rhopr-TRET transcript expression and suggests an activation of insulin signaling. Overall, the results support the hypothesis of a direct trehalose uptake by ovaries from the hemolymph through Rhopr-TRET, regulated by ILP and/or AKH. We also show that Rhopr-TRET may work cooperatively with AKH signaling to support the release of trehalose from the ovaries into the hemolymph during the unfed (starved) condition. In conclusion, the results indicate that in females of R. prolixus, trehalose metabolism and its hormonal regulation by ILP and AKH play critical roles in adapting to different nutritional conditions and physiological states.

Gene Characterization and Enzymatic Activities Related to Trehalose Metabolism of In Vitro Reared Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) under Sustained Cold Stress

Simple Summary

Trehalose is a non-reducing disaccharide that presents in a wide variety of organisms, where it serves as an energy source or stress protectant. Trehalose is the most characteristic sugar of insect hemolymph and plays a crucial role in the regulation of insect growth and development. Trichogramma species are economically important egg parasitoids, which are being mass-produced for biological control programs worldwide. Many Trichogramma species could be mass reared on artificial mediums (not insect eggs), in which components contain insect hemolymph and trehalose. These in vitro-reared parasitoid wasps were strongly affected by cold storage, but prepupae could be successfully stored at 13 °C for up to 4 weeks. The aims of the present study were to determine the role of trehalose and the relationship between trehalose and egg parasitoid stress resistance. Our study revealed that (1) trehalose regulated the growth under sustained cold stress; (2) prepupal stage is a critical developmental period and 13 °C is the cold tolerance threshold temperature; (3) in vitro reared Trichogramma dendrolimi could be reared at temperatures of 16 °C, 20 °C, and 23 °C to reduce rearing costs. This finding identifies a low cost, prolonged development rearing method for T. dendrolimi, which will facilitate improved mass rearing methods for biocontrol.

Abstract

Trichogramma spp. is an important egg parasitoid wasp for biocontrol of agriculture and forestry insect pests. Trehalose serves as an energy source or stress protectant for insects. To study the potential role of trehalose in cold resistance on an egg parasitoid, cDNA for trehalose-6-phosphate synthase (TPS) and soluble trehalase (TRE) from Trichogramma dendrolimi were cloned and characterized. Gene expressions and enzyme activities of TdTPS and TdTRE were determined in larvae, prepupae, pupae, and adults at sustained low temperatures, 13 °C and 16 °C. TdTPS and TdTRE expressions had similar patterns with higher levels in prepupae at 13 °C and 16 °C. TdTPS enzyme activities increased with a decrease of temperature, and TdTRE activity in prepupae decreased sharply at these two low temperatures. In vitro reared T. dendrolimi could complete entire development above 13 °C, and the development period was prolonged without cold injury. Results indicated trehalose might regulate growth and the metabolic process of cold tolerance. Moreover, 13 °C is the cold tolerance threshold temperature and the prepupal stage is a critical developmental period for in vitro reared T. dendrolimi. These findings identify a low cost, prolonged development rearing method, and the cold tolerance for T. dendrolimi, which will facilitate improved mass rearing methods for biocontrol.

What happens after a blood meal? A transcriptome analysis of the main tissues involved in egg production in Rhodnius prolixus, an insect vector of Chagas disease

The blood-sucking hemipteran Rhodnius prolixus is a vector of Chagas disease, one of the most neglected tropical diseases affecting several million people, mostly in Latin America. The blood meal is an event with a high epidemiological impact since adult mated females feed several times, with each meal resulting in a bout of egg laying, and thereby the production of hundreds of offspring. By means of RNA-Sequencing (RNA-Seq) we have examined how a blood meal influences mRNA expression in the central nervous system (CNS), fat body and ovaries in order to promote egg production, focusing on tissue-specific responses under controlled nutritional conditions. We illustrate the cross talk between reproduction and a) lipids, proteins and trehalose metabolism, b) neuropeptide and neurohormonal signaling, and c) the immune system. Overall, our molecular evaluation confirms and supports previous studies and provides an invaluable molecular resource for future investigations on different tissues involved in successful reproductive events. These analyses serve as a starting point for new investigations, increasing the chances of developing novel strategies for vector population control by translational research, with less impact on the environment and more specificity for a particular organism.

Effect of long-term cold storage on trehalose metabolism of pre-wintering Harmonia axyridis adults and changes in morphological diversity before and after wintering

Harmonia axyridis is a major bio-control agent of pests in agriculture and forest ecosystems. It is also a globally important invasive insect species. To test whether dark elytra colour is associated with greater cold hardiness, we compared the survival rate of prolonged cold exposure in both yellow and black colour morphs of female and male H. axyridis. We determined the trehalose and glycogen content, trehalase activity, and the dynamics of genes associated with the trehalose metabolic pathway. Yellow forms predominated before winter began, however black forms increased from 11.15 to 30.46% after overwintering. There was no significant difference in trehalose content between the females and males during overwintering. Glycogen content in over-wintering yellow females and black males increased significantly, while it decreased in black females. Soluble trehalase activity increased significantly in all the insects except black females. Membrane-bound trehalase activity increased in black males, and decreased in black females. Trehalose and glycogen content and trehalase activity were regulated by differential expression of TRE and TPS genes. Female beetles weighed more than males and survived in low temperatures for longer periods of time, regardless of elytra colour, suggesting that mass is a stronger predictor of overwintering survival rather than colour morph. Our results provide a guide for comparing cold resistance in insects and a theoretical basis for cold storage of H. axyridis for use as natural enemies of pests in biological control programs.

Evaluation of the Expression and Function of the TRE2-like and TRE2 Genes in Ecdysis of Harmonia axyridis

Harmonia axyridis is an important predatory insect and widely used in biological control of agricultural and forestry pests. Trehalose is directly involved in the energy storage of the H. axyridis and in the oxidative function of various physiological activities thereby providing an energy source for its growth and development. The aim of this study was to explore the potential function of membrane-bound-like trehalase (TRE2-like) and membrane-bound trehalase (TRE2) genes in H. axyridis by RNAi. In addition, the activity of soluble and membrane-bound trehalase and the expression of genes related to trehalose and glycogen metabolism were determined in the larvae injected with dsTRE2-like or dsTRE2. The results showed that wing abnormality and mortality appeared in adults, as well as the activity of soluble trehalase and glycogen contents increased when interfering with TRE2-like gene. However, the activity of membrane-bound trehalase, trehalose and glucose contents in the larvae decreased. The expression of glycogen synthase (GS) and glycogen phosphorylase (GP) genes were decreased after RNAi in the ecdysis stage. The expression of chitin synthase gene A (CHSA), chitin synthase gene B (CHSB), and trehalose-6-phosphate synthase genes (TPS) were decreased significantly after RNAi, especially in the ecdysis stage. These results indicated that RNA interference is capable of knocking down gene expression of TRE2-like and TRE2, thereby disrupting trehalose metabolism which affects the chitin synthesis pathway in turn and also leads to developmental defects, such as wing deformities. This study could provide some theoretical guidance for the function of TRE2 gene in other insects.

Glucose Utilization in the Regulation of Chitin Synthesis in Brown Planthopper

Glucose-6-phosphatase (G6Pase) and hexokinase (HK) are two key enzymes in the glycolysis and gluconeogenesis pathways, which catalyze the synthesis and degradation of glucose in insects, respectively. G6Pase and HK play an important role in insect growth by regulating the metabolism of glucose, leading to the efficient metabolism of other macromolecules. However, it is unclear whether these genes could be investigated for pest control through their actions on chitin metabolism. We studied the potential functions of G6Pase and HK genes in the regulation of chitin metabolism pathways by RNAi technology. Interference with G6Pase expression did not affect trehalose and chitin metabolism pathways in brown planthopper, Nilaparvata lugens (Stål). However, knockdown of the HK gene resulted in a significant decrease of expression of genes associated with the trehalose metabolic pathway but had no significant effect on trehalase activity, trehalose content, or glucogen content. Additionally, HK knockdown resulting in downregulation of the genes involved in chitin metabolism in the brown planthopper. These insects also showed wing deformities and difficulty in molting to varying degrees. We suggest that the silencing of HK expression directly inhibited the decomposition of glucose, leading to impaired chitin synthesis.

The Evolutionary History and Functional Divergence of Trehalase (treh) Genes in Insects

Trehalases (treh) have been found in different organisms, such as bacteria, fungi, yeast, nematodes, insects, vertebrates, and plants. Their biochemical properties are extremely variable and not yet fully understood. Gene expression patterns have shown differences among insect species suggesting a potential functional diversification of trehalase enzymes during their evolution. A second gene family encoding for enzymes with hypothetical trehalase activity has been repeatedly annotated in insect genome as acid trehalases/acid trehalase-like (ath), but its functional role is still not clear. The currently available large amount of genomic data from many insect species may enable a better understanding of the evolutionary history, phylogenetic relationships and possible roles of trehalase encoding genes in this taxon. The aim of the present study is to infer the evolutionary history of trehalases and acid trehalase genes in insects and analyze the trehalase functional divergence during their evolution, combining phylogenetic and genomic synteny/colinearity analyses.

Gene Cloning, Prokaryotic Expression, and Biochemical Characterization of a Soluble Trehalase in Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Trehalase is an indispensable component of insect hemolymph that plays important role in energy metabolism and stress resistance. In this study, we cloned and expressed the gene encoding soluble trehalase (HaTreh-1) of Helicoverpa armigera (cotton bollworm) and characterized the enzyme. HaTreh-1 had a full-length open reading frame encoding a protein of 571 amino acids. Sequence comparison indicated that HaTreh-1 was similar to some known insect trehalases. Two essential active sites (D321 and E519) and three essential residues (R168, R221, and R286) were conserved in HaTreh-1. The recombinant trehalase was expressed in Escherichia coli and purified by nickel exchange chromatography. Molecular weight of the recombinant protein was about 71 kDa, and the optimum HaTreh-1 enzyme activity is at 55°C with pH 6.0. Enzymatic assays showed a Km value of 72.8 mmol/liter and a Vmax value of 0.608 mmol/(liter·min). Inhibition assays in vitro indicated that castanospermine, a polyhydroxylated alkaloid, was an effective competitive inhibitor of trehalase with a Ki value of 6.7 μmol/liter. The inhibitor action of castanospermine was linked to its modification effect on trehalase structure. The circular dichroism spectrum showed that the percentage of α-helix increased under the presence of castanospermine. Results of our study will aid in developing effective trehalase inhibitors for controlling H. armigera in the future.

Knockdown of five trehalase genes using RNA interference regulates the gene expression of the chitin biosynthesis pathway in Tribolium castaneum

Background

RNA interference is a very effective approach for studies on gene function and may be an efficient method for controlling pests. Trehalase is a key gene in the chitin biosynthesis pathway in insects. Five trehalase genes have been cloned in Tribolium castaneum, though it is not known whether the detailed functions of these trehalases can be targeted for pest control.

Results

The functions of all five trehalase genes were studied using RNAi, and the most important results showed that the expression of all 12 genes decreased significantly from 12 to 72 h compared with the control groups, except GP1 at 72 h, when the expression of the TcTre2 gene was suppressed. The results also revealed different abnormal phenotypes, and the observed mortality rates ranged from 17 to 42 %. The qRT-PCR results showed that the expression of TPS, GS, two GP, CHS1a and CHS1b genes decreased significantly, while that of the CHS2 gene decreased or increased after RNAi after the five trehalases were silenced at 48 h. In addition, TPS gene expression decreased from 12 to 72 h after dsTcTre injection.

Conclusions

These results demonstrate that silencing of any individual trehalase gene, especially Tre1-4 and Tre2 gene can lead to moulting deformities and a high mortality rate through the regulation of gene expression in the chitin biosynthesis pathway and may be a potential approach for pest control in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-016-0297-2) contains supplementary material, which is available to authorized users.

Molecular characterization of soluble and membrane-bound trehalases in the cotton mirid bug, Apolygus lucorum

Trehalose, a major hemolymph sugar in insects, is hydrolyzed by trehalase. We identified a soluble and a membrane-bound form of trehalase and isolated the corresponding mRNA, ALTre-1, and ALTre-2 in the cotton mirid bug, Apolygus lucorum. The deduced amino acid sequences of ALTre-1 and ALTre-2 revealed mature proteins with 643 and 617 amino acids, respectively. ALTre-1 and ALTre-2 contained trehalase signature motifs, and ALTre-2 contained a putative transmembrane domain near the C-terminus, suggesting that ALTre-1 and ALTre-2 encoded a soluble trehalase and a membrane-bound trehalase, respectively. Comparison of trehalase activity at different developmental stages and in six tissues indicated that soluble trehalase activity accounted for the majority of total trehalase activity in A. lucorum. ALTre-1 and ALTre-2 were expressed in all tissues and stages, with the highest expression of both in the second instar nymphs, ALTre-1 in the ovary and malpighian tubules, ALTre-2 in the flight muscles and fat body. Following the exposure of second instar nymph to 20-E, the soluble trehalase activity increased gradually while the membrane-bound trehalase activity remained at its initial level. Similarly, 20-E upregulated ALTre-1 expression but had no effect on ALTre-2 expression. These results suggest that an increase of this soluble trehalase activity was upregulated by ALTre-1 gene.