Regulation of Carbohydrate Metabolism by Trehalose-6-Phosphate Synthase 3 in the Brown Planthopper, Nilaparvata lugens

Trehalose-6-Phosphate Synthase Contributes to Rapid Cold Hardening in the Invasive Insect Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) by Regulating Trehalose Metabolism

Rapid cold hardening (RCH) is known to rapidly enhance the cold tolerance of insects. Trehalose has been demonstrated to be a cryoprotectant in Lissorhoptrus oryzophilus, an important invasive pest of rice in China. Trehalose synthesis mainly occurs through the Trehalose-6-phosphate synthase (TPS)/trehalose-6-phosphate phosphatase (TPP) pathway in insects. In this study, the TPS gene from L. oryzophilus (LoTPS) was cloned and characterized for the first time. Its expression and trehalose content changes elicited by RCH were investigated. Our results revealed that RCH not only increased the survival rate of adults but also upregulated the expression level of LoTPS and increased the trehalose content under low temperature. We hypothesized that upregulated LoTPS promoted trehalose synthesis and accumulation to protect adults from low-temperature damage. To further verify the function of the LoTPS gene, we employed RNA interference (RNAi) technology. Our findings showed that RCH efficiency disappeared and the survival rate did not increase when the adults were fed dsRNA of LoTPS. Additionally, inhibiting LoTPS expression resulted in no significant difference in trehalose content between the RCH and non-RCH treatments. Furthermore, the expression patterns of trehalose transporter (TRET) and trehalase (TRE) were also affected. Collectively, these results indicate the critical role of LoTPS in L. oryzophilus cold resistance after RCH induction. LoTPS can enhance survival ability by regulating trehalose metabolism. These findings contribute to further understanding the role of TPS in insect cold resistance and the invasiveness of L. oryzophilus. Moreover, RNAi of LoTPS opens up possibilities for novel control strategies against L. oryzophilus in the future.

Disruption of trehalose periplasmic recycling dysregulates cAMP-CRP signaling in Escherichia coli during stationary phase

IMPORTANCE

Survival during starvation hinges on the ability to manage intracellular energy reserves and to initiate appropriate metabolic responses to perturbations of such reserves. How Escherichia coli manage carbon storage systems under starvation stress, as well as transpose changes in intracellular metabolite levels into regulatory signals, is not well understood. Endogenous trehalose metabolism may be at the center of these processes, coupling carbon storage with carbon starvation responses. The coupled transport to the periplasm and subsequent hydrolysis of trehalose back to glucose for transport to the cytoplasm may function as a crucial metabolic signaling pathway. Although trehalose has been characterized as a stress protectant in E. coli, the disaccharide also functions as both an energy storage compound and a regulator of carbohydrate metabolism in fungi, plants, and other bacteria. Our research explores the metabolic regulatory properties of trehalose in E. coli and a potential mechanism by which the intracellular carbon pool is interconnected with regulatory circuits, enabling long-term survival.

Regulatory function of the trehalose-6-phosphate synthase gene TPS3 on chitin metabolism in brown planthopper, Nilaparvata lugens

Brown planthopper (Nilaparvata lugens) is one of the important pests that damage rice. Trehalose-6-phosphate synthase (TPS) is a key enzyme responsible for catalysing the biosynthesis of trehalose, which is the energy substance of insects. In this study, combined with the reported N. lugens TPS1, TPS2 and newly discovered TPS3, we studied the regulation of TPS in chitin metabolism by RNA interference. Firstly, we found that the relative expression levels of TRE1-1, TRE1-2 and TRE2 increased significantly after 48 h of dsTPS3 injection, and the activity of TRE1 enhanced significantly. Secondly, abnormal and lethal phenotypes were observed after dsTPS3 and dsTPSs injection. The relative expression levels of PGM2, G6PI2, Cht1-4, Cht6-10 and IDGF decreased significantly after 48 h of dsTPS3 injection. At 72 h after injection of dsTPS3, the relative expression levels of CHS1, Cht2, Cht4, Cht7 and Cht8 reduced significantly, but the expression levels of G6PI1, Cht5 and ENGase increased significantly. The relative expression levels of GFAT, UAP, PGM2, G6PI2, CHS1, CHS1a, CHS1b, Cht2, Cht4, Cht8, Cht9 and Cht10 decreased significantly after 48 h of dsTPSs injection. However, at 72 h after the injection of dsTPSs, the expression levels of GNPNA, UAP, PGM1, G6PI1, HK, CHS1, CHS1a, CHS1b, Cht3, Cht5, Cht7 and ENGase increased significantly. Finally, the chitin content decreased in dsTPS1, dsTPS2 and dsTPSs treatments. In conclusion, the inhibition of TPS expression affected the metabolism of trehalose and chitin in N. lugens. The related research results provide a theoretical basis for pest control.

The Role of Insulin-like Peptide in Maintaining Hemolymph Glucose Homeostasis in the Pacific White Shrimp Litopenaeus vannamei

Insulin-like peptide (ILP) has been identified in various crustaceans, but whether it has a similar function in regulating hemolymph glucose as vertebrate insulin is unclear. We analyzed the components of hemolymph sugar in the Pacific white shrimp, Litopenaeus vannamei, and investigated the changes of hemolymph glucose concentration and the expressions of ILP and glucose metabolism genes under different treatments. We found glucose was a major component of hemolymph sugar in shrimp. Starvation caused hemolymph glucose to rise first and then decline, and the raised hemolymph glucose after exogenous glucose injection returned to basal levels within a short time, indicating that shrimp have a regulatory mechanism to maintain hemolymph glucose homeostasis. In addition, injections of bovine insulin and recombinant LvILP protein both resulted in a fast decline in hemolymph glucose. Notably, RNA interference of LvILP did not significantly affect hemolymph glucose levels, but it inhibited exogenous glucose clearance. Based on the detection of glucose metabolism genes, we found LvILP might maintain hemolymph glucose stability by regulating the expression of these genes. These results suggest that ILP has a conserved function in shrimp similar to insulin in vertebrates and plays an important role in maintaining hemolymph glucose homeostasis.

Silencing of the BtTPS genes by transgenic plant-mediated RNAi to control Bemisia tabaci MED

BACKGROUND

Whitefly (Bemisia tabaci) is a typical pest that causes severe damage to hundreds of agricultural crops. The trehalose-6-phosphate synthase (TPS) genes, as the key genes in the insect trehalose synthesis pathway, are important for insect growth and development. The whitefly TPS genes may be a main reason for the severe damage and may represent potential targets for the control of whiteflies.

RESULTS

In this study, we identified and cloned three TPS genes from B. tabaci MED and found that the BtTPS1 and BtTPS2 genes showed higher expression levels than the BtTPS3 gene. Then, RNA interference (RNAi) of BtTPS1 and BtTPS2 resulted in significant mortality and influenced the expression of related genes involved in energy metabolism and chitin biosynthesis in whitefly adults. Finally, the transgenic tobacco plants showed a significant effect on B. tabaci, and knockdown of BtTPS1 or BtTPS2 led to retarded growth and low hatchability in whitefly nymphs, and caused 90% mortality and decreased the fecundity in whitefly adults. Additionally, the transgenic tobacco with combinatorial RNAi of BtTPS1 and BtTPS2 showed a better efficacy against whiteflies than individual silencing.

CONCLUSION

Our results suggest that silencing of the BtTPS genes can compromise the growth and development of whiteflies, offering not only a new option for whitefly control but also a secure and environmentally friendly management strategy.

Effects of Different Nutritional Conditions on the Growth and Reproduction of Nilaparvata lugens (Stål)

Growth and reproduction are the two most basic life processes of organisms and the distribution of energy in these processes is a core issue of the life history of organisms. Nilaparvata lugens (Stål), the brown planthopper (BPH), is a single-feeding rice pest. In the present study, this species was used as a model for testing the effects of nutritional conditions on various growth and reproduction indicators. First, the third-instar nymphs were fed with three different concentrations (100, 50, and 25%) of artificial diet until the second day of adulthood. The results showed that as the nutrient concentration decreased, the body development and oviposition of BPH were hindered. The total lipid content in the fat bodies was also significantly reduced. RT-PCR analysis showed compared to the 100% concentration group, the expression levels of vitellogenin (Vg) genes in the fifth-instar nymphs, adults, and in different tissues (ovary, fat body, and other tissues) were significantly decreased in the 50 and 25% treatment groups. Western blot analysis showed that Vg protein expression was highest in the 100% group, followed by the 50% group, with no expression in the 25% group. These results indicate that growth and reproduction in the BPH are regulated by, or correlated with, nutrient concentration. This study is of great significance as it reveals the adaptive strategies of the BPH to nutritional deficiencies and it also provides valuable information for the comprehensive control of this pest.

Functional Characterization of a Trehalose-6-Phosphate Synthase in Diaphorina citri Revealed by RNA Interference and Transcriptome Sequencing

Trehalose-6-phosphate synthase (TPS) plays an important role in the synthesis of trehalose. In the current study, a TPS gene was obtained from Diaphorina citri, and named as DcTPS1 which encoded a protein of 833 amino acid residues. Real-time quantitative PCR (qPCR) analysis revealed that DcTPS1 had the highest expression level in the midgut and fifth-instar nymph stage. Knockdown of DcTPS1 by RNA interference (RNAi) induced an abnormal phenotype and increased mortality and malformation rate with a decreased molting rate. In addition, silencing of DcTPS1 significantly inhibited D. citri chitin metabolism and fatty acid metabolism, while the expression levels of fatty acid decomposition-related genes were downregulated. Furthermore, comparative transcriptomics analysis revealed that 791 differentially expressed genes (DEGs) were upregulated and 678 DEGs were downregulated when comparing dsDcTPS1 groups with dsGFP groups. Bioinformatics analysis showed that upregulated DEGs were mainly involved in oxidative phosphorylation, whereas downregulated DEGs were mainly attributed to the lysosome and ribosome. These results indicated that DcTPS1 played an important role in the growth and development of D. citri.

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.